Infrared Temperature Sensor with Controller: PyroCouple and ATR121

Infrared temperature sensors are commonly used in industry to control aspects of the process such as heaters, cooling systems and line speed.

One of the simplest ways to measure temperature without contact and obtain a control output is to use a Calex PyroCouple pyrometer and a low-cost indicating controller such as the ATR121. Here’s how.

Temperature Measurement

Calex PyroCouple infrared temperature sensor - simple, low cost, with a choice of analogue outputs

The simple, low-cost PyroCouple infrared temperature sensor is commonly used in a wide range of industrial applications. It measures non-reflective non-metal materials, or painted metal surfaces, and has a two-wire loop-powered 4-20 mA output.

A commonly-used model is PC151MT-0, which has a temperature range of 0°C to 250°C (other ranges are available), and 15:1 general-purpose optics to measure the surface temperature within a small area whose size increases with measurement distance.

PID Control

Pixsys ATR121B or ATR121AD indicating controller

The Pixsys ATR121 is a small, low-cost panel-mounted Proportional-Integral-Derivative (PID) controller with a 3-digit display and outputs for control and alarm including relay and Solid State Relay (SSR). It has a universal analogue input that can be connected to the PyroCouple sensor, and provides power to the sensor on the two-wire 4-20 mA loop. The ATR121 is available with supply voltages of 230 V AC (ATR121-B) or 12-24 V AC/DC (ATR121-AD).

Connection and Configuration

Firstly, connect the sensor and power supply to the ATR121. A quick configuration process is all that is needed to set the ATR121 to read the temperature output from the PyroCouple. The exact settings to use depend on the temperature range of the sensor. Step by step instructions are available here:

ATR121B – 230 V AC – Connection Instructions for 2-wire 4-20 mA sensors (PDF)
ATR121AD – 12…24 V AC/DC –  Connection Instructions for 2-wire 4-20 mA sensors (PDF)

With the measured temperature successfully displayed on the screen of the controller, the PID control parameters can then be tuned and adjusted via the ATR121’s configuration menu.

Control and Alarm Outputs

The ATR121 has two relays and an SSR output that can be configured in a choice of combinations of alarm and control.

Simple on/off control with hysteresis is possible, as is full PID control. If all 3 of the P, I and D terms are not necessary for good results in your process, you can use just the P, PI or PD terms if you prefer.

A full description of the configurable parameters and their function is available in the ATR121 Manual (PDF).

Other Temperature Measurement Options

Although the PyroCouple satisfies many industrial temperature measurement applications, there are often some specific technical aspects that need a more careful choice of sensor. There is something in our wide product range for almost all other applications:

  • Other temperature ranges: A choice of temperature ranges from -20°C to 500°C are available within the PyroCouple series. For temperatures above 500°C, consider using a short-wavelength sensor such as the PyroUSB PUA2 for improved accuracy.
  • For measuring reflective metal surfaces such as iron and steel, short-wavelength sensors provide more accurate results.
  • High ambient temperatures require the use of a sensor such as the PyroMini -HA, which has a sensing head that withstands 180°C without cooling, or the FibreMini (200°C). Cooled versions of the PyroCouple (and other models) are available.
  • If there are interruptions to the measurement, such as gaps between objects on a conveyor, or rotating mixer arms, use a sensor with peak or valley hold processing.
  • When measuring very small targets  or when a very fast response time is required, look at the PyroCube range.
  • Measuring thin plastic film requires a specialised sensor such as the PyroCube P. 
  • Contact Calex for assistance with any of these, or to discuss any questions you might have about your requirements.

Other Controller Options

The ATR121 is our lowest-cost controller; as with the PyroCouple sensor there are several other models available to suit more demanding requirements:

  • For reading temperatures above 999° a 4-digit display is required; models such as the ATR142 and DRR245 provide this.
  • Some control inputs require an analogue (current or voltage) signal; the DRR245 has this feature, and it is available on the ATR244.
  • Memory cards are available for copying configuration parameters between many controllers.
  • For other special requirements such as dual-input controllers, please contact Calex for more information.

Safety Considerations

Calex sensors must not be used as safety devices i.e. they must not be relied upon to ensure the safe operation of machinery.

By Anthony Smith