Original Fluke 87 Calibration... - Page 1
Forum section: electronics / testgear

author: Smokey
author_rank: Super Contributor
timestamp: March 12, 2015, 05:17:49 am
content: I inherited an original Fluke 87 that "didn't work". Turns out the 9V battery connector had a broken wire. Easy fix.Unfortunately it's pretty far out of cal. I found the service manual and the 87 cal procedure is surprisingly minimal. The whole procedure is pretty much:1) Set DC volts at 3.500VDC, make adjustment if necessary2) Set AC Volts at 3.513VAC 50Hz, make adjustment if necessary3) Set AC Volts at 100.0VAC 20kHz, make adjustment if necessary4) Set AC Volts at 3.500VAC 10kHz, make adjustment if necessary5) Set AC Volts at 35.00VAC 10kHz, make adjustment if necessaryThat's it. I was surprised there was no current or resistance procedures. The manual page is attached.I don't have a calibration standard, but I do have access to an in-cal 6.5 digit meter, and a voltage source that should be able to do the required voltages and frequencies. Anyone see a problem with adjusting the voltage source using the in-cal meter to the required values and then tweaking the 87 based on that? I'm not expecting lab quality certified cal, and don't plan on using the meter for anything serious. The meter is probably 30 years old. Just wondering if there is some magic to an actual calibrator that I can't recreate with a voltage source and a higher precision meter than what I'm trying to adjust to set the test signal levels.

author: leppie
author_rank: Frequent Contributor
timestamp: March 12, 2015, 05:20:08 am
content: Wow that is minimal, the PDF is just a blank page!

author: retiredcaps
author_rank: Super Contributor
timestamp: March 12, 2015, 05:31:27 am
content: Quote from: Smokey on March 12, 2015, 05:17:49 amI like the easy ones. When trying to repair a 87, I somehow damaged the black wire in the process and will have to resolder it.QuoteCan you give some examples? For example, what does a 1k ohm resistor read? What do you get for a 5V DC?I buy used and abused Flukes and it is rare that they are out of calibration. If this 87 was abused with high voltage, one or more of the input protection components may be damaged resulting with incorrect readings.QuoteYour attachment is blank.QuoteThe above should be fine. Again, I would check the input protection before making any adjustments.The input protection components are the MOVs, thermistor and fusible resistor. These are all shown in the schematic and BOM list. If you don't know how or what the correct reading should be, I can help with that.

author: Vgkid
author_rank: Super Contributor
timestamp: March 12, 2015, 05:36:35 am
content: Most 6.5 digits meters are easily10-20x more accurate than the fluke 87-1.I dont have access to a stable ac source, but my 87-1 agrees to its last digit with my 3456. My 87-1 doesnt have any cal stickers, my 3456 was cal'd in 2011.

author: Smokey
author_rank: Super Contributor
timestamp: March 12, 2015, 05:44:57 am
content: The attachment isn't blank.. It's invisible ink. Hold it up to a fire and it shows upHere is a link to the full manual.http://assets.fluke.com/manuals/83_85_87smeng0500.pdfCheck out this little quirk I accidentally found.If you have the 87 set to mA current mode and let it go to sleep, then hit the yellow backlight button to wake it up it comes up in DCV mode! beeping like crazy

author: Smokey
author_rank: Super Contributor
timestamp: March 12, 2015, 05:48:21 am
content: I just had another thought. The AC voltages they want for cal... are those peak to peak or +/- or rms?

author: Vgkid
author_rank: Super Contributor
timestamp: March 12, 2015, 05:53:12 am
content: Rms, after all it is a true rms meter. Though you could always convert between the two.

author: Smokey
author_rank: Super Contributor
timestamp: March 12, 2015, 04:09:54 pm
content: Good point. RMS it is. There is that interesting cal voltage of 3.513VAC 50Hz that you calibrate to 3.500 on the meter which the manual says has to do with the RMS linearity. I guess don't go measuring low voltage low frequency AC with an original 87.

author: Vgkid
author_rank: Super Contributor
timestamp: March 12, 2015, 04:46:07 pm
content: For that you would have to check into the specs of the trms converter chip.

author: arcitech
author_rank: Regular Contributor
timestamp: October 11, 2022, 02:28:14 pm
content: Quote from: Vgkid on March 12, 2015, 05:53:12 amWhen it comes to the AC voltage they "want for cal" [from the calibrator output], I'm guessing the calibrators of that era (I've touched, and have knowledge of, exactly zero calibrators) only had P:P set points. But of course, yes, the AC voltage they "want for cal" to be output on the meter is RMS.This confused me a smidge so I'm just plopping this in for others who stumble across it in their search quests to tweak pots with bolstered confidence, despite lack of gray beard/virginity/lingual protractor.