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Siglent SPD3303D review

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DSoldano:
Well, I'm having an interesting problem with my SPD3303D. I never tested it originally other than a power on test and then it stood in the closet for a while. I am working on a programmable DC load project and was using the SPD3303D as the circuit power supply (using the fixed 5V output) and also as the source input for the load - Channel 1 - set to 5v and 1A max at this point to limit the power and avoid magic smoke since I haven't mounted anything to a heatsink yet.

I noticed that every time I get above about 100 ma draw the voltage readout on my circuit was dropping. I thought it was a problem with my circuit until I put a handheld multimeter on the output. My circuit is fine. The voltage starts to drop off after 100 ma although the display on the power supply still shows 5V. at about .5A the power supply voltage drops off to about 4.85V yet the display still shows 5V.

Anyone notice a similar issue? Am I doing something wrong? If it's the power supply that's pretty crappy regulation with such a small percentage of the full current potential.

Dominick

FrankBuss:

--- Quote from: DSoldano on January 14, 2016, 12:10:52 am ---The voltage starts to drop off after 100 ma although the display on the power supply still shows 5V. at about .5A the power supply voltage drops off to about 4.85V yet the display still shows 5V.

--- End quote ---
Did you measure it at the connectors at the power supply or at your circuit? Could be losses in the cables.

DSoldano:
Frank,

Thanks for the quick response. I measured it at the terminals and at the circuit. I used the same brand of cables both for the meter and from the power supply to the circuit. Voltage read the same in both cases. If it was cable losses they should have been cut in half when I measured at the power supply terminals since it effectively reduced the length of the overall cable by half.

I have the mains/line voltage selector switch set to 120V on the back of the meter - I'm used to equipment labeled 110V/120V in the US but this doesn't have a 110V setting only 100V or 120V. I'm tempted to see if it's a low voltage problem and try the 100V setting but I don't want to blow up the supply.

Dominick

FrankBuss:
I can't reproduce the problem. I set 5 V for channel 1 and 1 A max, connected a 10 ohm resistor with some thick test wires, 1 m long each, and I can measure 4.97 V at the resistor and 4.999-5.0 V at the terminal (measured directly at the washers on the front panel). It is configured for 230 V. Mains voltage is 226 V (true RMS, all measured with a BM257s).

I think it should work with the 120 V setting, usually there is some safety margin and then it should only show problems with higher voltages, if it is not some low-voltage tap at the transformer which is right at the edge between two ranges. 100 V should not blow it up, it just gets a bit warmer. Try to measure your mains voltage (carefully, with a good meter).

Dave did a review of the SPD3303X and there were issues with the banana plugs. The socket was slighty too wide, so some banana plugs are a bit loose in it and this caused some voltage drop, too, if you wiggle it.

DSoldano:
Frank,

I tried checking the contact between the banana plugs and the binding posts - they are pretty tight and wiggling them provided no change.I even switched to the spade lug cables that came with the unit to be sure. Same behavior as earlier - it appears to drop off from 4.98V no load / open circuit to 4.78V at 1.2A. I tried both channels. The behavior is the same on both Channel 1 and Channel 2. I even tried running the channels in parallel - same behavior. The display on the SPD3303D reads 5.00V throughout the whole exercise, never wavers although the current reading changes.

I also tried changing the power setting in the back of the unit from 120V to 100V. The fan gets a bit louder but otherwise exactly the same behavior.

I'm not sure if I should bother trying a firmware update or not or just contact Siglent.

Dominick

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