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Fluke 540B Thermal Transfer Standard

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Hello Richard,

here is my setup.
DC source Valhalla 2701C (is very stable) warmed up and set to 800mV, checked with TEK DMM4050
AC source Valhalla 2703 (I hope is stable enough) warmed up and set to 800mV/100Hz, checked with TEK DMM4050

540B POWER switch REFERENCE, GALV + SEARCH voltage checked ok, the turned to ON
AC connected, MODE switched from OFF to AC SEARCH, RANGE turned down to 1, PERCENTAGE INPUT shows about 80, switch to AC TRANSFER and wait 20-30 min.
SESITIVETY LOW turn COARSE clockwise until it moves close to zero, in MED and with MEDIUM pot set to stable zero, in HIGH and with FINE adjust I check several times until there is almost no visible movement around zero.
Now MODE switch to DC SEARCH, RANGE is still at 1 and PERCENTAGE INPUT shows also about 80, switch to DC TRANSFER and check GALV

I made this test now on all three units that passed your suggested tests.
With your great help, one unit now seems to be fully working and showing good result compared to the TEK DMM 4050 (AC is 800.077mV and DC is 799,807mV)

But the other two units at "SESITIVETY LOW turn COARSE clockwise until it moves close to zero" they jump right out of scale, with no step near zero and no possibility to make it with MED.

Any ideas?


It is hard to know without fault-finding the hardware.

If the middle reference pot's wiper was going open circuit in part of its travel, you would get an effect like that.

Set the range to 10V , the course around middle, and the other knobs anticlockwise. Now adjust the input DC between 5 and 10V. Do not go above 10V - you might damage the sensor, particularly if the protection circuit does not work.

On the low range, you should be able to find the null by adjusting the input voltage. somewhere around 7.5 volts approximately.

thx a lot again.
I will try that, but I have to make a break and wait for new NiCds to be able to make the next tests.
I will come back, when I have a update.

Edit: Final update, new accu packs are finally installed, changed some more parts, but everything is now working well


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