Measuring DC-DC converter Efficiency

RE: Measuring DC-DC converter Efficiency

supercachai — Fri, 07 Nov 2025 20:34:17 GMT

Great post, thanks for the write up.

Did you consider using the Riedon PCS series? They are in a similar price range as RSN, but THT and can be mounted on a heat sink. So you can achieve a much better thermal coupling, which will probably eliminate any temp drift.

I am building something similar for currents up to 40 A so heat can lead to significant drift, especially when current ratios are very different.

RE: Measuring DC-DC converter Efficiency

Jan Cumps — Tue, 04 Feb 2025 19:34:36 GMT

> I have a DAQ970 system with a solid state multiplexer

Do you have this one: DAQM900A 20-Channel FET multiplexer module?

RE: Measuring DC-DC converter Efficiency

shabaz — Tue, 04 Feb 2025 04:18:13 GMT

Nice blog post! It would not have immediately occurred to me how much accuracy was needed, I learned a lot.

Very interesting resistor network parts too.

By the way your photo with a vice reminded me to show a photo of these new ones I purchased recently.

They are quite small. I actually got them for machining purposes, not holding boards, but they could be used to hold small PCBs or small cylindrical connectors etc since the brass one has V-notches.

AliExpress ads:

RE: Measuring DC-DC converter Efficiency

JWx — Mon, 03 Feb 2025 09:17:55 GMT

Very interesting article!

I have a question how do you manage pulsed input current - for example something like this: sparse pulses with sharp slopes, of amplitude (for example) ~ 0.5 - 1A and mean value about two orders of magnitude lower [during light load]?

I wonder if measuring current before an additional capacitor/bank (to average the signal) wouldn't provide better results than a direct measurement (given limited bandwidth and dynamic range of existing metering equipment) - but I am not sure if it doesn't introduce some additional complications...

RE: Measuring DC-DC converter Efficiency

Jan Cumps — Sun, 02 Feb 2025 20:41:19 GMT

I’m powering them with the little mains powered dual supplies described in this blog:

An isolated low noise +/-5V DC power supply

Have you been tempted to power them by (maybe) 1 (or 2) 9V battery(ies)?

RE: Measuring DC-DC converter Efficiency

Jan Cumps — Sun, 02 Feb 2025 18:39:12 GMT

I've been looking for shunts too. My bench meter has good currency options, but the extension card - that turns it into a 10 channel device - supports voltage (and R and T) only. I bought the switch card 2nd hand, and hope to get a few decent shunts that way too ... .
The bolt-on x10 amplifier PCB is appealing. I'd be OK with "reasonable" efficiency. Good enough to assess efficiency - maybe not up to the mark to fully specify a design.

For very low currents I use an EEVBlog µCurrent - in essence a x100 amplifier / I to U converter.

RE: Measuring DC-DC converter Efficiency

DAB — Sun, 02 Feb 2025 18:37:00 GMT

Very good blog.

RE: Measuring DC-DC converter Efficiency

michaelkellett — Sun, 02 Feb 2025 16:58:43 GMT

I'll be away from computers on 3rd and 4th Feb so might take a while to respond to questions.