Author Topic: DP832A output  (Read 12685 times)

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Online 2N3055

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Re: DP832A output
« Reply #25 on: January 15, 2019, 08:05:16 pm »
Ok this is what I see now.
After inductive spike at the beginning, there is a 300 msec event of negative going voltage on output. voltage ranges are 262,5 mV for CH1, 62,5 mV for CH2 and around 400 mV for CH3.

I presume that is negative offset needed for PSU to be true 0 output, before digital part sends calibrated zero to analog part of analog board.

That is very interesting, and it is there.

That voltage is probably not going to damage anything, only problem is that it seems to be without current limit at the time.  So if you have very low impedance on output, it can pull many amperes...

It is definitely there but it probably will not damage  anything because of very small voltages..

I don't really care, because for years I was working with old PSU's, some of which had no output disable. So I never power up PSU with outputs connected.

Of course that shouldn't be necessary, and brings me to my few real complaints to DP800 series:
1. They should have put relays that disconnect outputs.
(I'm thinking of making small piggyback board that will control 3 relays of the On/Off leds in enable buttons)
2. OVP is in software and not in hardware and is very slow. Even in software it could be done in few msec after A/D conversion with some clever programing.
3. If you setup OVP at 3V, and then go to channel and set output to 30V it will let you. Not only that, it will let you ENABLE the channel, that will send 30V to that channel for few hundredths of msec before OVP will kick in. That is easily avoidable in program. And will definitely evaporate whatever is connected to that channel.

So I just presume there is no OVP on it. I use external crowbar if I think it's needed. I also make it a point to use 8V CH  (CH1) for logic/low voltage stuff..
 
 
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Offline RoGeorge

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Re: DP832A output
« Reply #26 on: January 15, 2019, 08:33:59 pm »
Or maybe my unit is faulty. But look:


Wow, that's a very convincing test!  :scared:
Is that a 12V/20W halogen bulb? 

The only incandescent light bulb I could find was a 21W/12V (auto turn signal) and a 6.3V/0.3A (small flashlight bulb size, like the ones used to illuminate the scale of tube radios).  Not halogen, both were normal incandescent.  Couldn't see any light, but I guess the halogen bulb will light up much faster.  Or, maybe you have a faulty DP832.

Don't know what is happening, but now I'm very curious to measure how much energy is in that spike.
« Last Edit: January 15, 2019, 08:35:47 pm by RoGeorge »
 

Online 2N3055

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Re: DP832A output
« Reply #27 on: January 15, 2019, 09:06:37 pm »
Or maybe my unit is faulty. But look:


Wow, that's a very convincing test!  :scared:
Is that a 12V/20W halogen bulb? 

The only incandescent light bulb I could find was a 21W/12V (auto turn signal) and a 6.3V/0.3A (small flashlight bulb size, like the ones used to illuminate the scale of tube radios).  Not halogen, both were normal incandescent.  Couldn't see any light, but I guess the halogen bulb will light up much faster.  Or, maybe you have a faulty DP832.

Don't know what is happening, but now I'm very curious to measure how much energy is in that spike.

That is indeed a lot of energy..
I would vote for a problematic unit. No way even my worst channel can light up a bulb.
I connected 10 Ohms on output, and voltages dropped to 100mV, 15mV and 125mV...

I would like to see oscillogram of voltage on that output, with and without defined load (like 10 Ohm).

EDIT: Typo in mV
« Last Edit: January 15, 2019, 09:13:26 pm by 2N3055 »
 

Offline sd

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Re: DP832A output
« Reply #28 on: January 15, 2019, 09:37:06 pm »
I have the Rigol DP832A and the higher power E36313A (I don't think there are any other differences between the E36313A and the E36312A). The DP832A is my go to lab PSU.

What I dislike about the E36313A:
-fan is always on, even when the PSU is off (as in soft off from the front panel). It isn't loud when it's in "off" mode but it's still noticeable in a quiet environment.
-when setting current/voltage you can't use the arrows to position yourself on a specific digit, and then use the rotary encoder to make for example 10mV/100mV steps (as you can on the DP832). You either go one mV at a time using the rotary encoder, use the keypad, or spin the encoder fast and watch if overshoot like crazy if you didn't set OVP. I, for one, newer felt the need for encoder acceleration on a lab PSU.
-doesn't display power for each channel as the Rigol does. You have to press the "Meter view" to see power for one channel.

Nice things about the E36313A:
-sense terminals on the back

 
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Offline sd

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Re: DP832A output
« Reply #29 on: January 15, 2019, 09:43:50 pm »
No idea. If you want I can make a couple of measurements on both of them in about 2-3 days.
 
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Offline nctnico

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Re: DP832A output
« Reply #30 on: January 15, 2019, 10:59:50 pm »
I will redo my measurement and will report back. (24 hours)

Edit (still getting back tomorrow, but could do this now):
While the spike is for real, it doesn't seem to have enough energy to do any damage.
You'd think. Or maybe my unit is faulty. But look:
Wow!  :wtf: I vote you have a faulty unit. To make sure you should do a measurement (using a scope) with an open circuit and the voltage across a 10 Ohm resistor. See what kind of waveforms you get.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline RoGeorge

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Re: DP832A output
« Reply #31 on: January 15, 2019, 11:24:28 pm »
On the other hand, if the spike is not limited in current, I woudn't be surprised for the halogen bulb to light up at a 0.1V spike, or alike.

The inrush current for normal incandescent light bulbs can easily be 10 times more than their nominal current.  If we combine that with the logarithmic sensitivity of the eye, maybe there is not so much energy required for a halogen bulb to blink slightly.

I suspect my DP832 (or any other DP832) will light a halogen bulb, too, just that I don't have any halogen bulbs for the moment.

Online 2N3055

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Re: DP832A output
« Reply #32 on: January 15, 2019, 11:35:41 pm »
On my 831 voltage droped 4x with 10 ohm load that is 30ish ohms internal impedance.
Not enough current to light a lamp.
I tried with 55W 12V lamp and it took 800 mV and 1.5A to see glow.
I will try tommorow with current shunt.
 

Offline PartialDischarge

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Re: DP832A output
« Reply #33 on: January 16, 2019, 06:48:30 am »
All my channels in the dp832 produce 0.3V 0.3s outputs on startup, last one is ch2 with 10ohms.
The halogen bulb video is quite strange




 

Offline RoGeorge

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Re: DP832A output
« Reply #34 on: January 16, 2019, 08:05:45 am »
But look:


I found a halogen bulb, but it's not 20W/12V, it's 35W/12V.  Can not see any light, not even in a pitch black room. The 35W one starts to glow, very, very faint at about 0.8A/0.7V.  I'll keeping looking for a 20W/12V halogen bulb.  I suspect your DP832 is either from the first batch, the ones with a small radiator, or simply it's a defective unit.

What year and board version is your DP832?
Is it the model with a small, or with a big radiator?

Offline Jeroen3

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Re: DP832A output
« Reply #35 on: January 16, 2019, 07:21:26 pm »
I will redo my measurement and will report back. (24 hours)
As mentioned, I redid my measurement.
Please excuse the crude drawing, drawing on a tablet is still new for me.

I must conclude channel 1 behaves odd. It gives 0.7 Watts for around 250 ms. The other channels do not.
I'll ask if this is warranty or repairable. (Bough it 15 months ago)
 

Offline nctnico

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Re: DP832A output
« Reply #36 on: January 16, 2019, 07:24:46 pm »
That is definitely broken. A similar problem made Keysight to recall all the 3631xA power supplies and fix them.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline RoGeorge

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Re: DP832A output
« Reply #37 on: January 16, 2019, 08:26:13 pm »
Wow again!  My DP832 doesn't act like that.

There is a 3rd wire connected at the DP832, in the green banana plug.  I can not see in the pics where it is connected on the other side.

1. Where to does that wire go?
2. What happen when you measure CH1 with the ground wire (green banana) disconnected?

Offline Jeroen3

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Re: DP832A output
« Reply #38 on: January 16, 2019, 09:04:21 pm »
The wire going away is ground for my USB switch. I grounded negative of the supply to not have common mode glitches.
Removing this makes it worse.

Edit: blueskull, sorry for hijacking your topic.
« Last Edit: January 16, 2019, 09:10:19 pm by Jeroen3 »
 

Online 2N3055

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Re: DP832A output
« Reply #39 on: January 16, 2019, 09:19:13 pm »
Warranty in EU is 3 years.. I would invoke it. Let us know how it goes.
 

Offline RoGeorge

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Re: DP832A output
« Reply #40 on: January 16, 2019, 09:44:45 pm »
That grounding problem is strange.  My hope is that the DP832 is OK, but some other power supply from other equipment is faulty.

Let's do one last test:
- disconnect all wires (USB, LAN, I/O, all), except the mains power cord
- connect only the halogen bulb at CH1 of the DP832.  No oscilloscope, no other instruments, just the two banana plugs and the bulb (one banana at +, one banana at -)
- no other wires or external jumpers

Does this minimal setup still flashes the bulb?

Offline TurboTom

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Re: DP832A output
« Reply #41 on: January 17, 2019, 01:00:09 am »
I just did some switch-on transient tests with my two DP800 series PSUs (811 and 832, both "liberated"), recent H/W and both F/W 1.16 beta. I checked voltage with a 10 ohms resistor across the terminals and current with a dead short via a Tek P6042 probe ("oldie but goldie" and definitely better than nothing at all...). I'ld say the 832 is unproblematic while the 811, well  :-[
It's amazing though how much the channels of the DP832 differ.
 

Offline nihtila

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Re: DP832A output
« Reply #42 on: January 17, 2019, 08:54:01 am »
I have DP832 and E36312A I won from a Keysight contest. Need to check my DP832 output as well..

Anyway, Keysight has become my go to instrument because it is soooo much quieter. Yes it's annoying that the fan is always on but I switch off my whole bench when not in use. I only use the Rigol when I need the extra power, or if I need more than 3 outputs like in the current project. Both have their quirks; while Keysight looks more professional it has had loads of bugs and the usability is still not as good as you would hope from a unit in that price class (miles better than the old E3631A though!). Anyway, I maybe like to use Keysight more now but would still choose Rigol because of significantly lower price tag.

PS. Keysight's low voltage output can go a bit over 6V, 6.1 or so - may be enough for a 5V LDO.
http://nihtila.com - Vegan DIY audio electronics, does not contain snake oil
 

Offline Jeroen3

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Re: DP832A output
« Reply #43 on: January 18, 2019, 07:58:45 pm »
Not the answer I was hoping for...
« Last Edit: January 18, 2019, 08:29:06 pm by Jeroen3 »
 

Offline RoGeorge

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Re: DP832A output
« Reply #44 on: January 18, 2019, 09:05:10 pm »
That grounding problem is strange.  My hope is that the DP832 is OK, but some other power supply from other equipment is faulty.

Let's do one last test:
- disconnect all wires (USB, LAN, I/O, all), except the mains power cord
- connect only the halogen bulb at CH1 of the DP832.  No oscilloscope, no other instruments, just the two banana plugs and the bulb (one banana at +, one banana at -)
- no other wires or external jumpers

Does this minimal setup still flashes the bulb?

I am very curious about this ^.  Can you check if the bulb still flashes when there are no extra electrical connections, only the power cord and the halogen bulb, please?

No need to waste extra time for visual evidence, a simple "yes, still flashes" answer will be more than enough.

Offline bson

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Re: DP832A output
« Reply #45 on: January 19, 2019, 03:02:05 am »
I've had it for 3 or 4 years now.  It's pretty big and noisy for its power; the Keithley 2231A-30-3 with similar specs, for example, is the size of a bench DMM.  It had a whole slew of firmware bugs when new, which are fixed now.  It's very easy to calibrate yourself when needed with just a basic multimeter, mine needed updated calibration data when new, but has retained 1mA/1mA readout accuracy since with that initial calibration.  Not sure what they do in the factory, but it was pretty poor.  Those scripts we wrote are still around and get it calibrated.  The 5V output is slightly more accurate that the higher voltage ones.  CV/CC works like they should, OVP and OCP can be disabled if a nuisance with some particular load.

The display is nice, the silly keypad is well, silly, but at least it's a keypad.

I think it's fine budget bench tool, apart from the bulk.  It does the job.  I wouldn't trust it unattended 24x7 though, for any production use.

It can measure rms and averages fine, but has zero ability to analyze or track power transients.
« Last Edit: January 19, 2019, 03:04:03 am by bson »
 

Offline nctnico

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Re: DP832A output
« Reply #46 on: January 19, 2019, 11:46:26 am »
I've had it for 3 or 4 years now.  It's pretty big and noisy for its power; the Keithley 2231A-30-3 with similar specs, for example, is the size of a bench DMM.
Isn't that some kind of rebadge? BK Precision has a very similar looking PSU. Still the Keithley is pretty cheap.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Jeroen3

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Re: DP832A output
« Reply #47 on: January 19, 2019, 02:29:43 pm »
That grounding problem is strange.  My hope is that the DP832 is OK, but some other power supply from other equipment is faulty.

Let's do one last test:
- disconnect all wires (USB, LAN, I/O, all), except the mains power cord
- connect only the halogen bulb at CH1 of the DP832.  No oscilloscope, no other instruments, just the two banana plugs and the bulb (one banana at +, one banana at -)
- no other wires or external jumpers

Does this minimal setup still flashes the bulb?

I am very curious about this ^.  Can you check if the bulb still flashes when there are no extra electrical connections, only the power cord and the halogen bulb, please?

No need to waste extra time for visual evidence, a simple "yes, still flashes" answer will be more than enough.
Yes. Without any ground (just phase and neutral) it still does. Short circuit current of 2.5A for 280 ms. Or similar in a 10 Ohm of previous post.
With or without ground does not matter much. The supply leaks 0.2 mA.

I was looking to see if I can perform a soft reboot. But scpi does not seem to offer this.
 

Offline bson

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Re: DP832A output
« Reply #48 on: January 20, 2019, 07:37:40 am »
Also, it seems like VFD is a great source of noise.
Doesn't surprise me... (I meant audible fan noise.)

It's possible the Rigol has slightly better specs and precision, though the Keithley is fully floating on all outputs - but the K sure wins on size and (fan) noise!  This might matter if bench space is at a premium (like it is for me), and if you already have a precision supply or just don't need one.
 

Offline s8548a

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Re: DP832A output
« Reply #49 on: January 21, 2019, 12:15:12 pm »

Despite the higher rated noise (1mV rms) than its little brothers (350uV rms), measurements show the actual noise is way lower than 350uV even.


sorry for an off topic noob question.

What kind of applications needs like these low psu noise? is there any specification/document available regarding different PARD requirements for different applications?
 


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