This week I got a Siglent SPD1305X - hardware version V1.0 - cal date 26th of October 2018. It is my first proper adjustable bench power supply with current limiting and I like it a lot.
It looks like a proper piece of gear with nice quality plastics. The user interface of the device itself seems pretty intuitive to me and very easy to use. The rotary control works well - it is easy to turn it to the value you want without it skipping numbers or anything annoying. I really like the 4 wire setup - it works well. Voltage readback on the device measures very close to my multimeter.
The binding posts work well with all my unshrouded banana plugs, even with the knobs undone as far as they will unscrew. Not loosey goosey. Probemaster stackable banana plugs work well as an example.
It is audibly pretty quiet with low fan noise. I also have a Siglent SDS1104X-E oscilloscope which I also find to have low fan noise, and the SPD1305X is maybe a little quieter than that.
I had no problem installing the suggested ancient version of NI-VISA runtime, and the EasyPower 1.01.01.18 software in a windows 10 virtual machine. Shame it requires windows. I updated the firmware over ethernet without issue. EasyPower is ok but a bit clunky. Slightly annoying that you have to type in an IP address to connect to a network device each time. It does not seem to remember the IP after disconnecting and it does not seem to let you use a hostname instead.
I tried measuring electrical ripple and noise using a 1X probe and thought I was seeing about 8mV peak to peak and <1V RMS - with or without a load (56 Ohm 5 watt resistor), but then I tested measuring an alkaline AA battery and it looked exactly the same. So I can't really measure electrical noise this low properly (no 50 Ohm attachments, lack of technique). I have no doubt the constant voltage electrical noise meets its specs and is very quiet.
Measuring voltage of the output while turning on the main power (clunking switch) showed some transients. Keep in mind I am a beginner and may be measuring or interpreting it wrong. Don't know if the transients are real or picked up from the environment. They seem pretty small and harmless anyway.
image: main power (clunking switch) transients
Using the soft channel on button, I did not measure any voltage overshoot. It looked very well behaved in that sense.
I thought I would try measuring current overshoot. Tests done with a Keysight U1272A multimeter with "Peak detection of up to 250 μs".
Testing done with U1272A set to measure current in the 10A range (which seems to be a 30A range as it is a 30,000 count meter) rather than autorange. Then Peak detect enabled.
Test A SPD1305X settings:
3.000V
0.020A
SPD1305X connected direct (pretty much a short) to current measurement on multimeter, then power on the channel with the soft power button.
Result: Usually about 16.8A peak. Yes that is Amps. Sometimes 0.023A which I think means the peak measurement was missed due to current spike being very short, and the limitations on very short duration peak measurement with multimeters. I guess this is a capacitor discharging?
Test B SPD1305X settings:
3.000V
0.020A
SPD1305X powered on circuit open, then short the outputs and unshort/open, then connect to current measurement on multimeter. Basically trying to see if connecting after turn on reduces the initial current.
Result: overload - so more than 30A. Probably due to a spark?
Test C SPD1305X settings:
3.000V
0.020A
SPD1305X
SPD1305X connected to current measurement on multimeter with a green LED inline (in series), then power on the channel with the soft power button. Testing to see how this relates to a more real world scenario.
Result: LED lights up yellow for fraction of a second then changes to green constantly lit. It is a standard green LED which should not be yellow so I assume this is from too much current. note - see
Update4 below.
peak current measurement about 0.160A.
Test D SPD1305X settings:
5.000V
0.020A
SPD1305X
SPD1305X connected to current measurement on multimeter with a green LED inline (in series), then power on the channel with the soft power button.
Result: LED lights up for a fraction of a second then burnt out / open LED. Repeatable result with a second (initially good) LED. note - see
Update4 below
Peak current measurement about 3.145A
Test D SPD1305X settings:
5.000V
0.020A
SPD1305X connected direct (pretty much a short) to current measurement on multimeter, then power on the channel with the soft power button.
Result: about 20A peak
If I am testing wrong you are welcome to educate me.
So I am a bit of a electronics beginner and I don't know if it is typical for currently limiting to not work on initial turn on or if this is only a problem with certain power supplies. Maybe a trap for young players? But anyway I don't think this SPD1305X can be relied on to limit initial current with soft power on for delicate loads, or with connecting delicate loads after soft power on. Perhaps delicate loads should have a current limiting resistor installed as an extra precaution. This might be common knowledge - I don't know. At least I did not blow up the expensive 10A fuse in my multimeter.
I was really hoping/assuming that the current limiting would work 100% of the time but I don't know if that is realistic. Perhaps they have a capacitor connected after the current limiting so there is no way to limit that? Is that a typical arrangement? Probably is to ensure low ripple. Does the SPD1305X have too much capacitance after the current limiting? Probably a balancing act.
For now I will assume this is all normal for power supplies unless someone can advise if it is not. Overall I am still happy with this power supply.
Update: current overshoot seems to be normal and is a trap for young players
http://powersupply.blogs.keysight.com/2012/07/why-does-my-power-supply-overshoot-at.htmlUpdate2: It seems that power supplies can be designed to minimise voltage overshoot (voltage-priority mode) or to minimise current overshoot (current-priority mode).
https://www.electronicdesign.com/power/getting-your-priorities-straight-managing-overshootsPerhaps with Siglent optimising this power supply to minimise voltage overshoot, that might have compromised current overshoot. It could be argued that this is our (EEVBlog members) fault for complaining about voltage overshoot on power supplies all the time. Siglent is just giving us what we asked for.
Update3: learnt how to display the image inline with the text.
Update4: I have made a mistake testing the LEDs with too high voltage. I did mention I was an electronics beginner. So that could be the reason why they burned out rather than too much current. Or it could have been both. I don't think this invalidates the current measurements I took. I think better measurements are needed with a current probe (I don't have one) and oscilloscope to try and determine if the energy contained in the current surge (amps and duration) is significant.
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