ET5410 Electronic Load mod: add external sense

[klausES]

Yes, it is a shame that even the newer A+ models External Sense is still missing.

That's why I struggled with myself for longer whether I should take it or not
until I decided to create a way to compensate for the voltage drop until the entrance for my device.

[cybermaus]

Well, I checked, no calibration in software version 1.02

Also, if you think calibration would be useable for sense-compensation, you might be mistaken.
as you probably know, the voltage drop will vary with current as well as temperature. You'd have to have a separate calibration value for each cable and each current that you might use.

You do not need a exterbal sense, if you just want to stress test some power supplies, and need to dump the energy somewhere.
A simple multi-meter could be your voltage sense.

However, if you want to test some batteries, or simply want to have the convenience of not having to hook up an extra multimeter, yeah, it is a bit silly they still sell this without sense wires.

[mawyatt]

Hello. I just made a connection for 4 wires on 5410A+. I cut the traces and simply added a 22 ohm resistor between +V and +SENSE. Setting more then 20 Ohm will lead to an measurement error with 2-wires, and low values will cause voltage drop with 4-wires.
This made it possible to use both a 2-wire connection and a 4-wire connection without adding a switch. The standard behavior of the device has not changed.
Yes, it is possible that a voltage error may occur with a 2-wire connection but no more than 1 in the last digit on the screen. Tested in the range of 5-60V, 0-25A. And it still measures absolutely accurately with 4-wires connection. Also thinking of diode protection, but later.

part of original
(Attachment Link)

new one
(Attachment Link)

appearance
(Attachment Link) (Attachment Link)

And one more moment. The motherboards have been replaced due to a transistor that burned out on the first day. And I can't remember if the "software sense" function worked correctly when measuring the resistance of the wires connected to the battery or to other weak source.
The line resistance measurements are correct with a laboratory power supply. But when I try to measure the line resistance with the battery connected, I get incorrect data as the source voltage has a drawdown. Is it like this for everyone or is the new board also defective?
That was my the main reason to transfer it to 4-wires schema.

Interesting and clever mod

Would think you would also want a 22 ohm resistor between the - Power terminal and 119.2K 199.2K resistor and "SENSE -" between to balance out the differential amplifier.

Best,

[klausES]

Well, I checked, no calibration in software version 1.02
...

Thanks for the info.

...
Also, if you think calibration would be useable for sense-compensation, you might be mistaken.
as you probably know, the voltage drop will vary with current as well as temperature. You'd have to have a separate calibration value for each cable and each current that you might use.
...

No fixed values, i was already thinking of an activable / deactivable external sense (at the moment with a front microbutton, logical flipflop und gas tube relay).

Since i couldn't find a circuit diagram from Kunkin KP184, i would be interested to know how the Kunkin reacts
if you activated ext Sense in your menu and then didn't connect the sense cable to the source ?

[cybermaus]

if you activated ext Sense in your menu and then didn't connect the sense cable to the source ?

Not sure for that model, but for my model,
I described that on the very first post of this thread:

Originally, I had some worry on how the device would respond if there was accidentally no voltage on the sense wires. I worried about software hanging with "divide by zero errors", but it is behaving perfectly:
- CC mode: it does not care, just keep drawing the current, but V and W display go to 0, and back up when reconnect
- CP, CR and CV mode : the device just stops drawing current, but does not hang, Reconnect, and it starts up again.
Even repeatedly switching from internal to external sense seems to not bother the device.

[klausES]

I meant how the Kunkin would react, but if the ET5410 reacts as you write, this info is even more valuable.
Thank you for that.
Now i just have to wait until it is delivered. 

[DaneLaw]

What is the weight of the newer ET5410A+..? (just the unit alone)

[andobovsayvkub]

2940 grams (my 2 banana extra slots included)

[andobovsayvkub]

The external sense however is still very important. You really need to either have HUGE cables and clamps, or correct for the cables voltage drop.

I've tested batteries in both modes (2p and 4p) and the difference in capacity was about 1%.

• 18V-4Ah with 10A current and 2meters cable (4mm²) - 0.5% of Ah and 1% of Wh.
• 18V-4Ah with 10A current and 1.8meters cable (0.8mm²) - 1.2% of Ah and 5% of Wh.
• 48V-12Ah with 6A current and 2meters cable (4mm²) - 1.1% of Ah and 1.1% of Wh.

I'm guessing a 4-wire circuit isn't necessary for battery testing if you have decent cables.

Could you explain where the areas when this is really important? Power supply testing of course, but what else?

[cybermaus]

Well, your 0.8mm2 cable will have 5x the voltage drop of your 4.0mm2 cable in absolute sense and if same length.

So when ones focus is on voltage, this is important, but even then, how significant it is depends on the total voltage
0.2V vs 1.0V (random examples) on a 3.6V single cell is significant. But on a 48V pack (your last example) less so.
Maybe you also remembered to use really short cables

You soften the impact even more by discussing energy, because as voltage rises, current drops, which means the voltage drop drops... [sic]
Meaning on equal energy/power, the impact of the cable is indeed the inverse-square of what it was when one focused on voltage drop directly

But even then: You describe a 5% deviation. Not very precise now is it?
But indeed, maybe good enough for causal battery checking, if so, then indeed 2 wire is good enough.

[DaneLaw]

2940 grams (my 2 banana extra slots included)

Thx for the feedback, the reason why I was asking is that it seems to be cheaper, than what the older revision reflected ET54xx, and speculated if East Tester had cost-optimised it, as I noticed some months back when looking at their specs, there was quite a big difference in weight between old versus new model.
Fx the 40A 1ch. model.
ET5410 = 3.7kg (old model)
ET5410A+ 2.9kg (new model)

Its around 25% of the total weight that's been abracadabra-goneski.

[klausES]

The question is whether the 3.7 kg in the older model was right. The one dealer from China probably write down the wrong one from another ...

The weight difference mentioned from almost a kg appears to me on the basis of the pictures when you look at the same heat sink etc.
and the housing also seems to be of the same tin thickness, simply too big to be realistic.

[DaneLaw]

The question is whether the 3.7 kg in the older model was right. The one dealer from China probably write down the wrong one from another ...

The weight difference mentioned from almost a kg appears to me on the basis of the pictures when you look at the same heat sink etc.
and the housing also seems to be of the same tin thickness, simply too big to be realistic.

Looked at some of my older pictures.
A tad under 3.7kg, seems about right on the older model.

 

[klausES]

There are very different information, even up to 4.3 kg in one case a dealer writes 5 kg.
All of the written does not close to the scale with your weight. So I don't go from most information on the Internet.
This seems to me sucked out of their fingers. Really measured, hardly any of these retailers who otherwise also sell women's stockings.

Incidentally, a nice button for the Rotary Encoder. Hopefully your device doesn't weigh so much because of this 

[andobovsayvkub]

Interesting and clever mod

Would think you would also want a 22 ohm resistor between the - Power terminal and 119.2K 199.2K resistor and "SENSE -" between to balance out the differential amplifier.

Best,

I suppose you are right. Frankly I have no idea how it would change the result. I have seen that R114 has shunted already the entire circuit and suggested that there is some error in schematics or current going bypassing this circuit. I really tried to get the resistance between GND and GNDD and always got zero. Anyway worth a try to add. Someday.

The question is whether the 3.7 kg in the older model was right. The one dealer from China probably write down the wrong one from another ...

The weight difference mentioned from almost a kg appears to me on the basis of the pictures when you look at the same heat sink etc.
and the housing also seems to be of the same tin thickness, simply too big to be realistic.

Looked at some of my older pictures.
A tad under 3.7kg, seems about right on the older model.

According to "old" photos from topic it seems that there was a metal frame on front panel. Now it's a pure plastic. But 0.8kg  ? May be smth else lost weight.

[DaneLaw]

There are very different information, even up to 4.3 kg in one case a dealer writes 5 kg.
All of the written does not close to the scale with your weight. So I don't go from most information on the Internet.
This seems to me sucked out of their fingers. Really measured, hardly any of these retailers who otherwise also sell women's stockings.

As highlighted.
There is a big difference in weight between the old versus new [A+model] its just how it is, it ain't down to site-wording limbo.
Looking at the internals.. it's been cost-optimised/enhanced.

That doesn't always have to be a bad thing (even on a programmable sinkload) if the prices also drop noticeably.

Incidentally, a nice button for the Rotary Encoder. Hopefully your device doesn't weigh so much because of this 

No, its a beefy aluone, but not that weight potent...