Anyone have suggestions on a multimeter that would be adequate for geothermal testing?  My goal is to be able to provide electrical troubleshooting information when a situation arises and for annual system checks.

Suggestions that would be greatly appreciated would include specific features to look for, ranges, models you have or like, good buys, etc.  Feel free to mention features that are nice to have and the benefit.  I understand that this may increase the price of the unit.  Thank you!

I have 4 different ones and for most uses (non-geothermal), they all work the same. One has a thermocouple input. I'd consider a low cost one and then add one of these:

http://www.dealextreme.com/details.dx/sku.39749

Data logging or PC interface capability might also be useful.

The electrical quantity most often useful to me is current (amps). That is typically measured via a clamp meter - a ring is closed around one of the conductors. Knowing and tracking compressor and blower amps over time tells whether unit is in top form or if performance is degrading such as by heat exchanger fouling or dirty air filter / coil.

Virtually any voltmeter will suffice for that service - generally I only need to determine the presence / absence of control (24 VAC) or high (120 / 240 VAC) with a 5-10% tolerance.

I use a separate probe that connects to the voltmeter for clamp-on amps - I find it smaller and easier to get into place. Don't trust the current readings for AC - a non-unity power factor makes them somewhat wrong.

A datta logger makes most sense for your temp readings. Most inexpensive amp clamps will also do voltage and continuity tests at <$50 the orange store should be able to hook you up.
By and large my feeling is for our purposes, higher priced equipment has more to do with life expectancy through the rigors of use/abuse by a professional tech. So while I use a Fluke meter that can measure virtually anyting but CO2 it would be unwise for you to make that kind of investment.
I also just lost an Amprobe brand digital test meter that I've had for a dozen years so I can attest to their quality as well.
good luck,
J

Posted By joe.ami on 22 Sep 2010 12:20 PM
I also just lost an Amprobe brand digital test meter...

maybe I can find it.   

Thanks everyone that responded.  Other opinions are welcome too.  I'll do some checking and probably ask some stupid electrical questions.  Not my forte.