Escort EDM-3150

[l3VGV]

I got one broken before new year, and had fun fixing it. Since there is no service manual available, i spent some time drawing schematic. Its only part of analog board, but most important one!

Full kicad project and images on github
https://github.com/l3VGV/edm-3150

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Specs from http://bbs.38hot.net

EDM-3150 Digit Dual Display Bench DMM
200`000/20`000/2`000 count selectable
Multi-display, dual digit plus analog bargraph
0.01% basic DCV accuracy
DCV,ACV,DCA,ACA, frequency, capacitance, temperature, diode continuity
True RMS AC voltage, 20Hz-100kHz measurement bandwidth
AC current measurement bandwidth from 20Hz to 10kHz
Frequency measurements up to 1MHz, 0.01Hz resolution
Resistance measurement up to 200MΩ, 1mΩ resolution
True RMS(AC, AC+DC)
Direct dBm readout
Relative calculation
Dynamic recording(MIN/MAX/AVG)
Measurement rate selectable(5 1/2 - 2.5/sec, 4 1/2 - 15/sec, 3 1/2 - 80/sec in DCV function)
Backlit LCD display
Auto or Manual, comparator calculation
HI/LO/PASS direct readout
Fast electronic calibration
Peak hold(positive negative)
Data hold
RS232 interface
GPIB(IEEE-488) interface

List of SCPI commands same as for ESCORT 3136A it seems. Most of them worked fine, tested with ar488 GPIB-USB converter and putty.


This thing have LM299 as main VRef and LM399 for resistance measurements current source. How cool is that!
No 4W though.

But, can do capacitance. And, it have to be connected to A and mA terminals  what were they thinking...

Screen is pleasant too look at. Continuity is fast and loud, but not annoying.

Good device imo.

[Kleinstein]

The circuit with a 2nd LM399 ref. for the ohms current source is odd -  quite complicated and expensive way to add more noise and drift.

[Mickle T.]

I know about a dozen benchtop multimeters with a second voltage reference for ohms measurement.