Overview

Do you have an old, cheap multimeter with RS232 output lying around? Have another look... most of us do. Some good news, you can repurpose this meter into a much more useful data acquisition device!

The Digitech QM1538 multimeters (amongst others, see below) provide an opto-isolated RS232 logging output, and come with some interface software. But what do you do if you want to integrate the capabilities of such a DMM into a bigger project? Thats why we developed this C# component to read the values streamed by these multimeters.

The output of these meters is basically a screen dump, where each value in the 14 byte packet corresponds to various segments on the LCD. Sound painful? You are right, it is. But you are in luck, because all of the hard work has been done for you. 

Simply download the DMM interface source code and pass the packets received on any serial port to the "decode" method, and the measurement type and value will be returned. Its so easy, its almost fun!

Download DMM Interface Library & Source Code

 Multimeters

The multimeters which this code is expected to work with are:

• Digitech QM1538
• Digitech QM1537
• Digitech QM1462 
• Digitek DT-9062
• Digitek INO2513
• PeakTech 3330
• Tenma 72-7745
• Uni-Trend UT30A
• Uni-Trend UT30E
• Uni-Trend UT60E
• Voltcraft VC 820
• Voltcraft VC 840
  

The nitty gritty

Included in the zipfile is a static class for decoding the output of the DMM. This method takes a 14-byte packet which must start with 0x1X, and returns an enumerated type of the selected measurement (DC volts, temperature etc). For the VB programmers, you can just use the release binary as-is, and reference it in your project. There is only one public method (called "decode") to worry about.