siglent spd3303x-e can't set it to current mode - Page 1
Forum section: electronics / testgear

author: MarkKn
author_rank: Contributor
timestamp: January 13, 2022, 02:19:29 am
content: Hope this is the proper forum for this sort of question.After lots of research, I just bought a siglent spd3303x-e. I have reviewed the documentation and tried it out, and I simply can't figure out how to get it into constant current mode. The so-called getting started document is silent on the subject and there is no user manual that I can find. I set the current to some amount and the voltage to zero, and it doesn't take a hint. I am pretty close to sending it back and getting a different device, but wondering if someone here can give some insight here. I have to confess to some irritation that a close reading to all the available documentation does not explain how this works.I want to also note, and I have seen others mention this, the process to update the firmware is simply ridiculous. It requires not only the siglent program but some 1 gigabyte network type library. I foolishly installed it before I realized it has the current firmware. I note that the so-called uninstall left a number off service running for that national instruments network software which I was unable to delete. I also note that the siglent website is coming up as having an invalid ssl certificate, so maybe the entire thing is a virus. My mistake here for even installing it. I am doing a full system restore to a backup here to rid myself of that fetid software.Any thoughts before I log into amazon prime and initiate a return?Also, if I do return it, is there a consensus here on a good power supply? I want one with a clean output as I may work with audio, so I went with a linear. I read that the switching supplies have lots of output noise.

author: tautech
author_rank: Super Contributor
timestamp: January 13, 2022, 03:25:10 am
content: Quote from: MarkKn on January 13, 2022, 02:19:29 am0V = zero output.Set desired voltage and the current limit value.For these units they are shipped with a 0V and 0A setting and will not output without setting to required levels.These PSU's are very clean with a 300uV max ripple and noise spec.

author: MarkKn
author_rank: Contributor
timestamp: January 13, 2022, 03:46:32 am
content: Thank you for your response. It does not provide me enough information for me to understand what the relationship between voltage and current settings and constant current mode.Please provide a precise explanation of how constant current mode works or what it is supposed to do. There seem to be voltage settings involved, but how they relate to the current setting is undocumented.I do not want to return this power supply, I would prefer to use it. The constant current feature is very important to me and I think it would benefit siglent to fully explain it. I have a siglent scope and bench multimeter and in general like siglent products.Thanks in advance for a more comprehensive explanation. It will benefit siglent to provide a good explanation and then add it to their documentation to reduce questions from future customers.

author: Tjuurko
author_rank: Regular Contributor
timestamp: January 13, 2022, 04:38:38 am
content: Set themaximumvoltage of CH1/CH2Set the desired current of CH1/CH2Short-circuit the output of CH1/CH2 or connect your loadTurn on CH1/CH2

author: tautech
author_rank: Super Contributor
timestamp: January 13, 2022, 06:14:40 am
content: Quote from: MarkKn on January 13, 2022, 03:46:32 amThese auto switch from CV into CC mode based on the max currentyouset.You'll see the LED indicator go red and the OUT voltage fold away/down. At this point increasing the Set current will trigger the PSU back into CV mode.

author: MarkKn
author_rank: Contributor
timestamp: January 13, 2022, 02:58:13 pm
content: Thanks for the responses, I feel I am almost where I want to be.I thought I had a full understanding of it, but now I am not so sure. Here is how I understand it now, and I verified this behavior with the device and a circuit:1) If the current setting is zero, the device will be in CV mode and attempt to match the voltage setting. If it is unable to maintain that voltage due to excessive current demand, it will (some sort of overload behavior).2) If the current setting is greater than zero, it will be in CC mode and attempt to maintain the specified current. It will start the voltage at zero and increase the voltage until the current matches the current setting, or the voltage reaches the voltage setting. IF it reaches the set voltage and the current is less than the target current, it will switch to CV mode and maintain that voltage.Now I am wondering if there are conditions where both voltage and current are set and it is in CV mode and switches to CC mode--maybe the current setting acts as a max current and its a case of whether voltage or current reaches its setting first. I think one thing that is blocking my understanding is that I understand a voltage and current source and I am trying to apply that too literally to these settings. It makes sense that a real world current source has a limit in terms of voltage. In a similar respect, a voltage source in the real world has a limit as to how much current it can put out.I appreciate the help, and am wondering if my understanding thus far is correct. I will say at this point that I am satisfied that the power supply has a constant current mode that I can use so I will not be returning it. So this discussion retained a sale and saved everyone a lot of hassle. I will do some more expirementing in the lab after work today.

author: Kean
author_rank: Unknown
timestamp: January 13, 2022, 04:09:58 pm
content: Actually, if you set the current limit to zero the power supply will likely go into CC mode immediately and you'll get no output, and potentially an unstable voltage. How well it handles this depends on how well it can detect really low currents.If you want to supply a circuit 10V with up to 1A output, then you set those values. If you exceed 1A, the PSU will limit current by decreasing the output voltage.If you want to supply a circuit with 1A constant current output you still need to set a maximum (or compliance) voltage, which is the limit if there is less than the set current is being drawn.Unless you want no voltage at the PSU output, you would never set either the voltage or current to zero. And if you do want the output, setting the voltage to zero is much better as the current limiting at very low loads may not give you what you expect. Generally it is easier to disable the output than change the voltage to zero, and most modern PSUs provide a way to do that.

author: MarkKn
author_rank: Contributor
timestamp: January 13, 2022, 09:44:05 pm
content: Thanks for the explanation! I note that I really enjoyed playing commander keen back in the day. I did get through all levels, but I did it by saving the game after each level so I would not have to start over again...

author: MarkKn
author_rank: Contributor
timestamp: January 14, 2022, 09:00:53 pm
content: Ok, so I am getting the sense that this thing will be in constant voltage or current mode depending on the relative settings of voltage, current, and the resistance of the load. I suspect this is the way all of these power supplies work--maybe the only way it can work? Maybe I should have posted this in the beginners section. I think I will understand it once I do a bit more experiementing. Thanks, all for the assistance--it did keep me from sending the power supply back causing senseless hassle and cost on everyone's part.