Tektronix DMM912 Teardown

Tektronix DMM912 MultimeterTektronix may be known best for their industry-leading oscilloscopes, but they also sell other test equipment, including a line of handheld multimeters in the 1990s.

The model documented here is a DMM912, part of a series of multimeters that included the 912, 914, and 916.  All are RMS-responding, 4000/40,000-count models with a number of premium features like min/max/average, auto-hold, peak-hold, AC+DC, lead warning, and memory storage.  The display updates 4/sec in 4000-count mode or 1/sec in 40,000-count mode.  Accuracy and bandwidth increases with each model; this 912 is rated at 0.2% basic DC accuracy and a bandwidth of 1kHz.  The 914 and 916 make use of a secondary numeric display for simultaneous ACV and Hz readings, the 912 does not.

This unit arrives in good functional condition, needing no repairs other than a fresh 9V battery and a general cleaning.  The LCD lens has some spots that cannot be removed, but fortunately they do not obscure the display too much, despite the fact that the contrast is a bit on the low side.  Let’s take a look at how it’s made!

 

DMMCheck calibration check results for this Tek DMM912 [in 40,000-count mode]:

Reference Reading Notes
DC 5V 5.000
1mA 1000.5 (μA)
AC 5V 5.004
1mA 1006.7 (μA)
Ohms 100Ω 99.74 REL feature used
1K 0.9999
10K 10.003
100K 100.01

Update: It was speculated in the comments below that this meter was made by Brymen, but evidence is a little stronger that it may instead be manufactured by APPA Technology, another Taiwanese company.  The internals (switch, buttons, etc.) bear an uncanny resemblance to the APPA 100-series multimeters.  See this teardown of an Iso-Tech 105 as an example.

About modemhead

Fixologist and multimeter junkie.
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5 Responses to Tektronix DMM912 Teardown

  1. Harvey says:

    Ive never seen a meter like that before, as you stated we all knew tektronics for oscilloscopes and other test gear.

    From the pictures it looks every bit as complex as a fluke, but built around a known
    autorange tc8129 multimeter adc, so easyer to replace if it goes poof 🙂

    Not sure why they didnt use the complimentry tc8131 serial display driver i.c,
    perhaps it was too simple a device.

    The only downside is it wasnt broken lol 🙂

    Well worth keeping, great writeup and cracking pictures 🙂

    • modemhead says:

      It has been pointed out to me that there are some superficial clues this meter may have been manufactured by the Taiwanese Brymen Technology Corp. for Tektronix. I didn’t find any markings to actually prove it though. If you look at some teardown photos of older Brymen stuff you will probably see some resemblance.

      It seems more complex than a Fluke of the same era to me, probably because it has more bells and whistles. Maybe the extra features are why they needed the NEC chip instead of the TC8131. Fluke seems to put more functionality in their custom silicon, ending up with less supporting parts on the board.

  2. Harvey says:

    Yep the brymen bm830 series looks the same pattern, case wise.

    So tektronix cheated and got bryman to produce there multimeter.

    Its still a cracking good meter, and has a place in the wheelbarrow of excellence 🙂

    • modemhead says:

      If it is Brymen, I don’t think it’s a straight re-badging, more like made to spec. Looking at the Extech MM570A, there is a general similarity in the keypad, the peculiar slant of the power resistors, the rotary switch sandwiched between two boards, etc.

      My wheelbarrow runneth over, so this one will be passed on to a fellow multimeter enthusiast…

  3. repollo says:

    Does anyone know where to find the input jack connectors? I need the positive input banana jack connector.

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