Uploaded November 2023 | Updated September 2026, 1 week ago

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In this video documentary, I present the vintage Heathkit IM-102 digital multimeter, their first model of the type, dating from 1972. It is a clone of the Weston model 1240 digital multimeter, and this video includes comparative information between the two models.

Thanks to Brent Hilpert of madrona.ca for his generous permission to use his photographs of a Weston 1240 multimeter in this video.

I have added several IM-102 resources to my fileshare webpage:
serpentwebsite.com/fileshare.htm
including newly drawn annotated schematics, calibration instructions, a circuit theory write-up, more information on the A/D converter, a PDF of the front panel label I recreated, and an STL of my 3D printed light shield.

I have also added to the fileshare webpage a newly drawn annotated schematic set for the Weston/Schlumberger 1240 digital multimeter, which is mentioned in this video.

Table of contents:
00:00 History
12:38 Restoration
21:47 Overview (external & internal)
33:02 Demonstration
41:22 Beauty shot
41:47 Heathkit manual
53:18 Weston 1240 manual (overview)
59:48 Circuit theory of operation (lots of detail, almost 2 hours of it)
2:52:43 Making a 3D printed light shield for the IM-102

Keywords:
Heathkit, Weston, IM-102, 1240, multimeter, digital multimeter, Nixie tube