Electronics > Repair

Quick Repair: Standford Research PS350 5KV 5mA(Fixed but working on calibration)

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Dexter2:
Just re-burned my EPROM. Works without problems no CRC checks  :clap:.

Only one thing to watch out. To calibrate voltage you need a high voltage probe I used a HAMEG 50kV high voltage probe connected to a calibrated 10Meg input resistance DMM. The problem is as it seems these probes are not to precise, so before doing calibration determine the exact factor for the high voltage probe dont take the 1:1000 for granted it could be quite some % off.


alm:
Some DMMs have some variation in their input resistance (some even go to 10 GOhm). Also, I imagine a 50 kV probe might be adjusted for the end of its range (like the SR calibration, apparently ;)). Due to voltage coefficients, the division ratio may not be all that flat across its voltage range. I can see how that would make checking linearity of the power supply tricky without another HV source.

Dexter2:

--- Quote from: smgvbest on August 01, 2017, 10:55:31 am ---
1.  Continue looking at code to verify all calibration options.
2.  Verify calibration options (testing at DUT)
3.  Develop and test manual calibration procedure (for VSET looks like this may be done)
4.  Develop and test automated calibration procedure (python or perl code preferred as not everyone has other tools)


--- End quote ---

For me getting the calibration done is enaugh im happy. But would be interested in the unknown locations that we have not jet uncovered.

I know my calibration assist program is not in a free lauguage but it was the quickest i could make one as i use LabView all the time. I think National Instrument also has a LabView 45day free full working trial if you want to play with it. If required i can make an executable you would then only need to download a free runtime engine to get it working. To automate the software more it would be possible to read in the offset and the two factors, read values from a external DMM in all three calibration points for all parameters and then calculate the new factors but it probablly does not make sense for a home calibration.

Dexter2:
Just a quick note as i did not write any instructions for the calibration program. First you calibrate all the wanted factors then you read out the calibration memory with "Read calibration memory". Next open your original BIN of the whole EPROM content and than just press write new EPROM. The software generates the new BIN ready to be written into the EPROM.

Dexter2:
Updated the table alm created with locations for readback calibration below.


--- Quote ---WORD?   #           VALUE ROMHEX
0       2476        AC09 ; +pol vset offset
1       21988       E455 ; +pol vset exponent/multiplier/non-linear parameter if vset < word0
2       21003       0B52 ; +pol vset exponent/multiplier/non-linear parameter if vset >= word0
3       2500        C409 ; +pol vlim offset
4       21076       5452 ; +pol vlim exponent/multiplier/non-linear parameter if vlim < word3
5       21076       5452 ; +pol vlim exponent/multiplier/non-linear parameter if vlim >= word3
6       2492        BC09 ; +pol ilim offset
7       21017       1952 ; +pol ilim exponent/multiplier/non-linear parameter if ilim < word6
8       20051       534E ; +pol ilim exponent/multiplier/non-linear parameter if ilim >= word6
9       2491        BB09 ; +pol itrp offset
10      21032       2852 ; +pol itrp exponent/multiplier/non-linear parameter if itrp < word9
11      20053       554E ; +pol itrp exponent/multiplier/non-linear parameter if itrp >= word9

12      2476        AC09 ; +pol voltage readback display offset0
13      49126       E6BF ; +pol voltage readback display scale if VOUT < Word12
14      49634       E2C1 ; +pol voltage readback display scale if VOUT >= Word12
15      2493        BD09 ; +pol current readback display offset
16      49632       E0C1 ; +pol current readback display scale if IOUT < Word15
17      50148       E4C3 ; +pol current readback display scale if IOUT >= Word15
18      0           0000
19      17299       9343 ; **unknown**
20      17299       9343 ; **unknown**

21      2470        A609 ; -pol vset offset
22      21910       9655 ; -pol vset exponent/multiplier/non-linear parameter if vset < word21
23      20982       F651 ; -pol vset exponent/multiplier/non-linear parameter if vset >= word21
24      2500        C409 ; -pol vlim offset
25      21076       5452 ; -pol vlim exponent/multiplier/non-linear parameter if vlim < word24
26      21076       5452 ; -pol vlim exponent/multiplier/non-linear parameter if vlim >= word24
27      2513        D109 ; -pol ilim offset
28      20785       3151 ; -pol ilim exponent/multiplier/non-linear parameter if ilim < word27
29      19760       304D ; -pol ilim exponent/multiplier/non-linear parameter if ilim >= word27
30      2512        D009 ; -pol itrp offset
31      20818       5251 ; -pol itrp exponent/multiplier/non-linear parameter if itrp < word30
32      19746       224D ; -pol itrp exponent/multiplier/non-linear parameter if itrp >= word30

33      2470        A609 ; -pol voltage readback display offset
34      49170       12C0 ; -pol voltage readback display scale if |VOUT| < Word33
35      49634       E2C1 ; -pol voltage readback display scale if |VOUT| >= Word33
36      2514        D209 ; -pol current readback display offset
37      49784       78C2 ; -pol current readback display scale if |IOUT| < Word36
38      50308       84C4 ; -pol current readback display scale if |IOUT| >= Word36
39      0           0000
40      17299       9343 ; **unknown**
41      17299       9343 ; **unknown**
42      0           0000
43      51830       76CA ; **unknown**
44      0           0000
45      51830       76CA ; **unknown**

--- End quote ---

EPROM values are based on Sandra's EPROM and are helpfull for orientation.

The locations first thought to be model specific that turned out to be calibration factors for VLIM are probablly even not calibrated in factory and are just preset with default values as they are all the same for all EPROMs. So if you want to have the unit preset to default initial values to calculate the calibration factors for voltage/current set/readback afterwards this probablly are the initial ones. Offset:2500 Scale:21076.

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