UNI-T UDB3000S Series: UDP3305S / UDP3305S-E

[Self Bias]

These seem to be relatively new: https://instruments.uni-trend.com/EU-EN/powersupplies/udp3000s.html

I'm looking for a new bench PSU and stumbled across this one: It has more current than both the Rigol DP932 and the Siglent SPD3303, over the Siglent it also has a numpad (which I favor). Compared to the GW Instek GPP4342 it lacks a channel and the load sinking capability, but I don't need that anyway. I'd rather have something with more current.

I was curious enough to order the S version. I'll take some measurements when it's here. I'm especially wondering if they chose a linear regulator for pseudo channel 4, if so it'd be useful for USB powered test equipment like differential probes.

Did anyone else try them yet?

[thm_w]

Channel 4 is just a generic USB 5V/2A output, nothing special, probably not linear, +/- 0.25V accuracy. Still useful though.

Channel 1 and 2 are both 5A, so could be paralleled for up to 10A. Also seems to have internal relays for parallel/series. That is impressive.
For some reason load regulation in series tracking mode is not great (<300mV). Otherwise the specs look very good, essentially copy paste of the rigol. Weight is about the same, 10kg.

https://unitrend.oss-cn-hongkong.aliyuncs.com/20230301/1677654502688937.pdf

Price:
UDP3305S-E $370
UDP3305S $500

Hardware might be the same inside both.

[Self Bias]

I have received the unit (haha) today, but I won't be able to test much today. First impressions:

+ The 2A rating on the USB port is correct. It shuts off hard at 2.2A and recovers instantly once the load is removed.
+ Noise seems pretty low, even on the USB port. It might actually be a linear supply for that "Channel".
+ Set and Readback accuracy on the voltages is pretty good. Set voltages are off by mostly less than 2 mV, Readback is around the same.
+ I did not see an overshoot when activating the output with a load present or when adding a load and having current limiting kick in.
+ The user interface is great. There's a few typos here and there ("Templet" = "Template") and language selection is possible in two spots for some reason. But the overall workflow is intuitive.

- Channel 2 outputs a voltage of -243 mV when turned off. In parallel mode this drops to 127 mV, possibly because Ch1 takes some of it. Ch1 is at -11 mV, Ch3 at 0.03 mV . Changing settings doesn't seem to have an effect. The short-circuit current in this state is -0.5 mA. I'll see if that's still there tomorrow, it's not something I like to see. The maximum allowed reverse voltage for many logical gates is 0.5V, so it's about half of that. I don't know about more sensitive low voltage circuits though.

All in all I'm not fully happy yet. Pseudo-Channel 4 could at least have an on-off-switch, I already missed that when connecting a USB connector for measurement. The negative voltage when turned off is at least an annoyance. There's also no relay click when switching outputs, just when chhanging ranges, which indicates that the outputs are permanently connected.

I went to the Embedded World, an exhibition that is held this week. I spoke to the representatives from Siglent and GW Instek about their selection of power supplies, specifically mentioning that I just ordered the UNI-T for its 5A/Ch output rating. The responses were:
- Siglent: We have a new model planned for this year that will feature a higher output current, but we don't know when it will be released.
- GW Instek: It's on their list. I filled out a form to specifically request that and possibly bump up the priority.

Both said that multiple customers came with that specific request. So maybe UNI-T will soon have some competition.

[BillyO]

UNI-T are famous for having zero support.

If you have no problems with it then it's fine, but if you have trouble you are generally out of luck.

People with good to great support are Siglent, Rigol and Korad.

I have been on the sad side of UNI-T support twice.  Now my policy is buy nothing from them over $50.

[thephil]

Thanks for sharing your observations! Did you get to play with it some more in the meantime?

I stumbled upon this instrument and from a distance it looks quite sweet in comparison to some contenders like the Rigol DP832, the Siglent SDP3305x and the Owon ODP3063. I really like that it has a proper number pad which many competitors lack. The user interface looks promising and (in contrast to the Owon) the color coding seems consistent between case and display. So I am very tempted to get one but I'm reluctant because there are very few reports online at this point. But maybe I'll have to be among the guinea pigs...

Phil

[Self Bias]

I decided to keep it as the negative voltage issue when turned off seems to be common, even among more expensive PSUs.

Automation works like a charm, I haven't seen any odd behaviour when controlling it remotely via USB. I'll see if I can verify the spec sheet sometime soon, but at least Ch1 and Ch2 seem to work fine. I didn't use Ch3 much so far, but I have no reason to believe it doesn't.

[Self Bias]

I went ahead and tested all the channels. TL;DR: It is well within spec with a max error of 4.4 mV and 1.2 mA. For those who enjoy details:

Test Setup
I used a Keysight 34465A that is out of calibration (> 2 years since last cal), but I have no reason to significantly doubt its results.
It is set to automatic range for both voltage and current measurement, current measurement was done on the 10A socket. Voltage measurement is with no load, current measurement is with the DMM shorting the PSU.

Everything is controlled by a Python script that knows about the PSU's datasheet specs and runs a voltage/current curve with 25 points. The lowest value is the range's resolution, which also taken into account for each step. For each step, minimum and maximum allowable deviation is calculated and logged to a CSV file along with the actual deviation.

Terminology & Units
"Set" is is the comparison between the voltage set in the PSU and the actual voltage measured by the DMM. For current, it is the current limit set vs. the actual current measured.
"Readback" is the comparison between the actual voltage/current measured by the DMM and the voltage/current reported by the PSU.

In the attached CSV files, the column "Set" is in Volts/Amperes. Everything labelled "Diff" is in mV/mA. This is to make scaling easier when plotting.

Results
Channel 1 Max Set Deviation: -1.3 mV
Channel 1 Max Readback Deviation: +1.3 mV
Channel 2 Max Set Deviation: -4.4 mV
Channel 2 Max Readback Deviation: +4.4 mV
Channel 3 Max Set Deviation: +0.6 mV
Channel 3 Max Readback Deviation: -0.6 mV

Channel 1 Max Set Deviation: +1.2 mA
Channel 1 Max Readback Deviation: -1.2 mA
Channel 2 Max Set Deviation: +0.5 mA
Channel 2 Max Readback Deviation: -0.5 mA
Channel 3 Max Set Deviation:  -0.5 mA
Channel 3 Max Readback Deviation: +0.5 mA

Conclusion
It is obvious that the readback is lying: It always reported the same value that was set, which leads to the deviations being exactly the same with inverted sign. Since the magnitude is so low, I'm personally okay with it thouggh. I wonder if the deviations will differ in magnitude when the unit starts to drift over time.
I did not measure the accuracy of the voltage readout under load. The unit doesn't have a sense input though, which is a shame, and it seemed to loose a few millivolts at max current due to connector and trace resistances.

I had done a short measurement of transient response under sudden load changes. Sadly I didn't take scope screenshots of them, but they looked okay to me. If someone is really interested, I can do those again.

[hsorbo]

Anybody knows how the fan noise is on this compared to Rigol?

[iAleks]

This device works much quieter, I had a dp832 before, and I sold it, now I have this uni-t, and it completely suits me in everything. I would buy 2 of these uni-t power supplies instead of one dp832.

[thephil]

In the meantime, I have bought a UDP3305S and spent some time playing with it. overall I am very happy with the instrument. I tested it against some of it's specs as far as I could with my means and it did quite well. I also had a conversation with UNI-T support and they eventually provided a firmware image and instructions to perform the update.

If you are interested, I documented my experience in my blog (I'm not a pro so be gentle. However I'll be happy to receive constructive feedback):
http://techbotch.org/blog/lab-power-supply/index_en.html

So, I didn't regret my purchase.

[iAleks]

Hi! Сan you give a link to the firmware. 1.10

[thephil]

Hi,

Yes, I got the following url for downloading the firmware image (v1.10) https://25628395.fs1.hubspotusercontent-eu1.net/hubfs/25628395/Instrument%20%20FIRMWARE/UDP3305S%20Update.rar. I don't know if/how long the link will last. As described in my blog post(http://techbotch.org/blog/lab-power-supply/index_en.htm), the update worked fine on my UDP3305S. I have no Idea if the same image is also valid for the UDP3305S-E or if that would brick the device.

• Unpack the *.rar file to get the firmware image UDP3305S.bin.
• Put the image into the root folder of a FAT32 formatted usb thumb drive. Do not change the filename.
• Turn off the power supply.
• Insert the usb drive into the usb port on the back of the power supply.
• Press and hold the UTILITY button and turn on the instrument.
• Now the update process starts.
• Once the update has finished turn the supply off and on again.
• Done.

[audiotubes]

Thanks for your web page on the UDP3305S, this was interesting.

Why did you upgrade the firmware? Was it to solve some problem(s) you found, or just to have the latest?

It looks like one of my usual shops has this for 600 euros. If anybody has a reliable source in EU which is considerably cheaper please let me know.

I will probably get one of these in the next weeks.

Thank you!

[thephil]

No – I didn't have any issues. I just wanted to make sure I would be able to benefit from future updates once bugs have been found and fixed or new features are implemented. That's why I got in touch with support. Let's face it – every software has bugs and if I pay 600€ for a PSU I want to be able to benefit form future fixes. So once I learned there is a new firmware, I wanted it even if I don't know what was changed at this point ;-)

[audiotubes]

No – I didn't have any issues. I just wanted to make sure I would be able to benefit form future updates once bugs have been found and fixed or new features are implemented. That's why I got in touch with support. Let's face it – every software has bugs and if I pay 600€ for a PSU I want to be able to benefit form future fixes. So once I learned there is a new firmware, I wanted it even if I don't know what was changed at this point ;-)

Thanks. I'm a software guy so I am an intentional late adopter. Let the other guys break and after the company fixes their fixes, then I'll try it

[thephil]

BTW: Does anyone here have a UDP3305S-E? It would be interesting to compare the two and try to find out if they use different hardware or if the difference is only in firmware.

[iAleks]

I have UDP3305S-E, but in this weekend il take UDP3305S, I want to take them apart and compare, and make S-E version too S version

[thephil]

Cool! Would also be interesting if you could get the 1.10 Firmware image for the S-E from UNI-T and then compare if it's actually identical to the S image we already have. Could be identical or could contain the model number in the image somewhere...

[iAleks]

First, I upgraded the S-E version to the S version, using the ST link programmer (STM32 ST-LINK Utility) and the serial flash copy from S version, just copy firmware from STM32H750 and serial flash. The S version was later, it has first version of the PWR PSB, all other boards are identical.

DO NOT program my 2U4 24CL04.BIN too you without backup! its calibration data! For upgrade you dont need this file!!
Here some photo and firmware S version
https://drive.google.com/drive/folders/162RZpVvgZ5Ns_vbXwYi4y9uXyf6soXJO?usp=sharing

[thephil]

Very cool! Thanks for sharing. Apart from the PCBs looking pretty much identical, did you verify that the upgraded S-E now actually honors the 1mV steps? I'd expect it to but you never know...
And good to know about the calibration data – that may pave the way to an unauthorized calibration procedure in the long run.

[iAleks]

Oh, yes it work not correctly on S-E,
set           measure     show on displey
10.000     10.000        9.999
10.001     10.000        9.999
10.002     10.002        10.002
10.003     10.002        10.002
10.004     10.004        10.003
10.005     10.004        10.003
10.006     10.006        10.005
10.007     10.006        10.005
10.008     10.008        10.007
10.009     10.008        10.007
10.010     10.010        10.009

[thephil]

Well – I think it mostly did work: An unmodified S-E would only allows for 10mV steps while you seem to be getting 2mV steps which is certainly an improvement. You may just need a voltmeter with more resolution to see the difference in the 6th digit for the 1mV steps...

[thephil]

@audiotubes: Seems like it's cheaper in croatia: https://www.chipoteka.hr/alati/izvori-i-napajanja/laboratorijski-izvor-2x32v-2x5a-5v-udp3305s-uni-trend-9150044680.

Disclaimer: I have never bought from that shop so I wouldn't know if it's real or a scam...

[iAleks]

Okay, now i see, S version have on all channel ADC 16bit (ADS1118IDGSR) and 16bit DAC (DAC8562), S-E version have ADC 16bit (ADS1118IDGSR) and 14bit DAC (DAC8162).
Il try order DAC8562, after place new ic it need calibration.. but im try it.

[audiotubes]

@audiotubes: Seems like it's cheaper in croatia: https://www.chipoteka.hr/alati/izvori-i-napajanja/laboratorijski-izvor-2x32v-2x5a-5v-udp3305s-uni-trend-9150044680.

Disclaimer: I have never bought from that shop so I wouldn't know if it's real or a scam...

Thanks, I'll have a look at that in more detail. I wonder if they didn't include VAT in the price shown...

[thephil]

Good point. Missing VAT would explain the difference in price. I don't speak Croatian so I don't know...

[2N3055]

@audiotubes: Seems like it's cheaper in croatia: https://www.chipoteka.hr/alati/izvori-i-napajanja/laboratorijski-izvor-2x32v-2x5a-5v-udp3305s-uni-trend-9150044680.

Disclaimer: I have never bought from that shop so I wouldn't know if it's real or a scam...

That price should include 25% VAT. Chipoteka is a old (since 1990) electronics vendor and very serious and trustworthy company.
Chipoteka seems to have very good deal with UNI-T and UNI-T prices are very good, have been since forever.

[thephil]

Okay, now i see, S version have on all channel ADC 16bit (ADS1118IDGSR) and 16bit DAC (DAC8562), S-E version have ADC 16bit (ADS1118IDGSR) and 14bit DAC (DAC8162).

Oh – now the numbers you measured make perfect sense:

32 V / 2¹⁶ = 0.0004882812 V

32 V / 2¹⁴ =  0.001953125 V

So ≈ 2mV is the resolution of the 14bit DAC. May still be worth the software upgrade for some – even without replacing the DACs. But, of course, I'm curious to see if you can fully convert it and figure out the calibration. Keeping my fingers crossed.

[faktorqm]

Hello there, just about to buy one of this power supplies from UNI-T. The quality/price is awesome, vs Siglent/Rigol brands. We will wait for the iAleks mods to check if the mod works. Thank you! Regards!

[faktorqm]

Okay, now i see, S version have on all channel ADC 16bit (ADS1118IDGSR) and 16bit DAC (DAC8562), S-E version have ADC 16bit (ADS1118IDGSR) and 14bit DAC (DAC8162).
Il try order DAC8562, after place new ic it need calibration.. but im try it.

Hey iAleks! one question: could you please repeat the test made by thephil regarding channel power raising? I'm a little worried about those oscilloscope shots. I'm talking about the section "On/Off behaviour" on his blog https://techbotch.org/blog/lab-power-supply/index_en.html I think could be a good test to see if your units behaves same way.

@thephil: Thanks a lot for your review! I'm worried about the channel rising waveform, could be an escenario where this has to be a problem? I'm also looking for the owon ODP6033 and there is a review on youtube and this problem is not present, however it's a 3A power supply so I don't like it very much.

Thank you for your time guys!

[thephil]

Can the on-behaviour be a problem? I don't know.

Personally, I'm not too worried about it and have had no problems with it. But maybe someone with more knowledge could comment on this. Maybe it could confuse a sensitive circuit if the voltage struggles a bit before settling at the set value?

[RiRaRi]

Just one off topic question: if you lets say service a device for 2 hours and you use PSU for 5 minutes, then 20 nothing, then again for 5 minutes etc. Is it better to turn it off completly and then power it on after 20/30 minutes or just leave it on for 2 hours straight even if it not in use and just turn off channels?

BTW I am very happy with UNI-T model, feels very solid and everything is great for now. Highly reccomend but it is only in use for few days.

[faktorqm]

Thanks for your feedback. I want to wait if there are any black friday discount or something like that.

Answering your question, I would let the power supply ON and the reason is temperature. All the components are under working conditions and has been stabilized their own temperature drifts.

I hope iAleks will answer this thread!

[RiRaRi]

Okay. Like someone said before: in Chipoteka web shop from Croatia this E model cost 390 EUR which is very good price

[Doman]

I own a UDP3305S, and I'm having difficulty understanding how the Over Current Protection (OCP) function operates on this device. My unit is running software version 1.10 and bootloader 1.04.

The Power Supply does not allow setting the OCP lower than the Current; it can only be set higher or equal. On channel 1, when I set it to 1A, it shifts into Constant Current (CC) mode when I draw more than 1A but does not activate the OCP. However, the OCP is triggered when I set it to 0.999A or 0.993A. This is likely a rounding error. And it never ever wants to switch channel off when OCP is set higher than current.

I can't understand why it doesn’t allow the OCP value to be set lower than the current? Am I misunderstanding how OCP should work?

Hey iAleks! one question: could you please repeat the test made by thephil regarding channel power raising? I'm a little worried about those oscilloscope shots. I'm talking about the section "On/Off behaviour" on his blog [...]
@thephil: Thanks a lot for your review! I'm worried about the channel rising waveform, could be an escenario where this has to be a problem?

Mine rises voltage in exactly same manner, it is correlated with relays switching, and I don't think that it will ever be a problem for home lab.
I have oscope and current probe, so I can take few measurements of voltage and current rise if You want to.

[thephil]

I own a UDP3305S, and I'm having difficulty understanding how the Over Current Protection (OCP) function operates on this device. My unit is running software version 1.10 and bootloader 1.04.

The Power Supply does not allow setting the OCP lower than the Current; it can only be set higher or equal. On channel 1, when I set it to 1A, it shifts into Constant Current (CC) mode when I draw more than 1A but does not activate the OCP. However, the OCP is triggered when I set it to 0.999A or 0.993A. This is likely a rounding error. And it never ever wants to switch channel off when OCP is set higher than current.

I can't understand why it doesn’t allow the OCP value to be set lower than the current? Am I misunderstanding how OCP should work?

As far as I know, OCP is constant current modes big brother: When the OCP threshold is met, the PSU will turn off the output in certain time – think fancy fuse. So if you have set a current limit it makes no sense to set the OCP limit lower than that, because OCP would shut off the output before CC can even kick in.

[pope]

Okay. Like someone said before: in Chipoteka web shop from Croatia this E model cost 390 EUR which is very good price

I can't find it on their website. I can only see the UTP.

[Doman]

As far as I know, OCP is constant current modes big brother: When the OCP threshold is met, the PSU will turn off the output in certain time – think fancy fuse. So if you have set a current limit it makes no sense to set the OCP limit lower than that, because OCP would shut off the output before CC can even kick in.

Totally understandable, but as You can see on photo attached in my previous post - my psu is set to 0.9A OCP and 0.9A current and it is running in CC without tripping OCP. But if I were able to set OCP lower that current I bet that it would shut down output instead going into CC mode.

I think that I should be able to set OCP lower that current output, it works this way in any other power supply that I have/had contact with. Implementation can be different (when which action happens).

What use case has setting OCP above current limit? When it will trip output?

[faktorqm]

Mine rises voltage in exactly same manner, it is correlated with relays switching, and I don't think that it will ever be a problem for home lab.
I have oscope and current probe, so I can take few measurements of voltage and current rise if You want to.

Hi sir! I'm sorry I can't help you with the OCP problem, as I don't have currently a unit on my hands.
If you don't mind, it will be awesome if you can take some measurements of the voltage rise. Not just for me, it's good to compare vs the unit that "thephil" already has.
Reagarding the question if that behaviour could be a problem, I assume that if you connect the power supply to a PCB with proper power filtering and so on, those 30msec until the power supply gets stabilized don't will do any harm. I assume with a bunch of capacitors it has to be cleared.

Thank you for your time! Regards!

[thephil]

Totally understandable, but as You can see on photo attached in my previous post - my psu is set to 0.9A OCP and 0.9A current and it is running in CC without tripping OCP. But if I were able to set OCP lower that current I bet that it would shut down output instead going into CC mode.

I think that I should be able to set OCP lower that current output, it works this way in any other power supply that I have/had contact with. Implementation can be different (when which action happens).

What use case has setting OCP above current limit? When it will trip output?

I guess, if you want the PSU to trigger OCP immediately when the limit is reached, don't set a CC level but only OCP. That should do what you want.

I guess having both activated, OCP will only trigger, if a large over current occurs and CC does not manage to contain it in time. In my tests I manged to reliably trigger OCP even when it was at the same level as CC. So maybe it depends on the exact conditions?

I found a page where Keysight explain their OCP behavior and it says that OCP will not trigger on "... short current spikes and other acceptably short overloads ...". (https://edadocs.software.keysight.com/kkbopen/how-does-over-current-protection-ocp-work-620692888.html)

[faktorqm]

On this video review it states that OCP will automatically go in CC mode (2:40 aproximately)



So I suppose it is the expected behaviour. Latr in the video it shows something called "monitor mode" (4:20 aprox) and when the setting is reached the output goes off. Maybe is that what you are looking for? Regards!

[Xandr]

Hello!
I also ordered this power supply for myself.
Where did you find the last firmware under it? I looked on the site - there is no 1.10

[Xandr]

Hi,

Yes, I got the following url for downloading the firmware image (v1.10) https://25628395.fs1.hubspotusercontent-eu1.net/hubfs/25628395/Instrument%20%20FIRMWARE/UDP3305S%20Update.rar. I don't know if/how long the link will last. As described in my blog post(http://techbotch.org/blog/lab-power-supply/index_en.htm), the update worked fine on my UDP3305S. I have no Idea if the same image is also valid for the UDP3305S-E or if that would brick the device.

• Unpack the *.rar file to get the firmware image UDP3305S.bin.
• Put the image into the root folder of a FAT32 formatted usb thumb drive. Do not change the filename.
• Turn off the power supply.
• Insert the usb drive into the usb port on the back of the power supply.
• Press and hold the UTILITY button and turn on the instrument.
• Now the update process starts.
• Once the update has finished turn the supply off and on again.
• Done.

Hello!
Where did you get a new firmware, ate no secret?
On the official website I did not find anything.
I also have their own multimeter 8805, I would like to update it.

[thephil]

@Xandr: the link to the firmware file is literally in the post that you quoted.

So far, UNI-T appears not to provide the firmware for the PSU for download on their official homepage – only the PC software.

[tonyalbus]

Had contact with UNI-T support and they now have
Latest 1.10 firmware now on the official website available for download.
it is one zip file with both the S and S-E file and manual and a start of a releasenotes

Great tests by Phil on his blog btw, thanks Phil

[tonyalbus]

Testing firmware 1.11 there OCP can be set before CC, so as a user you can decide which kicks in first.
same for CV and OVP.. which now brings a new thing.. that when OVP left unintentionaly at low value .. you outputs go off
but then you just switch off OVP or set it correctly.
will update when release on the official website.

[thephil]

Excellent –  it appears gentle nudging actually worked!

WRT the new firmware version: Did they add a normal tracking mode that allows for joint control of two channels, yet?

[tonyalbus]

Here it is:

https://www.tonyplaza.nl/download/YT0376/Firm1_11.zip

Upgrade method:
1. Select the upgrade file according to the model and put it in the root directory of the FAT32 format U disk (the file name cannot be modified);
2. Insert the USB flash drive into the machine to be upgraded (power off);
3. Press and hold the "UTILITY" button to turn on the computer and start the upgrade;
4. After the upgrade is completed, manually restart the machine.

V1.11 update:
Strategy for changing the output setting value and protection value: The output setting value can be made greater than the protection value.

V1.10 update:
1. Optimize SOCKET connection mode;
2. Solve the bug of occasional loss of sent data in SOCKET connection.

V1.09 update:
1. Add SOCKET connection mode, the connection port is 5025;
2. Optimize network connection.

V1.08 update:
1. Improve SCPI standards;
2. Add memory-related communication commands;
3. Optimize the local file manager and display the applicable channels of this list file and delayer file before the file name.

V1.07 update:
1. Add large font display mode.

V1.06 update:
1. Add power-on output function.

V1.05 update:
1. Added new communication commands to adapt to the NeptuneLab platform;
2. Added German to multiple languages.

V1.03 update:
1. The time resolution of timer and delayer is upgraded to 0.1 seconds.
2. The change strategy is: when the output setting value is greater than the reasonable value, the current value will not be changed.
3. An "error status" is added to the list output running status. When the output value set by the list is greater than a reasonable value, an error will be reported.
4. Add a shortcut for setting UI language.

[faktorqm]

I'm seeing it about 500€ in Aliexpress for Europe. Good price I think!

[audiotubes]

I bought mine from eleshop.eu for 449 euro + VAT. After several orders, I can recommend the shop confidently. They answer email quickly and ship immediately.

Mine's still in the box due to some scheduling problems. Tomorrow a new bench arrives and by the weekend the chaos should have diminished entirely

[audiotubes]

I just opened the box and I don't see any manual, just a calibration certificate from about a year ago.

Does a manual come with this device?

[thephil]

I'm not sure if I got a printed manual with my instrument. I usually misplace them anyway, so I prefer to have the PDF and throw away the paper manuals (unless they are really nice).
It's available for download on UNI-T's website.

[audiotubes]

Thanks, yeah I found there on the site. But I was susprised, since all my Siglent gear came with quite nice manuals.

[Pfriemler]

Can't still decide if the UNI-T 3305S-E or a OWON ODP3033/3063 fits better my "needs" (they have their pro & cons). Collecting arguments, I stumbled on the Digital IO panel on the UNI-T's back side. Did I miss any information on that? Neither Google nor the manual explain the pins. What are they for?

[thephil]

The interface on the back provides logic pins for external triggering (both to and from the PSU). There is a little bit of information in chapter 4.12 Trigger. I haven't used that feature, so far, so I can't really say much more about it.

[Pfriemler]

Got it, thx. 4x 3.3 volts logic lines - >3.3 may kill the device. Not a game changer for me.

[Pfriemler]

still struggeling between OWON ODP3063 (2x 30A 6A) and a UDP3305S-E.

some new questions...
Some firmware improvements are still undocumented. In Tony Albus' review I had a look at the zoom function.

And in the Utility menu there's a "Recorder" function...?
The OWON has a remarkable recording option for logging output values, 10k points with different intervals (1s up to ...?), you can log values to a .csv file on a USB stick, up to hours, and view them instantly on the PSU. The "WAVE" function of the UNI-T looks interesting, but without any settings there are only some curves, not more. Does the "Recorder" in the UNI-T provide anything like that?


And do we have any informations about the output capacity here? I do not like the 100µF (?) output capacity on the OWON, since it may kill components before the CC/OCP kicks in. With Phil's report in mind (he stressed a led with 20 mA CC for a hundred switch on/offs without any damage nor flashing LEDs): my (odd) Voltcraft has "only" 47µF. Once I had a linear Basetech BT-305 with >600 µF, horrible, sent it back.


Here are my pro-cons on both devices
OWON:
o I think, I do not really need the 1mV resolution of the UNI-T's non-E version. But OWON has it for less money
+ the OWON has no fan if unloaded. I do like the silence, thus I switch off my KORAD KA3005P asap :-)
+ It gives me 2 amps more in parallel mode. Maybe I will need that sometimes, my old has 10 amps
o There are the channel couplings that @thephil still miss. I am not sure if I will need them at all, but you will have 2 coupled but still independent channels unlike the UNI-T in series mode
+ I like the separate buttons to set voltage/current to each channel (with the UNI-T you have to select/change to the channel first)
+ on/off behaviour is excellent
+ USB host on the front
+ teardown looks quite good (see https://www.eevblog.com/forum/testgear/owon-odp6033-triple-power-supply-teardown/msg4573375/#msg4573375)
- they offer firmware updates for end users, but not for this model
- switching from independent to serial or parallel mode is not convenient ... several menu steps and external cables
- 100 µF output capacitors on each channel

UNI-T:
+ I like the GUI (much) more with clear readings, the still undocumented Zoom function looks great (eyes are getting worse :-)). And display softkeys are fine to me.
+ quick serial/parallel mode
++ one all-off/on button
+ rules (monitor) to switch off or warn (more flexible than OCP/OVP)
+ they fixed some issues and offer firmware updates to end users
- more "strange" behavior (some tooths in on-ramps)
- additional cable needed to use the USB host port at back side

aaaand my thx to thephil for the great blog reviews!

edit(2): some (more) corrections

[faktorqm]

Hi there, I did this comparison on an excel file about 3 months ago. Please see the attachment. Nice comparison BTW.

[BillyO]

Another thing you might consider is support.  UNI-T offer none.  And I'm not just exaggerating.  UNI-T do not have any support system whatsoever.

If you think I'm not correct, then I have a challenge for you.  Whatever country/region you are in try to find a warranty and or support service center, when you do post it here to help others.  I would love to be proven wrong.

But in the end it's your money. 

[pope]

Another thing you might consider is support.  UNI-T offer none.  And I'm not just exaggerating.  UNI-T do not have any support system whatsoever.

If you think I'm not correct, then I have a challenge for you.  Whatever country/region you are in try to find a warranty and or support service center, when you do post it here to help others.  I would love to be proven wrong.

But in the end it's your money.

Wow, I wasn't aware of that. Good to know. I don't think that's even legal.

[Pfriemler]

From a professional point of view, it's necessary to have a functional support to get back working equipment in a short time at reasonable costs, no doubts. This disqualifies UNI-T for such purposes, but so does OWON, am I right?

As a hobbyist, my preferences are different. My Voltcraft DPS2010 (a rather efficient 1.8-3V linear regulator powered by a regulated SPU, sold under many brands 20 years before) is bad in nearly all points (slow load regulation, horrible overshoots in cc->cv changes, fan control, ...), but beside the very special digital control board it's easy to maintain/repair, I have a full circuit diagram and parts are easy to get. Korad KA3005P with much better behavior, nearly full circuit, too. Of course there are no wiring diagrams from OWON and UNI-T, but neither do the so-called "Service Manuals" from Siglent.
Of course I took a Siglent SPD3303X(-E) into consideration. Buying an OWON or UNI-T, a RIGOL or even a SIGLENT is the same game of chance to mee, with only one difference:
How many are fixed meanwhile by users regarding spontaneous reboots due to an overheated bridge rectifier? There are YT tutorials about that. I do not see Siglent PSU as more reliable than OWON or UNI-T, I think it's more important to have a "critical mass" of experienced users to get educated hints how to fix them. And I'd rather fix my stuff myself instead of sinking half the price of a new unit into some more or less good support after the 2 years warranty is over. And from the hobbyist's point of view, I try to get the most for my money. This is not the case with Siglent. GWInstek, R&S out of reach.

[pope]

Yeah that's all interesting but at least in the EU there are laws that protect the buyer. One of them is a minimum 1-2-3 year (not sure) of warranty.

[pope]

Yeah that's all interesting but at least in the EU there are laws that protect the buyer. One of them is a minimum of 1-2-3 years (not sure) of warranty.

[Pfriemler]

Yeah that's all interesting but at least in the EU there are laws that protect the buyer.

During the first two years, it is the dealer's responsibility to ensure that the appliance is repaired (or mostly replaced if necessary), whereby I as the customer am obliged to prove that the defect existed from the outset after the first six months. In the case of internal manufacturing defects, this is not usually a problem.
After these two years have expired, you are completely on your own. And from the day of delivery, if you made the purchase somewhere overseas, which can quickly make the supposed bargain expensive.

The right to repair, including a right to get replacement parts for the end customer, is still under discussion in the European Union.

[pope]

UNI-T seem to have a european online store with the following info

+49(0)821 710 498 26
service-eu@uni-trend.com

So, there must be some sort of support otherwise it's illegal practise. At least that's my understanding.

[dreamcat4]

well lets assume for a second that the device DOES develop an internal defect at some point during it's lifetime. What would also be nice is to see some dissassembly / teardown photos. To see how easy these unit(s) are to repair. To know how easy or hard it would be to effect our own psu repairs. In the situation that such warranty or servicing is not actually available?

I suppose we don't see that [yet] because ATM new customers still has an intact and worthwhile warranties for the time being?

[pope]

I suppose we don't see that [yet] because ATM new customers still has an intact and worthwhile warranties for the time being?

... or they believe so (?) 

[Pfriemler]

well lets assume for a second that the device DOES develop an internal defect at some point during it's lifetime. What would also be nice is to see some dissassembly / teardown photos. To see how easy these unit(s) are to repair.

That's what I mentioned above with the "critical mass" of users. For Siglent and Rigol, there are lots of photos and videos, even Dave made teardowns and repairs here.

But I'd appreciate to return to the topic. Discussing the reasons if to buy more or less cheap equipment or not is a more generally problem. Here we are about the UNI-T PSU and their technical pro and cons. Thx.

[BillyO]

Wow, I wasn't aware of that. Good to know. I don't think that's even legal.

Not sure what it's like on your side of the pond, but here in Canada there are statutory warranties.  I believe it is a full year on new goods.  If the manufacturer does not have a means to handle the warranty claims, it falls back on the retailer.  If the retailer is off-shore all bets are off.  I think you might find it's pretty similar throughout the 1st world.  A good manufacturer will honor their equipment warranties regardless.  Korad is such a company.   They don't have a service center in North America, but will do everything they can to help you out.  UNI-T on the other hand will just ignore you.  I have personal experience with both of these companies.  A power supply from Korad and a Oscilloscope and a benchtop DMM.  I will never buy anything from UNI-T again that has a value over $50.  Both the UNI-T scope and DMM sit as reminders in the back of my basement, dead and abandoned by the company that made them.

Siglent and Rigol are in a different league.  Both have service centers around the world and offer great support.


Edit:
I notice UNI-T now have a location in NA and EU:

Uni-Trend Technology US INC.
3171 Mercer Ave Suite 104 Bellingham WA, 98225

Uni-Trend Technology EU GmbH
Affinger Str. 12, 86167, Augsburg (Munich area in Germany)


Well, maybe things have improved since the dark ages.  We need to get some success stories then.

Edit #2:
Just sent the NA location a general query.  We'll see if they respond.

[BillyO]

But I'd appreciate to return to the topic. Discussing the reasons if to buy more or less cheap equipment or not is a more generally problem. Here we are about the UNI-T PSU and their technical pro and cons. Thx.

Support is not a consideration?   

[dreamcat4]

But I'd appreciate to return to the topic. Discussing the reasons if to buy more or less cheap equipment or not is a more generally problem. Here we are about the UNI-T PSU and their technical pro and cons. Thx.

Support is not a consideration?   

He didn't say that and neither did i (the guy whom was responding to)....

How to put it more diplomatically? The effective real-terms value of the support depends on both the reliability and the repairability of the specific product. And i would much prefer to promote those goals within our society and amongst manufacturers than assume that it's so bad to the levels that support is both a necessary and critical element to the functioning of my item(s)!

Of course support is important, but not normally at the expense of the aforementioned thing(s). Unless in a minority of more exceptional circumstances. And certainly that is relevant for other types of product(s). But this is a PSU.

[Pfriemler]

Of course, it is good and valuable to know whether a manufacturer offers repair support or not. As far as UNI-T is concerned, the information here is actually spot on, thx to BillyO. And of course I like to buy only technical devices whose insides I have seen before. There are photos and/or videos for the OWON and UNI-T power supplies I mentioned, otherwise I wouldn't know that the OWON use two toriod transformers for each channel and the UNI-T- only one big (which, btw may be the reason why it is less weight). Both look well constructed and easy to disassemble.
The OWONs have been on the market long enough that there should be experience of possible faults and repairs, but there is none only one unsolved without any result (just found after I posted). This may be because they work almost perfectly, but it is more likely that the possibly few buyers do not make their problems public. Feedback even on new devices is very low to non-existent in this forum, and for the even newer UNI-Ts, the number of users known here can be counted on one two hand(s).

edit: I just went once again through the whole thread, with BillyO's support concerns at the second entry and Phil's report that he spoke to the (non existent?) support. Now I am a bit confused ...

still waiting for some news regarding the Recorder function, maybe I join the guinea pigs...

[thephil]

Quote from: Pfriemler on 2023-12-12, 19:51:36

And in the Utility menu there's a "Recorder" function...?
The OWON has a remarkable recording option for logging output values, 10k points with different intervals (1s up to ...?), you can log values to a .csv file on a USB stick, up to hours, and view them instantly on the PSU. The "WAVE" function of the UNI-T looks interesting, but without any settings there are only some curves, not more. Does the "Recorder" in the UNI-T provide anything like that?

So – I had a brief look at the RECORDER. It seems that you can have the PSU log data to internal memory or USB stick in pre-set intervals (minimum 1s). In the end, you get a `*.rec` file which is in an undocumented binary format.
It shouldn't be too hard to reverse engineer the format, but out of the box, I'm not sure what exactly you are supposed to do with it Maybe it can be opened in the Windows software and exported to a more useful format?

As far as I can tell, there is no way to recall and show these files directly on the instrument.

[Pfriemler]

@thephil, Thank you for checking, that helps a lot to decide for the UNI-T.
It's about what I was hoping for, but not quite.
A possible use case for me would be a charging process or the longer monitoring of a device with short-term malfunctions (dropouts, reboots). Ultimately, it is enough for me to view the data on the PC.
I was about to ask to post any kind of recording here (maybe with a short description what is recorded), but I do not see a way to get the PC software running without having the UNI-T connected ... 

[thephil]

I have written to UNI-T support asking for documentation of the REC files and hinted that a plain old CSV would have been better. Haven't heard back, yet.

However, the format is pretty simple, so I went ahead, did some reverse engineering and wrote a very basic converter.

https://github.com/philpagel/udp3305s

It's not complete yet, but it can already give you the voltage and current readout for the three channels as well as serial or parallel mode. There seems to be some more information in each record, but the converter should be usable for most purposes already.

[gabrieLL]

I am on the same boat at this time. Can't decide between Rigol DP832 and UDP3305S-E. 

[Pfriemler]

You know about all the downsides the RIGOL has? If you can live with them, you don't have to worry. But be beware of them, as it will be your tool, not ours.
I went ashore again - I am expecting my UNI-T at home tomorrow and may then be able to provide a few more arguments.

[gabrieLL]

Haven't found anything specific against RIGOL so far. Only thing bothers me at them moment is the <3A and monochrome display and possibly a loud fan , higher price +80€.  Could you elaborate some more about the downsides of the RIGOL ? Thank you

my understanding of the rigol is :
DP832 is on the market for +-10years which is a good thing and still sells. HW issues were ironed out with board revisions, SW too. Components inside should be proven to work reliably. Lots of documentation , community , support , higher chance of self repair success or aftersales repair at all.

UNI-T
Nothing mentioned above. Only that it is nicer, more up to date. <5A , color display, numpad.
- Not sure about the internals. There is zero in-depth teardown of the UDP3305.

[faktorqm]

Hey gabrieLL, check the attached file. It's a comparison (excel sheet) with all the interesting parameters of each model of the power supplies in the same price level - quality. Please ignore the colors.

I will go for the UNI-T because I like it very much.

As you can see in the excel, on Rigol PS the ground between the channel 2 and 3 is shared, (which I found it unforgivable, but that's my personal opinion) and the voltage accuracy is better on the UNI-T S-E model. The current accuracy is slighty better (0.15 vs 0.2), the rigol is 3A per channel, UNIT is 5A. For me, it has more value the current rather tan voltage, again, my personal opinion. As last but not least, UNIT has a fourth channel 5A 2A fixed which personally, I really appreciate.

Regards!

[Pfriemler]

My first impression is excellent, not as big as I feared, with a permanently running fan, but much quieter than even the latest Korad KA3005P (the Welectron edition with the green-red display), good voltage accuracy even under full load, almost intuitive operation. I really like the calculator-like numpad (not the Rigol ring one). I was attracted by the series/parallel switching at the push of a button, the "rules" (switch off when output current is below xy) etc. and the easy-to-use additional functions (programming a voltage ramp etc. or quickly testing 100 on/off switches is quick without having to start the computer) or the built-in recorder that @thePhil described here.
Firmware 1.10 bootloader 1.06 is installed. I wonder why UNI-T does not publish the 1.11 Tony Albus offers here.
Yes, it may be that the Rigols' firmware and hardware have matured over time. There are definitely more users and therefore more potential advisors in the event of a fault. I hope the UNI-T users stay in touch here in case something happens to us after the first two years 

[Pfriemler]

Hmmpf. Looks like I will not sell my KORAD KA3005P ...

First: Set to 5 volts 10 mA and shorten the outputs with a 1R. This will result in spikes - the more output capacity, the more the curve is wide.

This is a comparison between my KORAD KA300P (dark purple), UNI-T's CH2 (light purple) and CH3 (green). Nearly 5A spikes. The KORAD is way faster than the UNI-T.

To get an idea how much the effective output capacity is: 10V shortened with 1R, KORAD vs UNI-T@CH1 vs a 10 volts charged 450 µF (measured capacity):

Damned. Did I cry about the 100 µF at the OWON ODP? I did.

So, if I attach an LED to an active output >10V, I may kill it? Checked it with an 230 mA LED: remarkable flashes with the UNI-T, barely noticable with the KORAD.


Second:
off > on behaviour 5V 3A with no load. As stated in @thePhils blog, the UNI-T power channels are rather slow with a small spike in the beginning, whereas Channel 3 is much faster with an app. 10% overshoot.


Well, the KORAD shows remarkable stairs ... no stairs at all if the current limit is set to max (5.1A).

Now we try 3.3V @ 0,1A:

Look at the beaty overshoot the KORAD (purple) makes. And the UNI-T does, too (yellow).

From the frying pan into the fire?

edit2: I forgot:

... Channel 2 outputs a voltage of -243 mV when turned off. In parallel mode this drops to 127 mV, possibly because Ch1 takes some of it. Ch1 is at -11 mV.

Nothing here, looks very fine: The CH1 and CH2 output voltage @OFF is both -2.2 mV with my UNI-T UDP3305S-E, -1.7mV if switched on and set to 0.00V

[faktorqm]

Good test! In which real life scenario that could be a problem...

a) the overshoot for a very short time period? 10% overshoot you stated in your post.
b) The active fuse time: In the first millisecond all three are below 50% of the voltage (Depending on the board, 1ms could be an eternity) but it looks like not a bad time. Isn't it?

The rise time but ch2 could be lower ch3 is behaving like it should. Thank you! Regards!

[Pfriemler]

Overshoots when switching a channel on is always a problem with cheapo regulated psu, as far as I experienced. A Basetech BT-305 peaks up to 4.8 volts when switching on to (preset) 3.3 volts with no load connected - if you set the current limit down to 0.2A, the overshoot is gone, although it takes about 100 ms to load the (from my point of view horrible big) 660 µF output damping capacitor.
Strange: Both Korad and UNI-T CH1+2 do not tend to any overshoot with no current limitation, but do when I lower the current limit. That's what I really do not expect: "be safe with low current limits" is not true here. But they are moderate here, I can live with that.

Active and fast current limitation may save boards with failures under test. I did not examine the behavoiur on a short circuit (or heavy load) when switching on the channel - here it shows if you plug in or (mechanical) switch on a device connected to an active output.
Even if the output stages reacts in microseconds, the energy stored in the output capacitors may blow something to heaven, thus a very low output capacity is important. I do not see any on the KORAD circuitry (although I think ther is some), my Voltcraft DPS2010 has something ~50 µF, the Basetec mentioned above 2x330 µF, the OWONs ODP board photos let me assume ~100 µF (although I have no idea how they would do in my test).
Looking to the curves in the first shot: Peak current is limited only by the 1R resistor. Whe have a full unlimited current of 5 amps for ~600 (CH1) and ~200 (CH3) microseconds before the current limitation kicks in, the discharge of a (presumed) output capacitor begins after that - but almost no delay at the Korad. Due to the decreasing, Korad and UNI-T CH1/CH2 may have a similar output capacity (pic2). Compared to the green cap discharge curve, it may be something ~100-200 µF. CH3 decreases much faster, but puts more even more energy to the DUT as the KORAD does.

Overall: It is not that bad. But I am impressed how fast(er) the KORAD acts.

It would be very interesting to see how a Siglent or Rigol react here: Simply set em to 5V 10mA, put a 1 ohms resistor on the active output and look how the voltage decreases.

[dreamcat4]

in the realm of power tools, and other industrial tools we have the concept of 'soft start' feature. so why cannot be possible a choice here for the on/off behaviour as a setting? for a slower ramp up of the voltage?

because for some certain endurance, and power cycling stress tests, then you do wants to go straight / full on. then full off very rapidly. or to bring up and switch on a circuit 'fast enough' for a clean boot or initialization of a digital circuit.

however at other times... then you might be testing some sensitive component. lets take driving a fet as an example. but it could be any sensitive things such as leds or whatever unprotected circuit. then we want the option for a slower ramping up (the voltage). not to overshoot. and with the cc on

this seems like reasonable feature to be asking of a bench top lab psus? given that not everybody can afford something too much expensive / higher quality.

[Pfriemler]

Do not misunderstand me: Of course it's very easy to setup a smooth voltage ramp, and even without that: If you know what the device does, you can set it to your needs.
Connecting a LED to an active channel will show the spikes as short flashes, but if I connect the LED to the inactive channel (set to 5V 10mA) and switch the channel on/off, there are no visible spikes - this works very fine as it should.
I will check that later and put the pic in here..

I think (real) professional PSU behave much better with that. But again: connecting an LED to an active KORAD set on 30V (!) 10mA let the LED flash barely noticeable. And it's really cheap, compared to the known brands.

[dreamcat4]

ah ok then! thanks so much for clarifying much appreciated 

[BillyO]

Wow, I wasn't aware of that. Good to know. I don't think that's even legal.

Not sure what it's like on your side of the pond, but here in Canada there are statutory warranties.  I believe it is a full year on new goods.  If the manufacturer does not have a means to handle the warranty claims, it falls back on the retailer.  If the retailer is off-shore all bets are off.  I think you might find it's pretty similar throughout the 1st world.  A good manufacturer will honor their equipment warranties regardless.  Korad is such a company.   They don't have a service center in North America, but will do everything they can to help you out.  UNI-T on the other hand will just ignore you.  I have personal experience with both of these companies.  A power supply from Korad and a Oscilloscope and a benchtop DMM.  I will never buy anything from UNI-T again that has a value over $50.  Both the UNI-T scope and DMM sit as reminders in the back of my basement, dead and abandoned by the company that made them.

Siglent and Rigol are in a different league.  Both have service centers around the world and offer great support.


Edit:
I notice UNI-T now have a location in NA and EU:

Uni-Trend Technology US INC.
3171 Mercer Ave Suite 104 Bellingham WA, 98225

Uni-Trend Technology EU GmbH
Affinger Str. 12, 86167, Augsburg (Munich area in Germany)


Well, maybe things have improved since the dark ages.  We need to get some success stories then.

Edit #2:
Just sent the NA location a general query.  We'll see if they respond.

Just an update on this.  I sent the NA location 3 separate queries requesting service information and I got no reply whatsoever.   So apparently hanging a hand painted shingle on an empty unit and taking a picture is what UNI-T think is all they need to do.  Buyer beware.

[faktorqm]

Thank you very much for your answer. Very clarifying. I hope anyone with the Rigol 832A or Siglent SPD3303X(-E) can post the same test to compare the behaviour.

I think I will end buying the UNI-T, at the end of the day, it has a lot of things I appreciate and it's affordable for me. Maybe not the best one but what I want is to don't buy a problematic device.

Regarding support, I really don't care I had a lot of problems with several different devices and always they wash their hands. Bah. Regards!

[Veteran68]

I have a SPD3303X-E (upgraded to SPD3303X) and can try to create the same test tonight if I get time.

[Pfriemler]

I have a SPD3303X-E (upgraded to SPD3303X) and can try to create the same test tonight if I get time.

Please, do!

Did some futher checks ... as mentioned above: connected a LED, set to 5V 20mA, switch channel on - absolutely no overshoot of current.

Next issue: draining external sources. I did check this with the KORAD KA3005P and the UNI-T channels, coupled in parallel with cables.

Korad 5V 200mA, UNI-T CH1 5V 200mA, both channels on: Korad reads 0mA, UNI-T 10mA. (UNI-T's output voltage is mV higher than the KORAD's)
If you increase voltage on UNI-T, KORAD voltage reading follows, current remains 10mA. Looks like the KORAD is draining 10mA constantly, also when ouput is switched off.
If you increase voltage on KORAD, UNI-T CH1 loads the Korad with 154mA, CH3 with 15mA. Voltage Readings show actual values. BTW: CH3 voltage reading limit is 7.38 volts.

I do not like this.. This is not the behaviour of an 1-quadrant psu.
So, putting a diode in series when charging batterys seems to be necessary like with the RIGOLs, otherwise the battery will be discharged. And we do not know if the UNI-T will bear this a long time.

So, the next task to check SIGLENT: couple both channels - do they load each other when set to different voltages, and how much?

[faktorqm]

I have a SPD3303X-E (upgraded to SPD3303X) and can try to create the same test tonight if I get time.

That would be great sir! I you can do the same test it would be great. We don't have a rush, so take it easy! And thanks for your time in advance!

[Pfriemler]

Next issue: draining external sources. ... UNI-T CH1 loads the Korad with 154mA, CH3 with 15mA...

Just to clarify this: It is not that easy...

So I did a general look how my power supply units act when an external voltage is applied to the output terminals, regarding if it's under/above the settings, channel output on or off.
First: "PEMENOL DC-DC USB Step Up/Down Modul" - a small chinese board with USB-in, QC/PD support or simply 4-12V, out adjustable 1..30V 0..2A max 15 watts (2023 ~15 EUR)
wether on or off, depending on the setting of the output voltage - I assume it's simply the output divider for setting the voltage ... acts like a resistor 4,7k(5V), 6,5k(10V), 8,2k(20V), linear behaviour,
maximum 6,44 mA in 5V setting with 30V external, ~200 mW in total. May damage the (small) resistor.

Second: "MATRIX MPS3206", cheapo switching PSU (2022 ~80 EUR). On or off, it acts like a resistor of 2k, drawing a maximum of 15 mA @ 30V = 0,5 watts. Nothing spectacular!
No difference if output is switched on or off.

Third: "KORAD KA3005P", well known. As with the "MATRIX",similar to a 480R resistor, i.e. 20,6mA@10V=206mW, slightly more current at 20V: 49mA@20V=0,98W, ~400R. Did not test above to avoid internal damages.
No difference if output is switched on or off.

Fourth: "Voltcraft DPS 2010PFC", similar to "McVoice SNNT-2010pc" etc, switching psu with linear regulater (~3V overhead)
Well, this drains much more as I expected. Starting with ~100mA when external voltage is 0.1V above the setting, I stopped examing with currents >1A. If set to 20V, putting in 20.7 volts, it draws 443mA, resulting in >9 watts dissipating power.
I did not check if there's any limitation. No wonder if I killed it a few months ago.
If output is switched off (relay), there's only a 10k resistor (attached by me to discharge the 47µ output capacitor)

Now let's come to the UNI-T UDP3305S-E Channel 1. In a few words: it depends on various things.
a) with output OFF, it drains ~45mA whenever the external voltage is lower than the setting of the channel
b1) with output ON or OFF, it drains between 52 and 157 mA whenever the external voltage is higher than the setting of the channel
e.g. apply 10v to the channel set to 12V, while switched off -> 45mA is drawn from external. Now set the channel to 9 volts -> 154 mA.

b2) current rises slowly from 150 to a maximum of 157@11.4 volts, then decreases down to 52mA@16.7 volts, then rises to a max of 60mA@33 volts.
Thus, the comsumed power has two maximums at 11.4 and 33 volts and do never exceed 2 watts.
That looks safe, so I assume that there's no risk to damage anything. Well done, UNI-T!

Last but not least: While experimenting with CH3 (remember: 6.2 vmax), I fired a crowbar inside at 10.6 volts. Nothing happened (current limitation).
So beware: Do NEVER apply any battery or something like that with >10V to CH3!

[thm_w]

From what I remember the Rigol had a ~20mA constant current load on its output, which is somewhat necessary as you need to discharge the output caps once you disable or reduce the voltage.

Either way, I would not use it to charge a large battery. You can get a Riden RD6006 or similar which has a dedicated battery charging function (will show you total Wh/mAh), output relay, and fuse. Though their prices have come up a bit in the last few years.

[Pfriemler]

Of course it makes sense to use dedicated battery charger, it's kind of overkill to use a laboratory PSU for that. I have something in that style, including balancer function etc, fine. But I thought of the UNI-T for some very special things which my small charger do not can. Although the UNI-T has no dedicated battery charge function, you can record values and calculate later. Or you may charge partly, in intervals, stop below a special current - which is easy to achieve with the "Monitor" inside (switch of channel if current is below x).
Well, I keep that in mind. Maybe I construct an relay output breaker, using the digital I/O on backside: you can program them to change level depending on the output state. It's even a workaround that the UNI-T makes some alert instead of switching off the channel.

[audiotubes]

Dave has a nice video on recharing Lions with a programmable PS.

[Pfriemler]

So, basically it's well known why you should not use lab psu for charging batterys -  and how to set if we have to use 'em. There was nothing new to me. Just in the comments to Daves video

a user reclaimed a damaged RIGOl DP832 after charging a 26v lithium battery pack (and with 12V nothing happens) and linked to a RIGOL document: https://www.batronix.com/files/Rigol/Labornetzteile/DP8_DP1_ActiveLoads.pdf
But yeah, the RIGOLS are known for those damages. I will not try to blow up my UNI-T in the same way, although I think it would be safe somehow. I think the RIGOL will draw much more than 20mA in that case.

[Pfriemler]

Had a deeper look @ RIDEN ... hm, not only a dedicated battery charging function as @thm_w said, but a separate relay switched battery charger output. Nice to know. A 6012P is added to the wishlist.


Next issue: I am struggling with network access. Something very stupid is going on here. I use (Germany's top model) AVM hardware, the UNI-T is coupled to a WLAN repeater ("1200") in a (so called) mesh to my 6591 router. Both DHCP and manual IP settings seem to work, net scans with 2 computers and mobile phone do find it, pings are fast, an open port 111 (rpcbind) is reported. Although, the UNI-T "Instrument application" do not find the device via network (USB works fine). Both computers are running stupid simple Windows 10/11 with defender only. No firewall setting popped up. Any hints, folkss?

and here's the solution (afterwards I remembered Tony Albus' video where he did so):

If I open the scan on my MS Surface Pro Tablets, I will see the upper dialog with the options USB / LAN /RS232.
You have to expand the window downwards to make an input line visible. Here you have to type in the exact IPv4 address of the UNI-T
Now scan - and tadaaa! It's there.
Once you did so, next time you won't have to expand the windows, as long as the software remembers the IP address of the UNI-T (here, at least).

So stupid! I even installed newer NI-VISA runtime versions on the third PC, but you won't have to do so, it works with the V17 as well.

[Pfriemler]

Another topic: the trigger settings. I experimented yesterday with strange results. Looks pretty like "work in progress". Hmpf.

The UNI-T has four digital I/O lines backside (3.3V level). They are marked as "G 4 3 2 1" on the housing, referred as D3, D2, D1 and D0.
All triggers are disabled if the UNI-T is switched off  ... and, unlike any active "monitor", there are no signs in the status line to show if a trigger is enabled.

They can act as input - The H/L line levels are named as "High Level" (3.3V) and "Low Level") 
You may short them to ground, resulting in a ~0.7mA current, so you can use it - as an example - to switch ouputs on/off/toggle by falling edge/rising edge/low level/high level, with a so called "Sensitivity", which seems to be a delay only for debouncing. Funny: set the trigger line to toggle the output at low levels and shortcut the line - and the output is blinking in different speeds, according to the "sensitivity" setting. Nevertheless: the first task, an external all-off-button, is very easy - simply attach a button or switch and define the trigger to set ouput off on all channels with high sensitivity and bob's your uncle, so to say... 
But: If you expect this to work after a reboot ... no, it's disabled. 


Now to the output mode. The H/L line levels now are named as "Positive" (3.3V) and "Negative" (0.0V). 
If you short the output to ground, a current of ~6mA (H level) and 0.7 mA (L level) is measured.
It looks like there are hardware flip-flops triggered by some conditions. 
Very stupid: there is simply one condition per output. So, if you switch the UNI-T on and find the ouput at H level (3.3V), you can trigger it to L let's say with the condition "output CH1 is off" to realize let's say an external relay trigger. Yes, it works - once. Now the output is at L level and you have no chance to get it to H again. You can go to the trigger menu, switch the condition to "auto" and change now the output level manually in the next field, that's all. I did not find any reaction in "Auto" condition when using the UNI-T. Do not look at the manual, it's useless here.

So, to set a trigger line to simply follow the output state of a channel is not possible, if I not missed any other setting. 

[faktorqm]

OK I finally get decided and purchased 3305S at eleshop.eu. Once it arrives I will start with some tests and let you know. Regards!

[ArcticGeek]

For those that are interested in one of these Power Supplies Uni-T currently has them on sale (20% off) if you are in USA if you order directly from Uni-T.  Perhaps the same is true for other countries as well.

https://uni-trendus.com/collections/dc-power-supplies

In the US, that puts the price of the 3305S-E at $295 and the 3305S at $415.  You will have to pay shipping charges for the 3305S-E but the 3305S will ship free since the order is over $399.  That puts the price of these power supplies at a very attractive price point.

I just ordered the 3305S for myself - I can't wait to try it out.

Best,

[Pfriemler]

For all German/European users that are interested in the S-E version:
https://www.pollin.de/p/uni-t-labornetzgeraet-udp3305s-e-4-kanal-programmierbar-328-w-353199
379 Euro, some promotion code or sell actions may clear the shipment costs to Zero.

[thephil]

And someone told me that you can get the S-E version for 342€ right now through the UNT-T subsidiary in Augsburg, Germany. But you have to ask them for the "promotion" price.

[elemakil]

Hey thephil,

can you shed any more light on the promotion that UNI-T is offering? Do I have to contact them through the webstore or Email (if so, which of the Emails listed on their homepage is appropriate for this request?). I'd appreciate some more information as the UDP3305S-E would be a great bargain at this pricepoint.

Best,

[thephil]

can you shed any more light on the promotion that UNI-T is offering?

Apparently, UNI-T has/had(?) advertised a 20% discount in the US. Someone told me that he saw that and simply asked the German UNI-T people about it and was offered the price I mentioned. He wrote or talked to these guys:

Uni-Trend Technology EU GmbH
Affinger Str. 12
86167, Augsburg
+49(0)821 710 498 26
service-eu@uni-trend.com

I don't know if it still works but can't hurt to ask.

[Duglum]

I wrote them and they replied with a discount code ("THANKYOU10") for their Shop.
The email claimed the code will only be valid until tomorrow.. but i kinda doubt it.

Anyway, it brought down the price for the UDP3305S-E to 296.10€ net (352.36€ gross for me, which means they applied the 19% german VAT).
Shipping was free. The shop also said delivery time will be 2-4 business days, so they most likely send it from Augsburg.. international express from china for such a heavy item would probably be far too expensive to offer it for free.

Oh and, did anyone ever try to replace the 14bit DAC with the DAC8562 chip iAleks mentioned earlier in this thread? Replacing the firmware with the "S"-one sounded like it was no problem. Don't really need that type of precision and would probably not do it before warranty runs out, but it would be nice to have the option.

[voltlog]

For those wondering if they can upgrade the UDP3305S-E to be a higher spec UDP3305S just by replacing the ADC/DAC chips (ADS1118 / DAC8562 ) and flashing new firmware, UNI-T says "It's not possible!"

At Embedded World 2024 in Nuremberg, I had the opportunity to talk to the senior engineer in charge of the team that developed this PSU at UNI-T and asked him if it would be possible to swap the ADC/DAC chips and flash different firmware for the conversion.

Our conversation was very limited because he only spoke little english but what I could understand is that there are two problems that one will face: there are other smaller changes on the PCB apart from ADC/DAC chips and then there is the very important calibration which is only designed to be done at the factory, not accessible to the user.

BTW I also have a reaview & teardown video of the UDP3305S.

https://youtu.be/h7XDSfOQJHI
https://youtu.be/d056TNS9aa8

[mws]

I also saw the offer here. Unfortunately, I can't find a way to enter the code on the UNI-T website.

[pope]

I also saw the offer here. Unfortunately, I can't find a way to enter the code on the UNI-T website.

It's been removed.

[tonyalbus]

A while ago i received new firmware 1.12 , i see it not on their website, so decided to post it here.
Also the change log is very limited on there website, so i have here the one i received.



V1.12 update:
Optimize list output function.

V1.11 update:
Strategy for changing the output setting value and protection value: The output setting value can be made greater than the protection value.

V1.10 update:
1. Optimize SOCKET connection mode;
2. Solve the bug of occasional loss of sent data in SOCKET connection.

V1.09 update:
1. Add SOCKET connection mode, the connection port is 5025;
2. Optimize network connection.

V1.08 update:
1. Improve SCPI standards;
2. Add memory-related communication commands;
3. Optimize the local file manager and display the applicable channels of this list file and delayer file before the file name.

V1.07 update:
1. Add large font display mode.

V1.06 update:
1. Add power-on output function.

V1.05 update:
1. Added new communication commands to adapt to the NeptuneLab platform;
2. Added German to multiple languages.

V1.03 update:
1. The time resolution of timer and delayer is upgraded to 0.1 seconds.
2. The change strategy is: when the output setting value is greater than the reasonable value, the current value will not be changed.
3. An "error status" is added to the list output running status. When the output value set by the list is greater than a reasonable value, an error will be reported.
4. Add a shortcut for setting UI language.

Upgrade method:
1. Select the upgrade file according to the model and put it in the root directory of the FAT32 format U disk (the file name cannot be modified);
2. Insert the USB flash drive into the machine to be upgraded (power off);
3. Press and hold the "UTILITY" button to turn on the computer and start the upgrade;
4. After the upgrade is completed, manually restart the machine.

Video how to:

[thm_w]

For those wondering if they can upgrade the UDP3305S-E to be a higher spec UDP3305S just by replacing the ADC/DAC chips (ADS1118 / DAC8562 ) and flashing new firmware, UNI-T says "It's not possible!"

That is cool that you asked.

I guess the ~$10 BOM difference is enough for them to make two different products (2pc ADS + 2pc DAC?). Other manufacturers wouldn't have bothered.
Teardown was good to see, you can always post the full link:

[pope]

Looks like they increased the prices. I was about to pull the trigger but now I'm gonna have to look for a different brand. Oh well...

[BillyO]

Looks like the increased the prices. I was about to pull the trigger but now I'm gonna have to look for a different brand. Oh well...

Yeah, they've given so many of them away lately to "influencers" they have to increase the price to make up for it.