Q
You state a worst case long term stability of 0,1°C in your application note
272. Is this value not connected to a maximum operation time where it is valid?
With other words: can I (for example) measure the temperature in the range of
-10°C...150°C within 5 years without any error caused by the AD590 larger than
0,1°C?
A
The AD590 datasheet guarantees that the error due to long terms long term drift
will be +/-0.1degC max. This assumes a constant +5V supply and a termperature
up to +125degC.
Long term drift is not generally linear with time. Instead it follows a semi
random pattern often referred to as a “drunk man’s walk”; it will drift up a
little then down a little. On average the drift is proportional to square root
time.
You are correct, however, we generally spec long term drift as degC/root(time).
The AD590 we have specified as max 0.1degC over the expected lifetime of the
product.
So to answer your question, we will guarantee the drift error will be less than
0.1degC over 5 years for temperature –10degC to +125degC. If the range is
extended up to +150deg the drift may increase.