How to Tap Into Multimeter and Connnect Output Voltage Readings to Arduino Uno

Projects Discussion and Showcase Device Hacking
1

Hey all,

I was wondering if someone could give me some advice on how to tap into a certain portion of a voltmeter in order to relay the digital voltage readings it obtains continuously to an Arduino Uno board.
I am kind of a novice when it comes to circuits, so I would greatly appreciate some help.

The end goal of my project is to take the readings that are obtained by the voltmeter function of the multimeter and to use a program on the microprocessor to take the voltage readings and use them to calculate the concentration of an analyte. Essentially, I have a sensor that obtains a voltage difference that is directly correlated to the concentration of a specific analyte. Thus I want the program to take the voltage reading and then match it up with the concentration (using a standard linear curve). Finally, this concentration would be displayed on an LCD screen.

So, I am only asking for help on tapping into the voltmeter portion of my multimeter.

Many thanks for your time!

2

look into this http://flashingleds.wordpress.com/2010/11/30/unlocking-rs232-output-from-your-multimeter/

apparently a lot of cheapo multimeters can do this with some modifications.

3

Thanks so much for your response, nemik, but the thing is that I don't think my multimeter has serial data capability (via rs232). How would I tap into the multimeter if I had a cheaper model?

Thanks again

4

nmehandru:
Thanks so much for your response, nemik, but the thing is that I don't think my multimeter has serial data capability (via rs232). How would I tap into the multimeter if I had a cheaper model?

Thanks again

I really don't think that would be possible, short of having a complete readable schematic of your meter, which most manufactures don't and won't provide.

Lefty

5

Isn't it simpler to build a multimeter from an Arduino? there are several samples over the forum/playground....

6

To do this you would need an oscilloscope and the knowledge of how to use it. You could then tap into the segment drivers for the display and read what is being sent to it. However there are different methods the the display could use and most of them involve multi level voltages not just logic. Couple that with the large number of segments on a display, you require one input and some voltage comparators for each segment, you will see that not only is it not easy, it is also not worth it.

7

nmehandru:
Thanks so much for your response, nemik, but the thing is that I don't think my multimeter has serial data capability (via rs232).

The multimeters in that article don't have RS232 capability, but the chip inside them does. Have you checked that chip inside your meter to see if it's the same one as in that article? Or one like it? Can you find a datasheet for the chip?