Due to the same reason I build some pseudo-4W-test-leads where the L- and U-lines are both soldered to a short and sharp test needle. That way the contact resistance is of course not compensated, but for quick comparison of many parts it´s more reliable - and you can always fall back to the true 4W-leads if doubts arise.
I thought about that as well, still have some DIY DMM probes lying around I could use for that. But wouldn't that effectively only eliminate the resistance of the leads from the equation? I'd assume contact resistance is the far bigger issue. When trying to use this meter in-circuit I noticed the dual tipped probes are too far apart to ever make contact with SMD parts. Maybe I should try ordering a clamp lead for it?
I´d build clamp leads for it. The quality you get if u build test leads yourself is so much better than everything you can get in the price class of these instruments.
Of course you´re right, you only compensate the test leads, but this means you can use thin and flexible test leads and cheap connectors all the way - that´s already a big advantage and - on the other hand - the contact resistance variation is quite low in most cases you use it on battery terminals or PCBs. So it´s absolutely okay to compare values, e.g. to find a short.
Ahh, yes, it used AC for resistance measurements, right? I already have an in-circuit ESR meter, was more thinking about using it for short finding. In a quick test I setup it was perfectly able to indentify which of the several resistors was the 0-Ohm one, so it should work.
I'll have to measure the current flow with my clamp meter but the open line voltage was already quite high. I'd be a bit afraid I'd fry something when doing measurements.
Yes, it uses 1kHz AC - else you couldn't measure a charged battery. Nice side effect is you technically can measure also charged capacitors in circuit.
My unit uses around 1V RMS with open load and the following short circuit currents (measured with shunt resistor + scope)
20mOhm range: 46mA RMS
200mOhm and 2 Ohm range: 5mA RMS
20Ohm and larger: 0.5mA RMS
That means the maximum power dissipation in the DUT is 2 Ohm * (5mA)^2 = 0.05mW. While ranges are switched 50mW may be possible. That´s from my point of view very safe to work on power components (at least safe to the components
)
Attached is a pic of the DIY-testleads. Costs are <10€, they´re not beautiful but they´re really versatile and more reliable than the pogo-pin ones out of the package. The DuPont-plugs in the middle can also be used to directly measure into groundplanes if any connector has two GND-pins next to each other.