[volt-nuts] Fluke 731B (adjusting tempco)
willvolts at gmail.com
Thu Feb 9 20:48:23 UTC 2012
That was actually my original idea because most of the zener current
comes through R4 and transistor current through R5-R6. Yesterday I
decreased the R5-R6 value by 20% but there was no change in tempco at
all. I thought I had misunderstood something again...
The overall tempco is higher than it should be. Maybe some other
component is dominating instead?
The output voltage is also high (trimmer R11 range is too small to
adjust to exact 10V). Any ideas?
2012/2/9, Rob Klein <rob.klein at smalldesign.nl>:
>> With a simple temperature compensated zener you can simply adjust the
>> current so that the zener and diode tempcos cancel each other...
> That's exactly what happens here too and it's the reason R5 and R6 are
> part of the Ref Amp Set. These
> are selected for minimum overall tempco.
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