Craftsman meter not reading current correctly. Anyone run into this?

[fastline]

Over all, this old meter has been pretty accurate over all. Recently, I was needing to test current and though the meter is conducting through it and turns on the load, it is NOT reading correctly. I have it in the 15A plug and load would not exceed 10A for sure. I just tested with a flashlight that has a .35ohm bulb at 4V and should be around 10A and is reading .7A. I them moved over the mA and it ranged out so I think that side might work ok. I typically only use it for reading mA anyway.

Thoughts? I am really confused since the meter conducts through it and the fuse in it is good. Just curious if anyone else has ever run into this? This has already cost some time in troubleshooting a battery drain on a car. I put the meter in series with the car battery to check for the drain. I think there is a drain and I just did not detect it.


EDIT: I ran some more tests and the meter seems to be working fine. I reached for some power resistors instead of a mag light bulb. Apparently they pick up resistance real fast when they heat up. Anyway, no worries.

 

[Reloadron]

Over all, this old meter has been pretty accurate over all. Recently, I was needing to test current and though the meter is conducting through it and turns on the load, it is NOT reading correctly. I have it in the 15A plug and load would not exceed 10A for sure. I just tested with a flashlight that has a .35ohm bulb at 4V and should be around 10A and is reading .7A. I them moved over the mA and it ranged out so I think that side might work ok. I typically only use it for reading mA anyway.

Thoughts? I am really confused since the meter conducts through it and the fuse in it is good. Just curious if anyone else has ever run into this? This has already cost some time in troubleshooting a battery drain on a car. I put the meter in series with the car battery to check for the drain. I think there is a drain and I just did not detect it.

Something seems strange. Looking at the flashlight bulb theory the bulb filament resistance cold is .35 ohms which yes, would be 4 volts / .35 ohms = 11.43 amps but that is likely 20 times or more what the flashlight bulb draws when hot and glowing. A bulb drawing 10 plus amps in a flashlight is going to need a pretty large battery to drag around. I would believe .7 amp to be correct.

The typical battery draw in an automotive system when off should be a few milli-amps depending on the system. Just to maintain the clock(s) and volatile memory electronics etc. I would guess. Not very much current at all. Though I must admit I never checked what our trucks draw with the ignition off.

Ron

 

[Mike_2545]

I never trust Craftsman for electronics...their hand tools are good but nothing electric is good from them...IMHO

 

[fastline]

Yeah, the truck situation is baffling at the moment. My dad said it will not have enough to start after only a week. I tested it last weekend and ran the truck. starter only pulls 350A, current draw with everything off was 50mA which is in line. Dad went to start it today, hardly turned over. I check the bat and it was at 12.1V. Opened the cab door which turned on a few lights and it dropped to 7V and further dropped to 3V trying to start. All things considered, it really looks like a bad battery but he said he has put 4 in the truck now due to the same issue. Cannot imagine 4 bats all being bad.

So, the test of the day was to pull the battery, charge it, then let it sit and load test next week. It is possible that it just will not maintain a charge. Dunno yet but I know every time I have found a draw on the battery, it was pretty obvious and an easy find.....

 

[fastline]

I never trust Craftsman for electronics...their hand tools are good but nothing electric is good from them...IMHO

Maybe you are not a mechanic but I feel their tools are right next to junk any more. Certainly every power tool they offer now is China junk with "craftsman" all over it. Drills, saws, etc, all junk. I still have mostly Craftsman hand tools though but I break more and more of them each week and have to get replacements. They are getting thin, soft, and weak. Diluted filler alloys are mostly to blame.

I will admit though that I do not break enough of them to warrant spending the super inflated, ridiculous price for Snapon but I have started exploring other tools. Not sure if people know but Kobalt tools from Lowes are decent quality. There are others like blue point, Mac, Proto, etc

 

[MikeMl]

...the truck situation is baffling at the moment. My dad said it will not have enough to start after only a week. I tested it last weekend and ran the truck. starter only pulls 350A, current draw with everything off was 50mA which is in line.....

0.050A × 24h = 1.2Ah per day is 36Ah per month, which will kill a new 84Ah battery in two months.

Even if the truck is started once every two weeks, the battery, on average is sitting around partially discharged, which promotes sulfation.

The answer is a float charger.

 

[KeepItSimpleStupid]

Woah. Cold filiment resistance is 10-15x lower than operating resistance. Is this an issue?

 

[audioguru]

Woah. Cold filiment resistance is 10-15x lower than operating resistance. Is this an issue?

If you are heated to 2000 degrees C or more then I think your resistance will also be 10-15 times higher.

 

[KeepItSimpleStupid]

You might think so, but this table Resistivity of Tungsten says otherwise.

at 27 C we have 5.6 and at 2000 C we have 56, leaving unit multipliers out it's a factor of 10x higher for resistivity and therefore since R=pl/A, resistance too.