Itech IT8512G+ DC Load strange behavior! Is this normal?

[Faranight]

Greetings, EEVBlog!

So I recently got an Itech IT8512G+ DC load that I planned to use for some PSU and solar testing. I've been messing around with this unit on some small solar panels, and I noticed that the constant voltage (CV) option causes the voltage to crash under certain circumstances. I wasn't able to pinpoint the exact conditions on a solar panel, but I decided to reproduce the issue with a lab PSU @ 10VDC and a 470Ω resistor in series. At some point the unit will not be able to accurately regulate the voltage any more (there will be a voltage offset) under the CV load option until the voltage is sufficiently reduced. I'm not sure what's going on here or whether this is normal behavior or not, but I want some opinions before I go pestering the ITECH tech support.

Is this a bug in the model or am I doing something wrong? It sort of acts like a schmitt trigger... crashes at high voltage, but recovers at low voltage. The thresholds are not constant and seem to be dependent on the source voltage and the resistor value.

Here's a short video for better demonstration


Kind regards!

EDIT: Changed video host to Vimeo.

[HKJ]

So I recently got an Itech IT8512G+ DC load that I planned to use for some PSU and solar testing. I've been messing around with this unit on some small solar panels, and I noticed that the constant voltage (CV) option causes the voltage to crash under certain circumstances. I wasn't able to pinpoint the exact conditions on a solar panel, but I decided to reproduce the issue with a lab PSU @ 10VDC and a 470Ω resistor in series. At some point the unit will not be able to accurately regulate the voltage any more (there will be a voltage offset) under the CV load option until the voltage is sufficiently reduced. I'm not sure what's going on here or whether this is normal behavior or not, but I want some opinions before I go pestering the ITECH tech support.

Is this a bug in the model or am I doing something wrong? It sort of acts like a schmitt trigger... crashes at high voltage, but recovers at low voltage. The thresholds are not constant and seem to be dependent on the source voltage and the resistor value.

I have not checked your links, but if the current is within a few mA of what is needed for the correct voltage, you will not get better.
The load adjust current and have a resolution of about 1mA, i.e. it cannot do smaller steps to adjust to correct voltage.

[Faranight]

Hmm, the odysee link doesn't seem to be working for me right now. I'll see, if I can upload it to vimeo later.

You think so? Here are the IT8512G+ specs from the datasheet.
I'm assuming the device switched to the lower measurement range (left column) since I did hear a relay click after lowering the current range down to 1A.
This range seems to have the resolution of 1mV in CV mode and 0.1mA in CC mode, respectively.