First T.C. measurement:
I decided to make a preliminary T.C. measurement on #5 (before shortening the legs to have "before" data).
I evaluated with 3 ADCs and 2 6,5 Digit Multimeters in 10 V range connected in parallel.
Room temperature changed about 3 deg C during measurement so the Multimeters (not shown in diagram) both drifted around 4.5 ppm.
The ADCs which are temperature compensated behaved much more stable. (below 1.2 ppm)
ADC16 shows best stability. Which is due additional temperature controller to 27 deg C environment.
The other 2 ADCs drifted around 4-5uV during measurement.
Picture over time:
the ADCs are additionally filtered with a 21 sample moving average filter additionally to the 1 minute integration time.
red ADC16 (around 2.5uV change)
pink ADC13 (5.4 uV change)
light blue ADC15 (4.2 uV change)
due to the large thermal mass I have difficulties to get the intended -0.1K/minute slope below 20 deg C.
And also minimum temperature reached was only 14 deg C instead of around 10 deg C.
there are 3 temperature sensors involved:
pink: heat spreader below the LTZ aluminium case (sensor of temperature controller).
green: NTC on top of the aluminium case of the LTZ#5
blue: NTC on PCB inside aluminium case (near zener) of LTZ#5
Picture ADC16 shows the noisy raw values together with the moving average filtered values
over LTZ#5 "environment" temperature (NTC on top of aluminium case).
The output voltage shows no dependancy from temperature.
The shift is more or less contributed by the ramp direction.
Negative temperature ramp gives a somewhat higher output voltage than
positive temperature ramp.
T.C. calculation is a bit useless in this case.
If I take the 2.5 uV filtered value as box T.C. together with the
14-37.8 deg C outside temperature. (23.8 K difference).
I get a "box TC" of 0.015 ppm/K.
With best regards
Andreas