Testing out a bridge rectifier if it works with only a multimeter

Question

Indulge me here with this scenario, but suppose the electronics shop I'm sourcing parts have dubious, faulty semiconductors parts -- damaged, counterfeit, etc. What have you.

How do I test if a bridge rectifier I've just purchased is in good working condition? This is straightforward with an oscilloscope, but all I have is a multimeter.

With load on the positive-negative leads, should what I measure across load still be what I measured as the AC voltage value of the raw AC, minus the 2*Vf of the diodes? I expect this, because most multimeter already have a rectifier for AC voltage & current measurements. So pre-rectifying it won't do anything to the material than adding incoming & draining diode voltage drops.

Answer 1

How do I test if a bridge rectifier I've just purchased is in good working condition? This is straightforward with an oscilloscope, but all I have is a multimeter.

I'm afraid that it's not straightforward (even) with an oscilloscope. For instance, you can't easily measure the reverse voltage withstand capability of the bridge rectifier (or indeed a single diode) without special effort and equipment (let alone a multimeter).

The reverse voltage withstand capability of a diode (bridge) is something that fundamentally underpins the quality and specification of the device so, if you can't measure this then you can't verify that the component is in good working condition.

With load on the positive-negative leads, should what I measure across load still be what I measured as the AC voltage value of the raw AC, minus the 2Vf of the diodes?*

If your meter reads true RMS then yes. However, most meters that measure DC will measure the average of the rectified output and not the RMS. If you try and use your meter in AC measurement mode then unfortunately there's no guarantee that the numbers will be similar at all.