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Miscellaneous => The Orphanage => Topic started by: Magnum on December 09, 2013, 12:26:32 AM

Title: Measure current draw
Post by: Magnum on December 09, 2013, 12:26:32 AM
This is a pic of my multimeter.

http://i1289.photobucket.com/albums/b516/drew77580/DSC_0016_zpsf0b5266a.jpg (http://i1289.photobucket.com/albums/b516/drew77580/DSC_0016_zpsf0b5266a.jpg)

I am trying to measure current drain.

I hooked up meter between the positive of the device, but not sure if it's right.

I was wondering what the Red Output port is used for ?

Thanks.
Title: Re: Measure current draw
Post by: TWell on December 09, 2013, 12:29:52 AM
Quote from: Magnum on December 09, 2013, 12:26:32 AM
This is a pic of my multimeter.

http://i1289.photobucket.com/albums/b516/drew77580/DSC_0016_zpsf0b5266a.jpg (http://i1289.photobucket.com/albums/b516/drew77580/DSC_0016_zpsf0b5266a.jpg)

I am trying to measure current drain.

I hooked up meter between the positive of the device, but not sure if it's right.

I was wondering what the Red Output port is used for ?

Thanks.
Maybe for measuring current ;)
manual (http://www.eserviceinfo.com/downloadsm/59444/Sanwa_YX-360TR.html)
Title: Re: Measure current draw
Post by: dedndave on December 09, 2013, 02:38:38 AM
ok - measuring current is a bit tricky
and - be careful what you connect to the input leads in this mode, as well as ohms mode
of course, many meters are fused to protect them, but not all - and not all fuses are fast enough

when you measure ohms, make sure the device is not powered
it's also sometimes necessary to make sure any capacitors are discharged before putting the meter in-circuit

to measure voltage (AC or DC), you put the leads across the voltage source
to measure current, the meter is typically placed in series, between the supply source and load

i sometimes find it simpler to put a small resistance value between the supply and load
then, measure voltage across that resistor - and calculate the current
I = E/R
I = current in amps
E = voltage
R = resistance in ohms

it depends on the situation
for light loads, i might be able to use a 10 ohm resistor, or even higher
for heavier loads, it may need to be 1 ohm. 0.1 ohm, or even lower
and - it doesn't need to be a multiple of 1 ohm - but it makes it easier to read the meter - lol

when i design circuits, i sometimes put a resistor in the design so that a meter may be
used to calculate current through that resistor by measuring the voltage across it
particularly handy if you want to monitor an AC current on an oscilloscope

the output jack is connected to the + input through a decoupling capacitor
sometimes, this is used on the output of an amplifier that has a DC offset, to measure AC voltage
you don't want a DC offset when measuring AC voltage - it will lead to improper readings

i have also seen the output jack used as an output in a similar situation
the meter + input may be used to monitor the DC offset
and the output is connected to another meter to measure AC voltage content

this is a manual to a meter that is similar to the one you have
www.elenco.com/admin_data/pdffiles/m1250.pdf (http://www.elenco.com/admin_data/pdffiles/m1250.pdf)