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Temperature transmitter vs RTD input modules:
Whether your application is using an RTD or a thermocouple, the temperature sensor will need a connection to your control system – either via direct wiring to an input module in the DCS or PLC, or via connection to a separate temperature transmitter. At first glance, it may seem easier to skip a transmitter altogether and wire temperature sensors directly, but temperature transmitters provide substantial benefits.
You might use a temperature transmitter instead of an RTD/thermocouple input module for a few reasons:
1. Remote sensing: If the temperature sensor is located far from the control room, a temperature transmitter can be used to convert the sensor output into a signal that can be transmitted over long distances without losing accuracy. In the case of thermocouples, using a temperature transmitter will reduce the cost of wiring, as you can use simple twisted-pair wiring instead of expensive thermocouple extension cable.
2. Standardized output: Temperature transmitters provide standardized output signal, such as 4-20 mA or HART protocol, which can be easily read by many types of control systems.
3. Signal conditioning: A temperature transmitter provides signal conditioning that can improve the accuracy and reliability of the temperature measurement. The transmitter can provide linearization, cold junction compensation and other signal conditioning functions that are not available in a basic input module.
4. Flexibility: Temperature transmitters can be used with a wide range of temperature sensors, including, RTDs, thermocouples, and thermistors, allowing for greater flexibility in system design and easier integration into existing systems.
5. Maintenance and diagnostics: Temperature transmitters can be easier to maintain than an input module. The transmitter can be calibrated and configured remotely using digital communication protocols, reducing the need for on-site maintenance. Additionally, the digital communication capabilities of a temperature transmitter can improve system integration and provide advanced diagnostic and troubleshooting features.
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