This document describes the use of AD7710 in a thermocouple application. The thermocouple is connected to the AIN1 pin and a burn-out detector current source is used to detect if the thermocouple is open circuit. The document also suggests measuring the cold junction temperature and subtracting it from the thermocouple reading in the digital domain. Additionally, the document provides recommendations for thermocouple interface design.
The document details the AD7710's application in thermocouple interfaces, specifically focusing on the use of the internal burn-out detector current source and the measurement of cold junction temperature using a thermistor. It explains how to connect the sensor to the AIN1 pin and discusses the benefits of measuring the cold junction temperature in the digital domain to improve accuracy.
| Burn-out detector current source | 100 nA |
|---|---|
| Thermistor excitation current source | 20 µA |
| Maximum ground resistor value | about 100 kΩ |
| Modulator frequency | 19.5 kHz |
| Maximum PGA sampling rate | 156 kHz |
It is measured using a thermistor excited by an onboard 20 µA current source.
It drives the AIN(+) pin to saturation if the thermocouple is open circuit.
It should not be larger than about 100 kΩ to avoid excessive Johnson noise.