FLUKE 2640A NetDAQ Data Acquisition Tools Owner’s Manual

Specifications

1-9.

Specifications are divided into three sections. The first section contains the combined specifications that apply equally to both the 2640A and 2645A instruments. The second section contains specifications that apply only to the 2640A instrument. The third section contains specifications that apply only to the 2645A instrument.

2640A/2645A Combined Specifications

1-10.

The following specifications apply equally to both the 2640A and 2645A instruments. The topics include:

· 2640A/2645A General Specifications · 2640A/2645A Environmental Specifications · 2640A/2645A Digital I/O and Totalizer Interface

1-8

1 Introduction and Specification Specifications

2640A/2645A General Specifications

1-11.

Table 1-5 provides the general specifications for the 2640A and 2645A instruments.

Table 1-5. 2640A/2645A General Specifications

Specification Channel Capacity I/O Lines Total Size Weight Power
Standards
Serial Interface (RS-232C)
Common Mode Voltage Measurement Speed (Scanning Rates)
Accuracy of Medium Scanning Rate Additional error if “Automatic drift correction” is turned off.

Characteristic
20
12
9.3 cm (3.67 in) high, 21.6 cm (8.5 in) wide, 36.2 cm (14.28 in) deep
Net, 4 kg (8.8 lb.) Shipping, 6.0 kg (13.2 lb.)
107 to 264V ac (no switching required), 45 to 65 Hz, 15 VA maximum 9V dc to 16V dc, 6W maximum. Specifications are for 50 or 60 Hz operation. If both sources are applied simultaneously, ac voltage is used if it exceeds approximately 8 times the dc voltage. Automatic switchover occurs between ac and dc without interruption.
Both instruments comply with: IEC 1010-1 UL 1244 CSA Bulletin 556B ANSI/ISA-S8201-1988 CSA C22.2 No. 101.1-92 Vfg. 243/1991 (when shielded cables are used) FCC-15B, Class B level (when shielded cables are used)
Connector: 9 pin male (DB-9P) Signals: TX, RX, DTR, RTS, GND Modem Control: full duplex Baud rates: 4800, 9600, 19200, 38400 Data format: 8 data bits, no parity bit, one stop bit Flow control: XON/XOFF Echo: Off
2640A 150V (300V on channels 1 and 11) 2645A 50V dc or 30V ac rms.
2640A Slow – 6 readings per second Medium – 48 readings per second (60 Hz) Fast – 143 readings per second (20 configured channels) Single Channel – 120 readings per second
2645A Slow – 54 readings per second (60 Hz) Medium – 200 readings per second Fast – 1000 readings per second (20 configured channels) Single Channel – 400 readings per second
Equal to (Fast Accuracy Rate + Slow Accuracy Rate)/2
If the instrument is fully warmed-up at the time drift correction was disabled, i.e., turned on at least 1 hour earlier: 1/10 of the 90-day specification per °C change in ambient temperature from the temperature when drift correction was disabled.
If the instrument was not fully warmed up at the time of drift correction was disabled: add an error equal to the 90-day specification for instrument warmup +1/10 of the 90-day specification per °C change in ambient temperature from the temperature when drift correction was disabled.

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NetDAQ Service Manual

2640A/2645A Environmental Specifications

1-12.

Table 1-6 provides a summary of the environmental specifications for the 2640A/2645A.

Table 1-6. Environmental Specifications

Specification Warmup Time Operating Temperature Storage Temperature Relative Humidity
Altitude Vibration
Shock

Characteristic
1 hour to rated specifications -or- 15 minutes if relative humidity (noncondensing) is 50% or less.
-10°C to 60°C (14°F to 140°F)
-40°C to +70°C (-40°F to +158F)
90% maximum for -10°C to 28°C (14°F to 82.4°F) 75% maximum for 28°C to 35°C (82.4°F to 95°F) 50% maximum for 35°C to 60°C (95°F to 140°F) (3 M range, reduce humidity rating by 25% for 1 hour warmup. The 3 M range meets full humidity ratings with 2-hour warmup.)
Operating: 2,000m (6,561 ft) maximum Non-operating: 12,200m (40,000 ft) maximum
0.7g at 15 Hz 1.3g at 25 Hz 3g at 55 Hz
30g half-sine per Mil-T-28800 Bench handling per Mil-T-28800

2640A/2645A Input/Output Capabilities

1-13.

The following specifications include the input/output functions, including the Digital I/O, Trigger Out, Trigger In, and Master Alarm output.

Digital I/O

1-14.

Table 1-7 provides a summary of the Digital I/O specifications for the 8 Digital I/O lines (0 to 7). Digital I/O is located on the DIGITAL I/O connector, terminals 0 to 7, and GND.

Table 1-7. 2640A/2645A DIGITAL I/O Specification

Specification
Maximum Input Voltage Minimum Input Voltage Isolation Threshold Hysteresis Specification Output Voltage – TTL Logical Zero Output Voltage – TTL Logical One Output Voltage – Non-TTL Load Zero Output Voltage – Non-TTL Load One

Characteristic
30V -4V None (dc coupled) 1.4V 500 mV Characteristic 0.8V maximum for an Iout of -1.0 mA (1 LSTTL load) 3.8V minimum for an Iout of 0.05 mA (1 LSTTL load) 1.8V maximum for an Iout of -20 mA 3.25V maximum for an Iout of -50 mA

1-10

1 Introduction and Specification Specifications

Trigger In

1-15.

Table 1-8 provides a summary of the Trigger In specifications. The Trigger In input is located on the ALARM/TRIGGER I/O connector, terminals TI and GND.

Table 1-8. 2640A/2645A Trigger In (TI) Specification

Specification Logical High – Trigger not set
Logical Low – Trigger set
Compatibility Isolation Minimum Pulse Width Maximum Frequency Repeatability

Characteristic
Minimum: 2.0V Maximum: 7.0V Minimum: -0.6V Maximum: +0.8V TTL or Contact Closure None (dc coupled) 5 µs Nominal 400 Hz 3 ms

Trigger Out

1-16.

Table 1-9 provides a summary of the Trigger Out specifications. The Trigger Out output is located on the ALARM/TRIGGER I/O connector, terminals TO and GND.

Table 1-9. 2640A/2645A Trigger Out (TO) Specification

Specification

Characteristic

TTL Logical Zero – Trigger Out Set TTL Logical One – Trigger Out Not Set Non- TTL Logical Zero – Trigger Out Set Non-TTL Logical One – Trigger Out Not Set Pulse Duration (Logic Low) Isolation

0.8V maximum for an Iout of -1.0 mA (1 LSTTL load) 3.8V minimum for an Iout of 0.05 mA (1 LSTTL load) 1.8V maximum for an Iout of -20 mA 3.25V maximum for an Iout of -50 mA 125 µs None

Master Alarm

1-17.

Table 1-10 provides a summary of the Master Alarm specifications. The Master Alarm output is located on the ALARM/TRIGGER I/O connector, terminals MA and GND.

Table 1-10. 2640A/2645A Master Alarm (MA) Specification

Specification

Characteristic

TTL Logical Zero – Master Alarm Set TTL Logical One – Master Alarm Not Set Non-TTL Logical Zero – Master Alarm Set Non-TTL Logical One – Master Alarm Not Set Isolation

0.8V maximum for an Iout of -1.0 mA (1 LSTTL load) 3.8V minimum for an Iout of 0.05 mA (1 LSTTL load) 1.8V maximum for an Iout of -20 mA 3.25V maximum for an Iout of -50 mA None

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NetDAQ Service Manual

2640A/2645A Totalizer

1-18.

Table 1-11 provides a summary of the Totalizer specifications. The Totalizer input is located on the DIGITAL I/O connector, terminals and GND.

Table 1-11. 2640A/2645A Totalizer Specification

Specification Maximum Input Voltage Minimum Input Voltage Minimum Peak Voltage Isolation Threshold Hysteresis Input Debouncing Maximum Transition Rate
Maximum Count

Characteristic
30V -4V 2V None (dc coupled) 1.4V 500 mV None or 1.75 ms (selectable) 5 kHz (Debounce disabled) 500 Hz (Debounce enabled) 4,294,967,295

2640A/2645A Real-Time Clock and Calendar

1-19.

Table 1-12 provides a summary of the battery powered real-time clock and calendar.

Table 1-12. 2640A/2645A Real-Time Clock and Calendar

Specification Accuracy Battery Life

Characteristic
1 minute per month for 0°C to 50°C range >15 unpowered instrument years for 0°C to 28°C (32°F to 82.4°F). >6 unpowered instrument years for 0°C to 50°C (32°F to 122°F). >4 unpowered instrument years for 50°C to 70°C (122°F to 158°F).

1-12

1 Introduction and Specification Specifications

2640A Specifications

1-20.

This section includes specifications specific to the 2640A instrument by measurement function.

2640A DC Voltage Measurement Specifications

1-21.

Tables 1-13 to 1-15 provide 2640A specifications for the dc voltage measurement function.

Table 1-13. 2640A DC Voltage General Specifications

Specification Input Impedance Normal Mode Rejection Common Mode Rejection
Channel-to-Channel Crosstalk
Temperature Coefficient
Maximum Input Voltage

Characteristic

100 M in parallel with 300 pF maximum for ranges <=3V 10 M in parallel with 100 pF maximum for ranges >3V
50 dB minimum at 50 Hz/60 Hz +0.1%, Slow Rate
120 dB minimum at dc, 50 Hz/60 Hz +0.1%, 1 k imbalance, Slow Rate 80 dB minimum at dc, 50 Hz/60 Hz +0.1%, 1 k imbalance, Medium and Fast Rates
120 dB minimum Slow Rate (e.g., 30V dc on channel 1 may cause a 30 µV error on channel 2) 100 dB minimum Medium and Fast Rates (e.g., 1V dc on channel 1 may cause a 10 µV error on channel 2)
For % input: Add 1/10th the 90-day specification per °C above 28 °C or below 18 °C For floor error (V): Add 1/20th the 90-day specification per °C above 28 °C or below 18 °C
The lesser voltage of: 300V from any terminal on channels 1 and 11 to earth; 150V from any terminal on channels 2 through 10, and 12 through 20 to earth; 300V from any terminal on channels 1 and 11 to any other terminal;
150V from any terminal on channels 2 through 10, and 12 through 20 to any other input terminal

Table 1-14. 2640A DC Voltage Range and Resolution Specifications

Range

Slow

Resolution

90 mV 300 mV 3V 30V 150V/300V

0.3 µV 1 µV 10 µV 100 µV 1 mV

1 µV 3 µV 30 µV 300 µV 3 mV

Note 300V range applies to channels 1 and 11 only.

Fast

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Table 1-15. 2640A DC Voltage Accuracy Specifications

Range

90 Day

Accuracy, 3 + (% input + V) 18°C to 28°C
1 Year

-10°C to 60°C 1 Year

Slow

Fast

Slow

Fast

Slow

Fast

90 mV

.01%+7 µV

.01%+17 µV .013%+8 µV

.013%+18 µV .042%+18.2 µV

300 mV

.01%+15 µV .01%+30 µV .013%+17 µV

.013%+35 µV .042%+39 µV

750 mV* .01%+40 µV .01%+70 µV .013%+50 µV

.013%+80 µV .042%+104 µV

3V

.01%+0.1 mV .01%+0.2 mV .013%+0.15 mV .013%+0.2 mV .042%+0.26 mV

30V

.01%+1.5 mV .02%+3 mV .013%+1.7 mV .026%+3.5 mV .042%+3.9 mV

150/300V** .01%+15 mV .04%+30 mV .013%+17 mV .052%+35 mV .042%+39 mV

• The 750 mV range is used internally to the instrument and not user selectable. ** 300V range applies to channels 1 and 11 only.

.042%+44.2 µV .042%+78 µV .042%+182 µV .042%+0.52 mV .084%+7.8 mV .168%+78 mV

2640A AC Voltage Measurement Specifications

1-22.

Tables 1-16 to 1-18 provide 2640A specifications for the ac voltage measurement function.

Table 1-16. 2640A AC Voltage General Specifications

Specification Input Impedance Maximum Crest Factor Crest Factor Error Common Mode Rejection Maximum Input Voltage
Maximum Volt-Hertz Product Temperature Coefficient
DC Component Error

Characteristic
1 M in parallel with 100 pF
3.0 Maximum 2.0 for rated accuracy
For nonsinusoidal input signals with crest factors between 2 and 3 and pulse widths >=100 µs, add 0.2% to the accuracy specifications.
80 dB minimum at dc, 50 Hz/60 Hz +0.1%, 1 k imbalance, Slow Rate
The lesser voltage of:
300V ac rms from any terminal on channels 1 and 11 to earth.
150V ac rms from any terminal on channels 2 through 10, and 12 through 20 to earth.
300V ac rms from any terminal on channels 1 and 11 to any other terminal.
150V ac rms from any terminal on channels 2 through 10 and 12 through 20 to any other input terminal. 2×106 Volt-Hertz product on any range, normal mode input. 1×106 Volt-Hertz product on any range, common mode input.
Linear interpolation between 2 applicable points for temperatures between 28°C and 60°C, or -10°C and 18°C, e.g., if the applicable specification at 28°C is 2% and the specification at 60°C is 3%, then the specification at 40°C is (3%-2%)x(40-28)/(60-28)+2%=2.375%.
The presence of a dc voltage will cause an indeterminate error in the reading of the ac voltage on the input.

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1 Introduction and Specification Specifications

Table 1-17. 2640A AC Voltage Range and Resolution Specifications

Range

Slow

Resolution

Fast

Full Scale

+30,000

+3,000

300 mV

10 µV

100 µV

3V

100 µV

1 mV

30V

1 mV

10 mV

150/300V

10 mV

100 mV

Note 300V range applies to channels 1 and 11 only.

Minimum Input for Rate Accuracy
20 mV 200 mV 2V 20V

Table 1-18. 2640A AC Voltage Accuracy Specifications

1 Year Accuracy + (%input + V) [1]

Range

Frequency

18°C to 28°C

-10°C to 60°C

Slow

Fast

Slow

Fast

300 mV 20 to 50 Hz

3%+.25 mV 6%+.5 mV

50 to 150 Hz

0.4%+.25 mV 1%+.5 mV

150 Hz to 10 kHz

0.3%+.25 mV 1%+.5 mV

10 kHz to 20 kHz

0.4%+.25 mV 1%+.5 mV

20 kHz to 50 kHz

2%+.3 mV

3%+.5 mV

50 kHz to 100 kHz

5%+.5 mV

5%+1 mV

3V

20 to 50 Hz

3%+2.5 mV 6%+5 mV

50 to 150 Hz

0.4%+2.5 mV 1%+5 mV

150 Hz to 10 kHz

0.3%+2.5 mV 1%+5 mV

10 kHz to 20 kHz

0.4%+2.5 mV 1%+5 mV

20 kHz to 50 kHz

1%+3 mV

1.5%+6 mV

50 kHz to 100 kHz

2%+5 mV

3%+10 mV

30V

20 to 50 Hz

3%+25 mV

6%+50 mV

50 to 150 Hz

0.4%+25 mV 1%+50 mV

150 Hz to 10 kHz

0.3%+25 mV 1%+50 mV

10 kHz to 20 kHz

0.4%+25 mV 1%+50 mV

20 kHz to 50 kHz

1%+30 mV

1.5%+60 mV

50 kHz to 100 kHz, V<20V 2%+50 mV 3%+100 mV

150/300V 20 to 50 Hz

3%+.25V

6%+.5V

50 to 150 Hz

0.4%+.25V

1%+.5V

150 Hz to 2 kHz Vx Hz<2 x106

0.3%+.25V 1.2%+.5V

2 kHz to 20 kHz, V<100V 0.4%+.25V 1.6%+.5V

20 kHz to 50 kHz, V<40V 1%+.30V

2.0%+.6V

[1] Sinewave inputs>6% of scale and signals with crest factors <2.

3.5%+.25 mV 0.5%+.25 mV 0.4%+.25 mV 0.7%+.25 mV 3%+.3 mV 7%+.5 mV 3.5%+2.5 mV 0.5%+2.5 mV 0.4%+2.5 mV 0.5%+2.5 mV 1.5%+3 mV 3%+5 mV 3.5%+25 mV 0.5%+25 mV 0.5%+25 mV 0.5%+25 mV 1%+30 mV 2.5%+50 mV 3.5%+.25V 0.5%+.25V 0.5%+.25V
0.5%+.25V 1.2%+.30V

7%+.5 mV 1.5%+.5 mV 1.5%+.5 mV 1.5%+.5 mV 4%+.5 mV 8%+1 mV 7%+5 mV 1.2%+5 mV 1.2%+5 mV 1.2%+5 mV 2%+6 mV 4%+10 mV 7%+50 mV 1.2%+40 mV 1.2%+40 mV 1.2%+40 mV 2%+50 mV 4%+100 mV 7%+.5V 1.2%+.4V 1.4%+.4V
1.8%+.4V 2.5%+.5V

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NetDAQ Service Manual

2640A Four-Wire Resistance Measurement Specifications

1-23.

Tables 1-19 to 1-21 provide 2640A specifications for the four-wire resistance measurement function. The four-wire measurements use 2 input channels a decade apart, e.g., channels 4 and 14.

Table 1-19. 2640A Four-Wire Resistance Temperature Coefficient

Specification Temperature Coefficient

Characteristic
Add 1/10th the 90 day specification per °C above 28°C or below 18°C.

Table 1-20. 2640A Four-Wire Resistance Range and Resolution Specifications

Range
300 3 k 30 k 300 k 3 M

Resolution

Slow

Fast

1 m 10 m 100 m 1 10

3m 30 m 300 m 3 30

Current Applied
1 mA 100 µA 10 µA 10 µA 1 µA

Full Scale Voltage
300 mV 300 mV 300 mV 3.0V 3.0V

Maximum Voltage Applied by Instrument
3.5V 3.5V 3.5V 3.5V 3.5V

Table 1-21. 2640A Four-Wire Resistance Accuracy Specifications

Range

90 Day

Accuracy, 3 + (% input + V) 18°C to 28°C
1 Year

-10°C to 60°C 1 Year

Slow

Fast

Slow

Fast

Slow

Fast

300

.015%+20 m .02%+80 m .02%+50 m .02%+120 m .084%+126 m .084%+336 m

3 k

.02%+.3

.02%+.8

.02%+.5

.02%+1.2

.084%+1.26

.084%+3.36

30 k

.03%+3

.04%+10

.03%+5

.04%+15

.126%+12.6

.168%+42

300 k .1%+40

.2%+100

.1%+60

.2%+150

.42%+168

.84%+420

3 M [1] .25%+800

.5%+10 k .25%+1 k

.5%+1.5 k

1.05%+3.36 k 2.1%+4.2 k

[1] The 3 M range is susceptible to the absorption of humidity under extreme conditions. If the instrument is operated normally within its specified temperature-humidity range, the 3 M range meets its accuracy specifications. However, if the instrument is “soaked” at 50°C, 90% relative humidity, the 3 M range may require 1 hour of “dry-out” time at 25°C, <40% relative humidity for each hour of soak time in order to achieve its specified accuracy.

2640A Two-Wire Resistance Measurement Specifications

1-24.

The 2640A specifications for the two-wire resistance measurement function is based on the four-wire resistance measurement specification (above) except you add a nominal 5-ohm (10-ohm maximum) positive offset. This value varies for each channel and with temperature (nominal +1%/ºC).

1-16

1 Introduction and Specification Specifications

2640A Four-Wire RTD per ITS-1990 Measurement Specifications

1-25.

Tables 1-22 and 1-23 provide 2640A specifications for the four-wire ResistanceTemperature Detector (RTD) measurement function. The four-wire measurements use 2 input channels a decade apart, e.g., channels 4 and 14.

Table 1-22. 2640A Four-Wire RTD Temperature Coefficient

Specification Temperature Coefficient

Characteristic
To calculate RTD accuracy for temperatures between 28°C and 60°C, or -10°C and 18°C, use a linear interpolation between the two applicable points. For example, if the applicable specification at 28°C is 0.2 and the specification at 60°C is 0.75, then the specification at 40°C is =(.75.2)x(40-28)/(60-28)+.2=0.406.

Table 1-23. 2640A Four-Wire RTD Specifications

Temperature

Resolution

90 Day 18°C to 28°C

Accuracy, 3
1 Year 18°C to 28°C

1 Year -10°C to 60°C

-200°C 0°C 100°C 300°C 600°C

Slow

Fast

Slow

0.003°C 0.003°C 0.003°C 0.003°C 0.003°C

0.007°C 0.007°C 0.007°C 0.007°C 0.007°C

0.06°C 0.09°C 0.10°C 0.14°C 0.19°C

Fast
0.16°C 0.20°C 0.23°C 0.30°C 0.53°C

Slow
0.09°C 0.13°C 0.16°C 0.21°C 0.30°C

Slow
0.33°C 0.53°C 0.63°C 0.83°C 1.20°C

Fast
0.63°C 0.86°C 0.97°C 1.20°C 1.60°C

2640A Two-Wire RTD per ITS-1990 Measurement Specifications

1-26.

The 2640A specifications for the two-wire Resistance-Temperature Detector (RTD) measurement function is based on the four-wire RTD measurement specification (above) except you add a nominal 5-ohm (approximately 13°C) positive offset. This value varies for each channel and temperature gradient (nominal +1%/ºC). Also note that the resistance of the RTD wiring adds directly to the error. After 100 million operations of a measurement channel, the offset will increase at an indeterminate rate.

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NetDAQ Service Manual

1-18

2640A Thermocouple per ITS-1990 Measurement Specifications

1-27.

Tables 1-24 to 1-25 provide 2640A specifications for the thermocouple measurement function per ITS-1990.

Table 1-24. 2640A Thermocouple General Specifications

Specification Input Impedance Open Thermocouple Detect
Temperature Coefficient

Characteristic
100 M minimum in parallel with 300 pF
Operates by injecting a small ac signal into the input after each measurement. A thermocouple resistance greater than 1k to 10k is detected as an open input.
To calculate Thermocouple accuracy for temperatures between 28°C and 60°C, or -10°C and 18°C, use a linear interpolation between the two applicable points. For example, if the applicable specification at 28°C is 0.6 and the specification at 60°C is 1.1, then the specification at 40°C is =(1.10.6)x(40-28)/(60-28)+0.6=0.7875.

Table 1-25. 2640A Thermocouple Specifications

Accuracy + °C

Thermocouple

Resolution

18°C to 28°C

-10°C to 60°C

90 Day

1 Year

1 Year

Type Temperature °C

Slow

Slow

Fast

Slow

Fast

J

-100 to 80

.03

80 to 230

.02

230 to 760

.02

K

-100 to -25

.04

-25 to 120

.03

120 to 800

.03

800 to 1372

.03

N

-100 to -25

.05

-25 to 120

.05

120 to 1000

.04

1000 to 1300

.03

E

-100 to -25

.03

-25 to 20

.02

20 to 600

.02

600 to 1000

.02

T

-100 to 0

.04

0 to 150

.03

150 to 400

.02

0.45

0.50

0.80

0.60

0.80

0.35

0.50

0.70

0.60

0.80

0.40

0.50

0.70

0.80

0.90

0.55

0.60

0.90

0.70

1.00

0.40

0.50

0.80

0.60

0.90

0.50

0.65

0.90

1.00

1.20

0.70

1.00

1.30

1.60

1.90

0.65

0.75

1.20

0.80

1.30

0.55

0.60

1.00

0.70

1.10

0.45

0.60

0.90

1.00

1.20

0.55

0.75

1.00

1.20

1.50

0.45

0.50

0.80

0.60

0.80

0.35

0.40

0.60

0.50

0.70

0.30

0.40

0.60

0.50

0.80

0.40

0.50

0.70

0.90

1.00

0.60

0.65

1.00

0.70

1.10

0.40

0.50

0.80

0.60

0.90

0.30

0.40

0.60

0.60

0.80

1 Introduction and Specification Specifications

Table 1-25. 2640A Thermocouple Specifications (cont)

Thermocouple

Accuracy + °C

Resolution

18°C to 28°C

-10°C to 60°C

90 Day

1 Year

1 Year

Type Temperature °C

R

250 to 600

0.1

600 to 1500

0.1

1500 to 1767

0.1

S

250 to 1000

0.1

1000 to 1400

0.1

1400 to 1767

0.1

B

600 to 900

0.2

900 to 1200

0.2

1200 to 1820

0.1

C

0 to 150

0.2

150 to 650

0.1

650 to 1000

.05

1000 to 1800

.05

1800 to 2316

.05

Slow
0.90 0.80 0.85 0.95 0.80 1.00 1.20 0.90 0.75 0.80 0.65 0.65 1.00 1.60

Slow
1.00 0.90 0.85 1.10 1.00 1.30 1.40 1.00 1.00 0.90 0.75 0.85 1.30 2.10

Fast
2.10 1.80 1.90 2.30 1.90 2.20 3.10 2.20 1.90 1.60 1.40 1.40 2.10 3.20

Slow
1.20 1.30 1.70 1.30 1.40 1.80 1.50 1.20 1.30 1.00 1.00 1.20 2.10 3.40

Fast
2.20 2.00 2.50 2.40 2.30 2.80 3.20 2.40 2.20 1.70 1.50 1.80 2.80 4.60

2640A Frequency Measurement Specifications

1-28.

Tables 1-26 to 1-27 provide 2640A specifications for the frequency measurement function.

Table 1-26. 2640A Frequency Accuracy Specifications

Frequency Measurement Accuracy, 1 Year, -10°C to 60°C

Range

Resolution

Accuracy + (% input + Hz)

Slow

15 Hz to 900 Hz 900 Hz to 9 kHz 9 kHz to 90 kHz 90 kHz to 900 kHz 1 MHz

0.01 Hz 0.1 Hz 1 Hz 10 Hz 100 Hz

Fast
0.1 Hz 1 Hz 10 Hz 100 Hz 1 kHz

Slow
0.05%+0.02 Hz 0.05%+0.1 Hz 0.05%+1 Hz 0.05%+10 Hz 0.05%+100 Hz

Fast
0.05%+0.2 Hz 0.05%+1 Hz 0.05%+10 Hz 0.05%+100 Hz 0.05%+1 kHz

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Table 1-27. 2640A Frequency Sensitivity Specifications

Frequency Measurement Sensitivity (Sinewave)

Frequency Range

Minimum Signal

15 Hz to 70 kHz

100 mV ac rms

70 kHz to 100 kHz

100 mV ac rms

100 kHz to 200 kHz 150 mV ac rms

200 kHz to 300 kHz 150 mV ac rms

300 kHz to 1 MHz

Linearly increasing from 150 mV ac rms at 300 kHz to 2 V ac rms at 1 MHz

[1] 300V range applies to channels 1 and 11 only.

Maximum Signal
V<150/300Vrms [1] and Vx Hz<2×106) 20V ac rms 10V ac rms 7V ac rms Linearly decreasing from 7 V ac rms at 300 kHz to 2 V ac rms at 1 MHz

2645A Specifications

1-29.

This section includes specifications specific to the 2645A instrument by measurement function.

2645A DC Voltage Measurement Specifications

1-30.

Tables 1-28 to 1-30 provide 2645A specifications for the dc voltage measurement function.

Table 1-28. 2645A DC Voltage General Specifications

Specification Input Impedance Normal Mode Rejection Common Mode Rejection
Channel-to-Channel Crosstalk
Temperature Coefficient
Maximum Input Voltage

Characteristic
100 M in parallel with 300 pF maximum for ranges <=3V 10 M in parallel with 100 pF maximum for ranges >3V 50 dB minimum at 50 Hz/60 Hz +0.1%, Slow Rate
120 dB minimum at dc, 50 Hz/60 Hz +0.1%, 1 k imbalance, Slow Rate 80 dB minimum at dc, 60 dB at 50 Hz/60 Hz +0.1%, 1 k imbalance, Medium and Fast Rates
120 dB minimum Slow Rate (e.g., 30V dc on channel 1 may cause a 30 µV error on channel 2) 80 dB minimum Medium and Fast Rates (e.g., 1V dc on channel 1 may cause a 10 µV error on channel 2) For % input: Add 1/10th the 90-day specification per °C above 28°C or below 18°C. For floor error (V): Add 1/20th the 90-day specification per °C above 28°C or below 18°C. The lesser voltage of: 50V dc or 30V ac rms from any input terminal to earth -or50V dc or 30V ac rms from any input terminal to any other input terminal

1-20

1 Introduction and Specification Specifications

Table 1-29. 2645A DC Voltage Resolution and Repeatability Specifications

Range
90 mV 300 mV 3V 30V 50V

3 µV 1 µV 10 µV 100 µV 1 mV

Slow

Resolution
6 µV 3 µV 30 µV 300 µV 3 mV

Fast

Table 1-30. 2645A DC Voltage Accuracy Specifications

Accuracy, 3 + (% input + V)

Range

90 Day

18°C to 28°C

1 Year

-10°C to 60°C 1 Year

Slow

Fast

Slow

Fast

Slow

Fast

90 mV .01%+20 µV .01%+50 µV .013%+23 µV .013%+50 µV

.042%+52 µV

300 mV .01%+40 µV .01%+90 µV .013%+49 µV .013%+93 µV

.042%+104 µV

750 mV* .01%+90 µV .01%+200 µV .013%+105 µV .013%+220 µV

.042%+273 µV

3V

.01%+.3 mV .01%+.6 mV .013%+.38 mV .013%+.64 mV .042%+.78 mV

30V

.01%+4 mV .02%+8 mV .013%+4.9 mV .026%+9.5 mV .042%+10.6 mV

50V

.01%+30 mV .04%+60 mV .013%+40 mV .052%+64 mV

.042%+78 mV

• The 750 mV range is used internally to the instrument and not user selectable.

.042%+130 µV .042%+234 µV .042%+520 µV .042%+1.56 mV .084%+20.3 mV .168%+156 mV

2645A AC Voltage Measurement Specifications
Tables 1-31 to 1-33 provide 2645A specifications for the ac voltage function.
Table 1-31. 2645A AC Voltage General Specifications

1-31.

Specification Input Impedance Maximum Crest Factor Crest Factor Error Common Mode Rejection Maximum Input Voltage
Maximum Volt-Hertz Product Temperature Coefficient
DC Component Error

Characteristic
1 M in parallel with 100 pF
3.0 maximum; 2.0 for rated accuracy
For nonsinusoidal input signals with crest factors between 2 and 3 and pulse widths >=100 µs, add 0.2% to the accuracy specifications.
80 dB minimum at dc, 50 Hz/60 Hz +0.1%, 1 k imbalance, Slow Rate
The lesser voltage of: 30V ac rms from any input terminal to earth. 30V ac rms from any terminal input to any other input terminal. 2×106 Volt-Hertz product on any range, normal mode input. 1×106 Volt-Hertz product on any range, common mode input.
Linear interpolation between 2 applicable points for temperatures between 28°C and 60°C, or -10°C and 18°C, e.g., if the applicable specification at 28°C is 2% and the specification at 60°C is 3%, then the specification at 40°C is (3%-2%)x(40-28)/(60-28)+2%=2.375%.
The presence of a dc voltage will cause an indeterminate error in the reading of the ac voltage on the input.

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NetDAQ Service Manual

Table 1-32. 2645A AC Voltage Range and Resolution Specifications

Range
Full Scale 300 mV 3V 30V

Slow
+30,000 10 µV 100 µV 1 mV

Resolution
Fast +3,000 100 µV 1 mV 10 mV

Minimum Input for Rate Accuracy
20 mV 200 mV 2V

Table 1-33. 2645A AC Voltage Accuracy Specifications

1 Year Accuracy + (%input + V) [1]

Range

Frequency

18°C to 28°C

-10°C to 60°C

Slow

Fast

Slow

Fast

300 mV 20 to 50 Hz

3%+.25 mV 6%+.5 mV

50 to 150 Hz

0.4%+.25 mV 0.8%+.5 mV

150 Hz to 10 kHz

0.3%+.25 mV 0.8%+.5 mV

10 kHz to 20 kHz

0.4%+.25 mV 1%+.5 mV

20 kHz to 50 kHz

2%+.3 mV

3%+.5 mV

50 kHz to 100 kHz

5%+.5 mV

5%+1 mV

3V

20 to 50 Hz

3%+2.5 mV 6%+5 mV

50 to 150 Hz

0.4%+2.5 mV 0.8%+5 mV

150 Hz to 10 kHz

0.3%+2.5 mV 0.6%+5 mV

10 kHz to 20 kHz

0.4%+2.5 mV 0.8%+5 mV

20 kHz to 50 kHz

1%+3 mV

1.5%+6 mV

50 kHz to 100 kHz

2%+5 mV

3%+10 mV

30V

20 to 50 Hz

3%+25 mV 6%+50 mV

50 to 150 Hz

0.4%+25 mV 0.8%+50 mV

150 Hz to 10 kHz

0.4%+25 mV 0.8%+50 mV

10 kHz to 20 kHz

0.4%+25 mV 0.8%+50 mV

20 kHz to 50 kHz

1%+30 mV 1.5%+60 mV

50 kHz to 100 kHz, V<20V 2%+50 mV 3%+100 mV

[1] Sinewave inputs>6% of scale and signals with crest factors <2.

3.5%+.25 mV 0.5%+.25 mV 0.4%+.25 mV 0.7%+.25 mV 3%+.3 mV 7%+.5 mV 3.5%+2.5 mV 0.5%+2.5 mV 0.4%+2.5 mV 0.5%+2.5 mV 1.5%+3 mV 3%+5 mV 3.5%+25 mV 1.2%+25 mV 1.2%+25 mV 1.2%+25 mV 1.2%+30 mV 2.5%+50 mV

7%+.5 mV 1%+.5 mV 1%+.5 mV 1.5%+.5 mV 4%+.5 mV 8%+1 mV 7%+5 mV 1%+5 mV 1%+5 mV 1%+5 mV 2%+6 mV 4%+10 mV 7%+50 mV 1.3%+40 mV 1.3%+40 mV 1.3%+40 mV 2%+50 mV 4%+100 mV

1-22

1 Introduction and Specification Specifications

2645A Four-Wire Resistance Measurement Specifications

1-32.

Tables 1-34 to 1-36 provide 2645A specifications for the four-wire resistance measurement function. The four-wire measurements use 2 input channels a decade apart, e.g., channels 4 and 14.

Table 1-34. 2645A Four-Wire Resistance Temperature Coefficient

Specification
Temperature Coefficient

Characteristic Add 1/10th the 90 day specification per °C above 28°C or below 18°C.

Table 1-35. 2645A Four-Wire Resistance Range and Resolution Specifications

Range

Resolution

Slow

Fast

300 3 k 30 k 300 k 3 M

10 m 100 m 1 10 100

30 m 300 m 3 30 300

Current Applied
1 mA 100 µA 10 µA 10 µA 1 µA

Full Scale Voltage
300 mV 300 mV 300 mV 3.0V 3.0V

Maximum Voltage Applied by Instrument
3.5V 3.5V 3.5V 3.5V 3.5V

Table 1-36. 2645A Four-Wire Resistance Accuracy Specifications

Range

90 Day

Accuracy, 3 + (% input + ) 18°C to 28°C
1 Year

-10°C to 60°C 1 Year

300 3 k 30 k 300 k 3 M

Slow

Fast

.02%+60 m .02%+.6 .02%+6 .5%+80 1.3%+1 k

.02%+.1 .02%+2 .2%+200 1%+2 k 2%+120 k

Slow
.02%+.1 .02%+1 .02%+10 .5%+150 1.3%+2 k

Fast

Slow

Fast

.02%+.2 .02%+3 .2%+300 1%+3 k 2%+200 k

.084%+.25 .084%+2.5 .084%+25 2.1%+336 5.46%+4.2 k

.084%+.42 .084%+8.4 .84%+840 4.2%+8.4 k 8.4%+200 k

2645A Two-Wire Resistance Measurement Specifications

1-33.

The 2645A specifications for the two-wire resistance measurement function is based on the four-wire resistance measurement specification (above) except you add a 700 to 1000 ohm positive offset. This value varies for each channel and temperature gradient (nominal +1%/ºC).

1-23

NetDAQ Service Manual

2645A Four-Wire RTD per ITS-1990 Measurement Specifications

1-34.

Tables 1-37 and 1-38 provide 2645A specifications for the four-wire ResistanceTemperature Detector (RTD) measurement function. The four-wire measurements use 2 input channels a decade apart, e.g., channels 4 and 14. There is no two-wire RTD capability for the 2645A.

Table 1-37. 2645A Four-Wire RTD Temperature Coefficient

Specification Temperature Coefficient

Characteristic
To calculate RTD accuracy for temperatures between 28°C and 60°C, or -10°C and 18°C, use a linear interpolation between the two applicable points. For example, if the applicable specification at 28°C is 0.2 and the specifications at 60°C is 0.75, then the specification at 40°C =(.75-.2)x(40-28)/(60-28)+.2=.406.

Table 1-38. 2645A Four-Wire RTD Specifications

Temperature

Resolution

-200°C 0°C 100°C 300°C 600°C

Slow
0.03°C 0.03°C 0.03°C 0.03°C 0.03°C

Fast
0.06°C 0.06°C 0.06°C 0.06°C 0.06°C

Accuracy, 3

90 Day 18°C to 28°C

1 Year 18°C to 28°C

1 Year -10°C to 60°C

Slow

Fast

Slow

Slow Fast

0.16°C 0.20°C 0.23°C 0.30°C 0.53°C

0.25°C 0.31°C 0.34°C 0.41°C 0.63°C

0.25°C 0.31°C 0.34°C 0.41°C 0.63°C

0.62°C 0.85°C 0.95°C 1.18°C 1.62°C

1.10°C 1.30°C 1.40°C 1.70°C 2.12°C

2645A Thermocouple per ITS-1990 Measurement Specifications

1-35.

Tables 1-39 to 1-40 provide 2645A specifications for the thermocouple measurement function per ITS-1990.

Table 1-39. 2645A Thermocouple General Specifications

Specification Input Impedance Open Thermocouple Detect
Temperature Coefficient

Characteristic
100 M minimum in parallel with 300 pF
Operates by injecting a small ac signal into the input after each measurement. A thermocouple resistance greater than 1 k to 10k is detected as an open input.
To calculate Thermocouple accuracy for temperatures between 28°C and 60°C, or -10°C and 18°C, use a linear interpolation between the two applicable points. For example, if the applicable specification at 28°C is 0.6 and the specification at 60°C is 1.1, then the specification at 40°C is =(1.1-0.6)x(40-28)/(60-28)+0.6=0.7875.

1-24

1 Introduction and Specification Specifications

Table 1-40. 2645A Thermocouple Specifications

Accuracy + °C

Thermocouple

Resolution

18°C to 28°C

90 Day

1 Year

-10°C to 60°C 1 Year

Type Temperature °C

Slow

Slow

Fast

Slow

Fast

J

-100 to 80

.3

80 to 230

.2

230 to 760

.2

K

-100 to -25

.4

-25 to 120

.3

120 to 1000

.3

1000 to 1372

.3

N

-100 to -25

.5

-25 to 120

.5

120 to 1000

.4

1000 to 1300

.3

E

-100 to -25

.3

-25 to 20

.2

20 to 600

.2

600 to 1000

.2

T

-100 to 0

.4

0 to 150

.3

150 to 400

.2

R

250 to 600

1

600 to 1500

1

1500 to 1767

1

S

250 to 1000

1

1000 to 1400

1

1400 to 1767

1

B

600 to 1200

2

1200 to 1550

2

1550 to 1820

1

C

0 to 150

2

150 to 650

1

650 to 1000

.5

1000 to 1800

.5

1800 to 2316

.5

0.8

0.9

1.6

0.7

0.8

1.4

0.7

0.8

1.3

1.0

1.1

2.0

0.8

0.9

1.7

0.9

1.1

1.8

1.2

1.5

2.3

1.4

1.5

2.8

1.1

1.3

2.3

1.0

1.1

2.0

1.0

1.2

1.9

0.8

0.9

1.5

0.7

0.7

1.2

0.6

0.7

1.1

0.6

0.8

1.2

1.1

1.2

2.2

0.9

1.0

1.7

0.7

0.8

1.4

2.4

2.7

5.6

2.0

2.3

4.6

2.0

2.3

4.5

2.6

2.8

5.9

2.0

2.3

4.6

2.3

2.7

5.3

3.6

3.9

8.5

2.1

2.4

5.0

2.0

2.3

4.7

1.9

2.0

4.0

1.6

1.7

3.5

1.4

1.7

3.2

2.0

2.5

4.5

3.1

3.8

6.8

0.9

1.7

0.9

1.5

1.0

1.5

1.2

2.1

1.0

1.8

1.5

2.2

2.0

2.9

1.5

2.9

1.3

2.4

1.2

2.1

1.6

2.4

1.0

1.6

0.8

1.3

0.8

1.2

1.1

1.5

1.3

2.3

1.0

1.8

0.8

1.5

2.8

5.7

2.4

4.8

2.8

5.1

2.9

6.0

2.6

5.0

3.3

5.9

4.0

8.6

2.6

5.2

2.7

5.0

2.1

4.2

1.8

3.6

2.0

3.5

3.2

5.3

5.1

8.1

1-25

NetDAQ Service Manual

2645A Frequency Measurement Specifications

1-36.

Tables 1-41 to 1-42 provide 2645A specifications for the frequency measurement function.

Table 1-41. 2645A Frequency Accuracy Specifications

Range

Frequency Measurement Accuracy, 1 Year, -10°C to 60°C

Resolution

Accuracy + (% input + Hz)

15 Hz to 900 Hz 900 Hz to 9 kHz 9 kHz to 90 kHz 90 kHz to 900 kHz 1 MHz

Slow
0.01 Hz 0.1 Hz 1 Hz 10 Hz 100 Hz

Fast
0.1 Hz 1 Hz 10 Hz 100 Hz 1 kHz

Slow
0.05%+0.02 Hz 0.05%+0.1 Hz 0.05%+1 Hz 0.05%+10 Hz 0.05%+100 Hz

Fast
0.05%+0.2 Hz 0.05%+1 Hz 0.05%+10 Hz 0.05%+100 Hz 0.05%+1 kHz

Table 1-42. 2645A Frequency Sensitivity Specifications

Frequency Range
15 Hz to 70 kHz 70 kHz to 100 kHz 100 kHz to 200 kHz 200 kHz to 300 kHz 300 kHz to 1 MHz

Minimum Signal
100 mV ac rms 100 mV ac rms 150 mV ac rms 150 mV ac rms Linearly increasing from 150 mV ac rms at 300 kHz to 2V ac rms at 1 MHz

Maximum Signal
30V ac rms 20V ac rms 10V ac rms 7V ac rms Linearly decreasing from 7V ac rms at 300 kHz to 2V ac rms at 1 MHz

1-26

Chapter 2

Theory of Operation

2-1. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 2-8. 2-9. 2-10. 2-11. 2-12. 2-13. 2-14. 2-15. 2-16. 2-17. 2-18. 2-19. 2-20. 2-21. 2-22. 2-23. 2-24. 2-25. 2-26. 2-27. 2-28. 2-29. 2-30.

Title

Page

Introduction ……………………………………………………………………………….. 2-5 Functional Block Description……………………………………………………….. 2-5
A1 Main PCA Block Description ……………………………………………… 2-7 Power Supply…………………………………………………………………….. 2-7 Digital Kernel ……………………………………………………………………. 2-7 Serial Communication (Guard Crossing) ………………………………. 2-8 Digital Inputs and Outputs…………………………………………………… 2-8 Ethernet Interface ………………………………………………………………. 2-8
A2 Display PCA Block Description ………………………………………….. 2-8 A3 A/D Converter PCA Block Description………………………………… 2-8
Analog Measurement Processor …………………………………………… 2-9 Input Protection …………………………………………………………………. 2-9 Input Signal Conditioning …………………………………………………… 2-9 Analog-to-Digital (a/d) Converter………………………………………… 2-9 Inguard Microcontroller ……………………………………………………… 2-9 Channel Selection………………………………………………………………. 2-9 Open Thermocouple Check …………………………………………………. 2-10 A4 Analog Input PCA Block Description ………………………………….. 2-10 20-Channel Terminals ………………………………………………………… 2-10 Reference Junction Temperature………………………………………….. 2-10 Detailed Circuit Description ………………………………………………………… 2-10 A1 Main PCA Circuit Description…………………………………………….. 2-10 Power Supply Circuit Description………………………………………… 2-10
Raw DC Supply ……………………………………………………………… 2-11 Auxiliary 6V Supply……………………………………………………….. 2-11 5V Switcher …………………………………………………………………… 2-11 Inverter………………………………………………………………………….. 2-12 Inverter Outguard Supply ………………………………………………… 2-12 Inverter Inguard Supply…………………………………………………… 2-13 Power Fail Detection ………………………………………………………. 2-13

2-1

NetDAQ Service Manual

2-31. 2-32. 2-33. 2-34. 2-35. 2-36. 2-37. 2-38. 2-39. 2-40. 2-41. 2-42. 2-43. 2-44. 2-45. 2-46. 2-47. 2-48. 2-49. 2-50. 2-51. 2-52. 2-53. 2-54. 2-55. 2-56. 2-57. 2-58. 2-59. 2-60. 2-61. 2-62. 2-63. 2-64. 2-65. 2-66. 2-67. 2-68. 2-69. 2-70. 2-71. 2-72. 2-73. 2-74. 2-75. 2-76. 2-77. 2-78.

Digital Kernel ……………………………………………………………………. 2-13 Reset Circuits…………………………………………………………………. 2-14 Microprocessor ………………………………………………………………. 2-14 Address Decoding…………………………………………………………… 2-16 Flash Memory………………………………………………………………… 2-18 Static RAM ……………………………………………………………………. 2-18 Real-Time Clock…………………………………………………………….. 2-19 FPGA (Field Programmable Gate Array)…………………………… 2-19 Serial Communication (Guard Crossing) …………………………… 2-21 RS-232 Interface…………………………………………………………….. 2-21 Ethernet Interface …………………………………………………………… 2-22
Digital Inputs and Outputs…………………………………………………… 2-24 Digital Input Threshold …………………………………………………… 2-24 Digital Input Buffers……………………………………………………….. 2-24 Digital and Alarm Output Drivers…………………………………….. 2-25 Totalizer Input ……………………………………………………………….. 2-25 External Trigger Circuits…………………………………………………. 2-25
A2 Display PCA Circuit Description…………………………………………. 2-26 Main PCA Connector …………………………………………………………. 2-26 Front Panel Switches ………………………………………………………….. 2-27 Display……………………………………………………………………………… 2-28 Beeper Drive Circuit…………………………………………………………… 2-28 Watchdog Timer and Reset Circuit ………………………………………. 2-29 Display Controller ……………………………………………………………… 2-29
A3 A/D Converter PCA Circuit Description ………………………………. 2-31 Stallion Chip……………………………………………………………………… 2-33 Input Protection …………………………………………………………………. 2-33 Input Signal Conditioning …………………………………………………… 2-33 Function Relays …………………………………………………………………. 2-33 Channel Selection Circuitry ………………………………………………… 2-34 DC Volts and Thermocouples Measurement Circuitry……………. 2-34 Ohms and RTD Measurement Circuitry………………………………… 2-36 AC Volts Measurement Circuitry…………………………………………. 2-37 Frequency Measurements……………………………………………………. 2-37 Active Filter (ACV Filter) …………………………………………………… 2-37 Voltage Reference Circuit …………………………………………………… 2-38 Analog/Digital Converter Circuit …………………………………………. 2-39 Autozero ……………………………………………………………………….. 2-39 Integrate ………………………………………………………………………… 2-40 Deintegrate1…………………………………………………………………… 2-42 Deintegrate2…………………………………………………………………… 2-42 Overhead……………………………………………………………………….. 2-42 Inguard Digital Kernel Circuitry ………………………………………….. 2-42 Open Thermocouple Detect Circuitry…………………………………….. 2-43
A4 Analog Input PCA Circuit Description…………………………………. 2-43 A1 Main to A3 A/D Converter Communications ……………………………. 2-44
Special Codes…………………………………………………………………………. 2-44 Resets ……………………………………………………………………………………. 2-44

2-2

2 Theory of Operation Introduction

2-79. Commands …………………………………………………………………………….. 2-45

2-80.

Perform Scan …………………………………………………………………….. 2-45

2-81.

Perform Self-Test ………………………………………………………………. 2-46

2-82.

Return Main Firmware Version……………………………………………. 2-46

2-83.

Return Boot Firmware Version ……………………………………………. 2-47

2-84.

Set Global Configuration…………………………………………………….. 2-47

2-85.

Set Channel Configuration ………………………………………………….. 2-47

2-86.

Do Housekeeping ………………………………………………………………. 2-48

2-87. Checksums …………………………………………………………………………….. 2-48

2-88. Errors…………………………………………………………………………………….. 2-48

2-89. Power-Up Protocol………………………………………………………………….. 2-49

2-90. Inguard Unresponsive ……………………………………………………………… 2-49

2-91. Inguard Software Description ………………………………………………………. 2-49

2-92. Hardware Elements …………………………………………………………………. 2-49

2-93.

Channel MUX……………………………………………………………………. 2-49

2-94.

Function Relays …………………………………………………………………. 2-51

2-95.

Stallion Chip and Signal Conditioning………………………………….. 2-51

2-96.

A/D ………………………………………………………………………………….. 2-53

2-97.

Timing ………………………………………………………………………….. 2-54

2-98.

Control Signals ………………………………………………………………. 2-54

2-99.

Counters………………………………………………………………………… 2-56

2-100.

Converting Counts to Volts ……………………………………………… 2-56

2-101.

DISCHARGE Signal ………………………………………………………….. 2-57

2-102.

Open-Thermocouple Detector ……………………………………………… 2-57

2-103. Channel Measurements……………………………………………………………. 2-57

2-104.

Reading Rates ……………………………………………………………………. 2-57

2-105.

Measurement Types……………………………………………………………. 2-58

2-106.

VDC, VAC, Ohms ………………………………………………………….. 2-58

2-107.

VDC Fast Rate, 2645A ……………………………………………………. 2-58

2-108.

Thermocouples ………………………………………………………………. 2-59

2-109.

Reference Junction …………………………………………………………. 2-59

2-110.

Frequency ……………………………………………………………………… 2-59

2-111.

VAC Discharge Mode …………………………………………………….. 2-60

2-112.

Autoranging ………………………………………………………………………. 2-60

2-113.

Overload …………………………………………………………………………… 2-61

2-114. Housekeeping Readings…………………………………………………………… 2-61

2-115.

Reading Types …………………………………………………………………… 2-61

2-116.

Reference Balance Readings ……………………………………………. 2-61

2-117.

Zero Offset Readings………………………………………………………. 2-62

2-118.

Housekeeping Schedule………………………………………………………. 2-62

2-119. Self-Tests ………………………………………………………………………………. 2-62

2-120.

Power-Up Self-Tests ………………………………………………………….. 2-62

2-121.

Self-Test Command……………………………………………………………. 2-63

2-122.

A/D Test………………………………………………………………………… 2-63

2-123.

Zero Offset Test……………………………………………………………… 2-63

2-124.

Reference Balance Test …………………………………………………… 2-63

2-125.

Ohms Overload Test ……………………………………………………….. 2-63

2-126.

OTC Test ………………………………………………………………………. 2-63

2-3

NetDAQ Service Manual
2-4

2 Theory of Operation Introduction

Introduction

2-1.

The theory of operation begins with a general overview of the instrument and progresses to a detailed description of the circuits of each pca.

The instrument is first described in general terms with a Functional Block Description. Then, each block is detailed further with Detailed Circuit Descriptions. Refer to Chapter 7 of this manual for full schematic diagrams. The Interconnection Diagram (Figure 2-1) illustrates the physical connections between each pca.

In all discussions, signal names followed by a ‘*’ character are active (asserted) low. All other signals are active high.

Functional Block Description

2-2.

Refer to Figure 2-2, Overall Functional Block Diagram, during the following functional block descriptions.

Digital I/O

Alarm/Trigger I/O

A2 Display

J1

AC Power RS-232

J5

J6

J2

P1

A1 Main

P2

J3 P3

J4 P10

10BASE-T 10BASE2 Debug

Channels 11… 20
TB1 P1
A4 Analog Input P2
TB2

J1

J10

A3 A/D Converter

J2

J3

Channels 1… 10

Program Power Figure 2-1. Interconnection Diagram

2-5

NetDAQ Service Manual

Terminal Strips Reference Junction
A4 Analog Input

Input Multiplexing Input Protection

Input Signal Conditioning

Analog Measurement Processor

A/D Converter

EPLD

Microprocessor, RAM, and Flash A3 A/D Converter

Inguard Outguard

Serial Communications

Guard Crossing

Vacuum Fluorescent Display
Display Controller
Front-Panel Switches A2 Display

RS-232

µP

Flash

RAM and

Memory

Real-Time

Clock

FPGA
Power Supply

Address Decoding

Ethernet Interface

Reset Circuits

Buffer RAM

10BASE2 10BASE-T
Digital I/O

+5.6V dc (Vddr) +5.2V dc (Vdd) -5.2V dc (Vss)

Inguard

+4.9V dc (Vcc) -5.0V dc (Vee)
Outguard -30V dc (display) 5.4V ac (display)

A1 Main

Figure 2-2. Overall Functional Block Diagram

2-6

2 Theory of Operation
Functional Block Description

A1 Main PCA Block Description

2-3.

The A1 Main pca description is divided into sections for each primary pca function as described below.

Power Supply

2-4.

The Power Supply functional block (Figure 2-3) provides voltages required by the outguard digital circuitry: +4.9V dc (Vcc); the vacuum-fluorescent display: -30V dc and filament voltage of 5.4V ac; the inguard circuitry: +5.2V dc (Vdd), +5.6V dc (Vddr), and -5.2V dc; and RS-232 interface voltage: -5.0V dc (Vee).

Within the power supply, the raw dc supply converts 107 to 264V ac line voltage into a dc level and applies it to the power switch, and/or the 9 to 16V dc input is applied to the power switch. The 5V Switcher (A1U9, A1U28) converts the dc from the power switch into 4.9V +/-0.05V dc, which is used by the Inverter (A1U22, A1U23) in generating the above-mentioned outputs. A Power Fail Detector provides a power supply status signal to the Microprocessor in the Digital Kernel.

Within the Ethernet interface (A1U16, A1U32) there is an inverter module that provides an isolated -9V dc supply for the 10BASE2 transceiver. The inverter module is powered from the 4.9V dc (Vcc) supply. There is also a small power supply that provides a programming voltage (Vpp) for the FLASH EPROM device on the outguard digital kernel.

107 to 264 V ac In
9 to 16 V dc In

Power Switch

5V Switcher

Inverter

Regulator

Regulator Regulator

+4.9V dc (Vcc) 5.4V ac (display) -30V dc (display) +5.2V dc (Vdd)
+5.6V dc (Vddr)

Regulator

-5.2V dc (Vss)

Regulator

-5.0V dc (Vee)

Figure 2-3. Power Supply Block Diagram

Digital Kernel

2-5.

The Digital Kernel functional block is responsible for the coordination of all activities within the instrument. This block requires voltages from the Power Supply and signals from the Power-on Reset circuit.

Specifically, the Digital Kernel microprocessor (A1U1) performs the following functions:

· Executes the instructions stored in FLASH EPROM (A1U21).

· Stores instrument calibration data in FLASH EPROM.

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· Communicates with the microprocessor on the A/D Converter PCA via the Serial Communication (Guard Crossing) block (A1U5, A1U7).
· Communicates with the Display Controller to display readings and user interface information (A1U1, A1U31).
· Communicates with the Field Programmable Gate Array (A1U31), which scans the user interface keyboard found on the Display Assembly and interfaces with the Digital I/O hardware.
· Communicates with a host computer via the Ethernet interface (A1U32).
· Communicates with a host computer via the RS-232 interface (A1U1, A1U13).
· Reads the digital inputs and changes digital, alarm, and trigger outputs.

Serial Communication (Guard Crossing)

2-6.

This functional block provides a high isolation voltage communication path between the Digital Kernel of the Main PCA and the microprocessor on the A/D Converter PCA. This bidirectional communication circuit (A1U5, A1U7) requires power supply voltages from the Power Supply block.

Digital Inputs and Outputs

2-7.

This functional block contains the Totalizer and Trigger Input buffers, eight bidirectional Digital I/O channels (A1U3, A1U4, A1U17, A1U27), Master Alarm output, and a Trigger Output (A1U17). These circuits require power supply voltages from the Power Supply and signals from the Digital Kernel.

Ethernet Interface

2-8.

This functional block contains the Ethernet Controller (A1U32), used for both 10BASE2 and 10BASE-T. When 10BASE2 is selected by the Ethernet interface, an additional Ethernet Transceiver device (A1U32) is used. These circuits require power supply voltages from the Power Supply and signals from the Digital Kernel.

A2 Display PCA Block Description

2-9.

The Display Assembly controller communicates with the A1 Main PCA microprocessor (A1U1) over a three-wire communication channel. Commands from the microprocessor inform the Display Controller how to modify its internal display memory. The Display Controller (A2U1) then drives the grid and anode signals to illuminate the required segments on the Display. The A2 Display PCA requires power supply voltages from the A1 Main PCA power supply voltages and a clock signal from the A1U4 microprocessor.

A3 A/D Converter PCA Block Description

2-10.

The following paragraphs describe the major blocks of circuitry on the A/D Converter PCA.

2-8

2 Theory of Operation
Functional Block Description

Analog Measurement Processor

2-11.

The Analog Measurement Processor (A3U30) provides input signal conditioning, ranging, and frequency measurement. This custom chip is controlled by the A/D Microprocessor (A3U5). The A/D Microprocessor communicates with the Main PCA Microprocessor (A1U1) over a serial interface.

Input Protection
This circuitry protects the instrument measurement circuits during overvoltage conditions.

2-12.

Input Signal Conditioning

2-13.

Here, each input is conditioned and/or scaled to a dc voltage for measurement by the a/d converter. DC voltage levels greater than 3V are attenuated. To measure resistance, a dc current is applied across a series connection of the input resistance and a reference resistance to develop dc voltages that can be ratioed. DC volts and ohms measurements are filtered by a passive filter. AC voltages are first scaled by an ac buffer, converted to a representative dc voltage by an rms converter, and then filtered by an active filter.

Analog-to-Digital (a/d) Converter

2-14.

The dc voltage output from the signal conditioning circuits is applied to a multi-slope A/D converter.

The input voltage is applied to a buffer/integrator that charges a capacitor for an exact amount of time. During this time, positive and negative reference voltages are alternately applied to the integrator. The references are switched in a sequence controlled by the A/D Electrically Programmed Logic Device (EPLD) (A3U18), which prevents the integrator from saturating.

The amount of time that each reference is applied to the integrator, and the amount of time required to discharge the capacitor, are measured by digital counter circuits in the A/D EPLD (A3U18). These times are used by the inguard microprocessor (A3U5) to calculate the level of the unknown input signal.

Inguard Microcontroller

2-15.

This microprocessor (A3U5) and associated circuitry controls all functions on the A/D Converter PCA and communicates with the digital kernel on the Main PCA. Upon request by the Main PCA, the inguard microprocessor selects the input channel to be measured through the channel selection circuitry, sets up the input signal conditioning, commands the A/D EPLD (A3U18) to begin a conversion, stops the measurement, and then fetches the measurement result. The inguard microprocessor manipulates the result mathematically and transmits the reading to the digital kernel.

Channel Selection

2-16.

This circuitry consists of a set of relays and relay-control drivers. The relays form a tree that routes the input channels to the measurement circuitry. Two of the relays are also used to switch between two-wire and four-wire operation. For signal switching and selection, the 2640A uses reed relays, while the 2645A uses solid-state relays.

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Open Thermocouple Check

2-17.

Under control of the Inguard Microprocessor, the open thermocouple check circuit applies a small ac signal to a thermocouple input before each measurement. If an excessive resistance is encountered, an open thermocouple input condition is reported.

A4 Analog Input PCA Block Description

2-18.

The following paragraphs briefly describe the major sections of the Input Connector PCA, which is the “Universal Input Module” used for connecting the analog inputs to the instrument.

20-Channel Terminals

2-19.

Twenty HI and LO terminal blocks are provided in two rows, one for channels 1 through 10 and one for channels 11 through 20. The terminals can accommodate a wide range of wire sizes, starting with 12 gauge as the largest size. The two rows of terminal blocks are maintained very close to the same temperature for accurate thermocouple measurements.

Reference Junction Temperature

2-20.

A semiconductor junction is used to sense the temperature of the thermocouple input terminals. The resulting dc output voltage is proportional to the block temperature and is sent to the A/D Converter PCA for measurement.

Detailed Circuit Description

2-21.

The following circuit descriptions describe the theory of operation for each Instrument pca. For these descriptions, refer to the associated schematic diagram in Chapter 7.

A1 Main PCA Circuit Description

2-22.

The following paragraphs describe the operation of the circuits on the A1 Main PCA. The schematic for this pca is located in Chapter 7.

Power Supply Circuit Description

2-23.

The power supply portion of the A1 Main pca consists of three major sections:

· Raw DC Supply The raw dc supply converts line voltage (107V to 264V ac) into a dc output of 8V to 35V.

· 5V Switcher Supply The 5V switcher supply regulates the 8V to 35V dc input into the 4.9V +/-0.05V dc (Vcc) source.

· Inverter Using the 5V switching supply output, the inverter generates the -30V dc and 5.4V ac supply levels needed for the vacuum-fluorescent display and the -5V dc supply for the RS-232 Interface. The inverter also provides isolated +5.6V (Vddr), +5.2V (Vdd), and -5.2V (Vss) outputs for the inguard circuitry.

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2 Theory of Operation
Detailed Circuit Description

Raw DC Supply

2-24.

The raw dc supply circuitry receives input from power transformer T401, which operates from an ac source of 107V to 264V ac. The power transformer is energized whenever the power cord is plugged into the ac line; there is no on/off switch on the primary side of the transformer. The transformer has an internal 275V ac metal-oxide varistor (MOV) to clamp line transients. The MOV normally acts as an open circuit. When the peak voltage exceeds approximately 400V, the line impedance in series with the line fuse limits transients to approximately 450V. All line voltages use a time-delay 0.15 A, 250V fuse.

On the secondary side of the transformer, rectifiers A1CR2, A1CR3, and capacitor A1C7 rectify and filter the output. When ON, switch A1S1 (the rear panel POWER switch) connects the output of the rectifiers to the filter capacitor and the rest of the instrument. Depending on line voltage, the output of the rectifiers is between 8.0 and 35V dc. Capacitor A1C2 is used for electromagnetic interference (EMI) and electromagnetic compatibility (EMC) requirements. Capacitor A1C1 helps supply the high frequency ripple current drawn by the switching regulator (described below).

When external dc power is used, the power switch connects the external dc source to power the instrument. The external dc input uses thermistor A1RT1 for overcurrent protection and diode A1CR1 for reverse input voltage protection. Capacitor A1C59 is used for EMI/EMC requirements. Resistor A1R48, and capacitors A1C102 and A1C39 are also used for EMI/EMC performance requirements. If both ac power and dc power are connected to the instrument, the instrument uses ac power when it exceeds approximately eight times the value of the dc voltage. Automatic switchover occurs between ac and dc power without interrupting instrument operation.

Auxiliary 6V Supply

2-25.

Three-terminal regulator A1U19, voltage-setting resistors A1R44 and A1R46, and capacitor A1C34, make up the auxiliary 6-volt supply. This supply is used to power the inverter oscillator and inverter driver.

5V Switcher

2-26.

The 5V switcher supply uses a controller/switch device A1U9 and related circuitry to produce the 4.9V dc (Vcc) output.

4.9V dc (Vcc) The 8V to 35V dc input is regulated to 4.9V dc (Vcc) through pulse-width modulation at a nominal switching frequency of 100 kHz. The output voltage of the switcher supply is controlled by varying the duty cycle (ON time) of the switching transistor in the controller/switch device A1U9. A1U9 contains the supply reference, oscillator, switch transistor, pulse-width modulator comparator, switch drive circuit, current-limit comparator, current- limit reference, and thermal limit. Dual inductor A1T2 regulates the current that flows from the raw supply to the load as the switching transistor in A1U9 is turned on and off. Complementary switch A1CR10 conducts when switching is turned off.

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The pulse-width modulator comparator in A1U9 compares the output to an internal reference and sets the ON-time/OFF-time ratio to regulate the output to 4.9V dc. A1C1 is the input filter capacitor, and A1C14 and A1C18 are the output filter capacitors. Proper inductor and capacitor values set the filter frequency response to ensure best overall system stability. A1R26 and A1C21 ensure that the switcher supply remains stable and operating in the continuous mode. The power supply current is internally limited by A1U9 to 5 amps.
Resistors A1R5, A1R6, A1R27, A1R29, A1R30 and A1R31 form a voltage divider that operates in conjunction with amplifier A1U28, which is configured as a voltage follower. A1U28-3 samples the 4.9V dc output, while A1U28-2 is the voltage divider input. The effect is to maintain the junction of R30 and R31 at 4.9V dc, resulting in an A1U28-1 output level of 6.14V dc, or 1.24V dc above the output This feedback voltage is applied to A1U9-2, which A1U9 interprets as 1.24V dc because A1U9-3 (ground) is connected to the 4.9V dc output. A1U9 maintains the feedback and reference voltages at 1.24V dc and thus regulates the 4.9V dc source.

Inverter

2-27.

The inverter supply uses a two transistor-driven push-pull configuration. The center tap of transformer A1T1 primary is connected to the 4.9V dc Vcc supply, and each side is alternately connected to common through transistors A1Q7 and A1Q8. A1R38 may be removed to disable the inverter supply for troubleshooting purposes. A1Q7 and A1Q8 are driven by the outputs of D flip-flop A1U22. Resistors A1R34 and A1R28, and diodes A1CR11 and A1CR12 shape the input drive signals to properly drive the gate of the transistors. D flip-flop A1U22 is wired as a divide-by-two counter driven by a 110-kHz square wave. The 110-kHz square wave is generated by hex inverter A1U23, which is connected as an oscillator with a frequency determined by the values of resistors A1R40 and A1R47, and capacitor A1C35. The resulting ac voltage produced across the secondary of A1T1 is rectified to provide the input to the inverter inguard and outguard supplies.

Inverter Outguard Supply

2-28.

The inverter outguard supply provides three outputs: -30V dc and 5.4V ac for the display, and -5.0V dc (Vee) for the RS-232 drivers and receiver.

-30V dc Dual diodes A1CR8 and A1CR9 provide full-wave rectification of A1T1 outputs (pins 4, 5, and 8), creating the -30V dc supply. Output filtering for the -30V dc supply is provided by capacitor A1C17.

5.4V ac The 5.4V ac supply is sourced from a secondary winding on transformer T1 (pins 6 and 7), and is biased at -24V dc with zener diode A1VR3 and resistor A1R22.

-5.0V dc (Vee) Dual-diode A1CR13 rectifies an input from the inverter circuit, with the diode and capacitors A1C30 and A1C31 configured as a voltage doubler, generating -12V dc. This voltage is applied to the three-terminal regulator A1U18, which regulates the output for the -5.0V dc (Vee) source. Capacitor A1C32 is used for transient response performance of the three-terminal regulator.

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2 Theory of Operation
Detailed Circuit Description

Inverter Inguard Supply

2-29.

The inverter inguard supply provides three outputs: +5.2V dc (Vdd) and -5.2V dc (Vss) for the inguard analog and digital circuitry, and +5.6V dc (Vddr) for the relays. Diodes A1CR5 and A1CR6, and capacitor A1C12 create a +6.8V dc source, while diodes A1CR7 and capacitor A1C13 create a -9.5V dc source.

+5.2V dc (Vdd) The +5.2V dc (Vdd) source is regulated from a +6.8V dc input to A1U24 with resistors A1R9 and A1R10 setting the output voltage, and A1C4 handling transient loads. Resistors A1R4, A1R130, A1R128 and A1R13, along with transistor A1Q1, comprise a current-limiting circuit, which prevents A1U24 from supplying more than 60 mA of load current.

-5.2V dc (Vss) The -5.2V dc (Vss) source is regulated from a -9.5V dc input to A1U25 with resistors A1R11 and A1R12 setting the output voltage, and A1C5 handling transient loads. Resistors A1R14, A1R15, A1R129, A1R122, along with transistors A1Q5 and A1Q6, comprise a current-limiting circuit, which prevents A1U25 from supplying more than 40 mA of load current. Capacitor A1C9 enables the regulator to start up.

+5.6V dc (Vddr) The +5.6V dc (Vddr) source is regulated from a +6.8V dc input to A1U6 with resistors A1R131 and A1R132 setting the output voltage, and A1C6 handling transient loads.

Power Fail Detection

2-30.

The power fail detection circuit generates a signal to warn the Microprocessor that the power supply is going down. Microprocessor supervisor A1U10 compares the divided-down raw supply voltage, via voltage divider A1R19 and A1R20. When the raw supply voltage falls below approximately 8V dc, A1U10-5 output is low. Resistor A1R99 is a pull up resistor for the A1U10-7 reset line, and A1C81 provides filtering of high frequency noise. The reference voltage internal to the A1U10 is nominally 1.3V dc.

Digital Kernel
The Digital Kernel is composed of the following 10 functional circuit blocks:
· Reset Circuits · Microprocessor · Address Decoding · Flash Memory · Static RAM · Real-Time Clock · FPGA (Field Programmable Gate Array) · Serial Communication (Guard Crossing) · RS-232 Interface · Ethernet Interface
Each of the 10 topics is discussed below.

2-31.

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Reset Circuits

2-32.

The Power-On Reset signal (POR, A1U10-7) is generated by the Microprocessor Supervisor, which monitors the voltage of Vcc at A1U10-2. If Vcc is less than +4.65 volts, then A1U10-7 is driven low. POR drives the enable inputs of the four tri-state buffers in A1U2, causing the HALT, RESET, and DRST signals to be driven low when POR is low. When POR* goes high, the tri-state buffer outputs (A1U2) go to their high-impedance state and the pull-up resistors pull the outputs to a high level.

When HALT and RESET are both driven low, the Microprocessor (A1U1) is reset and is in execution when they both go high. The Microprocessor may execute a “reset” instruction during normal operation to drive A1U1-92 low for approximately 10 microseconds to reset all system hardware connected to the RESET* signal.

The Display Reset signal (DRST) is driven low by A1U2-6 when POR is low, or it may be driven low by the Microprocessor (A1U1-56) if the instrument firmware needs to reset only the display hardware. For example, the firmware resets the display hardware after the FPGA is loaded at power-up and the Display Clock (DCLK) signal from the FPGA begins normal operation. This ensures that the Display Processor is properly reset while DCLK is active.

Microprocessor

2-33.

The Microprocessor uses a 16-bit data bus and a 20-bit address bus to access locations in the Flash Memory (A1U21), the Static RAM (A1U20, A1U30, A1U34 and A1U35), the Real-Time Clock (A1U11), the FPGA (A1U31), and the Ethernet Interface (A1U32). All of the data bus lines and the lowest 12 address lines have series termination resistors located near the Microprocessor (A1U1) to ensure that the instrument meets EMI/EMC performance requirements. When a memory access is done to the upper half of the data bus (D15 through D8), the upper data strobe (UDS) goes low. When a memory access is done to the lower half of the data bus (D7 through D0), the lower data strobe (LDS) goes low. When a memory access is a read cycle, R/W must be high. Conversely for any write cycle, R/W must be low.

The Microprocessor is a variant of the popular Motorola 68000 processor and is enhanced by including hardware support for clock generation, address decoding, timers, parallel ports, synchronous and asynchronous serial communications, interrupt controller, DMA (Direct Memory Access) controllers, and a watchdog timer.

The 15.36-MHz system clock signal (A1TP11) is generated by the oscillator circuit composed of A1U1, A1Y1, A1R2, A1C3, and A1C8. This clock goes through a series termination resistor (A1R17) to the FPGA (A1U31). This resistor is necessary to ensure that the instrument meets EMI/EMC performance requirements.

The Microprocessor has four software programmed address decoders that include wait state control logic. These four outputs are used to enable external memory and I/O components during read and write bus cycles. See “Address Decoding” for a complete description.

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2 Theory of Operation
Detailed Circuit Description
One sixteen-bit timer in the Microprocessor is used to keep track of the time to the nearest millisecond. The timer counter runs off the 15.36 MHz clock at a rate of 1/64th millisecond. The CINT signal from the Real Time Clock chip (A1U11) causes the timer counter to be sampled every 1/64th of a second. The CINT signal also interrupts the Microprocessor to provide a timing reference for the software. The combination of the counter and the interrupt are used by the software to keep track of the time to the nearest millisecond, referenced to the Real Time Clock Chip. A second sixteen-bit timer in the Microprocessor is used for an interval timer. It is also clocked at a rate of 1/64th millisecond. This timer interrupts the Microprocessor at a rate determined by the application. The Microprocessor has two parallel ports. Many of the parallel port pins are either used as software controlled signals or as inputs or outputs of timers and serial communication channels. Port A has 16 bits and Port B has 12 bits. The Microprocessor communicates to the Display Controller using a synchronous, three-wire communication interface controlled by hardware in the Microprocessor. Information is communicated to the Display Controller to display user interface menus and measur

References

• Test Equipment Rentals, Sales, Calibration | ATEC

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