The TENMA 72-7935 Pocket Sized Digital Multimeter has a big feature list but a miniscule price.
I have had fun reviewing products as part of electronics supplier Newark's blogger outreach program. When they asked me what I would like to review next, this little puppy came immediately to mind. I had seen it on the Newark web site and I was curious as to how a multimeter with so many features could sell for only $15. Well, I put it through its paces and found out what it can do.
The TENMA 72-7935 Pocket Sized Digital Multimeter has a big feature list but a miniscule price.
I have had fun reviewing products as part of electronics supplier Newark's blogger outreach program. When they asked me what I would like to review next, this little puppy came immediately to mind. I had seen it on the Newark web site and I was curious as to how a multimeter with so many features could sell for only $15. Well, I put it through its paces and found out what it can do.
The TENMA 72-7935 sure does have an impressive feature list. You can read the manual for specifics, but here is a summary:
- Tiny - 4.25" x 2.25" and less than 1/2 inch thick
- Case included
- Uses a single CR2032 3V button battery
- Auto-ranging
- Data hold mode
- Relative mode
- Lots of measurements:
- DC voltage
- AC voltage
- Resistance
- Capacitance
- Frequency
- Duty cycle
- Diode voltage drop
- Continuity with buzzer
Wow. I have never seen a meter with that many features at anywhere near that price. It's not all good news though.
- Not very sturdy
- Leads are not removable/replaceable
- Slow data acquisition time
- Not very accurate
When I say that it is not sturdy, I want to stress that this is just my opinion. Mine did not break in the few weeks that I worked with it. The meter itself is made from thin plastic and I would not recommend sticking it in your back pocket. The fact that it comes with a case, and you can use the meter while it is in the case, is a plus. However, I found using it in the case to be unwieldy, and the plastic straps that hold it into the case are very thin and feel like they could easily break if you insert and remove it from the case a few times.
The fact that the leads are not removable is probably just nit-picking, but any moving part is prone to failure, and attached leads would be very hard to replace. You are also limited to the 24" lead wires which is a little short for my taste.
The thing that I found most annoying while using the meter is the slow data acquisition time. Per the manual, the measurement is updated three times per second. This is typical for a low-end meter, but it is rather slow. Just slightly more expensive meters have acquisition rates of 7-10 times/second. I also noticed significant drifting of the readings. In measuring a very steady regulated power supply the readings fluctuated constantly. My cheap old Sperry DM-350A meter is rated at 3 measurements per second as well, but it acquires the reading much faster and does not fluctuate.
The accuracy is not bad for a meter at this price point, but not great. I will give an example, and try not to go into a treatise on multimeter accuracy measurements. The rated accuracy for 4 to 40 DC volts is 0.8%+1. That is, plus or minus .08% of the measured value, plus or minus 1 least significant digit. Given that, at that range, there are two decimal places the least significant digit equates to 0.01 volts. So, if you are measuring exactly 5 volts, the reading could be anywhere from 4.95 to 5.05 and 12 volts would read between 11.89 and 12.11. That seems pretty good, however I did not find the values to be that accurate when compared to readings taken with my oscilloscope which is very accurate. Even my Sperry meter is much more accurate (measuring voltage and resistance), and it is rated at 1%, albeit with smaller ranges, which that effects accuracy as well.
The inclusion of frequency and duty cycle is amazing on such an inexpensive meter, however I found those measurements particularly inaccurate - so much so, that I would not even use that function.
Conclusion
I may have been a bit harsh in my criticisms of the TENMA 72-7935. It's not a bad little meter, and at $15, the bang-for-the-buck ratio is through the roof. Going by the old adage "you get what you pay for," I would say that in this case, you get a lot more than you pay for.
The real question is: who is the right customer? My answer is: students. I think that this would make a good first meter for an elementary to high school student. It would be a great birthday present for your nerdy kid just getting into electronics. I know I would have loved one as a kid (my first meter was analog). I also think that it is the perfect meter if you need to buy a whole bunch of them for a class or workshop.
So, go ahead and pick one up. You might outgrow it in time, but you can always hand it down to the next generation of electronics nerds!