Products > Test Equipment
New project: Fluke 8840A/8842A continuity buzzer
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bikeNomad:
I've designed a board for adding a continuity buzzer to these wonderful old meters.

I'm having 5 made by JLCPCB, and should have them in hand by the last week of February.

Kicad design files and MicroPython code (untested) are here: https://github.com/bikeNomad/fluke_884x_continuity_buzzer.

The board uses an RP2040 microcontroller to watch the signals going to (and from) the display/keyboard module. It plugs in to the 16-pin DIP connectors on the display board, and the ribbon cables from the meter's main board plug into my board.

The next version may add a USB isolator and the ability to fake keypresses; this would allow for USB SCPI control of the meter (the USB port on the board is only for programming presently).

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Kleinstein:
Given the effort for the ciruit, why not a completely separate contuity buzzer with just the buzzer, no ADC or display.
bikeNomad:
I designed this because I have several of these meters, and the one complaint I have about them is the lack of a continuity buzzer. Since I have one living at my bench easily at hand, this will keep me from grabbing my portable multimeter (and waiting for it to start up). These meters have a very fast reading rate on the ohms range.
Chris56000:
. .  .That's even more reason to :–

a) . . .spend my strictly rationed pocket–money on an '8840/8842 – I've bought a Display Replacement Kit!) ;

b) . . .add yet another chapter to my already gigantic T & M Theory and Repair Book!!

Chris Williams
bikeNomad:
Well, I got the boards early, and then discovered that I'd made them too tall and they wouldn't fit. |O
But after having pulled a meter apart, I can at least test the board and my code before ordering new (shorter) ones.
I am a bit sad about having to get rid of the really nice routing of my first board. I had the autorouter re-do those traces so it is no longer as beautiful.
Perhaps on the next spin I will add 3.3V->5V level converter/buffers so I can also fake keypresses.
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