Fluke 185 Review

[mimi123]

Hello,

First, thanks for this review.

Second, sorry for my English, I hope all you understand it correctly, if not, tell me and will try to do it better.

I have a Tek TX3 and after a short circuit, the fuse F1 was dead. I changed it but did no work as it should be. It doesn't measure current correctly.

I think not only a calibration is needed but some part is dead.

I really wants to repair it because it's a very, very  good multimeter and I like it a lot.

Mine is physically immaculate because has very little use.

Board seems exactly as yours:



 


Regards

[Wytnucls]

Troubleshooting at a distance is not something I enjoy.
I'm not an expert, but if you ruptured the fuse with enough energy, you may have damaged something upstream. I would look closely at the current shunts, the MOSFETs and the A/D converter. Some parts will likely have to be replaced, if you can still find them.
Good luck with the fix.

[retiredcaps]

Second, sorry for my English, I hope all you understand it correctly, if not, tell me and will try to do it better.

I have a Tek TX3 and after a short circuit, the fuse F1 was dead. I changed it but did no work as it should be. It doesn't measure current correctly.

Your English is fine.  However, you could provide more information for us to help you.

1) How did you damage the meter?
2) What did you do get the short circuit?
3) If you measure a 1A current, does it show 1A or something else? 
4) Do the other functions like DCV, ACV, ohms work?

[Wytnucls]

If this is going to be a long back and forth repair attempt exchange, please start a new thread.

[mimi123]

Troubleshooting at a distance is not something I enjoy.
I'm not an expert, but if you ruptured the fuse with enough energy, you may have damaged something upstream. I would look closely at the current shunts, the MOSFETs and the A/D converter. Some parts will likely have to be replaced, if you can still find them.
Good luck with the fix.

Very thanks for your help.

Second, sorry for my English, I hope all you understand it correctly, if not, tell me and will try to do it better.

I have a Tek TX3 and after a short circuit, the fuse F1 was dead. I changed it but did no work as it should be. It doesn't measure current correctly.

Your English is fine.  However, you could provide more information for us to help you.

1) How did you damage the meter?
2) What did you do get the short circuit?
3) If you measure a 1A current, does it show 1A or something else? 
4) Do the other functions like DCV, ACV, ohms work?

Thanks for you too.

The meter was damaged when measuring voltage, 220V AC or 380V AC I'm not sure,  but with the probes connected to measured current. Then I do a short circuit.
The only malfunction after this was the current measurement. The four lower current scales measures less than the correct and a measure was displayed without any probe connected to the meter.

If this is going to be a long back and forth repair attempt exchange, please start a new thread.

Don't worry, not a long story, I hope

Last night I removed all the six mosfets (Q100 to Q105) used for the current measurement and I had found one shorted. The bad part is Q100, is a L2203NS from International Rectifier.

Then I had soldered Q102 to Q105, mount the meter and all is working fine but the two more bigger scales of the current meter, of course. 

Now I need to order this bad mosfet and test it. I think this is the only bad part.
When I fix it I will put here the results.

Take note that the meter has three hardware current scales and all six transistors involved in this (Q100 to Q105) are mosfets.

Thanks all you for your help 

[Wytnucls]

Good show. Should be an easy fix, if the ADC was not affected. Waiting for your final assessment.

[mimi123]

I fix it with one IRF3205 I have here and the old original mosfet that survive.

I have found the mosfets at Mouser but now I don't need other components and the shipping cost is too much. I will order later.

I think it's working right but I don't have a better multimeter to test it.

The measure is correct in both polarities. I think with a positive current is working one mosfet and with negatives the other.

I take some photos. All meters are in series.

With a positive current :



And with the probes reversed :




A good meter no doubt.


BTW and for if someday is needed, do you have the program or the instructions to enter into the calibration mode?

All the best!

[Wytnucls]

Replacing a MOSFET shouldn't need calibration, as it is just used as a switch.
Calibration is performed through the IR port, with 5520A calibrator. Sorry, I don't have the exact procedure for the calibration mode.

[Wytnucls]

The service manual is on post #2 already.
The calibration manual was also posted earlier, but it doesn't tell you how to set up the meter for IR calibration.

[retiredcaps]

The service manual is on post #2 already.
The calibration manual was also posted earlier, but it doesn't tell you how to set up the meter for IR calibration.

Whoops, didn't notice that.    I will delete my other post.

[mimi123]

Replacing a MOSFET shouldn't need calibration, as it is just used as a switch.
Calibration is performed through the IR port, with 5520A calibrator. Sorry, I don't have the exact procedure for the calibration mode.

Thank you anyway.

I forget to mention the original mosfets of my Tektronix TX3 (Q100 and Q101) are L2203NS, the same as the Fluke.

I think that as these mosfets are used to switch the shunt resistor(5mohms) any difference in their Rdson should change the measure because the two mosfets are both in parallel and then in series with the resistor.
L2203SN has 7 mohms and the IRF3205 8 mohms, but this is the maximum value that says the data sheet, real value should vary quite from part to part and with it the measurement.
Has this sense to you?

I think I've been very lucky with the result.

Another story is the consumption while in standby (OFF). I measure 40 uamps.   I think is for the gates of these mosfets that has 9volts when in off mode.

I read this consumption here but now I can't find it.

Did you measure it?

[Wytnucls]

No, I haven't measured current consumption in STBY mode. 40uA doesn't sound like much anyway.

One thing I have measured is the true RMS voltage of a train of pulses and I get strange results on the 185.
There might be a good technical reason for the discrepancy or my meter is faulty.
I'd appreciate your trying the same test, if you have a function generator:
5 pulses of 20uS each 50%, 5Vpp with 2.5V offset and 300uS period.

Here are my results, compared to other DMMs (AC+DC):

[Noise Floor]

Hi Noise Floor,
I'm glad to hear that about your Fluke 185. I just bought 185 a few days ago. I paid 250 euro, a little too expensive for a old Fluke model, but is MADE IN USA.
Can you tell me in a few words about this model of Fluke, information are quite a few on web. A few pros and cons you have over the years (calibration, accuracy, other problems encountered with it).
With special consideration,
Lucian Cernega.

Sorry for not responding earlier, I sometimes forget to check on threads I've posted in.
Pros - Durability (survived several drops), Battery life (better or on par of other handheld meters I've had, Accuracy been "good enough" for my troubleshooting testing I've done with it when calibrated
Cons - The display not always easiest to read (Got an OLED unit so I'm spoiled now), Cost was a little higher than competitor products

[mimi123]

No, I haven't measured current consumption in STBY mode. 40uA doesn't sound like much anyway.

One thing I have measured is the true RMS voltage of a train of pulses and I get strange results on the 185.
There might be a good technical reason for the discrepancy or my meter is faulty.
I'd appreciate your trying the same test, if you have a function generator:
5 pulses of 20uS each 50%, 5Vpp with 2.5V offset and 300uS period.

Sorry I don't have a function generator like yours. I can measure a square wave if is useful for you.
Did you select the bandwidth at the generator?
If not maybe the problem is here. The Fluke seems to have a lower BW.

[Wytnucls]

Yes, you could try a 4V square wave 20kHz 50% with no offset in AC mode only.
I get 1.8297 instead of 2V on the other meters.
Either the bandwidth is over optimistic or my meter is faulty.
Reducing the frequency gives a more accurate result. At 2kHz, the measurement is correct.

[mimi123]

I have about the same results as yours with square waves.

I measure it with a sine wave and seems that the meter is BW limited with a filter at 25Khz -3dbs.

This is at 1Khz:



And this at 25Khz:



My other multimeters are worse than the Tek but for this type of waveforms I only use the oscilloscope.

I think that this multimeter is designed to measure the normal AC 220 50Hz and their harmonics or AC 110 60 Hz of course but not much more. 

[shakalnokturn]

Recently bought a used Fluke 183 and thought I'd bring this topic back from the dead.

Thanks to Wytnucls for the good review.

I'm already considering the possibilities of up-hacking this 183 to a 185 plus maybe adding Bluetooth.

PCB and CPU seem identical including the function selector contacts.
Accessing the extra position for temperature range isn't hard.
Don't know the size of the SPI EEPROM on the 185 on the 183 it's a 2kB 25LC160
Expect the accuracy differences between 183 and 185 to be based on factory sorting and not on manufacturing differences.
Expect the only other differences (other than accuracy) to be stored in EEPROM.
Expect the key and function selector mapping also to be in EEPROM, considering that the 185 has temperature position in place of Amps position on the 183. (Remapping the function selector would allow to leave the Amps position as-is and have temperature in next CW position.)

I've dumped my EEPROM with following default settings:
POFF: 021
LOFF: 016
Beep: OFF
HiRes: ON
Pol: OFF
Edge: POS
delta AC:1.31mV
delta DC:0.08mV
delta AC+DC:0.1mV
Cal date: 12-2014

FW version: 1.01 (I suppose this is in the CPU only.)

Serial number seems to stand out in the dump although I cant confirm, the back label is missing on my DMM.

Details and dumps from Fluke 185 EEPROM's welcome, I'll fool around with them.

[shakalnokturn]

Someone on the TekScopes@groups.io group was nice enough to send me a copy of the command set. There isn't much regarding calibration in it unfortunately.

Could anyone with a Fluke 185 or Tektronix TX3 run the key test by holding F2 while powering on (press F2 twice to pass the LCD and beeper test), turn selector to "temperature" and check what code that returns, same when turning to "Amps"?
The 183 returns "06 00" on "Amps" but the previous position (capacitor) is "04 00" so I'm expecting the 185 to return "05 00" on "temperature", just trying to confirm that the key positions are software defined.

Now I have the commands I suppose the next step will be setting up a RS-232 interface and throwing them at my DMM while capturing the SPI communication to the EEPROM to try and map as much of that memory as possible.

If anyone has a copy of the Tek WSTRM software (WaveStar for Meters) I'd be pleased to have a copy of that!

[msquared]

Hello shakalnokturn,

I've got a TX3, here's the codes returned for each switch position and button.

Rotary Switch positions:
V          = 01 00
Hz        =  02 00
Ω/->|-  = 03 00
-|(-       = 04 00
°C         = 05 00
A           = 06 00

Buttons (Rotary in V position)
F1          = 01 07
F2          = 01 08
F3          = 01 09
F4          = 01 10
blue       = 01 03
Light       = 01 04
Range     = 01 02
M/M/A    = 01 01
Hold       = 01 05
delta      = 01 06

Hope this helps.

btw.
Thanks for the programming manual.

[shakalnokturn]

Thanks for going to the trouble msquared.

The switch test returns a code corresponding to the function selected and not the physical position of the switch.
Either the switch functions are individually defined in EEPROM or only DMM model is stored in EEPROM and the layout is defined in CPU ROM.

[shakalnokturn]

By now my Fluke 183 is good enough to call a 185, it has all the extra functions including the 30 memory allocations.

While reading around the forum to see what information could be found on these meters I came across member "giosif" who had read the EEPROM from his meter.
Although I hadn't been able to help at the time of his posts:

https://www.eevblog.com/forum/repair/help-calibrate-adjust-a-fluke-185/
https://www.eevblog.com/forum/repair/fluke-185-repair-attempt-_uncal_-startup-message/

A couple of PM's later I had his copy of the EEPROM and he had mine. I was hoping that I'd be able to spot the difference in the dumps between the two models.
Giosif beat me to it, trying my dump in his un-calibrated meter worked well and shut it up about being "uncal", but it was now more a 183 than 185. Anyway he spotted the difference quickly: Memory location h600 contains h01 for the 183/TX1 meters or h02 for the 185/TX3 meters. (I'd bet that all this can be changed in factory mode over I.R., unfortunately nobody knows how to get to it...)
Changing this on mine turned it into a 185 model -not quite- of course Amps position was now displaying a temperature.
Next rerouted the Temp. and Amp. switch positions and cut a chunk off the rotation limit.

[n3mmr]

The OP says:

Calibration manual: http://www.transmille.net/ProCal/Procedure%20Library/Fluke%20Digital%20Multimeter%20185%20%5b1.10%5d/Technical%20Data/Fluke%20183-185%20(PN%201610436%20Rev%201%206-02)%20Calibration%20Manual.pdf

However, that link fails.

Has anyone got a copy to share, or an up-to-date link?

(I've got a Tektronix TX3, which is exactly the 185, and it's time to recalibrate..)

[shakalnokturn]

Here's the calibration manual however it doesn't give much useful information for adjustment other than reference to the "MET/CAL-PROC/0008" (Fluke PN: 1620265).

[n3mmr]

Here's the calibration manual however it doesn't give much useful information for adjustment other than reference to the "MET/CAL-PROC/0008" (Fluke PN: 1620265).

Well.
Not very useful, I agree.

I'll have to try looking at the eeprom contents, unless the "calibration comments" returned over the IR port provides some clue.

[DK ekectro]

 with modifying this dump file, the problem is that I can't change the label h01 to h02 ... I've tried several programming applications but I miss the last three column to display the address, so at the top of the program I only have; 0123456789ABCDEF columns, but I'm still missing these next three columns; 012, where in the end is the data needed for the modification ... Can anyone help with this problem ...? Thank you!