Monday, April 04, 2011

High-Resolution Temperature Measurement

The AD8494 thermocouple amplifier includes a temperature sensor, normally used for cold-junction compensation. Grounding the thermocouple inputs allows it to be used as a standalone Celsius thermometer. In this configuration, the in-amp produces a 5-mV/°C voltage between its output and reference pins. This article suggests two ways that this output voltage can be offset and scaled to facilitate high-resolution temperature measurement.


At 1:48 AM, Anonymous Bertrand said...

An outstanding article.
A very easy to implement and usefull schematic.
Many thanks.

At 2:49 AM, Anonymous Ronnie Yujuico said...

What is the advantage of Figure 2 compared to amplifying the output by 20 times and grounding the reference pin?

At 1:51 PM, Anonymous Moshe Gerstenhaber said...

Thank you Ronnie, you asked a very good question. The fact is that both solutions will work, but the circuit. in fig 2 addresses the difficulties of systems running under a single supply, where the output is close to 0 Volts (i.e. the negative supply rail)

For example if the temperature is 1degC the solution you propose is trying to produce 5mV at the ad8494output. Very close to the negative rail. The circuit in fig. 2 produces an output of 100mV at 1degC. This larger signal is easier to handle even for the output buffer opamp.


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