Current leakage

[Magnum]

I test a small alarm for current leakage with the switch in the OFF position.

Runs on 4.5 volt D.C.

It showed a drain of 2 uA.

Is that typical ?

Thanks,
         Andy

[dedndave]

more details please

"small alarm" = __________________________

model numbers are nice - description helps

[Magnum]

Intermatic SP440B

I am using 3 AA batteries instead of expensive button cells.

Andy

[dedndave]

in that case, 2uA sounds ok
that is a very small amount of current, really
although, if i had designed it, it would be pica-amps - lol

[Magnum]

You have a meter that can detect that ?

One million millionth (10-12) of an ampere

[dedndave]

no - but it can be calculated by measuring voltage drop across a series resistance
many CMOS circuits draw pico-amps or nano-amps when idle
in fact, many projects i've built use a 9V battery
in the idle state, so little current is drawn that i don't bother using an on-off switch
the 9V battery will last nearly as long as if it were sitting on the shelf

[Magnum]

I was told that caps may be sucking some current.

The caps are not labeled, so I suspect they are bottom of the barrel stuff. :-)

http://i1289.photobucket.com/albums/b516/drew77580/Alarm2_zpsb07c41ef.png

http://i1289.photobucket.com/albums/b516/drew77580/Alarm1_zps4b8db9fa.png

I saw a procedure for determining the Farads, but it looked rather involved.

Andy

[dedndave]

2 uA is a small amount of current
i doubt the capacitors are leaking

[MichaelW]

Alkaline AA batteries rated at something like 2000mAh should be able to sustain a 2uA current for far longer than the shelf life of the batteries.