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A Brief Introduction Into Key Functionality of Temperature Sensors and Temperature Transmitters

Posted August 16, 2019

Temperature is different from heat despite the two terms closely linked to each other. Heat is a unit of measurement that energy transforms from one body or entity to another. Temperature, on the other hand, is a measurement of a system’s internal energy.

Various devices exist to help measure the temperature of different bodies. Two of these gadgets are temperature sensors and temperature transmitters.

Temperature measurement device. Image credit: Barescar90 via Pixabay (Free Pixabay licence)

Temperature measurement device. Image credit: Barescar90 via Pixabay (Free Pixabay licence)

What is the Temperature Sensor?

Understand the differences between a temperature sensor and a temperature transmitter to know the main functions of each device. For the former, it’s a device providing temperature readings using an electrical signal. Temperature sensors may come as two devices: thermocouples (T/Cs) and Resistance Temperature Detectors (RTDs).


The T/C is a combination of two unlike metals generating electrical voltage. The generated power is equal or in direct proportion to any temperature changes of a body. These metal wires connect on one end to measure the temperature at its junction. This device generates a measurement signal in response to the difference between two points: the measure and reference junctions.

Resistance Temperature Detector

As an RTD, the device has a variable resistor that changes when differences in temperature levels appear in the entity. Many materials will conduct greater or lesser degrees of electrical flows. RTDs measure the temperature signals by reading the electrical voltage passing through its conductor.

Unlike T/Cs, RTDs can only use two copper wires to connect to an electrical circuit. However, manufacturers may connect a third path as compensation and help deliver more accurate temperature readings.

There are also two other temperature sensor models you may find. These devices are the Negative Temperature Coefficient (NTC) thermistors and semiconductor-based sensors.

Different temperature sensor manufacturers produce various product lines. Ultra-sensitive temperature sensors exist to help users gauge temperature levels for accurate readings.

What is the Temperature Transmitter?

The temperature transmitter works with a temperature sensor. When these devices work together, users can connect these gadgets to a measure or control device (e.g., loop controller, display, data logger, etc.).

Temperature monitoring system. Image credit: U.S. Air Force / Beau Wade via, Public Domain

Temperature monitoring system. Image credit: U.S. Air Force / Beau Wade via, Public Domain

The temperature transmitter may help in amplifying, isolating, converting, and linearizing an input signal from the sensor. Then, this device transmits an output signal to the control device for users to read the temperature level of the connected body. Transmitters can convert the signals going to the temperature sensor to a 0-10V DC or 4-20mA range.

4-20mA transmitters may be common on the market. The reason behind its popularity may lie in the presence of the majority of current industrial equipment. Many industrial types of machinery use a format that can communicate well within the temperature range of 4.20mA transmitters.

Users can scale the device depending on the requirements of the tasks. Temperature transmitters work by capturing or drawing current from a remote DC power source. The connected transmitter sends signals to the control element for every change in the power supply.

The Advantages of Using Temperature Transmitters

Temperature transmitters have a few benefits in comparison with traditional methods of measuring temperature in specific entities. These advantages may include:

  • AC power isn’t a requirement during operations in need of a two-wire transmitter.
  • A minimal amount of electrical noise in the two-wire transmitter.
  • Temperature transmitters may be cost-efficient than specific temperature-reading devices. Copper wires might be less expensive than other electricity-conducting metals.

What are the Differences Between Temperature Sensors and Transmitters?

Despite these two devices having different constructions, roles, and components, they can work together. Both temperature sensors and transmitters may have essential functions in letting users read accurate temperatures.

Perhaps the most noticeable difference between these two devices is their primary role. For the temperature sensor, it helps users measure the physical temperature of a body. Then, it converts the temperature in measurements gathered in electrical current units. You can read the temperature from a sensor in voltage or resistance.

Conversely, the transmitter connects to the sensor to convert measured temperature readings. The converted readings become signals so users can see, log, and maintain specific temperature levels in an entity.


Choosing the right sensor or transmitter may be critical in delivering an accurate temperature reading from a connected body. Consider factors like the measuring junction, insertion length, stem (sheath), and style of the device before you buy a sensor.

As for transmitter, check the device’s temperature signal corruption and temperature transmitter overview to ensure compatibility with a connected sensor. You may even look for sensors and transmitters with an extra layer of protection for reading temperatures in hazardous environments.

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