https://www.parts-express.com has a really nice selection of digital multimeters and many are under your $40 limit.
- Try to get one that is auto-ranging. Yes, you can select the voltage range, say, for 1-10, 1-100, 1-1000, etc, but it is very
convenient to have a meter that can just auto-range and display the correct reading. These cost a little more, but
I think they are worth it.
- Make sure you get one that can handle up to 5A or even 10A on the current readings. Some smaller meters can only
read fractions of an amp and for our model train world, a few amps is sometimes needed.
Personally, my current digital meter is one I bought at Radio Shack about 7 years ago, back when they still sold some tools and meters. Every once in a while, they would have sales and you could get some really good buys on things like this. But alas, they don't have squat now.
I also still have an analog meter - a Kentrix my father gave me 40 years ago. It is very accurate and I wouldn't trade it for the world. I find I still need both. There are many applications where the sensitivity and constant jumping of the digits on a digital meter in a noisy circuit can be a real nuisance. In motor circuits, sometimes a digital meter just freaks and won't display a steady value just from the electrical motor noise. And analog meter, by its very "slower" nature tends to display more of an "average" value of what's going on, and sometimes that's just what I need.
The digital meter is very handy for measuring very small voltages and currents without placing much load on the tested circuit.
I think for most bread-and-butter train and around-the-house electrical work, any of those digital meters at Parts Express will do a fine job.
