Measuring Current For Dummies

[free electron]

You can get a reasonably priced active dummy load kits from China, especially the 20$ one looks quite good:

Some time ago i started to work on my own, based on Teensy LC. Didn't have much time to work on it lately, but i hope to get back to it soon.




What i often use is this small power meter i designed few years ago:



It's really handy when troubleshooting a board full of pedals. Just plug it between the supply and the pedal and it will tell you the voltage and current consumption of whatever is connected to the power output. While it doesn't have any current limiter built in, it features an alarm function. You can set a max current threshold, if the device draws more, it will beep as hell. I plan to put one of these, together with a set of audio jacks as an audio and power signal sniffer with BNC outputs for scoping.

[antonis]

 

Man, you've just turned Rock 'n' Roll into rocket science..!!! 

What's your dummy load solution?

It happens to have "inherited" an old fashion RF 50R/500W dummy load (BNC con. type) but I prefer to use some low ohmic value wirewound resistors (metal case mounting type)

[anotherjim]

I've tried multiple times to measure my pedals' current draw with the aforementioned method, but my multimeter won't seem to register anything, even at microampere settings. Other than that, my multimeter works perfectly for measuring resistances and voltage. Am I doing something wrong?

1) Fuse blown
2) Leads plugging into the wrong sockets on the meter

+100
When you buy a DMM, you may as well seal the Amperage socket permanently out of use. You will very soon blow the fuse or damage something otherwise.

Good old AVO 8. See the button at the bottom centre. A thermal cut-out, which must have saved many service techs from severe embarrassment or, possibly, dismissal. 

[blackieNYC]

Like Merlin said, some meters have a + connection for voltage measurement and another for amperage. Also, there is probably a setting for AC and for DC amps. 
PS negative straight to the circuit, PS plus to "DC amps red" on meter, black from meter to the 9?volt input to your circuit.
And some meters have rather cryptic symbols for AC ( ~ ) and DC  ( ---- ) on the jacks or knob. You probably know this but it must be said. YPKTBIMBS?

[merlinb]

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Ooh that's a neat typing trick!

[Agung Kurniawan]

Is that anyway to measure pedal's draw?

[duck_arse]

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Ooh that's a neat typing trick!

I squinted at it at the time, too (but now I know the method).

Agung, is your pedal all boxed up, still a nude PCB, or on the breadboard? if either of the second two, perhaps the least messing about method to measure "current draw of a pedal" is to measure the VOLTAGE across the supply-line filter resistor, the one that usually comes just after the protection diode. the R//C filter may not be fitted, so you could just add a 100R (or less (or more)) resistor in line w/ the supply to the circuit. measure the voltage across that resistor, then apply Ohm's Law to find the current.

[antonis]

Duckie, I hate myself for doing it  but I have to inform you that there are meters that can straightly measure current..
(just be carefull when putting something to whatever..)