RS PRO 238-7241 Infrared Temperature Sensor with Voltage Output and UART Instruction Manual

238-7241 Infrared Temperature Sensor with Voltage Output and UART
Instruction Manual

Instruction Manual
RS Pro Infrared
Temperature Sensor with
Voltage Output and UART
Stock Number: 238-7241

Introduction

The RS Pro UART Infrared Temperature Sensor is a device for measuring the temperature of the surface of a solid or liquid without contact. Its extremely small size makes it ideal for installation where space is restricted.
The sensor works by detecting infrared energy that is emitted by the target object. The temperature is available digitally via UART using the Modbus RTU protocol, or it can be
monitored continuously via the DC voltage output, e.g. with industrial process instrumentation.
The sensor also has a configurable alarm output.

Specifications

GENERAL

hysteresis, configurable via UART
Field of View| 15:1 divergent optics
Accuracy| t 1.5% of reading or t 1.5°C, whichever is greater
Repeatability| t 0.5% of reading or t 0.5°C, whichever is greater
Response Time| 250 ms
Emissivity| Default setting 0.95, adjustable via UART
Emissivity Setting Range| 0.20 to 1.00
Max Temperature Span (Linear Output)| 1000°C
Min Temperature Span (Linear Output)| 100°C
Spectral Range| 8-14 pm
Supply Voltage| 24 V DC (max 28 V DC)
Min. Supply Voltage (at Sensor)| 6 V DC when using voltage output
5 V DC when using UART only
Max Current Draw (Sensor)| 30 mA
Open Collector Alarm Output| 6 to 24 V DC, 50 mA max (see Electrical Installation)

ENVIRONMENTAL

CONFORMITY

Electromagnetic Compatibility (EMC)| EN61326-1, EN61326-2-3 (Electrical Equipment for Measurement, Control and Laboratory Use – EMC Requirements)
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RoHS Compliant| Yes

CONFIGURATION

Configurable Parameters| Temperature range (linear analogue output) Alarm output threshold and hysteresis
Emissivity setting Reflection compensation (e.g. target in oven/furnace)
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Temperature Units| °C / °F
Signal Processing| Averaging Period (0.25 to 60 seconds)
Peak / Valley Hold| Hold Period (0.25 to 1200 seconds)

MECHANICAL SPECIFICATIONS

Optics (Field of View)
The sensor measures the average temperature within a spot. The size of this spot depends on the distance between the sensor and the target surface.
The sensor may be used at longer distances than shown, and will measure a larger spot.
The measurement accuracy is not affected by the measurement distance.
**Target Size
The size of the measured spot must not be larger than the target. The sensor should be positioned so that the measured spot size is smaller than the target.
Ambient Temperature
The sensing head may be used in ambient temperatures of up to 70°C. Avoid thermal shock. Allow 20 minutes for the unit to adjust to large changes in ambient temperature.
Atmospheric Quality
Smoke, fumes, dust and steam can contaminate the lens and cause errors in temperature measurement. In these types of environment, the optional air purge collar should be used to help keep the lens clean.
Optional Accessories
An adjustable mounting bracket and air purge collar are available. These may be ordered at any time and added on-site.
Mechanical Installation**
The sensor can be attached to brackets or mountings of your own design, or you can use the optional mounting bracket accessories shown below. Use two M3 mounting screws (included) to fix the sensor to a mounting plate or bracket with a third, central hole for the sensor to “see” through. We recommend a hole of diameter 13 to 16 mm in a mounting plate of up to 2 mm thickness. Ensure the mounting does not obstruct the sensor’s field of view (FOV); refer to the optical diagram in Specifications and allow a clear area twice the size of the FOV cone for maximum accuracy.

Dimensions and Connections (Analogue Output)

For UART connections, see “Connections (UART)”.
Mounting Bracket (RS Stock No. 905-8777)

Air Purge Collar (RS Stock No. 905-8770)
The optional air purge collar is used to keep dust, fumes, moisture and other contaminants away from the lens. Air flows into the hose barb fitting and out of the front aperture. Air flow should be 5 to 15 litres per minute. Clean or “instrument” air is recommended.

Two M3 screws (included) secure both the air purge collar and the sensor to the mounting.

Electrical Installation

Check the length of the cable run between the temperature sensor and the measurement instrument. If necessary, the cable can be extended using a shielded cable with 4 or more
cores (3 if the alarm output is not used). Ensure the shield is also extended.
Connect power between the PWR+ and PWR- wires. Do not apply voltage to the incorrect wires as this will damage the sensor. See “Dimensions and Connections (Analogue Output)” and “Connections (UART)” for wiring.
Ensure the supply voltage is suitable for the selected output type.
Alarm
The sensor has an open collector alarm output. In an alarm condition, the alarm wire AL will sink current to ground through the attached load (e.g. a relay).
The alarm is deactivated for 30 seconds after power-up to allow for UART communication.
If using the alarm output, choose a load that draws no more than 50 mA when powered from 12 to 24 V DC. For example, if the alarm supply voltage is 24 V DC, ensure the load is at least 480 Ω (24 V / 0.05 A = 480 Ω).
Analogue Output
If using the analogue output, use a 12 to 24 V DC power supply.
The temperature output is a 0-5 V DC signal measured between OP+ and PWR-. The output voltage is linear with measured temperature. The temperature range is configurable via UART.
UART Interface
The sensor’s open collector alarm wire functions as the UART receive wire. The alarm is deactivated for 30 seconds after power-up to allow for UART communication. Once a valid Modbus command has been received, the sensor will remain in UART mode until powered down.
Connections (UART)
With power off, connect the sensor wires as follows:

Ensure all connections are secure before applying power.

USB Adapter

The sensor is compatible with the FTDI USB adapter (RS Stock No. 687-7786).
Power is provided by the USB connection – no separate power supply is required when using the USB interface.

Connections (USB Adapter)

Use a terminal block to connect the sensor to the USB adapter. Ensure the USB adapter is not connected to the computer while making or breaking wire connections.
Connect the wires as follows:

Ensure all connections are secure, then connect the USB interface to the PC.
RS Pro Config Software
The sensor is compatible with the RS Pro Config software, available as a free download from the RS website (note: alternatively, third-party Modbus software may be used).
System Requirements

• Windows 7 or newer
• USB 2.0 port, Internet access (for software download)

Installation

1. Download and run the software installer from the RS website
2. Follow the on-screen instructions.

Accessing the Settings Menu
Configuration settings are password protected. To access the Settings menu, go to the Unlock screen and enter the password. The default password is 1234.

Grounding

The sensor is tested for electromagnetic compatibility (EMC) as shown in Specifications. For maximum protection against electromagnetic interference, the sensor must be connected to earth at one point, either the cable shield termination or the metal sensor housing, but not both.  To minimise electromagnetic interference or “noise”, the sensor should be mounted away from sources of electromagnetic interference such as motors and generators.

Operation

Once the sensor is in position and the appropriate power, air, water and cable connections are secure, the system is ready for continuous operation by completing the following simple steps:

1. Turn on the power supply
2. Turn on the connected measurement instrument
3. Read or monitor the temperature

IMPORTANT

• If the sensor is exposed to significant changes in ambient temperature (hot to cold, or cold to hot), allow 20 minutes for the sensor body temperature to stabilise before taking or recording measurements.
• Do not operate the sensor near strong electromagnetic fields (e.g. around arc welders or induction heaters). Electromagnetic interference can cause measurement errors.
• Wires must be connected only to the correct terminals. Check all connections before applying power.
• Do not damage the cable, as this could provide a path for moisture and vapour into the sensor.
• Always turn off the power before modifying electrical connections.
• Do not attempt to open the sensor. There are no user-serviceable parts inside. This will damage the sensor and invalidate the warranty.

Modbus over Serial Line
Interface

Supported functions

The list below includes all available addresses. R = Read; W = Write

R/W
0x09| 1| Transmissivity Setting (1 LSB = 0.0001) Minimum 0.2000, Maximum 1.0000| R/W
OxOA| 1| Output range low (Temperature @ 0 V)| R/W
OxOB| 1| Output range high (Temperature @ 5 V)| R/W
OxOC| 1| Alarm setpoint| R/W
OxOD| 1| Alarm hysteresis| R/W
OxOE| 1| Alarm settings
0/1 for Off; 2 for Low alarm; 3 for High alarm| R/W
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OxOF – Ox11| –| Not used| –
0x12| 1| Hold Mode
0 for Off; 1 for Peak; 2 for Valley| R/W
0x13| 1| Hold Period (1 LSB = 0.1 seconds)
Minimum 0.1 seconds, Maximum 1200.0 seconds| R/W
0x14| 1| Average Period (1 LSB = 0.1 seconds) Minimum 0.1 seconds, Maximum 60.0 seconds| R/W
0x15| 1| Average Temperature| R
0x16| 1| Minimum Temperature| R
0x17| 1| Maximum Temperature| R
0x18| 1| Filtered Temperature| R
0x19| 1| Unfiltered Temperature| R
Ox1A| 1| Sensor Temperature| R
Ox1C| 1| Status (bits active high)
Bit 0: Measurement error
Bit 1: Sensor temperature low Bit 2: Sensor temperature high
Bit 3: Object temperature low Bit 4: Object temperature high| R
0x27| 1| Reflected Temperature (not saved to non-volatile memory)| R/W
0x28| 1| Emissivity (not saved to non-volatile memory)| R/W

Notes:

1. All temperature are in tenths of degrees C
2. With the exception of addresses 0x27 and 0x28, all write operations are saved to nonvolatile memory
3. For further information please refer to http://www.modbus.org/specs.php

Configurable Settings

Emissivity Setting| Enter the emissivity setting (between 0.2 and 1.0). The emissivity setting should match the emissivity of the target surface. This can be determined experimentally by comparing measurements with a trusted contact probe, or estimated using an emissivity table.
Non-reflective non-metals, such as rubber, foods, thick plastics, organic materials and painted surfaces, generally have a high emissivity, around 0.95. This is the default setting.
Bare, clean metal surfaces can have a very low emissivity, and are often difficult to measure accurately. If possible, a measurable area of the surface should be painted or coated to reduce reflections and increase the emissivity.
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Transmissivity Setting| When aiming the sensor through an IR-transmissive window, this setting should be adjusted to compensate for the presence of the window. Enter the transmissivity of the window (Enter “1” if no window is present.
Reflected Energy Compensation / Reflected
Temperature| In most applications, the target surface has the same surroundings as the sensor (for example, it is in the same room). In this case, Reflected Energy Compensation should remain OFF for an accurate measurement.
However, if the sensor is positioned outside an oven or furnace, with the target object inside, the reflection of the hot furnace interior can affect the measurement. In this case, Reflected Energy Compensation should be ON and Reflected Temperature should be set to the temperature inside the oven or furnace.
Average Period| To slow the response time of the sensor, or to reduce fluctuations or noise on the measurement, enter an averaging period (in seconds) here.
Hold Mode / Hold Period| If required, hold processing can be applied by setting Hold Mode to Teak” or “Valley” and setting the hold period (in seconds). This is useful if the temperature reading is interrupted by gaps between moving objects, or by an obstruction.
Output Range Low/High| Set the lower and upper temperature range limits for the voltage output. The relationship between the measured temperature and output voltage is linear.
Average Temperature| Measured temperature including averaging only (excluding hold processing).
Minimum/Maximum Temperature| Highest and lowest temperatures measured during the hold period.
Filtered Temperature| Measured temperature including averaging and hold processing.
Unfiltered Temperature| Measured temperature without averaging or hold processing.
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Sensor Temperature| The temperature inside the housing of the sensor.
Alarm Set Point| The temperature at which the alarm will be triggered.
Alarm Hysteresis| The temperature difference between the Set Point and the reset level. The alarm will be reset automatically when the temperature passes the reset level.
Alarm Settings| 3 (High): The alarm is triggered if the temperature is higher than the Set Point.
2 (Low): The alarm is triggered if the temperature is lower than the Set Point.
0 or 1 (Off): The alarm function is disabled.

Calibration
Every sensor is calibrated to within the published specification at the time of manufacturing.

Maintenance

Our customer service representatives are available for application assistance, calibration, repair, and solutions to specific problems. Contact our Service Department before returning any equipment. In many cases, problems can be solved over the telephone. If the sensor is not performing as it should, try to match the symptom below to the problem. If the table does not help, call RS for further advice.

Troubleshooting

wiring
Inaccurate measured temperature| Target too small for sensor’s field of view| Ensure the sensor’s view is completely filled by the target. Position the sensor closer to the target to measure a smaller area.
Incorrect emissivity setting| Choose the correct emissivity setting for the target material. See “Emissivity” for more information
Target is a reflective metal surface| Try using a low emissivity setting, or paint or coat a measurable area of the target to make it non-reflective
Field of view obstruction| Remove obstruction; ensure sensor has a clear view of target
Dust or condensation on lens| Ensure lens is clean and dry. Clean gently with a soft lens cloth and water. If problem recurs, consider using an air purge collar.
Voltage output does not match displayed temperature| Output temperature scale mismatch| Check if the output temperature range has been adjusted via UART, ensure the output scale matches the input range of the measurement instrument
No alarm output| Incorrect wiring or configuration| Check electrical connections (see Installation) and Alarm Output settings

Guarantee

For RS Pro Warranty Terms & Conditions please visit our website: www.RSPro.com

FOR MORE INFORMATION VISIT THIS SITE
www.RSPro.com

References

• RS PRO, the own brand of RS | Authorized Distributor

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