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| GW Instek PEL-3032E Constant Resistor values seem inaccurate, is this normal? |
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| CatNinja:
I just got a Lecroy T3EL50015P (OEM is GW Instek PEL-3032E) Electronic Load. The Constant Current and Voltage readings are accurate, but for the life of me, I can't seem to get an accurate Constant Resistor reading. Input is a E3631A set at 10.00V. Here are the readings on the PEL-3032E. 500 Ohm 10.005V 0.0020A 200 Ohm 10.005V 0.0290A 100 Ohm 10.005V 0.0790A 50 Ohm 10.005V 0.1795A 20 Ohm 10.002V 0.4805A 10 Ohm 10.000V 0.9815A The readings are only reasonable at 20Ohm or less. The E3631A voltage and current readings match the PEL-3032E, so I think those are accurate. My understanding is that the resistance is simulated, and the PEL-3032E just sinks the appropriate current to match the resistance setting. Since it measured the voltage correctly, and it knows what the resistance is set at, why is it not sinking the correct current? Am I misunderstanding how electronic loads work? Or am I expecting too much of the accuracy of the resistance settings on this type of device? |
| alm:
I don't have experience with this specific load. In general I don't expect electronic loads to be particularly accurate in constant resistance mode, although clearly the 500 Ohm current is off by an order of magnitude. Does it help if you increase the voltage? I could imagine it's having difficulty with the very low current. What does the data sheet say about constant resistance accuracy? Is there some offset off the form R * X mA to be added? |
| HKJ:
Most electronic loads are not very precise when you get down to a few mA. It may have a few mA in offset on the current measurement/setting, check the specifications. |
| nctnico:
It is also very possible the DC load is oscillating because the power supply likely has a weird, complex impedance due to the output capacitor. |
| Martin72:
Agree to nicos post. We got several for the first time "mysterious" problems when connecting electrical loads to switching supplies, they interacting together in a resonant way, mostly observed by the cheaper PSUs. On linear regulated ones we never got any issues in that direction. At the lab we got tons of "Zentro" loads and several from Rigol, when time will allow it, I´ll do some tests with linear and switching supplies. |
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