Design of loop-powered thermocouple temperature measurement circuit

 This article brings you a 14-bit 4-20mA loop-powered thermocouple temperature measurement system circuit design diagram. This circuit is a complete loop-powered thermocouple temperature measurement system that uses a precision analog microcontroller. The PWM function controls 4 mA to 20 mA output current. Offers the advantage of higher resolution PWM driving 4mA to 20mA loops, supporting T-type thermocouples with a temperature range of −200° C to +350° C.

Circuit functions and advantages

The circuit shown in Figure 1 is a complete loop-powered thermocouple temperature measurement system that uses the PWM function of a precision analog microcontroller to control a 4 mA to 20 mA output current.

Figure 1. ADuCM360 controls 4 mA to 20 mA loop-based temperature monitoring circuit.

Circuit principle : This circuit integrates most of the circuit functions on the precision analog microcontroller ADuCM360, including a dual-channel 24-bit Σ-Δ ADC, an ARM Cortex™-M3 processor core, and a control loop voltage up to 28 The PWM/DAC feature of the 4 mA to 20 mA loop of V provides a low-cost temperature monitoring solution. In it, the ADuCM360 is connected to a T-type thermocouple and a 100Ω platinum resistance temperature detector (RTD). RTD is used for cold junction compensation. The low-power Cortex-M3 core converts the ADC readings into temperature values. The supported temperature range for Type T thermocouples is −200° C to +350° C, and the temperature range is 4mA to 20mA. This circuit has the advantage of driving a 4mA to 20mA loop with higher resolution PWM. PWM based output provides 14-bit resolution. The circuit is powered by the ADP1720 linear regulator, which regulates the loop power supply to 3.3 V to provide power for the ADuCM360, operational amplifier OP193, and optional reference voltage source ADR3412.