Multimeter Selection

[phoenix3200]

I need to get a new meter.  I'm getting ready for some experiments, and I'd like to spend $40 or less to get a meter that suits my needs.

For starters, here's my current meter, a Digitek DS830B+.  There's almost no information about it online.  If you do a Google search for the model #, LPF comes up as the fourth link!

Anyways, while this cheap meter has served me well, I need one with at least two additional features:  temperature measurement (e.g. it comes with a thermocouple) and capacitance measurement.

The first meter is the Viot M7, a 30-mode multimeter, which I can find for $30.  I can find an identical-looking meter from MSSOC and B&A Computers.

Second is the Eclipse 400-047, which has 32 modes, and I think I can also get this for $30.

Last is the Uni-Trend UT57, which I can probably get for $40.  It has 22 modes listed on the dial, plus hold functionality and buttons to decide between DC/AC/DC+AC (which makes it closer to 38 modes, maybe more if it does AC resistance).

Do any of you own the above meters, especially the Uni-Trend UT57?  How reliable are they? Edit: No thermocouple.  Dangit

If you have a different meter that does capacitance and temperature measurement, let me know about it.

 

[jonrobertd]

Get a Fluke... LOL... they are overpriced as heck. Mine was a gift, but If I was to buy one I like the Eclipse 400-047.

 

[phoenix3200]

lol...the company name cracks me up like crazy...

Yea...there's no way I'm getting a Fluke on $40.
---
I found a sweet-looking DMM for $30+$12 S/H and decided to order it:

Circuit Specialists Inc CSI345 (alternate link). This is seemingly identical to the MAS345 that you can find on eBay/elsewhere.

It's got a serial connection, a 4000-count display, auto ranging, an included thermocouple, and capacitance measurement. I found some compatible open-source software called QtDMM that I can't wait to try out with it..

 

[Kris.J]

You can't go wrong with Fluke - I would not call them overpriced, you get what you pay for - and Fluke = good stuff, The Best.

For $40, you're not going to get good stuff. :-/

 

[rog8811]

Fluke all the way for me, autoranging makes life so easy and they are so well built.

Worth the extra money IMO.
Regards rog8811

 

[CoZZm0_AU]

I've got one of these:

http://jaycar.com.au/productView.as...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=


I bought it mainly because its very accurate (for the price) for resistance and DC voltage (0.09%), but unfortunately, it doesn't do capacitance or temp. The next model up does cap and temp but its almost double the price and i couldn't afford it at the time, but i have considered upgrading.

 

[Benm]

Fluke meters are certainly nice, though the base models obviously arent the best meters on the planet either.

As for measuring capacity: consider if you will actually use it. Most multimeters will have ranges from 2 nF to 2 or 20 uF or so, and will not measure electrolytic capacitors properly.

I found a sweet-looking DMM for $30+$12 S/H and decided to order it:

Circuit Specialists Inc CSI345 (alternate link). This is seemingly identical to the MAS345 that you can find on eBay/elsewhere.

The feature set looks really impressive for this price, gets me a 'too good to be true' kind of feeling. I don't know this brand or have any idea on the build quality, but at this price its hard to go wrong - unless it turns out to be far less accurate than claimed.

The DC voltage range is usually quite accurate even in the cheapest of meters though (even the $10 ones do better than 1%). Might be wise to verify it against a known-good meter to be sure.

 

[phoenix3200]

As for measuring capacity: consider if you will actually use it. Most multimeters will have ranges from 2 nF to 2 or 20 uF or so, and will not measure electrolytic capacitors properly.

Well, that is one downside of the meter - The capacitance will only go up to 400 nF, and I was wanting to get 100 uF.  Capacitance measurement would have been more of a novelty than a required feature, so I guess I won't be using that.

The feature set looks really impressive for this price, gets me a 'too good to be true' kind of feeling. I don't know this brand or have any idea on the build quality, but at this price its hard to go wrong - unless it turns out to be far less accurate than claimed.

The DC voltage range is usually quite accurate even in the cheapest of meters though (even the $10 ones do better than 1%). Might be wise to verify it against a known-good meter to be sure.

Honestly, any digital multimeter is better than the Digitek one I showed in the first post.  

It IS the Mastech MAS345, and it seems like Mastech makes a lot of DMMs.  Mastech must allow other places to rebrand their products - because the only difference between mine and the Mastech one is there's a different brand silkscreened into the lower left corner (Here's another rebranding).

I've got a USB-RS232 adapter on order right now, so I can't say how good the computer connection is, but I think it's only useful for single-range data logging at 1-2 second intervals.  If I really need better testing, I can get access to HP/Agilent countertop DMMs and oscilloscopes at my school.

I took it apart, and the fuse isn't immediately visible.  However, the unit does have six potentiometers for calibration (if I had any idea how to calibrate it).  When plugged into an outlet, it registers a fairly close RMS value (120.4 in the U.S.), but from what I'm finding online, Mastech probably only made it a sinewave-calibrated RMS and not a true RMS.  I'll test this and get back to you guys.

The probes are high quality - they came with caps to protect the ends - and I got the meter in a vinyl-covered storage box.  Obviously Mastech expects you to keep this meter for a while.  I'm not confident in the AC measurement, but my main reasons for getting it were better DC measurement, temperature measurement, data logging, and capacitance.

 

[Benm]

When plugged into an outlet, it registers a fairly close RMS value (120.4 in the U.S.), but from what I'm finding online, Mastech probably only made it a sinewave-calibrated RMS and not a true RMS.

This is very common to multimeters. If they actually support true-RMS it's usually proudly advertised, otherwise the measurement is simply the top of the input signal divided by 1.41 to get the sine equivalent. I don't think it matters much though - by the time you want to know the RMS power, you'll likely want to know what the signal looks like too and use a scope anyways.

 

[Kris.J]

http://cgi.ebay.com/FLUKE-79-SERIES...5|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

I've got one of those - a Fluke Model 79 Series II that I bought brand new in college, like 15 years ago. It's a 'Mac Truck' of a meter, and I love it!

 

[jwc]

http://dealextreme.com/details.dx/sku.9636

It's cheap, but great.

(If I need something better, I can always borrow someone else's.)

 

[artix]

Is this a good meter?

http://www.dealextreme.com/details.dx/sku.10018

What setting do you need to put it on to read how much current is coming from the driver? (I know you need a testload : )

 

[Kris.J]

Is this a good meter?

http://www.dealextreme.com/details.dx/sku.10018

What setting do you need to put it on to read how much current is coming from the driver? (I know you need a testload : )

That's 15 bucks that I think is better spent on a used Fluke off eBay.

When measuring current, the meter is connected in series with your circuit - the meter actually completes the circuit.

 

[phoenix3200]

You can't go wrong with Fluke

I've got one of those - a Fluke Model 79 Series II

That's 15 bucks that I think is better spent on a used Fluke off eBay.

I think we all got the picture. However, some of us are not willing to spend the money on a Fluke if we're not likely to use it on a normal basis.

Is this a good meter?
http://www.dealextreme.com/details.dx/sku.10018

If you just need a meter for simple DC/Resistance measurements, that's more than adequate.

What setting do you need to put it on to read how much current is coming from the driver? (I know you need a testload : )

When measuring current, the meter is connected in series with your circuit - the meter actually completes the circuit.

NO. ABSOLUTELY NOT. While this may be the "proper" way to measure current, DO NOT do this!!! Do NOT use the current setting on your meter for sensitive electronics. A number of things will occur, including, but not limited to:
-You'll add an unintended resistance/capacitance load to your circuit, which will affect the test load/your driver's operation.
-You'll momentarily disconnect the circuit (because you're trying to hold the probes in place), charging up a capacitor, in which the eventual voltage spike when reconnected will damage sensitive electronics.

The second one is key, and is the main reason why diodes get blown. The driver itself will also not appreciate an infinite resistance load.

INSTEAD, you should get the common test load shown around here, or build your own: 6x 1N400x diodes, and 1x 1 ohm resistor, all in series. If you take your multimeter and measure the DC voltage drop across the 1 ohm resistor, the voltage shown on your meter = the net amount of current flowing thru the circuit. Since a multimeter is usually 1 M Ohm when it's in the DC measurement mode, you won't affect the circuit.

The ONLY location in the circuit which is acceptable to use the current measurement is between the battery and the driver - but unless you're using a linear drop out driver like the DDL, this will not equal the current that your diode will recieve!

 

[Bionic-Badger]

Yup, I've blown circuits by stupidly changing the meter's dial as it was running. It's a lot easier to measure across a known resistance anyway.

 

[Benm]

 Do NOT use the current setting on your meter for sensitive electronics.  A number of things will occur, including, but not limited to:
-You'll add an unintended resistance/capacitance load to your circuit, which will affect the test load/your driver's operation.
-You'll momentarily disconnect the circuit (because you're trying to hold the probes in place), charging up a capacitor, in which the eventual voltage spike when reconnected will damage sensitive electronics.

The second one is key, and is the main reason why diodes get blown.  The driver itself will also not appreciate an infinite resistance load.

Two notes on that:

The second problem will only occur if you connect things when the circuit is powered up. It is perfectly safe when you first wire the current meter between driver and diode, and power it up after that. Just dont mess with the connections as long as you're powered up and all is well.

On the first point: Especially the 10/20 amp rangens are no problem. The actual shunt in most multimeters for that range is wired as a separate terminal, and consists of about an inch of ca 2 mm thick copper wire. Its insertion loss is minimal (and has to be, otherwise 10 amps would melt it right off).

Shunt resistance of the 200 mA range can be as bad as 1 ohm, so that IS best avoided.