AD596 and AD597AH (H package) has the alarm function for detecting an open thermocouple. There's following description in the datasheet."If the thermocouple loop becomes open, one or both of the inputs to the device will be deprived of bias current causing the output to saturate. "
Q1. Does the Output saturation alive in AD597AR (SOIC package)? Looking at the function diagram, it is clear that alarm function is not equipped to AD597AR but not clear the output saturation is.
Q2. When an open thermocouple is occurred and -IN (#8 pin) becomes open (+IN (#1pin) remains grounded), is output (Vout #6pin) saturated to [-Vs +2.5V]? Or it can be either [-Vs +2.5V] or [+Vs - 2V]?
AD597 analog output will saturate with an open thermocouple the same way as in the other parts in the series.
I will need to get back to you on which way it moves.
Thanks a lot for your answer to Q1.
Sharing more information on Q2, one of my customer said that most of AD597AR outputs [-Vs +2.5V] but rest of AD597AR (not so many) outputs [+Vs - 2V] with the open thermocouple condition. In the rare case, output turns to [-Vs +2.5V] by cooling IC.
I am looking forward to getting feedback on Q2.
How is the feedback on which way it moves?I am waiting for your feedback.
I don't see anything in our datasheet indicating what will happen when the thermocouple is open. I did not expect the behavior to be different for different thermocouples and different temperatures.
>> Thus I don't think this particular chip model is suitable for the expectation. <<
The AD8495 seems to be more suitable according to this EZ article thread.
The AD8495 is a much newer design.
Even newer and maybe more suitable is the AD7124-4.
App Note CN0384 describes this approach:
Excuse me the links just above are not correct.
For the article on causing the AD8495 output to go to the negative side see:
The article describing the most up to date thermocouple measurement system is here:
CN0384 Circuit Note | Analog Devices