Fluke 5440B Problems

[e61_phil]

Hi,

I bought a Fluke 5440B. Unfortunately, the unit has two issues. The first one is a fault message on power up "INSIDE GUARD FAULT  CHECK GUARD CONTROL BUS". I think that isn't a big deal. And everything seems to work after pressing any key.

The real problem is a instability of the output voltage, if the voltage is above aprox. 500V. The reading on my HP 3456A jumps up a few tens of mV (10NPLC) at 1000V every few seconds and returns.

I attached two scope measurements (only different time scales). The measurement was taken with a 10nF capacitor in series to 1:10 Probe.

My guess is, there is a high voltage breakdown anywhere (component or PCB) and the output stage of the 5440B isn't fast enough to regulate the voltage.

I've measured the driving waveform which drives the high voltage transformer and the peak-peak values matches the values given by the service manual. But the rise time of the square wave isn't as steep as described in the manual (1µs). The waveform looks stable on the scope.

I also measured the voltage on the high voltage capacitor on the output PCA and on the Filter B PCA. The voltage is about 30V higher than the output (the manual says 27V, but I think that is ok). And one can measure these instabilities already on these caps.

I wrote this, because I sold my Fluke 343A to buy the Fluke 5440B (cause of the WAF ). Therefore, I have only a few days left with my Fluke 343A which could deliver stable high voltages instead of the high voltage transformer.

Or does anyone has a guess which part could be damaged?

Thanks
Philipp

[zlymex]

Try cleaning all the relays first, that is the suggestion from someone who has successfully repaired many 5440Bs.

[e61_phil]

That sounds relaxing

Do you know a preferable cleaning procedure?

[Dr. Frank]

@Philipp:
Sorry, I was not able in the weekend, to make your requested comparison measurements.
Maybe I find a bit of time during the week.

@zlymex:
I also wonder, how to clean these relays contacts, without scratching or destroying this sensitive Au plating.

I also thought about cleaning, as my 5442A shows a difference between plus and minus polarity regarding offset, gain and linearity behaviour. Everything is inside specification, but if the negative range would behave exactly like the positive, which I would suspect due to the relays switching scheme, then my instrument would be much more consistent and precise.

Thanks - Frank
 

[e61_phil]

@Dr. Frank: I already thought you have no time to do this measurement. In cause of your fast reactions to my questions everytime Thanks a lot for your time!
I think I should try to clean the relays before you spend your time in measuring anything for me.

[RobK_NL]

@Philipp:
The power-on fault message may be due to  malfunctioning of the inguard Power-on-Reset circuit (#GPOP). I had a similar problem and tracked it down (eventually) to a dead cap; C31 on the A10 board.

[e61_phil]

@Philipp:
The power-on fault message may be due to  malfunctioning of the inguard Power-on-Reset circuit (#GPOP). I had a similar problem and tracked it down (eventually) to a dead cap; C31 on the A10 board.

Someone has already replaced C31 with a new 100µF Cap... But that is a good starting point Thanks

[zlymex]

I cleaned all the relays of my 5440B once, it showed some guarding related error messages before the cleaning.
I used paper card soaked with pure alcohol to rub all the contact.

[ManateeMafia]

I used the same method as zlymex on a Fluke 5450A. I also followed the cleaning with some Deoxit Gold on card stock. It did a great job cleaning the contacts.

[e61_phil]

This evening I started cleaning the relays on the output PCA. I started with the big relays (they were much easier to open). As I finshed cleaning the big relays I want to go to bed, but first I have to give it a try

Therefore, I selected 1000V on the Fluke 5440B and had a look on my HP 3456A. The reading was very stable (except the warm up drift, but that is only drift no jump). I left it running for about 10 to 15 minutes and then the jumping output was back. It seems to be a thermal issue. What do you think? I wouldn't expect such a behavior from a dirty relay contact? Or should I?

[acbern]

better check caps.

[e61_phil]

@acbern: which caps do you mean? The high voltage ones or electrolytics?

Below approx. 500V these jumps vanishes. Therefore, I would expect something in the high voltage path.

[RobK_NL]

The high voltage is generated by a converter on the "Filter B" PCA. The supply voltage for it is changed based on the output voltage range. I would check C21 and C22 and also the opto triacs that do the switching.

[BU508A]

Hi,

@acbern: which caps do you mean? The high voltage ones or electrolytics?

Below approx. 500V these jumps vanishes. Therefore, I would expect something in the high voltage path.

Yes, probably. But it is always a good idea to replace in such old gear all the tantalum caps.
Did it so in my Fluke 3330B and jumping of the output calms down significantly.
Tantalums have a tendency to "sparkle", especially the old ones.

Andreas

[e61_phil]

Yes, probably. But it is always a good idea to replace in such old gear all the tantalum caps.
Did it so in my Fluke 3330B and jumping of the output calms down significantly.
Tantalums have a tendency to "sparkle", especially the old ones.

Andreas

Thanks. I already started replacing most of the electrolytics. I will go on with the tantalum ones. Did you replace these caps with anything special?

[BU508A]

Thanks. I already started replacing most of the electrolytics. I will go on with the tantalum ones. Did you replace these caps with anything special?

Yes. First, I look into the schematic if it is available. Most of these Tantalums are used as blocking capacitors. These I'll replace
with Wima MKP caps (Polypropylen dielectricum) if the capacity and mechanical dimensions fits.
If the Wima doesn't fit, I'm looking for low ESR, low leakage  types, e.g. from Panasonic.

I'm trying to avoid Tantalum caps for some reasons:
- I do not trust them at all, even the new ones (Yes, I know they have improved. But ...)
- Tantalum is political problematic
- piezoelectric effect

I suspect, that in the 70's and 80's a lot of Tantalums were used because it was new, fancy and they have usually a real low ESR.

Btw, here is a nice overview from Wima, comparing some different caps:

English version:
  http://www.wima.de/EN/characteristics.htm
  more information: http://www.wima.de/EN/technicalinformation.htm

German version (interestingly, they show a bit different information, compared to the english one):
  http://www.wima.de/DE/technicalinformation.htm
  http://www.wima.de/DE/characteristics.htm

Panasonic caps (Yes, I know, these are SMDs, but soldering some silver coated copper wire will do the job  ):
  http://www.mouser.de/ds/2/315/ABE0000C65-911134.pdf
  http://www.mouser.de/panasonic-polymer-caps/

Andreas

[ap]

Instead of Wima PP (which may not fit) I would recommend Oscons. They are especially good at filterung and do not have the ripple current restrictions that should have led to the conclusion  back then to not use them. How do I know? We built industrial computer boards at that time, and when we looked at that, we found there was no way to use Tantalums as 5V blocking specs, so we had to change them. We learnt it the hard way, unfortunatelly...

[Echo88]

I also recently got my Fluke 5440B/AF which had an error. Maybe someone has the same problem and my solution might help.
 
Calibrator starts okay, but after a few seconds doenst respond anymore to the Frontpanel, all Frontpanel-LEDs flickering, Display shows "Fluke DV Calibrator", Fault-LED lights. Sometimes it also did show Front-Communic-Error or Memory-Error.

The solution: The 5V-supply-voltage (Test point 2, not 5V-HR) on the Outguard-control-Supply was jumping between 4.8 - 3.9V, which led to the Frontpanel-Errors and the flickering LEDs. In my case the pcb under R1 (current shunt) was slightly dark due to the heating of R1. I checked the value of R1 and found it to be about 350mR while it should be 150mR according to the service schematic. After changing the resistor the 5V-supply-voltage was nice and smooth again with the correct value.

[Bill158]

The solution: The 5V-supply-voltage (Test point 2, not 5V-HR) on the Outguard-control-Supply was jumping between 4.8 - 3.9V, which led to the Frontpanel-Errors and the flickering LEDs. In my case the pcb under R1 (current shunt) was slightly dark due to the heating of R1. I checked the value of R1 and found it to be about 350mR while it should be 150mR according to the service schematic. After changing the resistor the 5V-supply-voltage was nice and smooth again with the correct value.

How interesting.  I had the same failure of R1 in my 5440B when I first received it.  But what made things a little more interesting was that the resistance would go radically up as the temperature of R1 went up.  So when I first turned on the unit everything was ok and then things would start going bad slowly.  I also saw that the 5V was dropping slowly until it was below what was needed to make everything work correctly.  I replaced R1 but increased it to a 5W just in case.  FLUKE must have gotten a batch of bad resistors but of course they were OK in the beginning and only became defective over the years.
Bill

[Echo88]

Just tried to do the Intern Calibration Routine, but it gets stuck in the +10V Zero Calibration and just clicks relays. Seems i also need to clean the relays? Hopefully its nothing serious. Analog and Digital Self Test states no errors. I also wanted to build a RS232-cable to get the capability of reading out the calibration values/analog self test results. Anyway, gotta read the handbooks. 

[Echo88]

Couldnt get the RS232-cable to work properly today (need to get my hand around the DTR-stuff the calibrator requires). But then again i tested the calibrator after 2h warm-up time with the Internal Calibration Routine and it did work today without problems. After a ACAL of my 3458A i was absolutely flabbergasted: It shows spot on 10.000000V when the Calibrator puts 10V out. 

And all that after the trip from the USA to here and i see no sticker on it / cant conclude when it was last calibrated. I love this thing. 

[e61_phil]

Couldnt get the RS232-cable to work properly today (need to get my hand around the DTR-stuff the calibrator requires). But then again i tested the calibrator after 2h warm-up time with the Internal Calibration Routine and it did work today without problems. After a ACAL of my 3458A i was absolutely flabbergasted: It shows spot on 10.000000V when the Calibrator puts 10V out. 

And all that after the trip from the USA to here and i see no sticker on it / cant conclude when it was last calibrated. I love this thing. 

Great!

The RS-232 doesn't need anything special. I built one in december and I only connected TX and GND to the PC.

[Dr. Frank]

.. But then again i tested the calibrator after 2h warm-up time with the Internal Calibration Routine and it did work today without problems. After a ACAL of my 3458A i was absolutely flabbergasted: It shows spot on 10.000000V when the Calibrator puts 10V out. 

And all that after the trip from the USA to here and i see no sticker on it / cant conclude when it was last calibrated. I love this thing. 

Congrats!

What about the other ranges, 22V, 275V and 1100V, to which degree  do they linearily agree with the 11V range, when measured with your 3458A?
(Test 300V on the 1100V range..)

Frank

[Echo88]

@Dr. Frank: Its a little late today, i will let both instruments run over night and make those measurements tomorrow. Can you specify the needed datapoints? Otherwise i will just measure
+-10V,15V,22V,100V,220V,300V,400V,500V,600V,700V,800V,900V,1000V. How much time is needed for the 3458A to thermally stabilize at the high voltages? I know the 3458A will be a few ppm off at the high voltages.
@e61_phil: Thanks, the RS232-cable works well now that ive disconnected the DTR/DTS-wires. Thought they were necessary.

Just did a Analog Selftest and Internal Calibration Routine. I have absolutely no idea if that plotted data might help someone fix their 5440B or show them which values are plausible, but here it is:


JOHN FLUKE MFG. CO., INC.                          5440  ANALOG DIAGNOSTICS

---------------------------------------------------------------------------

     ADM1: +.000000V
     ADM2: -.002547V
     ADM3: +2.53159V
     M1: +13.0654V
     M1: +13.0654V
     M3: -11.6912V
     M4: -16.7795V
     C1: +5.08826V
     M5: -5.05291V
     M6: -16.5145V
     M7: -9.67262V
     C2: -13.0935V
     M8: -13.0935V
     C3: ¼.000000V
     M9: -4.96851V
     M10: -1.51081V
     C4: -3.23966V
     M11: -3.24050V
     C3: +.000844V
     M12: -15.5156V
     M13: -16.7690V
     C5: +1.25335V
     M14: -10.0664V
     M15: +9.97923V
     M16: -.045014V
     M17: +.000000V
     M18: -.001394V
     C6: +.001394V
     M19: -.000236V
     M20: -.001776V
     C7: +.001539V
     M21: -.000285V
     M22: -.000348V
     M23: +.000058V
     M24: +.000066V
     M25: +.005150V
     M26: +10.0026V
     M27: +20.0420V
     M28: -10.0026V
     M29: +.000000V
     M30: +19.9995V
     M31: -.093966V
     M32: +19.9995V
     M33: -.000371V
     M34: +20.0350V
     M35: +20.0280V
     M36: +17.8040V
     M37: -.157540V
     M38: +.188073V
     M39: +.839009V
     M40: +.857412V
     C8: -.018403V

END OF ANALOG DIAGNOSTICS

JOHN FLUKE MFG. CO., INC.                        5440  INTERNAL CALIBRATION

---------------------------------------------------------------------------

+10V ZERO
     1: N1=  8, N2=13514, Offset    +.3uV

RESOLUTION RATIO
     1: N1=  7, N2=20763, Offset    +.4uV

-10V ZERO
     1: N1=  8, N2=10489, Offset    -.1uV

+20V ZERO
     1: N1=  8, N2=13189, Offset   +1.2uV

-20V ZERO
     1: N1=  8, N2=10805, Offset    +.6uV

+250V ZERO
     1: N1=  8, N2=12818, Offset   +1.0uV

-250V ZERO
     1: N1=  8, N2=11163, Offset   +7.5uV

+1000V ZERO
     1: N1=  8, N2=12830, Offset  +30.5uV

-1000V ZERO
     1: N1=  8, N2=11155, Offset  +29.5uV

GAIN SHIFT
     +10:  -285.21uV
     +20:  -347.95uV
     +Hi:  -370.59uV
     -Hi:  +463.96uV
     -20:  +441.90uV
     -10:  +378.15uV

END OF INTERNAL CALIBRATION

[e61_phil]

How much time is needed for the 3458A to thermally stabilize at the high voltages? I know the 3458A will be a few ppm off at the high voltages.

I think one can't specify that exactly. We have two 3458A at work and both behave quite different at 1kV.

[Dr. Frank]

@Dr. Frank: Its a little late today, i will let both instruments run over night and make those measurements tomorrow. Can you specify the needed datapoints? Otherwise i will just measure
+-10V,15V,22V,100V,220V,300V,400V,500V,600V,700V,800V,900V,1000V. How much time is needed for the 3458A to thermally stabilize at the high voltages? I know the 3458A will be a few ppm off at the high voltages.
.....

GAIN SHIFT
     +10:  -285.21uV
     +20:  -347.95uV
     +Hi:  -370.59uV
     -Hi:  +463.96uV
     -20:  +441.90uV
     -10:  +378.15uV

END OF INTERNAL CALIBRATION

Hi,

The 3458A is not compensated for self-heating, therefore at 1kV, you will have an additional deviation from linear.
This is specified 12ppm *(Ue/1kV)^2 (note 6 on page 82 of the calibration manual).

In my case, it's about -6ppm at 1kV. This parameter is varying over different instruments.
The time constant for the 3458A is about 1 minute, until it stabilizes.

The 5440B also needs some time to stabilize at 1kV, also about 1minute, but the oven compensates the self- heating completely.

The deviation and the time constant were determined identically by my 5442A, and a precision Hamon divider.

At 300V, this self-heating is negligible, so I propose for these three ranges:

10V, 20V, 250V, 300V, 1000V
At first, you might test the linearity, i.e. 0... 11V in 0.1V steps, to calculate the non-linearity factor of the D/A, between 300V and 1kV.

I have not fully understood, how the autocal process of the 5440B works, regarding these listed parameters, or what the real limits are.. but I assume, that your gain shift factors may be too high, and that your 5440 needs a proper external ratio calibration.

 This should be visible by the above mentioned ratio checks.

Frank

[Echo88]

Didnt have time to write a fitting script because my LTZ1000A turned up and eagerly wanted to be mounted in the KX-Boards. So i just took measurements by frontpanel and didnt already calculate linearity and so on.
During the whole measurements i also found out:
-i indeed should clean the relays, since on one point the relays did clatter without ending (one gentle stroke on the case ended that, the relay apparently found contact and the Internal Calibration continued without errors) 
-up to 800V the calibrator works okay, at 900V it says Output Limit Fault, Output Undervoltage 

Measurement Results:

3458A and 5440B/AF, thermally stabilized the whole day, ACAL and Internal Calibration just before the measurement, 100NPLC, after 100V i did wait >= 1min after every calibrator-value-change to thermally stabilize

3458A 10V Range

0.1V...1V...11V ->

0.1000009V
0.2000015V
0.3000018V
0.4000023V
0.5000032V
0.6000031V
0.7000031V
0.8000030V
0.9000027V
1.0000029V
2.0000032V
3.0000030V
4.0000029V
5.0000020V
6.0000018V
7.0000009V
8.0000003V
8.9999991V
9.9999981V
10.9999975V

100V Range

10V,20V,50V,100V ->
9.999983V
19.999960V
49.999980V
99.999930V


1000V Range

100.00000V
249.99982V
300.00103V
400.00127V
500.00177V
600.00231V
700.00300V
800.00397V
900V -> Output Limit Fault, Output Undervoltage

Now i somehow want a 752A and a good aged 732A/B 

Edit: I suppose the Guildline 7520 is just an automated Fluke 752A + LTZ1000A + Nullmeter (but optical  )? -> http://www.guildline.com/new-products/released/7520-automated-precision-voltage-divider

[e61_phil]

I was interested in the 10V range. Therefore, I throwed the measurements in Excel.

[Dr. Frank]

Now i somehow want a 752A and a good aged 732A/B 

Your 5440B already serves as a (Super-) 732A/B, as it is well aged, and it contains an ovenized, double SZA263 reference. So no wonder, that your 3458A shows exactly 10V on its 10V range. Your instrument has a very good linearity of 0.25ppm INL, as calculated by e61_phil.

The ratio auto-calibration seems also to be ok, although your 3458A should have been nulled in its 100V and 1kV ranges, before you have taken the measurements. There's an offset of about -15µV in its 100V range, and about -740µV in its 1kV range, if you calculate the regression line of the different ranges.

These offset errors of the 3458A are directly visible, when you compare the 10V measurements in its 10V and 100V range.
That's already a -1.5ppm error between these readings, consisting of this offset error, and the autocal ratio error of the 3458A..

If you calculate the ratio error of 20V / 10V and 100V / 10V, measured in the 100V range of the 3458A, these are about 0.75 and 1.36ppm (with compensated offset), so the 22V and the 275 ranges are probably precisely auto-calibrated in the 5440B.
The 1100V range is a bit off at about 3.4ppm, if you calculate the 300V / 100V ratio error.
But these measurements in the 1kV range of the 3458A are all not well consistent, 800V already show -7,9 ppm deviation from a linear relation.
That may be due to the heating effect inside the 3458As divider, or may be the HV generation is not working properly at that voltage already, so you'd first have to repair this.

I also recommend to properly zero your 3458A, when you calibrate the 2.2V and 220mV ranges of the 5440B.

Frank

[Echo88]

I already thought about using the SZA-reference inside the 5440B as a good aged reference, but wasnt sure if using the reference-voltage via an extra cable would have an impact on the calibrator. Also: The 5440B draws considerable more current than a 732A/B (have to measure what it really draws and the resulting electricity-costs) and cannot be shipped to be calibrated to serve as "The Volt" in my home.
I didnt know about the 100V/1000V-offset in the 3458A, good to know for the next measurement. I did buy the 3458A mainly because of its unbeaten linearity and accuracy in the 10V-range, which interests me most. You are right about the nulling of the 3458A for those low divider-voltage, i wanted to check the drift/low-frequency-noise of my 3458A in those small voltage regions for a long time, to compare it to my Keithley 181 Nanovoltmeter. 

In the coming time i will clean the relays in the 5440B and maybe will make separate Pomona jacks and connections to the 5440B-SZA-reference. This could then maybe be used as my main-reference, which has a different drift characteristic (SZA drift up, the LTZ1000/A down...or just the opposite) compared to the 7x LTZ1000A that i have.

[Dr. Frank]

I already thought about using the SZA-reference inside the 5440B as a good aged reference, but wasnt sure if using the reference-voltage via an extra cable would have an impact on the calibrator.

That's not good an idea, because that would be a path for disturbances.
Also, it's not necessary at all, because the 5440B outputs a precise 10V already, due to its very linear D/A, and its precise gain auto-calibration.

Also: The 5440B draws considerable more current than a 732A/B (have to measure what it really draws and the resulting electricity-costs) and cannot be shipped to be calibrated to serve as "The Volt" in my home.

Well, for volt-transfer you could as well use your new LTZ1000.

I didnt know about the 100V/1000V-offset in the 3458A, good to know for the next measurement. I did buy the 3458A mainly because of its unbeaten linearity and accuracy in the 10V-range, which interests me most.

The best feature of the 3458A is its very precise autocal process, i.e. the 10:1 ratio transfer, which of course is a consequence of its ultra linear ADC.
This transfer is typically precise to about 0.33ppm per range, see hpj 4/1989.

But that may vary. It's mostly spot on, but sometimes it's off by up to about 1ppm.
That's simply the natural variance of this technique, including gain and offset errors.
 
I check that comparing the measured 10V in the 10V and the 100V range, 100V in the 100V and 1kV range, and analogously for the 2V and 220mV ranges.
Either there's an offset, that can be compensated, or it's necessary to repeat the ACAL procedure.

That way, you can afterwards check the 5440B ratio much more precisely by the 3458A.

You are right about the nulling of the 3458A for those low divider-voltage, i wanted to check the drift/low-frequency-noise of my 3458A in those small voltage regions for a long time, to compare it to my Keithley 181 Nanovoltmeter. 

The 220mV is not so precise at 3mV.. an additional precise Hamon 100:1 divider is better suited for that purpose.

In the coming time i will clean the relays in the 5440B and maybe will make separate Pomona jacks and connections to the 5440B-SZA-reference. This could then maybe be used as my main-reference, which has a different drift characteristic (SZA drift up, the LTZ1000/A down...or just the opposite) compared to the 7x LTZ1000A that i have.

Again, I would simply use the 5440B as-is, that's sufficient.

You may monitor the 5440B vs. the 3458A, and the LTZ1000 vs. the 3458A.
Then you have 3 references, and maybe you can decide, which one drifts...
The more LTZ1000 references you have, the better, but they usually have a negative timely drift.
The 5440B may drift upwards, but as it's off for most of the time, drift will probably be very small, same goes for the 3458A.


Frank