Fluke 185 Review

[Wytnucls]

I recently bought for less than 150 USD, a rare second-hand Fluke 185 DMM, which was first released in 2000, as part of the 180 family, which included the 187 and 189. The lesser Fluke 183 was also available, but came without temperature and 4~20mA loop measurement and with less memory and accuracy. In those days, the 185 wasn’t cheap, selling for about 450 USD in the UK. As you can see, the meter I bought on eBay is in pristine condition.



The meters had originally been developed and produced by Tektronix as the TX3 and TX1 multimeters.
It isn’t clear, to me at least, why Fluke decided to include Tektronix meters in their line-up. Strangely, some old Fluke ads I found, mentioned that the meters were only available in the European market.
The Fluke 185 was sold with a set of TL75 leads, alligator clips and a user manual. It was identical to the Tektronix model, apart from a different rubber boot and an 11A rated fuse instead of 15A on the TX3.
Mine was sold without the test leads and also without the bail, which went AWOL a long time ago. I think that the original meter came with a small rubber insert to secure the serial cable to the top of the meter. That’s also gone missing.
While I have your attention, if anyone knows of 185 spare parts anywhere, I would be keen to acquire the ones missing on my meter, especially the original bail.




1.   Ergonomics:
The meter is unusual, as some of the range selections are made through the top F1 to F4 keys, with the relevant labels appearing on the large LCD screen. It also has a single jack for current measurement and a single position on the range switch, while retaining the usual uA, mA and A ranges. The automatic or manual switching between the current ranges (10A~500uA) is seamless, with no interruption of the circuit under test, as happens with conventional multimeters.
I found the 7 position range switch a little stiff, but the strong spring action makes intermediate positions near impossible.
Although the meter comes with a good protective rubber boot, the large LCD screen will most likely get damaged in a fall, if it comes in contact with a sharp object.
The bail has an extra position, where it tilts to 90 degrees, allowing a sliding rubber insert to provide a secure grip on a ledge, for hands-free measurements. Normal bail position reclines the meter to a 45 degree angle.
The cover for the 2 AA batteries unclips very easily, making battery replacement in the field, a cinch.
It is not a small or light meter at 200x100x50 mm and 540gr with the holster on.



2.   Features:
The true RMS (AC+DC) meter comes with the usual DMM features, plus 4-20mA process loop measurements with % readout, dB/dBm, Auto Hold, Min-Max, Peak Hold and enough memory for 30 readings with time stamps. Values can be recalled and read on the screen.
Two IR LEDs are used for serial PC logging and calibration.
The continuity test is lightning fast and latched (<1ms, 1.25V open voltage and 250uA). Why can’t all meters be like that?
For frequency measurement, the Fluke 185 is always AC coupled, unless the duty cycle mode (+ or - option) is activated. It then becomes DC coupled on all relevant ranges. Like the Fluke 87V, triggering can be changed from rising to falling edge, which may help with an unstable waveform.
Remaining battery voltage can be displayed and warning messages appear for a ruptured fuse or test lead placement when the selector leaves the amp range.
Soft green LEDs light up the screen on request with an adjustable timer to save batteries. The timer can be disabled, providing continuous lighting, when necessary.





A K-type probe is required for temperature measurement, with the possibility of ice bath calibration for better accuracy, with the offset amount retained in memory. Ambient temperature is displayed in the secondary window at the same time as probe temperature.
The meter, like the Fluke 289, has an unusual 50 Ohm range, where it prompts the user to short the test leads for automatic zeroing and then increases the test open voltage to 1.2V instead of 300mV, presumably for better accuracy.
I couldn't see much difference in accuracy between the two resistance measuring modes.



Measuring a resistor of 5.615 Ohms (4W value), gave me fluctuations between 5.58 and 5.62 Ohms in both modes, giving the meter 5 minutes to settle down.
 
Some screenshots of the Min/Max and Fast Min/Max in operation for a 4Vpp sine wave:
Max, Min and Avg show the RMS value of 1.414V. Max-Min shows the small difference between Max and Min. (1-4 samples per second)



Fast Max shows the upper limit of the sine wave (2V), Fast Min shows the lower limit of the sine wave (-2V) and Max-Min shows the Vpp value of 4V (1 sample per mS). That information also allows you to calculate the crest factor (Vpp/RMS) to see if your measurement is within the meter's accuracy statement (Max crest factor 3~6).



The diode test is pretty useful, the meter being able to light up white (80uA), green (210uA), yellow (210uA) and red (210uA) LEDs and also display the voltage drop for each of them. I haven't tried a blue LED yet. Open voltage is 3.3V. Standard diode like 1N4002 has a test current of 480uA.



3.      Safety:
The meter is rated for CAT III/1000V CAT IV/600V with the usual Fluke safety standards and independent testing. The protection consists of 1 PTC, 2 spark gaps, 1 fusible resistor and one 11 amp 1000V HRC fuse, catering for all ranges.

4.   Accuracy:
The meter can be set up to be used with a fast 5,000 count or a slower 50,000 high resolution mode, with a DC accuracy of 0.05%+1 (+10 in HiRes mode). The last closed-case calibration date is retained in memory.
My meter was never calibrated and has the original software version. After some comparison tests, I have established that for the most part, it has remained within the published one-year tolerance.
True RMS bandwidth is a respectable 20kHz for voltage and 5kHz for current, with a crest factor between 3 and 6.





Capacitance resolution is 1pF and the highest range is 50mF. A 5mF capacitor takes about 8 seconds for a reading (5,000 count only).



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

5.   Construction:
Two self-tapper screws hold the two halves of the meter together, with the help of two locking tabs at the top of the meter.
The batteries are held in a separate compartment which clips on the main body of the meter.
The double-sided PCB is held in place by 2 self-tapper screws in the middle of the board and a few clips at the top.
The circuit design doesn’t need a mA fuse, as any overcurrent is automatically routed to the beefiest MOSFETs and the 11A fuse. My board has the Fluke reference on the silkscreen, including the revision number 003, with 007 hand-written underneath it.
Less elegant are the 3V battery leads snaking haphazardly to the 3V and 5V DC to DC converters, on the top half of the PCB.
The band-gap voltage reference is a 1.2V Maxim ICL8069BCSA with 1ppm/1000hr long term stability and a max tempco of 25ppm/C.
Strangely, a loose pogo stick is used to make contact with the shielding plate in the bottom half of the meter case.



The major PCB components are:
3 microcontrollers
2 power MOSFETs IR L2203NS (HEXFET)
2 PhotoMOS relays

3 Dale Vishay current shunts (50, 0.5 and 0,005 Ohms)
1 NAiS relay
1 EEPROM
2 crystal oscillators
DC to DC converters for 3V and 5V
2 IR diodes
1 Maxim band-gap voltage reference 1.2V ICL8069BCSA (1ppm/1000hr 25ppm/C)





6.   Operation:
I like the logical layout of the function keys, which makes the meter very user-friendly, especially if it is used infrequently.
One only has to remember to push the yellow button for 2 seconds, to access the menu and most of the available settings.
Unusually, the burden voltage is very low on the 500 uA range, as the current shunt is a meager 50 Ohms (50uV/uA on the 500uA scale, equal to half the burden voltage of the Fluke 87V or Fluke 189, which is pretty good already) .
The ‘Auto Hold’ takes a reading with a beep after approximately 1 second of probe contact.
The bar graph has 20 segments with 20 updates per second.
The small 30 readings memory size seems weird by today’s standards, but still useful if one doesn’t have the dedicated serial PC logging cable. Data can only be saved manually in memory, by pressing the STO key repeatedly. The meter is compatible with the FlukeView Forms software (version 1.6 or higher). Both software and special cable are still available from Fluke (FVF-SC2).

Fluke 185 manual: https://www.eevblog.com/forum/testgear/fluke-185-review/?action=dlattach;attach=127443



Keep in mind that the update speed is slow in HiRes mode, at one update per second, instead of four. Also remember to discharge caps before measurement to avoid any damage.
The screen green lighting is average at best, but does the job and what I like the most is that it can be kept on at will for lengthy measurements in dark places.
Here are screen shots of the AC, AC+DC, dB and dBm displays for a test 2Vpp sine wave with a 1V offset, to highlight  easiness of operation.
True RMS AC is 0.707V
True RMS AC+DC is 1.22V (SQRT(0.707^2+1^2))
-3dB [20 log V/Vref(1V)]
-0.79dBm [10 log 10^3 x V^2/Rref (Rref=600Ohm audio standard and 1mW reference)]
The dB 1V reference can be modified in the menu and the new value retained until the meter is switched off.



Frequency measurement is good up to 1MHz. Duty cycle can be toggled between positive or negative percentage in the menu and is displayed at the same time as the frequency on the screen. The meter also gives you a choice of triggering either on the upslope or downslope of the waveform.

7.   Final Assessment:
To conclude, I think that the most attractive features of this meter apart from the low price, are the fast continuity test, the continuous amp range, the low burden voltage and diode test current.
Features that let it down a little are the small memory size, the cumbersome access to the 11A fuse, the slow screen update rate in HiRes mode and the lack of a cap discharge circuit.
Still, it is my favorite meter at the moment, just for the simplicity of its user interface, the sophistication of measurements and the legendary USA made Fluke quality, even if the meter was conceived by Tektronix.

[Wytnucls]

More pictures

[Wytnucls]

Here is the back of the meter listing quick access to some features on start up and the service manual for the TX3, also valid for the Fluke 185:

[retiredcaps]

Great writeup and teardown photos. 

I have always wanted one of these.  I love the bigger digits and AA batteries 

Two things that would "bother" me are that it defaults to ACV (I think) and the slow higher resolution update speed.

Mark Z, a member here, has done youtube videos on the Tek TX3

[cs.dk]

4-20mA process loop measurements with % readout

Nice review.
Sorry to interrupt your thread, but whats the 4-20 mA used for? My Brymen 869 has the same scale and % readout.

[Wytnucls]

Read these articles about 4~20mA current loop technology:
http://en.wikipedia.org/wiki/Current_loop
http://www.murata-ps.com/data/meters/dms-an20.pdf

10mA reads as 37.5% with 4mA as 0% and 20mA as 100%

[Lightages]

I am sure that if the 185 was still available today that it would sell. Thanks for the review.

[tautech]

Nice review. 

The continuity test is lightning fast and latched (<1ms). Why can’t all meters be like that?

How does this measure up against the parameters required in this thread?
https://www.eevblog.com/forum/testgear/multimeter-with-low-continuity-test-voltage/msg475506/#msg475506

[Wytnucls]

Pretty good at 1.25V open voltage and 250uA.

[BillyD]

Ergonomically that's a great looking meter. Bet I wasn't the only one to go and do an Ebay search after seeing this thread - and of course all it brings up is a rash of those bloody VC97s!

[Wytnucls]

Yes, they are as rare as hen's teeth. I haven't seen any on international eBay for the past 3 months. TX3s might be easier to get, but most of those I saw were in a sorry state.

RS did sell them in the UK:
http://uk.rs-online.com/web/p/digital-multimeters/4070772/

http://docs-europe.electrocomponents.com/webdocs/0082/0900766b80082638.pdf

codeboy2K has a TX3:

[Wytnucls]

The meter, like the Fluke 289, has an unusual 50 Ohm range, where it prompts the user to short the test leads for automatic zeroing and then increases the test open voltage to 1.2V instead of 300mV, presumably for better accuracy.
I couldn't see much difference in accuracy between the two resistance measuring modes.

Measuring a resistor of 5.615 Ohms (4W value), gave me fluctuations between 5.58 and 5.62 Ohms in both modes, giving the meter 5 minutes to settle down.

[helius]

Having Tek choose them as a manufacturing partner could have been a PR coup, being a "prestige" brand.
By comparison most of Tek's other "DMM" branded meters are made by APPA in Taiwan.

[codeboy2k]

codeboy2K has a TX3:

It's a great meter ! I love the fact that it has a single Amps input jack. By the way, that PC board is an exact duplicate of mine. 

I bought mine back in the late 90's I think, at Fry's Electronics in Palo Alto, back when I lived there.

Original cal date on the certificate is Oct-29-1998.

I have always wanted one of these.  I love the bigger digits and AA batteries 

Two things that would "bother" me are that it defaults to ACV (I think) and the slow higher resolution update speed.

I love the AA batteries too, and I use Sanyo Enerloops in my meter. Yes, it annoys me that it defaults to ACV, as I almost never use it.  I suppose that an electrician might want that, but everything I do is DC. The meter speed on hi-res mode is not that bad, but perhaps I'm used to it now. Usually by the time I place the probes and look at the meter, it's done already.

[Wytnucls]

Common A/mA jack is the way to go, assuming it doesn't affect safety and accuracy. Gossen has seen the light and all their modern meters have the feature. Fluke seems to be ambivalent about it, with the more recent meters having 3 jacks only, like the 233 and 117.

[Wytnucls]

Slow update speed on the Hires range is not really an issue, since the last digit would be unreadable anyway. Fall back on the 5,000 count and the 4 updates per second for fast changing voltages or currents, Fast Min/Max capture or the 20 updates per second bargraph.

[Wytnucls]

Great writeup and teardown photos. 

I have always wanted one of these.  I love the bigger digits and AA batteries 

Two things that would "bother" me are that it defaults to ACV (I think) and the slow higher resolution update speed.

It does default to AC Volt, but all is not lost, as fortunately, it defaults to DC on the A range, unlike the Fluke 87V.

[Wytnucls]

I am sure that if the 185 was still available today that it would sell. Thanks for the review.

I'm with you on this one. The more I use it, the more I feel it is close to the ideal meter. It would need some modern updates, like a larger internal memory with adjustable logging interval, brighter backlight and a tightening of the accuracy.
Some may also want a few extra features like 'Pass/Fail', LoZ and VFD.

[Handyman32]

I still have the original Tektronix TX3.
It was my perfect DMM until the paint began to peel off and the screen became foggy.
It is also out of calibration. The holster, knob and test leads are still in perfect condition though.
Those problems are not often encountered by Fluke DMMs.
It also has the most brilliant holster and stand design to be found on any handheld multimeter.
Compared to newer models available, it looks like a bit outdated.

[Wytnucls]

I ran a calibration as per Fluke's procedures, using the best tools I have. Seems to be mostly within specs, even after all those years.
Fluke uses good plastics for their enclosures. My meter looks like new still and the screen is flawless.
Here are the results:

[cluca1969]

Hi Wytnucls,
Today I bought a second-hand Fluke 185 he looks almost new considering his age.
I could use some advice from you like:
- how to test accuracy.
- how to do to see what firmware has, and if it has been calibrated in factory.

I paid for it 250 euro w/o leads. Initially wanted a Tektronix TX3 (hard to find and more bucks for me + paint that cleans). Second option was a Brymen 867s but I had a hesitation when i see a review with many differences (accuracy) between same model BM867s. I still have a Uni-t UT70B, pretty good price and performance.
*The photos has been made of first and second (re)seller.
With special consideration,
Lucian Cernega.

[Wytnucls]

For accuracy test, you will need to buy a voltage reference.
Power up with F1 depressed will show last calibration (month and year) and firmware.
(1.01 and 9977/77 on mine, which doesn't make much sense)

[cluca1969]

Thank you very much for information Wytnucls. Which reference voltage do you have ?

[Noise Floor]

Wonderful review, thank you.  I have had a 185 for about 8 years, still like it a lot.

[cluca1969]

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.

[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!

[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!

[shakalnokturn]

 :)All Hex editors won't have the same number of columns, it's just a question of display layout.
Look for address location Hex:600 no matter how many columns there are in your editor, if you're really as bad as I am for looking through hex files count back from an easily identifiable position such as start of serial number.
While you're at it could you please upload a copy of your original EEPROM contents if available? It could help understanding organisation for people in need of manual readjustment.

Edit: I figured you were using my memory dump anyway so if you really can't do the job with your hex editor, I can send you the modified file.

[shakalnokturn]

I have just received a Tektronix TX3 with a lowish serial number (<2000), F.W. version 0.0716. Funny thing about it is the back label is factory marked "DEMO NOT FOR SALE" above the serial.

Any other TX1 or TX3 owners noticed this?

[shakalnokturn]

My two meters side by side comparing the modified Fluke 183's uncalibrated temperature readings to the long ago factory calibrated TX3's.

Note that the meters do have some differences, I prefer the plastics used and keyboard colours on the Fluke. The LCD is better on the Tek though.

I also noticed in the Tek that other than the spring contact there is a pogo-pin contact to the back shield near the relay, the pin is free to drop out and be lost (at the worse left floating in the DMM). I lightly squashed the end of the barrel on mine to hold it captive. As I remember it was already missing on the 183 leaving me puzzled to the purpose of the part at the time I opened it.

[DK ekectro]

Hello everyone! First, I would like to very much thank the shakalnocturn member for the detailed description and presentation of everything he has done so far regarding this work on the TX1/TX3 measuring instrument. I believe that, like me, it helped everyone a lot. I bought a used TX1 but in very bad shape and with a UNCAL problem. Thanks to a member  shakalnocturn I made a complete modification to make the TX3 officially now... Everything works great except that there are deviations in some measurements, for example 80mV-100mV difference in AC and DC in all rankings, other measuring areas are not quite accurate either. Maybe someone has a very original dump file of TX3 so let me try it with him because the one that is currently in it is from Fluke 185. who knows...? I can live with that but after so much effort to paint the case again, polish the plastic of the screen, print the markings( it's not all over yet), I'd be sorry if some other instrument that was paid $20 in a supermarket showed more accurately than it...!

[shakalnokturn]

Wow! Nice job on restoring the plastics!

When I get round to it I'll dump the EEPROM from my TX3 and post it here.

It isn't really a TX3 dump you need, no matter the dump you may be better or worse off than now. Your voltage measurements could be closer if you're lucky but you could also end up worse off on other functions.

The correct way to do things would be going through the software assisted adjustment procedure.
I'm pretty confident there are a couple of people around that know the procedure and have the software, I tried asking on Tektronix@groups.io without much luck.

The more painful option is identifying memory locations in EEPROM for each adjustment and tweaking them by trial and error until gathering enough understanding of gain and offset.

[DK ekectro]

Thank you. I had no problem removing the old paint with an IPA and a soft cloth. I have a friend who prints various pictures on T-shirts, lighters and other items, so he made the print that can be seen in the picture, because of the equipment he has it was difficult to make a print at the area between keys and the rotary switch, so we will do it with stickers...I don't know why but I just love this instrument, it's simple and yet it has all the functions I need in working with electronics. And I believe that there are people who know the calibration process or even who could share information about which items in the eeprom file should and how they should be changed for certain measuring areas... It would be a shame if such old classics became useless...

[shakalnokturn]

Finally found a good enough excuse to drag the TX3 out and dump the 25LC160 contents.
Still looking for the calibration commands over infrared. Anyone?

[jchw4]

I took some high resolution photos of my Tektronix TX3 PCB.
These are aligned, you can overlay them and do some tracing.

Components side.

[jchw4]

I took some high resolution photos of my Tektronix TX3 PCB.
These are aligned, you can overlay them and do some tracing.

Sockets side.

[jchw4]

A few close up photos of nice resistors.

[jchw4]

A few close up photos of nice resistors.

[jchw4]

A few close up photos of nice resistors.

[ErnestB]

Hallo, I have read this post and am curious if there is any progress on the calibration procedure of the Fluke 185 / Tek. TX3? I got one 185 in physical good condition, but with UNCAL massage after the power-on. It was used in my company (by me for several years), but several years ago it came back from the calibration service with a vague massage that it couldn't be calibrated or something similar my company wrote it off, and it could end up in a "dumpster".  The meter is still working quite good, but I am not sure which ranges of functions are actually off, and by how much. And of course, there is the UNCAL massage at the power up every time. Anyway, it would be interested to find out how does that calibration procedure actually works. As already stated above, the Service Manual is very clear about it: if you want to calibrate it send it to us, there is no other way. The thing is of course, these meters economic value at this moment would be much lower then the cost of the official calibration. So, if I can help in any way with mine 185 let me know. I am not such a hacker (yet) though as you guys but with some guidance maybe I could contribute something. We would need calibration procedure description, including function-key-combination and the proper set of commands needed, with some cal voltage references. Greetings from Holland.

[bdunham7]

the Service Manual is very clear about it: if you want to calibrate it send it to us, there is no other way.

The calibration manual specifies the exact procedure, unfortunately it appears to be done through the IR port and with MetCal software only.  It certainly doesn't need to go back to Fluke, there are many calibration facilities  that have these tools.

https://www.industrialcalibration.co.uk/downloads/Fluke%20183-185%20(PN%201610436%20Rev%201%206-02)%20Calibration%20Manual.pdf

[ErnestB]

Thank you for responding and posting the document. I have read this Cal manual and the part regarding the Calibration Adjustment is very short and does not describe anything specific:
"The Fluke 183 and 185 require adjustment only when they fail the performance tests or have been repaired. Software adjustment is performed through the meter’s IR port using a semi-automated Fluke Met/Cal procedure and Fluke 5520A. The meters have no physical adjustments and cannot be manually adjusted".
I have seen what Fluke 5520A costs    30-40k And maybe/suppose other "calibration facilities" still could do the calibration on this discontinued model, the expected price would be above the economical value, so that would not be an option I suppose...
Maybe/probably the software "talks" to 185/TX3 as well with the 5520A during this semi-automated Fluke Met/Cal procedure, and change the settings on 5520A accordingly, ingaging various voltages and currents on it's output during the procedure.

[ErnestB]

There is MET/CAL software Reference manual document 1252 pages long: http://download.caltech.se/download/fluke/metcal/metro_meeting/ReferenceManualV71.pdf

[bdunham7]

I think the manual is specific enough, it just doesn't seem substantial because there isn't much to it.  You connect the meter and the 5520A to your PC and run the MetCal procedure.  It prompts you to select a certain range, then it tells the 5520A to output a specific stimulus and then after the reading stabilizes it it tells the 185 to store a new calibration constant for that particular range and reading.  Rinse and repeat until done.

I wouldn't assume the calibration is more than the value of the meter without a quote.  I think maybe here in the US the price might be $80 or so?  If the meter isn't worth that, then nobody really cares.  What I would worry about is that calibration might not work--it might have some fault that prevents the process from completing or storing the constants.  Then you'd be out the calibration cost and still have no meter.

If you could reverse engineer the MetCal commands, perhaps you could come up with some alternative.  However, I think you'd need a complete working setup and meter to do that and their really aren't too many of those about.

[ErnestB]

Good point: "Then you'd be out the calibration cost and still have no meter". So yeah.. I don't know. There has to be a (valid) reason, I suppose, that the calibration facility couldn't calibrate this meter anymore in the first place. Maybe the eeprom (or some sections) is damaged in some way.. But the meter seems to works fine, so far I have seen, but of course I have not checked every range and every function to abs values and tolerances.

[ErnestB]

...and of course there could be various reasons (beside the eeprom) why this 185 have not "made through" the official CAL. I will try to check myself so far I can on different ranges and functions to see how far off the stated accuracy actually it is at this moment, and then make a conclusion.

[ErnestB]

I know, long shot, but would somebody maybe know what value and type the 2 capacitors C99 and C100 are?
I suspect these throwing off my ACV reading. Thanx in advance.
Edit: I measure (in circuit) about 45pF each.

[shakalnokturn]

I don't know if he values but the values you have measured seem consistent with placement in circuit and ceramic colour.

They're there for frequency compensation on the higher frequencies. Unless they've both gone resistive there's little chance they'll be causing measurement error at 100Hz.

I'd be more suspicious of the opto-isolated analog switches if anything.

[ErnestB]

Hi, thanks for the answer and valuable insight. What I have found when doing some tests today is that the measured value strongly decay with frequency. I did the test on about 100, 1kHz, 10kHz en 20kHz. Fron 1kHz to 10kHz bigger jump down. Within this freq. range the decay was about 7.5% on both 0.5V and 5V range (0.4V and 4Vrms sinus used). First I was thinking that the main coupling capacitor ESR was high, but when I shorted that C I have not seen much difference. Than I was thinking about those capacitors parallel to every "range resistor" (1k, 10k, 100k and 1M). But because both 0.5V and 5V range behaving almost the same that was less obvious. So I have de-soldered those 2 AC compensating capacitors and have experimented with some regular through hole ceramic capacitors instead. Some values made it more freq. depended. At the end used 2x 10p and I have to say I do not have a very good capacitor meter for lower values, so the original one's could also be about 10p.
So maybe you know more about the capacitors used in this meter, as you said regarding the color? Are those MLCC? As I see the compensation is very critical. I could imagine that if the capacitor would have some ESR, also freq. dependable then it can throw off the whole AC measurement. Maybe for that 10k could use adjustable resistor to try to adjust the values...

[helius]

The ceramic compensating capacitors are in a measurement circuit, so they are going to be C0G (NP0) caps. The color of this material is typically gray. When people talk about "MLCC" they are usually referring to barium titanate based dielectrics which are more beige or brown in color. Those Class II dielectrics are not very stable and not suitable imho. (See the recent thread on "MLCC X5R Capacitor Degradation")

[ErnestB]

Thanks. These capacitors are not beige indeed, more gray. Indeed NPO capacitors would be necessary here. But I have to figure out the values, as I think those are responsible for the AC measurement being out of specs. Frequency response of this 4 component network have to be as flat as possible between 40Hz and 20KHz, and they probably calibrate the last part (offset) in the firmware. I can not do that, but I could place a small Pot. instead of that 10k resistor to tweak the last part.. But I suppose it will not be easy, as the input and output impedance plays the role...
Edit: hmm, and what am I compensating for anyway :-) so this is a very specific case high pass filter, that works in conjunction with the rest of the measuring circuit. And you have different ranges too....

[shakalnokturn]

How much of a full performance check have you made? Enough to see that ACV measurements are no good, anything else?
In your situation I'd start by swapping the suspicious EEPROM for a copy of one of the dumps provided here, at least with that you should be able to find out if the ACV being wrong is due to a lost calibration or hardware fault.

[ErnestB]

Hi. Thanks for replying. The DCV is within the +/-0.05% compared to HP3478A. Frequency measurement is correct. I will check the resistance mode. I do not think it just "lost" the calibration data from the EEPROM, but I don't rule out anything yet. The meter was several years in the annual calibration program and one year they couldn't calibrated it anymore (they don't gave the specifics about the fail). That's why the meter ended up as a hobby project. I have ordered the meter and was only used by me all the time. Regarding the AC voltage being out of the specifications I see a clear strong frequency dependant behavior so first I suspect one of the capacitors, or a RC combination. Resistors being more stable over the time and could easily being measured, and even have clear value marking on it. As the capacitors doesn't makes it more difficult without the parts list. Now I will try different C values to try to understand better what it does. As I can see on the block diagram it should be some kind of high pass filter or better compensation network. But I suspect they did some part of the compensation with hardware and some in the firmware. That would be a bummer as I can not do the calibration. If I put a random cal data in it I do not expect much accuracy, and still can not calibrate the damn thing.

[ErnestB]

Did some testing but still don't know what is causing this systematic AC Voltage reading error. There are a lot compensating capacitors, for every range a few, but I think that chance that all of them are wrong is very low. There must be one main source of error. The main AC couple capacitor C72 is common for all ranges, but if I short circuit that one not much change. Then we have the serial combination of C99 and C100, that are maybe also used for all ranges. These could be the source of common error for all (tested) ranges.

[maxniz]

hi,
i friend gave me an'185 .. it is a bit inaccurate but above all when I measure a voltage it takes 20 seconds for a correct indication. it rises very slowly and stops at the end showing the more or less correct value and this for any measure and on any scale. it makes me think that there is an altered resistance but I have no diagram and no values..can someone help me thanks

[shakalnokturn]

That sounds typical of PCB contamination. Any signs of battery leakage such as deposit or corrosion on the battery terminals?

[maxniz]

no.... it looks new... the battery are  in a separate compartment ..clean compartiment.

[DrMr]

Hi, all,
do hope this thread is still alive, I would like to join conversation on Fluke 183 /185 (TX 1 & 3)!
I am (formaly!) newbee on this site, joined it few days ago!
The reason is problem I have with my Fluke 183!
This istrument I bought as new 20+ years ago, and have been using it for more than 10 years, being very satisfied with it, it was joy using it!
And, then he became partialy defective, and put out of use because new instrument replaced it!
Now, I have found it forgoten on shelf, and decided to try to bring it back to use, if possible!
So much of introduction, let me explain problem:
Instrument measures perfect voltage and current including frequency, but not at all resistance / capacitance, continuity / diode / 50 ohm range!
On these measurements he is just randomly shoving some values, or even behaving as being leads short circuited on diode / continuity / 50 ohm range!
I have measured test voltage on the leads while being on some of these measurments, and it seems there is (almost) no voltage at all, meaning there is no constant current flowing at all, or it is very low!
This to say because sometimes it seems that instrument recognises short circuited leads, for example, when he ask to make short on 50 ohm range, or being on continuity range, showing 0 or some milivolts!
Indicative for this problem is also that he newer shows on these measurements 0L when being at open leads!
Meanwhile I have checked as well photo MOS relays, which by my knowledge have function at these ranges, and they seems to me OK!
At least they are changing output side when input diode is being activated!
My PCB is Fluke 185 - 3001 REV 003  , it seem that difference between 183 and 185 models was mainly in firmware, beside mechanical possition on range switch!
Only strange behavior I have noticed, while testing it by internal tests, is that button MIN / MAX shows value 99 instead 01!
Is it same on other units or is it real fault on my instrument?
I would appreciate any help from you, guys, and would also thank you all for help provided on this forum!

[ErnestB]

Hi. I don't know if you have further worked on your instrument in the meantime and maybe you have solved it? I read that for those measurements the instrument uses current source. Maybe to search in that direction. Time ago I was trying to solve the AC deviation that I have on my Fluke 185. You can see the short explanation about the current source in the photo few comments before this one.