What is the long term drift of the AD590?
The AD590 datasheet guarantees that the error due to long term drift will be +/-0.1degC max. This assumes a constant +5V supply and a temperature up to +125degC. Long term drift is not generally linear with time. Instead it follows a semi random pattern meaning it will drift up a little then down a little. On average the drift is proportional to square root time. The AD590 max drift spec of +/-0.1degC means the drift will be less than 0.1degC over 5 years over a temperature range –10degC to +125degC. If the range is extended up to +150deg the drift may increase.
Where in the datasheet it is statet, that +/-0.1degC is applicable for 5 years only for AD590S? Why is the long term drift in the Mil-Spec (http://www.dscc.dla.mil/Downloads/MilSpec/Smd/87571.pdf) given with +/-0.1degC per month? How can the temperature drift over a lifetime of 15 years be calculated?
The datasheet does not mention 5 years, instead it’s specified at +/-0.1degC/mth
Being a precision part, there is known inherent drift over time which can be important to customer’s applications. This is why this specification was added so customers could design systems with this known drift effect. In practice, long term drift is not generally linear with time. Instead it follows a semi random pattern meaning it will drift up a little then down a little. On average the drift is proportional to square root time.
To get some typical numbers on this for 15 years would require an analysis of the HTOL data over 1000 hours and extrapolating what this would be using some statistical techniques to come up with a number for 15 years. However, this is only a limited sample so could only be used as another reference input to the above estimation based on the specification.
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