Fine print, up front: I’m not a professional product reviewer. Nor do I have access to precision voltage, resistance, temperature, sound level, light or current sources.
The working title for this video was “UXWBill Maunders About a Multimeter” and at over an hour, I think you’ll readily see why.
The RadioShack meter has some better specifications on paper, while the Mastech does more and seems to be better made. Although some of RadioShack’s specifications are honest, I know for a fact that my example of the 22-811 multimeter would *not* test capacitors up to 400 µF as their spec sheet claimed, no matter how much time it had to do so. Testing capacitors above 50 µF did not work reliably.
This video is so long because it is meant to be reasonably thorough. If you’re in a hurry, here’s how it breaks down (all times are approximate):
0:00 – What, why, how, “lead up”, etc.
5:40 Cen-Tech Meter Box Shot
6:35 Pricing Information
7:00 Manufacturer Information
9:45 Box Close-Up, Overview of Features
12:05 Close-up of the Meter
14:20 Undocumented Features (actually RS-232, not USB)
15:00 Display/Buttons/Dial/Sensors Close-up
18:05 Batteries Installed / Fuse Overview
20:30 Viewer Suggestions: Requiem for a RadioShack Meter
22:25 Illuminated Test Lead Connection Safety Feature
24:45 Initial DC Voltage Test (SLA Battery)
25:25 Accuracy Limits Commentary
26:10 Availability Service Literature / Accuracy Adjustments
27:10 More DC Voltage Tests
29:50 Backlight Test
32:22 Resistance Tests (audible continuity test tone, low (0.1 ohm), high (51 K ohm)
36:02 Diode Test, 1N4007 low voltage drop diode
36:39 Capacitor Tests (400 V 22 µF, 100 µF, 50 V 22/44/66/88 µF)
41:36 Temperature/Humidity Accuracy Tests (internal sensors)
43:41 Test Lead Misconnection Safety Alarm
44:44 Various AC Voltage Measurements, Accuracy, lack of true RMS measurement capability
47:45 Frequency Measurements, Limits and Accuracy
51:54 Sample Rate
52:15 Assorted External Thermocouple Tests and Accuracy
56:16 Sound Level Meter Tests, Useful Frequency Range and Accuracy
1:04:23 High/Low Current Tests
If anyone has a good idea as how I could accomplish accuracy testing of the light range in an informal environment *without* special tools or calibrated sources beyond light bulbs having known light output in lumens and current draw, such suggestions would be appreciated.
Sawtooth waveforms at high audio-range frequencies (20 kHz) are not handled well by this meter’s frequency measurement range.
Unlike some other multimeters, the 10 amp test socket is fused. The low current test socket claims to have self-resetting protection.
I spoke incorrectly regarding the Mastech / Cen-Tech meter’s communication capability. It is not USB, but rather RS-232 serial. There is even an RS-232 indicator in the display, suggesting that this feature almost made it to the finished product. (Neither Mastech nor Harbor Freight sell a variant of this meter with RS-232 capability.) You can read more about the modifications here:
I’ll probably do one of those modifications when the warranty on my meter runs out.
Battery life, even when running from carbon-zinc “heavy duty” batteries, seems like it ought to be pretty good. Current drawn under normal test ranges with the backlighting turned off hovers around 2.04 mA. Turning the backlight on kicks things up to 25.6 mA and it appears that the backlight stays on until you specifically turn it off.
Figures online seem to suggest that the “average” carbon zinc AAA battery has about 320 mAH worth of energy storage capacity. Deducting a little from that figure to account for energy lost while in storage, and these being cheap batteries probably leaves around 250 mAH per battery, which you won’t get at all at once without significant voltage drop and certainly not for anything like an hour.
If I figured it right, the batteries should be good for at least 300 hours of no-backlight operation after deducting a bit more to account for the threshold at which the low battery warning might be set. Using the backlight knocks that figure down tremendously, to about a day’s worth of operation. I’ve not tested to see where the low battery threshold is set, perhaps I will do that later and amend this description accordingly.
It is not the backlight that ultimately draws the most current. That honor goes to the “error” and continuity test beeper, which spikes things up to between 35 and 43 mA.
Harbor Freight Tools later had this very multimeter on sale and refunded me the difference in price.