Products > Test Equipment
GW Instek PEL-3032E Constant Resistor values seem inaccurate, is this normal?
alm:
The 10% of full scale condition was for Rigol and Siglent loads. I didn't notice it in the GW-Instek data sheet. But it wouldn't surprise me if this load is also more accurate for higher voltages and currents.
Naively you'd think it's the multiple of voltage read back error and current programming accuracy. Plus some sort of leakage term at high resistances (I think that's what the + 002 mS is about). I haven't done the math to see if that matches.
Note that these should be the worst case specs. You're unit might well perform better. Still, I think it's odd that they offer resistance in the kiloOhms with such barndoor-wide specs. Maybe send Lecroy or GW-Instek an email to ask them to check. I wonder if they slipped a decimal somewhere in the data sheet.
HKJ:
--- Quote from: alm on September 26, 2022, 10:03:08 am ---Note that these should be the worst case specs. You're unit might well perform better. Still, I think it's odd that they offer resistance in the kiloOhms with such barndoor-wide specs. Maybe send Lecroy or GW-Instek an email to ask them to check. I wonder if they slipped a decimal somewhere in the data sheet.
--- End quote ---
As I wrote before the issue is probably with the current. Use a higher voltage and it will handle higher resistance, because the current is higher.
alm:
I agree, but that doesn't make the specifications that say the unit has resistance ranges up to 50 kOhm, but there might be 16 Ohm in parallel with that 50 kOhm, less ridiculous. Maybe they missed a prefix and in should be 0.06 mS?
Hexley:
The data in the table below was taken from another GW Instek product, the GPP-4323 power supply/active load. While this 32V/3.2A load is not in the same class as the PEL-3032E, perhaps the data may be of interest to some.
Channel 1 was set to Load mode, constant resistance, and the load was stepped from 500 ohms to 10 ohms.
An external voltage source was applied, and the voltage at the load terminals was measured with a 5.5 digit voltmeter.
The current flowing into the load was measured with a 6.5 digit milliammeter.
The equivalent load resistance was off by just under 4% at 500 ohms, and was much less than 1% for loads <50 ohms.
GW Instek GPP-4323 Load Behavior (Channel 1)
CRVloadIloadReq.Err5009.953519.175193.84%2009.875848.312042.21%1009.747496.421011.09%509.8934197.2500.34%209.7299486.620-0.02%109.4674947.910-0.12%
Hydron:
I'll have a quick go with my cheap AliExpress load later tonight, see what results I get out of that (also a 500V load, but nowhere near as nice as the Lecroy one, kinda regretting not grabbing one of those when I had the chance).
Btw don't try and use the GPP-4323 load in constant resistance mode for anything dynamic - the resistance simulation is only done at 10Hz or something (on the earth referenced processor, not the floating one doing the fast current/voltage control loop) so it's ugly and ~unusable. Constant current/voltage don't have the issue. Load mode is basically just a nice bonus on the PSU, it's not really a first class feature.
@CatNinja: I also invite you to open up the Lecroy load and see what's going on in there - it's certainly not built down to a price!
Edit:
Checked my DCL6104A @ 500 ohms 10Vin, it says 20mA but actually draws ~17mA, with a fairly large ripple (a few mA RMS with spikes of a little under 10mA, this load is not great at low currents!). -3mA offset is the same at any resistance or in current mode though, so it's just a calibration issue, nothing fundamental. For some reason the offset seems to change to +7mA when I use 4-wire mode (a little hacked addition I made to the 6104A), which makes less sense. The load also disagrees with being driven by my SMU when in CR mode, but that's not a big surprise (SMU is fussy).
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