AWESOME TESTING TOOL!

i've built a few of these now, for myself & for others. BRILLIANT for testing electrolytic capacitors! i've found it works on even higher voltage non-polarised caps down to about 470nF.

it's called an esr (equivalent series resistance) meter. the esr of a capacitor is mostly more important than it's actual value( apart from in timing circuits, of course). the esr is kinda the the 'strength' with which a capacitor can hold a voltage stable.

the only 'controls' are a pushbutton, although i've added a slide switch to make sure it turns off fully, & can't be accidentally switched switched back on by an unintended press of the switch. it has a 2 digit led 7 segment display, to show the reading. it will measure up to 100 ohms, & it will test plain old resistors too' up to 100 ohms. ther's a lookup table on the front of it, showing expected esr's of new capacitors of various capacitances & voltage ratings.

it easily measures down to hundredths of an ohm! you can even zero out the resistance of it's test leads! the leads have a combined resistance of about 0.23 of an ohm!

it automatically switches itself off if you don't use it for 5 or 10 minutes. it will also tell you if it's battery is getting low. as you may have guessed, this clever little device has a pic microcontroller inside it. there's even an updated version with self-fault diagnosis! the board it fairly closely packed with components, but it really was a pleasure to build.

it doesn't work properly with inductors & coils, as it passes 'pulses' through whatever you're testing, & coils produce inconsistent readings.

but the real beauty of it is that in 90% of cases, you don't even have to remove the capacitor from the pcb, as the electros in the circuit are usually the lowest impedance device. the other thing is that once you get used to using it, you can guess the approximate reading to expect from a given capacitor just by looking at it's physical size, regardless of it's value or voltage rating.

yep, you might have guessed - I LOVE IT!!! - & I built it!

it sits next to my multimeter, & is a most invaluable tool.

it's a kit from jaycar electronics, from the silicon chip magazine.

cost me less than 70 bucks too!

if you're pretty good at soldering, & are involved in electronic repairs, i couldn't recommend it too strongly!