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Fluke 731B (adjusting tempco)

W
Will
Thu, Feb 9, 2012 12:05 PM

What would be the best way to minimise the SZA263 (U2) tempco?

With a simple temperature compensated zener you can simply adjust the
current so that the zener and diode tempcos cancel each other...

731B schematic on last page:
http://assets.fluke.com/manuals/731B____umeng0000.pdf

What would be the best way to minimise the SZA263 (U2) tempco? With a simple temperature compensated zener you can simply adjust the current so that the zener and diode tempcos cancel each other... 731B schematic on last page: http://assets.fluke.com/manuals/731B____umeng0000.pdf
RK
Rob Klein
Thu, Feb 9, 2012 5:58 PM

Will,

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.

Regards,
Rob.

Will, > 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. Regards, Rob.
W
Will
Thu, Feb 9, 2012 8:48 PM

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@smalldesign.nl:

Will,

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.

Regards,
Rob.


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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@smalldesign.nl>: > Will, >> 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. > > > Regards, > Rob. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. >