View Full Version : ammeter problem
bimmer
03-25-2009, 07:19 PM
Trying to figure out a solution to the problem of having to use a battery to power the ammeter. if i try to power it from the source its measuring (the car) it blows the meter anyone figured out a way to overcome this?
alpha-dog
03-25-2009, 07:58 PM
That doesn't sound right. But you may try BoyntonStu's R-shunt method of a 12inch piece of 10 guage solid core wire. If your not using that much amps you could use 8 inches of 12 guage solid core wire in series with the (+) post of the battery. You measure amps with a millivolt meter for a 1mvdc straight conversion to 1 amp.
Gary Diamond
03-25-2009, 08:21 PM
Trying to figure out a solution to the problem of having to use a battery to power the ammeter. if i try to power it from the source its measuring (the car) it blows the meter anyone figured out a way to overcome this?
Please ask the question again, but in a different way i'm confused, on what excatly what your problem.
Can you draw it out, and then post it.
cully
03-26-2009, 02:20 AM
Trying to figure out a solution to the problem of having to use a battery to power the ammeter. if i try to power it from the source its measuring (the car) it blows the meter anyone figured out a way to overcome this?
yes you are correct ! i have had the same issue with the cheep Chinese amp meters from ebay the only way around it is to power the meter via a 9v alkaline battery so its isolated from the voltage your testing
what is happening
the meter is powered via 12v the measurement is done on 75mV max but because the meter has a common + or - voltage on the test and supply. the full 12-14v is going into the meters IC chip frying it where it only wants 75mV MAX
burnt electronics.........
bimmer
03-27-2009, 12:03 PM
yes you are correct ! i have had the same issue with the cheep Chinese amp meters from ebay the only way around it is to power the meter via a 9v alkaline battery so its isolated from the voltage your testing
what is happening
the meter is powered via 12v the measurement is done on 75mV max but because the meter has a common + or - voltage on the test and supply. the full 12-14v is going into the meters IC chip frying it where it only wants 75mV MAX
burnt electronics.........
OK well would you happen to know a way around this without a battery?
cully
03-27-2009, 02:47 PM
this is an untested thought ! but might be worth a try
put your shunt in the 0 volt side of the cell you should only get a max of 75mv across the chip
i have not tested this idea on your head if you try it
cully
03-27-2009, 04:34 PM
on the board of the meter there is a 7805 already i also fitted a 7810 and still fryed the amp meter ic chip