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Original Fluke 87 Calibration...

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Smokey:
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 necessary
2) Set AC Volts at 3.513VAC 50Hz, make adjustment if necessary
3) Set AC Volts at 100.0VAC 20kHz, make adjustment if necessary
4) Set AC Volts at 3.500VAC 10kHz, make adjustment if necessary
5) Set AC Volts at 35.00VAC 10kHz, make adjustment if necessary

That'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.

leppie:
Wow that is minimal, the PDF is just a blank page!  ^-^

retiredcaps:

--- Quote from: Smokey on March 12, 2015, 05:17:49 am ---I inherited an original Fluke 87 that "didn't work".  Turns out the 9V battery connector had a broken wire.  Easy fix.

--- End quote ---
I 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.  :palm:


--- Quote ---Unfortunately it's pretty far out of cal.
--- End quote ---
Can 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.


--- Quote ---The manual page is attached.
--- End quote ---
Your attachment is blank.


--- Quote ---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?

--- End quote ---
The 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.

Vgkid:
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.

Smokey:
The attachment isn't blank.. It's invisible ink.  Hold it up to a fire and it shows up :)

Here is a link to the full manual.
http://assets.fluke.com/manuals/83_85_87smeng0500.pdf

Check 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 :)

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