Temperature transmitters convert the input signals from electronic temperature sensors, such as RTDs and thermocouples, into digital or analog output signals. Safety and efficiency require selecting the right transmitter for specific applications.
Temperature transmitters are a fundamental component in the process industry. These devices convert the input signal from a wide range of temperature sensors, such as resistance thermometers, thermocouples, and potentiometers, into a standardized analog or digital output signal.
Depending on the output signal, the temperature transmitter might be suitable for direct connection to evaluation instruments with voltage or current inputs, such as programmable logic controllers (PLCs) or Analog/Digital (AD) conversion cards. Using analog outputs, such as 0…10V and 4…20 mA, the value of the actual measurement is represented by the output of the range specified in the temperature transmitter. For example, if the range of your temperature transmitter were 0°C to 500°C (32°F to 932°F) and your sensor measured 250°C (482°F), the output for a 4…20 mA transmitter would be 12 mA. You can see the correlation by using the midpoint of both the temperature and mA variables.
The various output signals are related to certain industries and applications. The following is a brief overview:
Analog Outputs of Temperature Transmitters
0…10 V output signals are prevalent in power engineering, heating, air conditioning, ventilation, and refrigeration as they are easily integrated to evaluation instruments. WIKA offers a variety of temperature transmitters with output voltage signals.
4…20 mA is the predominant output signal in process control, machine building, and plant construction; many industries have adopted this standard for current loop communication. WIKA has an extensive portfolio of 4…20 mA temperature transmitters, depending on sensor type.
Digital Outputs of Temperature Transmitters
The HART (Highway Addressable Remote Transducer) protocol is a combination of analog and digital communication. In its simplest explanation, it utilizes existing 4…20mA instrumentation and provides additional digital communication, which makes it the most versatile digital communication method for temperature transmitters. The WIKA T32.xS temperature transmitter has HART protocol and offers high accuracy, galvanic isolation, and excellent protection against electromagnetic influences (EMI).
FOUNDATION™ Fieldbus protocol and PROFIBUS® PA (Process Automation) are more often used for process automation. These smart transmitters are a two-way communication platform that allows multiple devices to be connected on the same wire loop, resulting in enhanced diagnostics for the device(s). The WIKA T53.10, a fieldbus temperature transmitter with automatic switch between protocols, is suitable for temperature measurement with resistance thermometers and thermocouples.
The temperature measurement specialists at WIKA can help you decide whether to use an analog or digital instrument for your application.