breadboard component; press to break/make circuit and measure current

I assume you know about clamp-on current meters / probes?

A pair of 0.1" pin headers? Connect the open ends of the headers to your series current meter and then remove the shorting block. Replace block and remove the leads when finished. No power interruption.

pin headers, |pairs wired |vertically v o o from .|--|. to -------|o o|------- source '----' load ^ | |shorting block

(created by AACircuit v1.28.6 beta 04/19/05

If you're using a plastic "rows of connections" breadboard, just stick each pin header pair into its own row and short between them with the jumper block.

Assuming the OP doesn't have such clamp-on methods (*), one of those earphone jacks that disconnects the speaker when the earphone is plugged in could probably be configured to work with a DVM.

(*) I have three, DC -> 50Mhz, 50 Ohms out, from my Bosch motor control days ;-) ...Jim Thompson

There _is_ a glitch, a _step_ in applied voltage.

...Jim Thompson

The clamp-on meters tend to get either inaccurate or expensive for currents in the ten's of mA and below which (filling in the missing requirement statements with assumptions) is what I'd guess the OP is looking for on a breadboard.

Something like

Why not add a low-value resistor or a current shunt to the circuits in question, and just measure the voltage drop with a DVM?

Look, free current shunts!

Sure, just put in a momentary contact NC pushbutton. It has to be normally closed (NC) so the current meter can be unplugged.

To make a current reading, plug in the current meter (across the switch) and push the button, then read the meter.

The voltage burden on the meter may allow other switch types (like a pass diode), or you might be able to do Hall effect measurements of DC current in a wire loop, but those get into accuracy and functional and cost tradeoffs.

John stole my fire -- that's what I'd suggest. It's rare that such a resistor will interfere with circuit operation. Think about how much drop you can stand, then put in a resistor. I usually us 1, 10, 100, etc., to make the math easy when I look at the voltage.

Those free shunts are about 6 milliohms. The one on the far right is for calibration.

Digikey and Mouser now stock milliohm resistors.

John Larkin brought next idea :

The usual heap of crackpot solutions that the OP probably does not understand then comes the obvious, just a simple small resistor shunt. It was my first thought. l-) Thanks John.

diode),

re loop, but

Went with the momentary. Thank you. Good suggestion.