ET5410 added external sense with BNC - Page 1
Forum section: electronics / testgear

author: andyB2022
author_rank: Regular Contributor
timestamp: June 23, 2022, 07:24:05 am
content: Hi! As I've saw here on the forum another colleague modified his East Tester Electronic load to have external sense capability, so I've thought to do mine too. The overall job is very easy, just buy a DPDT switch and a BNC connector in my case (it's more versatile than just 2mm banana female plugs imo..). Hardest part is getting the holes drilled and aligned as best as possible with the oem banana plugs. Now this 200$ thing can beat with 1k$ loads out there (as functionality and not precision in measurements) Enjoy the photos!

author: DaneLaw
author_rank: Frequent Contributor
timestamp: June 23, 2022, 09:44:41 am
content: Interesting..well donejust took the plunge today on the ET5410after been eying these budget electronic loads for some years, and if I actually needed an electronic load .was unsure if it should be ET5410 (old gen) or UnitT UTL8211 or DCL6104 or ET5410 (new gen) that looks like a revision of the DCL6104, or UTL8211.Kunkin184 was not in the picture, simply down to the 7segmented display, which can be quite cumbersome for a unit with certain features, settings, and overview - even though the inner hardware does seem quite solid with the price in mind.Landed on the ET5410 (old gen) from EU stock, as it was the cheapest and seems to do as intended, and as far as I could tell, there was nothing that stood out, versus any of the other LCD variants' to add another +35% in cost.

author: andyB2022
author_rank: Regular Contributor
timestamp: June 23, 2022, 01:57:58 pm
content: You won't regret it.

author: Curious
author_rank: Contributor
timestamp: May 12, 2023, 09:24:39 pm
content: Hello AndyB,Beautiful job on the upgrade!Before I snip the green & blue sense wires, I'm wondering if the sense wires MUST be connected to either 1)original Banana jacks or 2) external source DUT? In other words, if I did the new pair of small banana plugs approach, MUST there be sense wires to the source DUT or original Banana jacks? You used a DPDT switch suggesting that this is true.Thanks!

author: mawyatt
author_rank: Super Contributor
timestamp: May 12, 2023, 11:14:22 pm
content: One needs to be very careful about opening the feedback with cuts/opens, this could cause unknown feedback which may drive the controlling loop to the rails, and maybe even cycling between the rails with disastrous results to the DUT and load.Without a verified schematic, a safer approach would be to place small (100~1K) resistors across the cuts/opens so when nothing is connected by the sense wires or they aren't used but switch is in the remote sense position, then the resistors still provide some feedback across the cuts/opens, maybe with a slight error. When the switch is in the remote sense position the resistors are effectively shorted by the sense leads and have little to no effect, and when the switch is in the normal direct sense the resistors have no effect since they are directly shorted by the switch.IMO this is a much safer approach and costs almost nothing, we would never implement a feedback sensing capability, nor modify for such, without the ability to keep some level of remote sensing feedback in effect in all cases, even when the sense wires are not used, fall off, or open, and the system is setup for remote sensing.This is basically a fail safe approach as high gain negative feedback systems (like these electronic loads) can do nasty things when the feedback is opened, even momentarily!!Anyway, we do like the addition of the remote sensing capability, and the use of a BNC is a nice touchBest,

author: andyB2022
author_rank: Regular Contributor
timestamp: May 13, 2023, 09:19:18 am
content: The load doesn't care about the sensing at all, if I set it to draw 10A it will draw it even if the input voltage is 0V.Ofc, I don't recommend operating the load without any "voltage".

author: mawyatt
author_rank: Super Contributor
timestamp: May 13, 2023, 02:47:46 pm
content: Quote from: andyB2022 on May 13, 2023, 09:19:18 amFirst you can't draw current from a zero voltage source with a passive non-source real load (read not a negative R). As you've shown the load is reading zero volts but the DUT source is 20 volts, so the load "thinks" the power is zero and shows such, but is really dissipating 200 watts (10A*20V), not 0!!!BTW the power FETs know this isn't 0 watts but actually 200w and they will quickly see a temperature rise even tho the ET5410 is showing 0 watts, IMO this is not an acceptable condition!!Can see that constant current load wouldn't care about remote voltage sensing as it's just sensing the current as feedback, and that's totally internal, but will get the power wrong as you've shown.But, what about under constant voltage, resistance or power modes? Be careful here, without a schematic it's hard to predict what will happen if the voltage feedback is opened.For example in Constant Power mode what could happen as Power is Current Voltage product, so measuring a unknown voltage could cause the load Current demand to rail if the unknown voltage isinterceptedinterpreted as low voltage, yet the electronic load is actually "experiencing" a high voltage from the DUT source. This condition would likely quickly overheat & damage the load power FETs, and if the DUT is a high capacity battery even worse!!Anyway, just trying to prevent/warn of a situation where one could damage the load and DUT. If we had a proper set of schematics then this could be analyzed, but without such as we said better to fail safe (2 resistors don't cost much)!!Best,

author: andyB2022
author_rank: Regular Contributor
timestamp: May 27, 2023, 07:31:27 am
content: Now I see your point, thanks!