Author Topic: Applent AT8612 DC load - a quick tear down  (Read 23607 times)

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Offline sstepane

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Re: Applent AT8612 DC load - a quick tear down
« Reply #50 on: June 19, 2017, 01:06:41 pm »
I installed it successfully over A2.5, but now, I am getting a "Runtime error 9, subscript out of range" late into the connection process of the 1.0.0 software. Flashing back to A2.5 fixes the issue. Anybody either has this error or has been successfully running the 1.0.0 sw on A2.9 (or has a more up to date version of the sw)?

I've seen this error as well, did not try on 2.5 version though. I think it is a good idea to email Vera about this. Hope they will fix it (it should take couple of minutes as far as I understand - just to change parsing function in software).
Here's Vera's email - vera@applent.com. Let me know if You're not going to write to her - I will then.
 

Offline LaurentR

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Re: Applent AT8612 DC load - a quick tear down
« Reply #51 on: June 19, 2017, 02:30:17 pm »
I installed it successfully over A2.5, but now, I am getting a "Runtime error 9, subscript out of range" late into the connection process of the 1.0.0 software. Flashing back to A2.5 fixes the issue. Anybody either has this error or has been successfully running the 1.0.0 sw on A2.9 (or has a more up to date version of the sw)?

I've seen this error as well, did not try on 2.5 version though. I think it is a good idea to email Vera about this. Hope they will fix it (it should take couple of minutes as far as I understand - just to change parsing function in software).
Here's Vera's email - vera@applent.com. Let me know if You're not going to write to her - I will then.

Thanks sstepane. Just shot her an email.
Screenshot attached for reference.

 

Offline sstepane

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Re: Applent AT8612 DC load - a quick tear down
« Reply #52 on: June 20, 2017, 12:46:02 pm »
Hi,

Vera said to address this issue when engineer will come from a trip.
 

Offline LaurentR

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Re: Applent AT8612 DC load - a quick tear down
« Reply #53 on: June 20, 2017, 04:08:03 pm »
Hi,

Vera said to address this issue when engineer will come from a trip.

Now we know how many people they have working on this  :)
 

Offline thefamilyman

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Re: Applent AT8612 DC load - a quick tear down
« Reply #54 on: June 21, 2017, 05:17:57 am »
Mine has died.
wouldn't go over 10A and now cant even do 1A load on any setting.
cant be bothered repairing it.
 

Offline sstepane

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Re: Applent AT8612 DC load - a quick tear down
« Reply #55 on: June 21, 2017, 07:44:43 pm »
Hi,

Anyone got it to work via serial port? Can't get any answer from it. Might be software related or I'm doing something wrong. Tried HyperTerminal and Putty under Windows, no response from the device. Original software queries the device ok.
 

Offline sstepane

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Re: Applent AT8612 DC load - a quick tear down
« Reply #56 on: June 21, 2017, 08:55:58 pm »
Found it - you need to lock the keypad for the device to react to scpi commands over serial.
 

Offline sstepane

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Re: Applent AT8612 DC load - a quick tear down
« Reply #57 on: June 26, 2017, 12:27:42 pm »
Hello,

Another nuance - if you're going to use SCPI commands with this device - some commands need a bit more time to execute - for example mode change command needs some delay (I use 0.5 sec) to complete.
For the moment I'm experimenting in writing some Labview routine to test li-ion battery along with temperature sensing from another device.
 

Offline rsivan

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Re: Applent AT8612 DC load - a quick tear down
« Reply #58 on: November 11, 2017, 11:34:22 am »
Hello I try to upgrade from fw A1.9 to A3.1, but after stuck at boot logo then I discovered there is 2 version of fw 8612 and 8612A
so the only fw which starting now is A2.2 for non "A" version, now calibration is gone ,I tried to enter password in service menu but cannot make calibration,if press zero key unit stuck in loop quickly triggering relay inside, does someone have procedure for calibration or also newer fw for non A version? I try to write vera@applent.com still waiting for a answer.

thanks
« Last Edit: November 11, 2017, 11:36:33 am by rsivan »
 

Offline TurboTom

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Re: Applent AT8612 DC load - a quick tear down
« Reply #59 on: November 11, 2017, 05:41:28 pm »
...similar situation here. Found a quite strange behavior on a newly shipped AT8612 (A?) which would display all current readings in CC mode if the set current hasn't been reached (i.e. unregulated) some odd 200mA too high. So if no current was applied (terminals unconnected) it read something like 203mA if for example a set current of 1A was selected and the load turned on. If the set current was below these displayed 2xx mA, the reading would be truncated at the set current. Otherwise, the device performed as expected. I purposely use past tense since...

Well, couldn't leave my hands off the "TFT equipped p..." and since the calibration access password was supplied here, I tried my luck and...of course...ruined the calibration completely. Is there any native chinese speaker present on this forum who could help with translating the messages displayed during calibration if I take a series of step-by-step photos of the screen? It's sill questionable if this would really help since the messages appear to be rather short and apparently no numbers (like currents/voltages to preset) are provided. But it may be worth a try nevertheless.

If someone would agree to assist, I'll go ahead and take some photos...

Even if the recalibration would be successful, I'm not sure if there might be another (hardware) problem with my instrument that caused that current offset to be displayed. Currently I'm somewhat reluctant to send it back to China since shipping would cost an arm and a leg and I can't be too sure if I'll ever get the device returned. And once in a while I like a challenge like this, I take it like a kind of sports...

Cheers,
Thomas
 

Offline casinada

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Re: Applent AT8612 DC load - a quick tear down
« Reply #60 on: November 11, 2017, 06:11:16 pm »
Did you try Google translate?  :-//
 

Offline TurboTom

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Re: Applent AT8612 DC load - a quick tear down
« Reply #61 on: November 11, 2017, 08:12:52 pm »
Problem is: I can't even enter the chinese symbols or know how to find them in a list or so. And considering the quality of an "automatic" chinese -> english online translation, I doubt that the result will be too useful. I might be wrong though. Does anybody know of some kind of "ocr translator" for chinese language where one can input photos of the symbols?

Cheers,
Thomas
 

Offline luciof

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Re: Applent AT8612 DC load - a quick tear down
« Reply #62 on: November 11, 2017, 09:17:02 pm »
Hi there,

I experienced a similar problem a few months ago.

Starting the load after a long time, I found both current and voltage readings quite wrong.
A few weeks later I found the system password on this forum and made a try, but without success.
I also managed to get a translation of some chinese sentences which popped out during this process, but the problem is, I can't figure out what's the logic behind the required calibration procedure.

In attachment a Word doc with the pictures of the chinese sentences above and their translations (from an Asian languages scholar). Hope this helps - but I doubt it...
 
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Offline rsivan

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Re: Applent AT8612 DC load - a quick tear down
« Reply #63 on: November 12, 2017, 08:13:44 pm »
Thanks Lucio, I done some try also google translator android app can translate from pics,just add chinese lang and take shot,but for me procedure which is working are:
Reset(select label and press enter)it make kind of "cal reset" and make just row pecise but not 100% like 1A=830nA 2A=1998,3A=3.1A,4A=4,2A and so on,just need to cal voltage.
zero key=system going in loop triggering a  relay  but if quickly press trigger or enter key some time (10-20) is going out and show 0v at standby

voltage cal is working, ask you 2 reference value one for low range=18v and one for high=150v  ,I used 20v for high and 10v for low with rigol power supply and make cal ok 100% precise about V

current cal will ask you 2 reference,it drain 5,2A then 1.1A when ask I presume you should input a real value readed from PS,but in both any value you write don't change any for me I think there is some bug in fw,

if any one can dump flash  would be great because serial number can be  changed form service menu and adapt to other instrument is easy.

I write to Vera they are investigate about issue,send me 2 fw but stuck at boot with both.

Update
After contacted Vera they send me a 2.4 firmware which is working ,now calibration is working as well,instrument is up again and very precise!
if someone have problem I suggest you to contact Vera with serial number they are very fast and will send right fw to update without problem.


« Last Edit: November 15, 2017, 08:21:23 am by rsivan »
 

Offline luciof

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Re: Applent AT8612 DC load - a quick tear down
« Reply #64 on: November 17, 2017, 10:25:19 am »
Hi rsivan,

I have the same problems in calibration: managed to get correct voltage readings, but current is always way off (and current readings are not even linearly related to actual values).

My current firmware is A2.8, which Vera sent me two years ago to correct some bugs. This version allows me to use the AT8612 up to 300 V instead of 150 V.
My newest FW file is AT8612.151119.B2.9, with a minor bug correction in serial programming, but limited to 150 V (so I removed it after a quick test).

If I understand correctly, your 2.4 firmware version allows you to fully calibrate the instrument; is it accurate in both current and voltage?

Also, this sounds a little strange to me, because 2.4 looks like an old FW version.
But, if it enables calibration I may install it, perform calibration and then install back the A2.8.
So, may you kindly post the 2.4 FW for a quick try?

Thanks,
    Lucio.



 

Offline TurboTom

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Re: Applent AT8612 DC load - a quick tear down
« Reply #65 on: December 27, 2017, 12:56:02 am »
Recently I found some time to have a closer look at the peculiar behavior of my AT8612A - I reported that before but didn't get into too much detail. Actually, I found the cause and I was quite amazed that this slipped through Applent's QC... But let's first have a look what was strange: The first photo shows the load, set to CC mode with a current of 1A dialed in and switched off and nothing connected to it. Everything's fine, the display readings are as one would expect.

Now, all I did was activating the load's input, still nothing is connected to it and nothing else has changed to the previous photo: Mysteriously, the load is reading a current of 212mA now. I did some basic reverse engineering of the passbank circuitry which consists of eight individual current sinks, all controlled by the same control voltage that is generated by the circuitry around the main shunt. This configuration makes sure that the power dissipation is spread evenly across all eight passbank transistors. See the photo of my ugly whiteboard drawing of one channel's simplified schematic.

Some probing around didn't show anything special initially -- except gate voltage at the mosfets at the second glance... It was around 9V with the load enabled on EVERY transistor. Moreover, before the gate resistor(s) I measured something like 10.8V which means that the gate-source protection clamps started to conduct. And that's the cause of the current being displayed when the load is switched on. As soon as the load is actually controlling the current, the gate-source voltage of the passbank transistors will be lowered to a value slightly above the individual transistors threshold voltage -- considerably below the 9V that the clamps become conductive at. That's why the load appeared to work normally when it was controlling an external current. As soon as the external current is lowered below the preset value, the gate voltage is increased and again the clamps become conductive, which results in a current reading offset by the 200 odd milliamps.

The zeners of the gate voltage clamps have apparently been 8.2V type while they probably should have been rated at 12V. Seems like somebody installed the wrong feeder on the p&p machine... Whatsoever, I replaced all 16 zeners with 12V types and the problem was gone.

Since I had to remove the main PCB for this job, I found some ugly details in an otherwise neat design -- probably the "Danger" sign had been placed there to indicate the tiny creepage distance around the mains switch area  ;) - especially to the switch's metal mounting bracket. The pitch of the nearby connectors is 2.54mm for comparison. I'm quite surprised of this since in the other areas where mains power is routed across the PCB, the creepage clearances are ample or even isolation slots are milled through the FR4. Apparently, this ugly detail didn't cause any trouble yet.

I had been in touch with Vera who's really very kind and helpful. I discussed the calibration issue and the benefit of being able to do the job myself and she was so kind to send me a short instruction sheet (see attached PDF - slightly edited by me). With the help of this, I've been able to get the CC mode accurate again. It seems the voltage slope calibration requires a "proper" lab supply with at least 250V output voltage which I haven't got. I experimented with an electrophoresis supply but this is way too picky and shuts the output down all the time. Calibration of the current slope actually requires a power supply that outputs more than 30A - I used a 12V 1kW server PSU for that job and it worked a treat. I'll add the information about how to calibrate the voltage mode and what kind of PSU will do once I succeed.

At least there's some hope for all those of us who messed up the calibration or just want to do the job themselves. I'm most impressed by the amount of cooperation at Applent and can only say "Thank you, Vera".

All the best,
Thomas
 
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Offline Safar

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Re: Applent AT8612 DC load - a quick tear down
« Reply #66 on: January 18, 2018, 02:24:27 am »
Very interesting TurboTom.

I just received device and then I test it, I noticed one strange thing:

If the source device have current limit (for example on 3,000A in CC mode lab PSU) and if I try to set current on AT8612 more than this limit (3,500A for ex.) then Ammeter of AT8612 shows the value more then real current on 170..190mA (3,178A). It's not depend of Voltage or Current limit values. For example it shows 2,175A for 2,000 A limit or 1,179A fot 1,000A limit. Of course I checked real current with Multimeter. And I checked it with two Lab PSU (Agilent, GWInstek).

Can somebody reproduce this issue?

Also very strange action on low Ohm 0.1...2.0 in CR mode, not tested carefully yet.

Firmware REV A2.5.

Wrote Vera
 

Offline Safar

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Re: Applent AT8612 DC load - a quick tear down
« Reply #67 on: January 18, 2018, 03:43:59 pm »
Mysteriously, the load is reading a current of 212mA now.

Seems like I has the same issue.

But all gone just after reflash to A3.2 (attached)
« Last Edit: January 18, 2018, 03:46:22 pm by Safar »
 

Offline Safar

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Re: Applent AT8612 DC load - a quick tear down
« Reply #68 on: January 18, 2018, 04:00:50 pm »
But ghost current still here under the load  :-BROKE

Think same problem like TurboTom's device. Control current drain via protection circuit.

« Last Edit: January 18, 2018, 05:31:25 pm by Safar »
 

Offline TurboTom

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Re: Applent AT8612 DC load - a quick tear down
« Reply #69 on: January 18, 2018, 04:28:28 pm »
This is exactly the same behavior that I noticed on my AT8612A - I guess yours is suffering from the wrong zeners as well.

Open the casing, and just check the voltage between gate and source of an arbitrarily selected passbank transistor while the instrument is not connected and the input enabled. If you read round about 9V, the zener problem is present, if it's more like 11V, the passbank clamps are likely okay.

Good luck and all the best,
Thomas
 
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Offline Safar

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Re: Applent AT8612 DC load - a quick tear down
« Reply #70 on: January 18, 2018, 05:28:43 pm »
Yes, I did.

But I have another voltage, even more less.

In normal current regulation on 3A (17.5V source) voltage is 3,76V (#1 on pic). In short (CC 3.2A on source) voltage is 7,06V (#2).
It seems like 6,2V zeners installed in my device.

Exactly the same is happens if you push "on" without any source connected.

And I measure voltage drop on gate resistor: almost no current (#3) as expected in normal mode and about 2.74V (#4) on shorting. It correspond ~6mA for 470 Ohm gate resistor. All 8 resistor have almost the same voltage drop. So it about ~48mA total drain. OpAmp heated till 50 C degrees on this mode.

But why ghost current drain is 170mA? Anyway it need to fix.

Many Thanks for very helpful find! And where are zeners for outside MOSFETs? Under the heatsink?

And about A3.2 - it is very strange but it seems like just program cut small current for displaying when all gates opened (source not connected or source limit current). Not right solution. Do not recommend for install.

I will write to Vera and ask for another FW.
« Last Edit: January 18, 2018, 06:19:35 pm by Safar »
 

Offline TurboTom

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Re: Applent AT8612 DC load - a quick tear down
« Reply #71 on: January 18, 2018, 06:29:22 pm »
The indicated "ghost" current is higher than the actual current flowing through the gate-source voltage clamps since this current isn't flowing only through the (main) shunt resistor but also through the ground plane of the sense amplifier(s) where no load current ever should flow. This results in too high a reading.

Replace all 16 zeners with 12V versions and you should be okay. You'll have to remove the PCB from the casing, though, since some zeners are assembled on the solder side. Moreover, to access some of the zeners on the component side, you've got to temporarily remove the source resistors (the white power "bricks") of the passbank transistors. Otherwise, the job is straight-forward...

Cheers,
Thomas
 
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Offline Safar

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Re: Applent AT8612 DC load - a quick tear down
« Reply #72 on: January 19, 2018, 12:52:54 pm »
I wrote yesterday all measurements to Vera and ask engineer for information about zener nominal.

And the answer is 6.2V. Not funny.

Ok, I wrote now all explanations of ghost current and ask to provide this to engineer deps.

Let's see...
 

Offline Safar

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Re: Applent AT8612 DC load - a quick tear down
« Reply #73 on: January 19, 2018, 12:55:10 pm »


The indicated "ghost" current is higher than the actual current flowing through the gate-source voltage clamps since this current isn't flowing only through the (main) shunt resistor but also through the ground plane of the sense amplifier(s) where no load current ever should flow. This results in too high a reading.

Replace all 16 zeners with 12V versions and you should be okay. You'll have to remove the PCB from the casing, though, since some zeners are assembled on the solder side. Moreover, to access some of the zeners on the component side, you've got to temporarily remove the source resistors (the white power "bricks") of the passbank transistors. Otherwise, the job is straight-forward...

Cheers,
Thomas

Thanks a lot for this helpful info
 

Offline audun

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Re: Applent AT8612 DC load - a quick tear down
« Reply #74 on: January 23, 2018, 11:34:59 am »
Hi!

Trying to decide if I should buy this load...

Would 1N5349B zeners be a good choice, if needed?

Anyone successfully connected the load to a computer via the front panel USB, instead of using the RS232 on the back?

Best regards Audun
« Last Edit: January 23, 2018, 11:42:09 am by audun »
 


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