Elektro-Automatik EA PS 2042-20B Power Supply Unit  - Page 1
Forum section: electronics / testgear

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: October 26, 2021, 02:26:58 pm
content: There are lots of lab PSUs on the market, but I found the Elektro-Automatik EA PS 2042-20B rather interesting. It's powerful (42V, 20A, 320W) and designed and made by a reputable German manufacturer (no rebranding!)I have not seen any reviews of this device yet, so I made my own in which I discuss the unit, check its UI, and subject it to testing. Overall, a quite satisfying device I think!

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 01, 2021, 02:49:44 pm
content: I did a couple of extra tests that address some gaps the video left: indicative PSU noise & ripple measurements (this post), and the possible delay when measuring current in the setup I used in the video (next post).In the datasheet, the ripple for model EA PS 2042-20 B is provided as <150 mVPPand <2 mVRMS. I measured the noise of my unit using a custom coaxial cable with the shield as close as possible up to the measuring plug - given the EA PSU does not support ‘standard’ 4mm banana to BNC adapters. This way, the risk that the wires act as antennas picking up HF signals is minimized. The PSU is set to 41V (so almost the maximum) and there is no load connected. In line with the manufacturers’ noise specifications, the oscilloscope is set to 20MHz channel bandwidth, and I use averaging statistics for different time periods (see below). Note that because measuring PSU noise and ripple is a specialized task, I consider the below to be indicative and surely not definitive measurements.The noise I measure is 91mVPPand 2.8mVRMS(see more below on the large difference between these). Under and close to the stated specs, respectively.The noise on the PSU is not constant. Typically, every 2mS or so, there is a short period of increased noise level, lasting about 0.2 mS. During these shorter periods, the measured noise level 81mVPPand 10.4 mVRMS.Whether this increased noise during short intervals is acceptable for your applications or not is up to you to consider. For the applications I have in mind it is not a big issue (I bought this PSU for heavy lifting) but it’s always good to be aware. (And for heavy applications that really require low noise as well, well, there is always the option to take a car battery ;-)

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 01, 2021, 02:54:05 pm
content: Now the second additional measurement. When I did measurements in the video when turning this Elektro Automatik PSU on and off, I noted that the current in my setup was measured by the electronic load – a Siglent SDL1020X-E load that has a BNC output for current monitoring, representing a current between 0 and 30A as a signal between 0 to 10 Volt. When doing so, I have been wondering whether some measurements I was doing suffered from delay in the current measurement. (So this post is related to the setup, not the the PSU as such.)I now did some more measurements. The below screenprint shows current alternating between 0 and 15A (in a 200mS cycle). The green line is a contactless (field strength) current probe with a bandwidth of 800kHz – not very fast but certainly more than enough for this test. With this current probe, we see a near-instant change from 0 to 15A (approx. 30uS rise time). The orange line is the output of the electronic load. That one takes much longer to show changing levels; its rise time is approx. 25mS, so 1000 times longer (!) than the current probe. So yes, there is certainly some delay.We also see quite discrete values – in fact, 8 discrete steps over half scale. Now it might be tempting to think the current monitor output would distinguish only 16 steps (4 bit)! But investigating a much slower changing signal (see below, where I used a constant R and manually varied the input voltage), the output shows a much finer detail. So, when we saw the discrete steps, we were e probably seeing limitations related to the sample rate. When working with relatively fast signals changes, this sample rate is something to be aware of. So, while I like the idea of having a current monitor in this electronic load, it’s a better idea to resort to current probes unless the changes to be monitored are very slow.

author: IAmBack
author_rank: Regular Contributor
timestamp: November 01, 2021, 04:33:37 pm
content: I have two such units in older version, one was purchased new, second was used. These units differed in operation - resolution of current and voltage was different. I was supplied with a new firmware, and both units works in the same way. However, this includes one weirdness: displayed resolution of set u/i values is lower than actoal resolution. I don't have them around me, but I think that U resolution is 0.1 (changing every two "clicks" of the pot), while actual output changes 500mV "per click". Noise on the output is high, but much lower when measured in differential mode (by probe or two inputs of oscilloscope). In general - nice unit for some tasks.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: November 01, 2021, 05:31:24 pm
content: Thanks, IAmBack.QuoteDid they send the firmware directly to you? I did not see any firmware posted on their website (and neither where EA announced they would appear) so I have no idea what the latest version is.QuoteJust wondering: by which standards do you think the unit's noise is high? For switching PSUs? The noise specs for this EA are not much different from the other switched PSUs I have.I was considering to do noise measurements with a differential probe, but when I investigated the differential probe I have here at my deposal, I noted its noise level was higher than that of the PSU (it's a high voltage differential probe). I'd need a high precision, low noise differential probe for that.I might try measurements with two scope channels and do mathematics, but I'd need to dig deeper into that. Having that said, PSU noise measurements are not trivial. I found this a useful resource:http://c1233384.r84.cf3.rackcdn.com/UK_EXS_LXC85-1050SW_AN5.pdf

author: IAmBack
author_rank: Regular Contributor
timestamp: November 01, 2021, 07:42:39 pm
content: As to fw, I've contacted them, and it was sent to my mail.As to noise, I've compared it to a Voltcraft/Manson psu (also switching psu) and afair, it performed better.