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billca
09-29-2002, 12:10 AM
I see advertised from Sears several clamp-type ammeters that measures direct current without breaking the circuit. The new Auto Restorer Magazine also reviews the Craftsman Clamp Meter #82062. What I want to know is the maximum sensitivity of these meters for DC. The Sears catalogs and online info don't mention this specification; they just say they measure up to 400 amps.
If they are sensitive enough to measure an ampere, they will be very helpful for checking wiring other than the starting curcuit.

Does anyone have experience with these things?

Bill C.

aeronca65t
09-29-2002, 07:51 AM
Some of the units we have at work can measure down to about 50 ma.

For the record, I’ve never borrowed one (from work) even though I’m sure I could. I’m not convinced that these things have great use in automotive service. They’d be excellent for long runs of wire that might fray mid-span due to movement and flexing. A person running LAN cable or COM cables might find a good use for one.

Since they can’t easily be placed around device connectors (such as the plug connection on a windshield wiper motor), I’m not sure I’d use one as much as an ordinary digital volt-ohm meter. Most of the problems I’ve seen in auto electric stuff (Lucas or otherwise) has been at the “connections to devices” and “large molded multi-pin plugs”. These clamp-type meters don’t seem useful in that context. They also go crazy near powered electric motors and magnetic fields, giving false readings. Regular $20 DVOM (and a schematic) is usually the best tool, in my opinion. It can be drudgery though!

If you *do* decide to buy one of these meters, be sure it’s a self-powered unit (with batteries). The meters powered by the pick-up current (no batteries) are much less sensitive.

Charles #677556
10-10-2002, 02:17 AM
Billca;
I purchased a Snap-On "clamp on" type Amp Meter back in the eighties. It's original intent was to do a "basic" check on charging systems on cars fitted with alternators. (I worked on "older cars" even then images/icons/wink.gif )
I have used it on "lesser" draw items as well as starter amp draws..
The one I have looks like an Amp Meter right out of the dash of a car except there are no "lugs" on the back, only a "U" Shaped channel and a "thumb-screw" clamp. The meter can simply be place over a circuit in question, or, by using the "clamp" feature, be attached for "hands off" use.
Trying to read "one amp" is difficult, but I will say, if you are chasing a short, the draw is likely to be higher that one amp, for this it is a servicable tool. For lesser draws of current, I agree with aeronca65t that a VOA meter is the way to go.. Radio Shack, etc. offer digital read-out jobs at a down-right cheap price (No plug intended). Plus, to be effective, this unit must be placed on only one wire at a time.. requiring one to "slice open" a wire harness just to check a single circuit.
About ten years ago, I acquired an old (late 60's early'70's)and fully functional Snap-On Anal-O-Scope complete with the four tester set, the Alt/Gen/Reg tester, Vac gauge tester, Tach/Dwell meter and an Exhaust Gas Analyzer (pre-emission version).. Complete with the original "Lighted Hood" that houses the five piece set... Now this is a tool every "old car nut" should have. graemlins/crazyeyes.gif
Needless to say, my dependence on the clamp-on amp meter has been greatly reduced, but it still comes in handy when checking a suspect circuit.
Isn't there an old saying that says You can never have too many tools?? images/icons/wink.gif

billca
10-20-2002, 01:31 AM
Thanks for the comments on clamp-on ammeters. For $50 I got one of the Craftsman 82062 models and have tried it out on a couple of problems with my Morgan.

While it definitely doesn't replace the conventional volt-ohm-amp meter, it is sufficiently senistive to be useful in tracking a poor wiring connection at a ground connection.

While reading currents of about 5 amps, the meter read within 0.1 amp on both the positive and negative leads to the load. It was much easier than breaking the circuit to insert a conventional ammeter. It's also small enough to be handy under the dash of an older car with discrete wires.

There is a conventional digital voltmeter included which has a convenient hold feature for the readings.

If you like tools, I think this is a useful gadget to have. If you just want to confirm that the current to a light bult is too low, you can observe that it's dimmer than the other similar bulbs. But that's no fun!

Bill C.

aeronca65t
10-25-2002, 10:29 AM
Good info...thanks!