Hi,
I bought an electronic load from a Chinese eBay seller (shipment from uk) for 280 €. It looks similar to other loads I found on the forum, but there are differences. Here is a quick description of the device. I haven't used it much since, but so far, I it performs fine for the price.
There are a few other threads mentioning the RK8511.
It came with a printed Chinese manual, a power cord (I think for the UK) and a travel adaptor. The power cord felt very cheap and I was able to touch the contacts with the plug half inserted into the travel adaptor. I threw those away and used a standard IEC power cord.
-> Photos
coming soon. Compared to the similar looking, but higher priced units from other vendors, I noticed at least a missing varistor and I'm sure there are more differences to get the price down...
-> Features
It supports CC, CV, CR, CP, CC+CV, CR+CV and "short mode" which should give zero ohm resistance.
You can set it to switch on and off at certain voltages and it has a transient mode (settings are low current, high current, rise time, fall time, high time, low time and trigger modes (continuous, pulse, trigger). There is a battery test function which counts the Ahs up.
You can set the maximum voltage and current through the menu. If you set it to > 3A or > 16V, a relay clicks and you get one digit less resolution for U or I.
Compared to other brands, the display output of the last digit is truncated. But in the pc software, you see all digits.
-> PC connection and software
There is a serial output (ttl, not isolated from the load!, can be dangerous, the shield of the DB9 connector is connected to GND of the source...). No isolating adaptor was included. There are kits available on eBay which include a software cd and an isolating rs232 or usb converter.
I built a converter using a serial ttl to usb converter (ebay) and 2 slow optocouplers... should have used faster ones because my construction only works up to 9600 baud.
The Chinese seller was not able to give me a link to a working software, although the eBay offer said "free software". But it turned out the Maynuo software works fine
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
.
-> Calibration
When I got the unit, it was not accurate. There was a large offset. So even when set to 0A, there was a current of about 40mA. Thanks to LaurenceW I was able to figure out how to calibrate the load. It's now spot on with my Rigol 3061 and the Hameg HMP4040 power supply.... but only at the right temperature. It has a high drift.
For calibration, you need a 150 V voltage source (low current) and a 30A current source and of course a meter that can measure 30A....
I'll post the procedure and a description of my setup soon.
good_cap/bad_cap