Electronics > Metrology

LTZ1000 digitally controlled oven temeprature

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Kleinstein:
The heater has a square law effect and is thus nonlinear. The linarized loop gain for the temperature loop thus depends on the current heater level. The higher the power, the higher the loop gain. For this reason the control loop in the standard circuit needs to be quite conservative, not to get unstable when at higher power and thus higher loop gain. At a very low power level the loop gain goes down, but likely still high enough.
So while one could linarize the the loop and add more gain for the low power range, this would probably not make a real difference.

The standard current for T2 is at a little under 100 µA, which is perfectly fine noise wise. Even less current would be OK - the problem is more that higher value resistors tend to be less stable.

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