Electronics > Repair

Repair : HP 3245A precision DC/AC source

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crispy_tofu:
 :o :o Can't wait!!  :-DMM

nidlaX:

--- Quote from: TheSteve on November 13, 2015, 10:19:51 pm ---
--- Quote from: ManateeMafia on November 13, 2015, 10:05:48 pm ---Wait until you see the next project. Fluke 87V with LTZ1000! :) Don't ask about battery life.

--- End quote ---

The best 4.5 digits of your life!

--- End quote ---
Don't give Fluke the wrong idea. We don't need voltage standard wars between multimeter manufacturers like they did resolution wars for digital camera sensors. :box:

TiN:
Hmm, no good.



Perhaps I should hook more DMMs to log LTZ itself (7.1V) and +11.6V output REF, to see if it's output stage drifting, or issue with reference circuitry.

Also I'll separate heater drive power, as I suspect that one..

TiN:
Aha.

Separated heater supply from opamp supply, now it's playing nice. Trap for young players, pay attention of proper signal and power current paths on your precision designs, or it can easily cause utter failure like in post above.

Also rigged some measurement, source running open cover with ref module hanging on side.
LTZ itself stays ~0.4ppm window over last hour (measured via 2002)
3245A output set to 10V on DMM (actual output setting is +9.71203V) stays within 0.35ppm (meas with 3458A) in last hour.
Ambient temps +28.3°C (no AC in room, to prevent pesky airflow).



For those who still feeling dizzy grasping all these PPM scales, here's same 1ppm division graph:



Day and night, eh?
Now time to pack unit back in with covers, run it few hours to get thermal equilibrium and perform calibration.
I tried calram backup tools from 3458A to capture 3245A calibration data, but both linux and windows verisons failed. Seems 3245A using different address for CAL data. Not big deal anyway.

P.S. horisontal time frame of latter graphs - ~1 hour.

Dr. Frank:

--- Quote from: TiN on November 14, 2015, 09:36:59 am ---
I tried calram backup tools from 3458A to capture 3245A calibration data, but both linux and windows verisons failed. Seems 3245A using different address for CAL data. Not big deal anyway.


--- End quote ---

As the control PCB is exactly the same as in the 3458A, all memory chips must be on the same physical location!

If you look onto the 3245A board, it does not have the 2kx8 nvRAM, its socket is empty !

It only contains the two 32kx8 nvRAMs (and also the four 32kx8 SRAMs).

Therefore, the calibration data probably will also be inside these, but without this elaborate access-lock.

Another question is, if the 3245A firmware also contains the hidden MREAD command.


Frank

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