Bargain instrument, very useful, sale ends 21 Apr

[Duke McMullan n5gax]

Especially useful if you're just getting into electronics, the Cen-Tech 92020 digital multimeter is on sale at Harbor Freight Tools for $2.99, tax not included. The cost of a nine-volt battery isn't included either, but it's still a bargain.

At the risk of sounding like HFT is paying me (I wish!) to do this, here's a breakdown of the meter's capabilities:

7 functions, 19 ranges:

DC Voltage: 200 mV, 2 V, 20 V, 200 V, 1000 V

DC Current: 200 uA, 2 mA, 20 mA, 200 mA, 10 A

Resistance: 200 ohms, 2 kohms, 20 kohms, 200 kohms, 2 Mohms

AC Voltage: 200 V, 750 V (No AC current capability)

Diode polarity & forward/reverse resistance ratio

Battery test (external batteries)

Forward current gain (beta, or h_fe of bipolar junction transistors)

Built-in backlight

Low battery indicator (internal battery)

Auto-off (a real battery saver!)

Power switch is separate from the function/range selector

Red plastic case with black label.

The display is the usual black-numerals-on-gray-background that can give you trouble if you're wearing polarizing sunglasses. 3 1/2 digits.

Comes with a pair (red & black) of test leads -- skirted banana plugs that fit the meter on one end, and rather sharp-pointed probes on the other that can (Will!) draw blood if you get careless.

Remember, never measure the resistance of the AC line. (This is experience speaking!)

It's Harbor Freight's item number 92020. Probably, HFT is the only source. I don't know of anyone else that carries the Cen-Tech line.

Harbor Freight Tools, a.k.a. The Orange Tool Store or The Cheap Tool Store, is at Juan Tabo and Menaul. Look in the large shopping center on the northwest corner. You'll find 'em.

As DMMs go, these really are not very impressive, but they're a LOT of meter for three bucks. They're not bad, even at their nominal price of ten bucks.

Again, if you're just starting with electronics, go grab a couple of these. You WILL find them useful. Promise.

(And if you damage or lose one, pffft! Three bucks!)

[Matt Grommes]

Thanks for the heads up Duke, I've heard before that this little meter is a good buy at $10 so 3 for $10 is great.

Btw, if you or anybody else would be willing to give a short talk about DMM use sometime, I would greatly appreciate it. I'm still finding my way around my meter.

[Duke McMullan n5gax]

I'd be happy to do that . . . I could even bring along my DMMM (digital multi-multimeter, made from eight of these cheap DMMs) so everyone might have a meter to work with. Measure voltages, currents, resistances, and why you shouldn't try to measure the current of the power line. ;^)

Oh, and a sort of broad-spectrum warning about electronic measuring instruments. NEVER try to use the instrument to measure its own innards. Most likely mistake: trying to use one of these meters to measure its own battery voltage. There may be a few designs out there that will do this without difficulty, but generally it simply won't work, and there's a good chance of damaging the instrument. Most instruments can't safely look at themselves. Anti-narcissistic, you might say.

d