Author Topic: ET5410 Electronic Load mod: add external sense  (Read 24630 times)

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Offline klausES

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Re: ET5410 Electronic Load mod: add external sense
« Reply #75 on: June 21, 2024, 06:29:10 pm »
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.
regards klaus. "Art is when you can't do it ... because if you can, it's not art"
 

Offline cybermausTopic starter

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Re: ET5410 Electronic Load mod: add external sense
« Reply #76 on: June 21, 2024, 06:44:21 pm »
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.

 

Offline mawyatt

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Re: ET5410 Electronic Load mod: add external sense
« Reply #77 on: June 21, 2024, 08:35:59 pm »
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,
« Last Edit: June 22, 2024, 02:05:54 am by mawyatt »
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Offline klausES

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Re: ET5410 Electronic Load mod: add external sense
« Reply #78 on: June 22, 2024, 01:38:51 am »
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 ?
« Last Edit: June 22, 2024, 01:42:19 am by klausES »
regards klaus. "Art is when you can't do it ... because if you can, it's not art"
 

Offline cybermausTopic starter

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Re: ET5410 Electronic Load mod: add external sense
« Reply #79 on: June 22, 2024, 03:38:07 am »
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.
 

Offline klausES

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Re: ET5410 Electronic Load mod: add external sense
« Reply #80 on: June 22, 2024, 11:05:34 am »
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.  :)
regards klaus. "Art is when you can't do it ... because if you can, it's not art"
 

Offline DaneLaw

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Re: ET5410 Electronic Load mod: add external sense
« Reply #81 on: June 22, 2024, 11:41:44 pm »
What is the weight of the newer ET5410A+..? (just the unit alone)
 

Offline andobovsayvkub

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Re: ET5410 Electronic Load mod: add external sense
« Reply #82 on: August 06, 2024, 12:52:00 pm »
2940 grams (my 2 banana extra slots included)
 

Offline andobovsayvkub

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Re: ET5410 Electronic Load mod: add external sense
« Reply #83 on: August 06, 2024, 01:11:23 pm »
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?
 

Offline cybermausTopic starter

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Re: ET5410 Electronic Load mod: add external sense
« Reply #84 on: August 06, 2024, 01:32:16 pm »
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.





« Last Edit: August 07, 2024, 01:06:09 pm by cybermaus »
 

Offline DaneLaw

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Re: ET5410 Electronic Load mod: add external sense
« Reply #85 on: August 06, 2024, 04:16:37 pm »
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.
« Last Edit: August 07, 2024, 11:46:35 am by DaneLaw »
 

Offline klausES

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Re: ET5410 Electronic Load mod: add external sense
« Reply #86 on: August 07, 2024, 12:36:04 pm »
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.
regards klaus. "Art is when you can't do it ... because if you can, it's not art"
 

Offline DaneLaw

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Re: ET5410 Electronic Load mod: add external sense
« Reply #87 on: August 07, 2024, 12:50:58 pm »
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.

 
 

Offline klausES

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Re: ET5410 Electronic Load mod: add external sense
« Reply #88 on: August 07, 2024, 02:54:41 pm »
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  ;)
regards klaus. "Art is when you can't do it ... because if you can, it's not art"
 

Offline andobovsayvkub

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Re: ET5410 Electronic Load mod: add external sense
« Reply #89 on: August 07, 2024, 03:11:32 pm »

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  ;D? May be smth else lost weight.
 

Offline DaneLaw

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Re: ET5410 Electronic Load mod: add external sense
« Reply #90 on: August 07, 2024, 03:21:59 pm »
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... ;D
 

Offline MF-jockey

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Re: ET5410 Electronic Load mod: add external sense
« Reply #91 on: September 03, 2024, 10:03:24 pm »
My ET5410A+ arrived on September 2nd, 2024.
The device without cable weighs 2923 g.
First I checked the accuracy of the voltage measurement.
When the inputs are open or short-circuited, 0.012 to 0.019 V are displayed. It changes slightly when switched off and on again.
With a connected battery, an exactly the same voltage of 13.755 V is displayed compared to the OWON XDM1241 (accuracy 0.05%). A 10V reference voltage is measured once at 10.006 V and a little later at exactly 10,000 V.
This was followed by a check of the current measurement in the range up to 11 A, the XDM1241 cannot do more than that. It was noticeable that the load does not always regulate the setpoint exactly. The largest deviation of 0.23% between the two displays was at 7 A. However, the OWON is only specified with an accuracy of 0.5% in this range.
The next test was the contact resistance up to the circuit board. To do this, I connected the terminals with a solid copper wire and measured the resistance between the circuit board points with the DE-5000 from DER EE; it was 3 mOhm.

Now for the modification with sense inputs. I don't like the solution with a switch because I expect contact resistance in the long term. You also have to pay attention to the switch position.
I prefer the solution with two low-resistance resistors and have calculated their measurement error. As a result, I decided on 10 Ohm resistors.

This results in a small additional error of only -0.005% for 2-wire measurements (e.g. -0.6 mV at 12 V or -2.4 mV at 48 V). This is negligible compared to the error that typically occurs due to the resistance of the wiring.
When measuring with 4 wires, you should also pay attention to low-resistance measuring cables, otherwise the voltage drops in the load cables will affect the measured value via the 10 ohm resistors. If you have to deal with longer cable lengths, you should choose the 22 ohm variant, as this will result in an additional error of -0.011% in 2-wire operation.
I am attaching the calculation with both variants here and hope that it is presented in an understandable way. Please see the attached "error-calculation.pdf".
In a 30 A load test with very good load lines (2x 10 AWG parallel, approx. 10.5 mm² Cu, only 0.27 m long), the additional sense lines produced voltage values ​​about 50 mV higher.
« Last Edit: September 03, 2024, 10:46:38 pm by MF-jockey »
 
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Offline MF-jockey

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Re: ET5410 Electronic Load mod: add external sense
« Reply #92 on: September 04, 2024, 04:42:57 pm »
Better is the enemy of good.
Afterwards I noticed that you should connect the resistors closer to the source.

This avoids the voltage drops on the internal power rails (each has about 1 mOhm).
For 2-wire measurements, the voltage measurement is then better than in the original state (even with 22 ohm resistors).
For 4-wire measurements, the measurement error is also reduced somewhat.
At the moment I only use it about halfway.
When I open the device again, I will correct this.
« Last Edit: September 04, 2024, 04:50:11 pm by MF-jockey »
 

Offline mawyatt

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Re: ET5410 Electronic Load mod: add external sense
« Reply #93 on: September 04, 2024, 06:45:02 pm »
Have you considered what will happen when just the High Current cable/wire from the Source to Load is interrupted? This should cause the Load/Source to seek or force current thru the Sense Lead and thus the 10 ohm Resistor, which will result in High Currents attempting to flow thru the Resistor which may Open due to I^2*R heating and the Load will loose feedback!!

Maybe consider a "Safer" mod would include a High Current SBD in parallel with the Resistor and with a Higher Wattage Resistor. Also adding a Low Current PTC Fuse in Series with SBD and Parallel Resistor to not allow the High Current to be sustained thru the Sense Leads and potentially damaging them.

Doing some "Safety Tests" with just Power Supply Controlled Sources while disconnecting various leads from the PS to Load should reveal how the Load misbehaves under these conditions, and one doesn't "find out" with an expensive Source  :o


Best,
« Last Edit: September 04, 2024, 07:22:18 pm by mawyatt »
Curiosity killed the cat, also depleted my wallet!
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Offline MF-jockey

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Re: ET5410 Electronic Load mod: add external sense
« Reply #94 on: September 04, 2024, 10:28:34 pm »
Yes, that is a sore point of this solution, that the load line must be carefully connected, especially at higher voltages. In the event of a fault at higher voltages, the affected 0.3 W resistor acts like a fuse and must then be replaced.
You should also connect a polyswitch fuse (e.g. RXEF010 from Littelfuse, is safe up to 60V, safe up to 240V is BOURNS MF-RM012/240) in series with the resistor and at the same time use a resistor with a higher power (>= 3 W). Due to the resistance of the polyswitch (2.5 to 7.5 ohms), the measurement error in 2-wire operation increases slightly.
Please do not place the polyfuse or PTC in the measuring line, this will significantly impair the voltage measurement.
« Last Edit: September 04, 2024, 11:46:28 pm by MF-jockey »
 

Offline mawyatt

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Re: ET5410 Electronic Load mod: add external sense
« Reply #95 on: September 05, 2024, 12:32:19 am »
Agree putting the PTC Fuse in series with the Resistor and not directly with the Sense lead is probably better. If a big enough power resistor is used, that can withstand the peak current, then the SBD can be omitted.

You can compensate for the PTC resistance by matching a pair for equal ~0 current resistance.

Or possibly even better, use a matched pair of PTC fuses in place of the 10 ohm resistors, then no need for the SBD or the Resistors!!

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline MF-jockey

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Re: ET5410 Electronic Load mod: add external sense
« Reply #96 on: September 19, 2024, 09:01:47 pm »
*** A safe 4-wire mod with PTCs ***
Inspired by mawyatt, I looked at the data sheets of common PTCs from TDK/Epcos. For a safe solution even at higher voltages, I can recommend the TYPE B59860C0080A070, https://www.mouser.com/ProductDetail/EPCOS-TDK/B59860C0080A070?qs=MD70nW2XBGhXaRINHeKp0g%3D%3D.
This PTC has a transition temperature of around 80°C, so it doesn't get that hot when switched off. The cold resistance is around 15 ohms, which is very suitable for this application.
In general, PTCs with 10 to 25 ohms are suitable. See also the EPCOS data sheet as first appendix.
A lower value reduces the influence of the 2-wire measurement. A higher value improves the 4-wire measurement, especially at high currents (higher voltage drop in the load lines).
Since I couldn't get hold of the PTC B59860C0080A070 so easily, I had other common PTCs (10 Ohm, 150°C) in stock, but I ordered Polyswitch 250V 0.1A from Aliexpress on suspicion https://de.aliexpress.com/item/1005004908820722.html.

These turned out to be a stroke of luck for this purpose, suitable resistance around 10 Ohm and quick response at relatively low temperatures. Knowing that the resistance increases after response, I connected 6 of the 10 PPTCs directly to 32 V DC. After a short current surge (approx. 3 A) they limit at around 40 mA. When they cool down they have a resistance that is around 15% higher, which is hardly a problem here. I have summarized the measured values ​​in the attached table.
Today I installed two of these PPTCs in my ET5410A+, it works well as expected.

« Last Edit: September 20, 2024, 09:02:54 am by MF-jockey »
 

Offline MF-jockey

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Re: ET5410 Electronic Load mod: add external sense
« Reply #97 on: September 20, 2024, 09:47:48 am »
Thermostat for fan, according to the mod by ceut -> there is a problem with ET5410A+

I got myself some 45 °C temperature switches and after testing them I installed one in the fan cable of the ET5410A+.


Unfortunately, the device was no longer usable. The fan symbol appears at the top right and all inputs are blocked. The software of the ET5410A+ works differently in terms of fan monitoring than the older one in the ET5410.
The fan only has two connection cables, monitoring is done using a 0.5 ohm resistor via the current flow.


I will now build a solution with an additional resistor to achieve the necessary current flow.

« Last Edit: September 20, 2024, 03:42:14 pm by MF-jockey »
 

Offline klausES

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Re: ET5410 Electronic Load mod: add external sense
« Reply #98 on: September 20, 2024, 04:05:11 pm »
Satisfied the fan monitoring with a minimum current by resistance and a decent temperature curve control to the fan,
(with a adjustable quiet minimum speed, because a complete standstill fan is not good for other components).
« Last Edit: September 20, 2024, 04:07:25 pm by klausES »
regards klaus. "Art is when you can't do it ... because if you can, it's not art"
 

Offline MF-jockey

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Re: ET5410 Electronic Load mod: add external sense
« Reply #99 on: September 21, 2024, 05:53:00 pm »
A sensible fan control according to temperature would be the responsibility of the manufacturer, especially since all the components for this are installed. Instead, a medium speed is set when the device is cold and when a higher power is set, it is regulated to full speed, even when the device is still cold. This is a quick solution and no programmer has thought about a quieter device.
After analyzing the circuit, I assume a current threshold of less than 80 mA. There are two different solutions for activating the thermostat solution.
Firstly, a parallel load resistor to the fan and thermostat so that the monitoring detects current flow. The fan can stay off until the temperature threshold is reached, but is not monitored.
Secondly, a bridging resistor on the thermostat that lets the minimum current for the fan monitoring through. This slows the fan down until the temperature threshold is reached.
I chose the second solution and determined the maximum resistance value with a potentiometer. At 27 ohms, the fan just about starts safely. For a little safety, I soldered 20 ohms onto the thermostat. This means that the fan runs much more quietly until the cooler reaches the switching temperature of the thermostat.
 


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