metrolog ICAS and ICAH Strain Gauge or Load Cell Embedded Analog Amplifier User Manual

metrolog ICAS and ICAH Strain Gauge or Load Cell Embedded Analog Amplifier User Manual

Introduction to the ICAS and ICAH Range of In-Cell Amplifiers

Two new families, the ICAS (industrial stability) and ICAH (high stability) have been introduced into the Mantracourt range of In-Cell Amplifiers. They offer improved performance and easier installation over the original designs.

The following points detail the main changes:

• The ICA1 and ICA2 output ranges have been changed to cover 0.1V to 10.1V and 0.1V to 5.1V respectively to facilitate calibration and interpretation of the output level.
  The linearity has been improved at the lower end of the scale (down to 70mV output).

• Excitation is standardised at 5V DC on the ICA1,2,3,4 and 6.

• The performance of the ICA family has been much improved over the operating temperature range by using high performance, auto-zero amplifiers and low drift resistors.
  The standard (‘S’) versions give a 200% improvement compared to the earlier versions.
  The high performance (‘H’) versions are fitted with higher-specification resistors to offer a 400% improvement over the earlier versions.

• The user-selectable span resistor is mounted via two standard plated through holes in the printed circuit board making it easier to change if required.
  There is also provision for a second resistor (not normally fitted) to give an offset zero if required for example, 5.1V ±5V for an ICA1.
  Refer to chapter 3 for calculating the values or Rgain and Roffs

• All wire connections are via plated through holes instead of the single-sided pads used in the original design.
  This allows all wires to enter from either side of the board resulting easier installation and improved joint reliability.

• Multi-layer printed circuit boards and additional filtering has been added to further improve the EMC performance.

• Faster and easier mounting/installation: The mounting hole size and position has been standardised on all models and also provides the capacitive-coupling connection to the sensor body which further improves the
  EMC performance.
  The hole will accommodate a 2mm (#0-80) screw with adequate clearance for the head.
  As this mounting method is compatible with our range of ‘D-Cell’ products, a single pocket design will accept either digital or analogue conditioners.

• An ATEX (Intrinsic Safety) certified version of the ICA5 has been introduced.

• All variants are RoHS compliant.

• All models have a reduced height of just 7.6mm. The diameter remains at 19.5mm.

• A new model, the ICA6 has been introduced which will provide a ±10 Volt output from a uni-polar 15 to 28V supply.

• Non-interaction between the trimmers makes calibration easier and faster.

Chapter 1 The ICAS and H Range

Figure 1.1 Block Diagram

The ICA is a Strain Gauge Amplifier, converting a strain gauge input to a Volt or mA output – otherwise known as a Signal Conditioner.
The ICA provides a wide range of signal conditioning for Strain Gauges, Load Cells, Pressure and Torque Transducers.
Offered in 6 versions and two performance categories, ICAS and ICAH. The ICAH offers lower drift over the operating temperature range.

• ICA1 – 3 wire – 0.1 to 10.1V
• ICA2 – 3 wire – 0.1 to 5.1V
• ICA3 – 4 wire – ± 10V / ±15V supply
• ICA4 – 3 wire – 4 to 20mA
• ICA5 – 2 wire – 4 to 20mA
• ICA6 – 3 wire – ±10V / 15-24V supply

This manual only deals with Versions ICA1 and ICA2 S and H, separate manuals exists for versions ICA3 and 6, ICA4 and ICA5.

Transducer SENSITIVITY of between 0.5 mV/V and 150mV/V are possible. It is optimised to 2.5 mV/V. This range covers most – but not all – strain gauges.
Sensitivity adjustment is achieved by a combination of gain (span) resistor ‘R’ change and associated fine adjustment by potentiometer.

Similarly transducer ZERO can be compensated for in the module. This adjustment is to compensate for slight errors in the strain gauge and not to offset tare.

Mantracourt’s SGA (Strain Gauge Amplifier) covers a range from 0.06 mV/V to 30mV/V and it’s 79% offset can provide tare compensation.

Chapter 2 Installing the ICA1 and ICA2 S and H

Pre Installation

See Specification details in Chapter 8 for details of Environmental Approvals.
Carefully remove the ICA unit from its shipment box. Check that the unit is complete and undamaged.
The ICA units can be operated in any industrial environment providing the following limits are not exceeded.

Operating Temperature     -40ºC to +85ºC
Humidity                               95% non condensing
Storage temperature          -40ºC to +85ºC

The following installation practices are advised:

• Minimise vibration
• Do not mount next to strong electrical fields (transformers, power cables)
• Ensure easy access to the module
• Install electrical protection device as the unit is not internally fused
• Always ensure the package is secure and protected

Figure 2.1 Dimensions

The module is designed to fit in the strain gauge pocket. Use the 2.1mm hole to secure the unit if required.
The mounting hole will accept an M2 screw or American equivalent #0-80.
Important Note: DO NOT USE #2 screw size.

Take care soldering cables to the pads.
Use a temperature controlled soldering iron set to a maximum 330 ºC, for no longer than 2 seconds per pad.
Excessive heat or increased soldering time may result in damage to the PCB.

If changing resistor ‘R’ do so at a workbench and not on site.
Check the relevant details for model ICA1 and 2, – ensure the module matches the instructions –

The ICA1 and 2 solder pads are as shown in the wiring diagrams:
4 pads for the strain gauge.
3 pads for power supply and output.
The fixing screw hole provides a ground connection to improve EMC performance.

Power Connections
The power supply for the ICA1 is nominally 24V dc (between 13 and 28V) and ICA2 is nominally 12V dc (between 8.5 and 28V).The power supply is commoned with the output at the ‘com’ connection.

Figure 2.2 Connection Details for the ICA1 and ICA2

The strain gauge cable should be attached to the solder pads as illustrated
For most applications 3 wire un-shielded field wiring is quite adequate.
For best EMC performance use the connections shown in Figure 2.3

Figure 2.3 Connection Details for Best EMC Immunity

Take note of the grounding arrangement particularly the bolt hole which capacitively couples the common of the ICA electronics to the strain elements in the load cell which improves the EMC performance.

Table 2.1

This typical cable data is provided for information only.
The cable should have 2 x twin twisted cables. Ideally each pair should be individually shielded and with an overall shield.

If possible segregate the signal cable from Power Cables; allow a 1metre (3 feet) distance from such cables.
Do not run signal cables in parallel with power cables and cross such cables at right angles.
The ground connection conductor should have sufficient cross-sectional area to ensure a low impedance path to attenuate RF interference.

Output Connections

The ICA1 S and H versions provide a 0.1 to 10.1V dc output, while the ICA2 S and H versions provide a 0.1 to 5.1V dc output.
While they utilize the same PCB they have different components on board.
Connect the output as shown in Figure 2.2 or alternatively Figure 2.3

Chapter 3: Calculating the gain resistor value

The ICA1 and 2 are supplied un-calibrated but optimized for a sensitivity of 2.5mV/V. To accommodate other sensitivities the gain resistor ‘Rgain’ shown in Figure 2.2, can be changed according to the following formula.
N.B. a high quality component e.g. 1% 25 ppm metal film resistor should be used for optimum performance (the ‘H’ versions should use 10-15 ppm metal film devices). It may be necessary to use a value from the less common E96 series to optimize the trim range:-

Table 3.1 ICA1 (0.1V to 10.1V)

Table 3.2 ICA2 (0.1V to 5.1V)

Table 3.3 ICA1 and 2 Offset Resistor

The ICA1 and 2 can be used in a pseudo ‘bipolar’ mode by fitting a resistor ‘Roffs’ as shown in Figure 2.2.
This will shift the output voltage to a known level (Voffs) when the input is zero (0mV/V) allowing both tension and compression of the load cell to be measured.

Use the following formula for the ICA1 and 2 to calculate the value of Roffs in k Ohms:

The gain of the ICA will need to be reduced to account for the lower output swing required for a given input change.
For the ICA1, re-calculate Rgain by scaling the load cell’s mV/V by the ratio 10V/(bipolar output change) and 5V/(bipolar output change) for the ICA2 and use the above formulae.

For example, an ICA2 is required to operate at 2.5V ±2.4V for a ± 2.5mV/V input:
Fit Roffs = 61.7k (as above) and re-calculate Rgain from Table 3.2 using (5V/2.4V) x 2.5mV/V = 5.208mV/V i.e. Gain = 35.71 therefore Rgain = 1152 Ohms. the nearest preferred value is 1k15 (E96 series)

Chapter 4 Calibration

he ICA1 and ICA2 S and H versions can be calibrated with the transducer connected provided that two calibration points can be implemented e.g. by applying known weights or forces. If this is not possible, a stable mV source or load cell simulator can be used if the precise sensitivity (mV/V) of the transducer is known.

Figure 4.1 Connection Details for Calibration

1. Apply the known low calibration conditions (weight, force or mV/V). This may be zero if required, and set the output to 0.1V using the ‘Z’ potentiometer.
2. Apply the known high calibration conditions (ideally between 75% and full scale) and adjust the ‘S’ potentiometer to give an output of 10.1V for the ICA1 and 5.1V for the ICA2.
3. Apply the known low calibration conditions and re-adjust the Zero if required.

Chapter 5 Trouble Shooting

1. No Output
   a) Check power supply is present and the correct polarity
   b) Check the output connections are correct with no open circuit connections
   c) Check terminations (ensure there are no dry joints)
   d) Check the sensor is connected (typically reading 350 Ohm across output + & -) with the power off
   e) Check the Excitation voltage is correct
   f) Check the load is connected and is not open or short circuited
   g) Check Span and Gain calibration

2. Low Output
   This is when an output is present but not of sufficient magnitude to meet the required value. Remember to allow for
   Tare Weight and ensure it is measured and allowed for in the output from the ICA.
   a) Check power supply is within specified limits (i.e. is not low)
   b) Check the sensor is connected (typically reading 350 Ohm across output + & -) with the power off.
   c) Check the Excitation voltage is at 5V dc
   d) Check the calibration
   e) Check the Zero (offset) is correct for the sensor, this too is a common reason for low outputs

3. High Output
   This is when an output is present but higher (in span or zero) than expected.
   High output is not normally a problem. It is most likely to be incorrect connections and as such the output would be high and fixed
   a) Check the sensor is connected (typically reading 350 Ohm across output + & -) with the power off
   b) Check the Excitation voltage is at 5V dc
   c) Check the Zero (offset)
   d) Check the calibration

4. Unstable Output
   This is when the output is unstable or varies. The cause could be (a) poor installation or (b) a noisy environment.
   Poor Installation -This is when an output is present but higher or lower (in span or zero) than expected:
   a) Check the installation for problems and repair where necessary
   b) Poor termination
   c) High resistance on cable leads
   d) Low insulation impedance
   e) Proximity to High Voltage Equipment – Transformers, Contactors, Motors etc.
   Noisy Environment-
   a) Check if the source can be found and remove noise
   b) Check the cable shielding and ensure it is correctly installed and terminated.

5. Calibration
   This section assumes that the unit is providing an output that is not stuck at top or bottom of the scale.
   (See paragraphs 1-3 if this is the case)
   Ensure you are connected to the correct sensor and not to another adjacent unit.
   Ensure you have the correct calibration data from the sensor manufacturer. This must include a certified table with offset, zero and linearity.
   Ensure you have the calibration set-up correctly installed i.e. mV source and output as required.
   Ensure the temperature and other environmental parameters are within specification and where necessary taken into account when calibrating should such parameters have an effect on the calibration.

6. Fine Span (Gain) and Zero (Offset) Adjustment Problems
   If the adjustment cannot reach the maximum output desired then, check the tare is not too high.
   If the potentiometer does not alter the output the unit must be repaired – remove from service.
   It is always wise to check a known good ICA against the problem installation before rejecting the suspect ICA.

Chapter 6 Product Care

A worn out component, excessive use in harsh environments, an overly zealous operator; regrettably some circumstances necessitate repair.

At Mantracourt Electronics Ltd we can’t guarantee that a product will never require repairing. We can, however, promise a repair service of exceptional quality, one which is governed by a rigorous procedure.

Detailed below is our pledge to you: a defined set of ground rules and procedures to which we will adhere. All we ask in return is that you assist us with our procedure, such that we can maintain our promise to you. Please note that warranty repairs may not be available on overdue accounts, and that a strict interpretation of our conditions of trading invalidates warranty claims where late payment has occurred.

Please refer to ‘Customer Repair Service Procedure’ document – contact your distributor for a copy.

In the unlikely event you have problems with the ICA module we would advise that you take the following
precautions:-

• The unit is installed as instructed.
• Recommended spares are kept in stock. We can assist.
• Sufficient expertise available for first line maintenance.
• Routine maintenance checks are performed – annually is recommended.
• The necessary documentation for the product is available to the maintenance personnel.

We recommend you keep on file – as a minimum

• This Manual
• The calibration figures for the attached sensors
• A record of the ‘normal’ output – if applicable
• A calibration record of the ICA
• A contact phone number from the supplier for assistance

Chapter 7 Glossary

Chapter 8 Specifications for the ICA1 and ICA2 S and H

Table 8.1 ICA1S and ICA1H (0.1 to 10.1V)

Electrical and Environmental

Note 1: Not including excitation current.
e.g. when connected to a 350 Ohm load cell, excitation current = 5/350 = 14mA
Total current = 22mA

Measurement

FR=Full Range (10V)
Note 1: Set by calibration resistor

Table 8.2 ICA2S and ICA2H (0.1 to 5.1V)

Environmental

Note 1: Not including excitation current.
e.g. when connected to a 350 Ohm load cell, excitation current = 5/350 = 14mA
Total current = 22mA

Measurement

FR=Full Range (5V)
Note 1: Set by calibration resistor

CE Approvals

European EMC Directive
2004/108/EC
BS EN 61326-1:2006
BS EN 61326-2-3:2006

Other Mantracourt Products

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Signal Conditioning

In the interests of continued product development, Mantracourt Electronics Limited reserves the right to alter product specifications without prior notice.

Distribuidor

Brasil e América do Sul

www.metrolog.net

metrolog@metrolog.net

Distribuidor no Brasil e América do Sul | Metrolog | www.metrolog.net | +55 (16) 3371-0112 | +55 (16) 3372-7800 | metrolog@metrolog.net

metrolog@metrolog.net

mantracourt.com

tel +55 (16) 3371-0112

References

• Strain Gauge Instrumentation & Strain Gauge Measurement - Mantracourt Electronic Instrumentation
• Metrolog Measurement Control Systems

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