Siglent SDL1030X-E strange sense voltage readings? - Page 1
Forum section: electronics / testgear

author: tubularnut
author_rank: Regular Contributor
timestamp: May 11, 2020, 06:08:24 pm
content: Is my SDL1030X-E broken or is this normal?I was doing some battery capacity testing, and decided to wire up the sense terminals to counter the voltage drop at higher currents, and started getting strange results.I then realised that the sense voltage was lower than the actual battery voltage. I checked out the sense wiring, and confirmed with a bench meter that the leads were ok, and the correct voltage was present at the sense terminals on the back of the SDL.After a bit of poking around with buttons, it seems that when the unit is set the the 36V range, it progressively reads a lower voltage than is present at the sense terminals.e.g. at 12V input it will displays approx 9.5V, and at 30V it displays 22V. Up until around 5V it is reads correct.However, if you switch the range to 150V, it reads correctly all the way up to 32V (the highest I've tested so far).As a further example I connected my PDVS2mini set to 10 volts, and checked the reading on 36V and 150V range.Firmware is the latest (1.1.1.21) and system has been reset to factory defaults with remote sensing enabled, nothing connected at main input terminals.

author: tautech
author_rank: Super Contributor
timestamp: May 11, 2020, 06:37:42 pm
content: Check the input impedance as it may not be suitable for high impedance voltage references.Another DMM in parallel should confirm SDL input impedance is dragging down the voltage reference output.

author: tubularnut
author_rank: Regular Contributor
timestamp: May 11, 2020, 06:46:11 pm
content: Quote from: tautech on May 11, 2020, 06:37:42 pmI've tried it with a lead acid battery (12V 7Ah), a Siglent SDP3303X-E, and the voltage reference. They all display the same low voltages on the 36V range, but correct on the 150V range.I have also probed the screw heads on the sense input terminal with a Keysight 34465A, and a Brymen 869s, and they confirm the correct voltage is reaching the terminals, and not being dragged down by the SDL.

author: tubularnut
author_rank: Regular Contributor
timestamp: May 11, 2020, 07:00:38 pm
content: Apologies for the obscure angles:Rear terminals probed by Brymen.Pic 1, 10V (reference) on 150V rangePic 2, 10V (reference) on 36V rangePic 3, 32V (SPD3303X-E) on 150V rangePic 4, 32V (SPD3303X-E) on 36V range

author: tubularnut
author_rank: Regular Contributor
timestamp: May 11, 2020, 07:19:57 pm
content: In response to the post that has disappeared with regards to 'reading the manual'??I get the point, that the sense input is for compensation, the manual does not mention 'regulation' anywhere.I just need to be sure that when the SDL is being used for testing battery capacity, that the sense readings are correct. At present I have no confidence when using the 36V range, which I would have expected to be more accurate and relavent when testing 12V batteries.

author: tubularnut
author_rank: Regular Contributor
timestamp: May 11, 2020, 07:37:27 pm
content: Ok, I think I've sort of resolved it.It turns out I have two bad lead acid batteries (I was only expecting one to be bad), so I was getting low readings on both even with the remote sense enabled.I connected up the SPD supply in 4 wire mode to the SDL, and drove it at 30V 5A.With remote sensing on both 36V and 150V ranges it was pretty close to actual voltage, as confirmed by bench meter.Without remote sensing it dropped by around 200mV on each range, so it does appear to to function correctly.Turns out you can dig your own hole, and make it deeper!