Products > Test Equipment
ARRAY electronic loads
free_electron:
ah , good. i just bought a 'out-of-spec' 3711 for cheap on fleabay. so i can compare.
saturation:
Nice, and congratulations. I'd be interested in your comments, free_e-. I was wondering what happened to this unit.
http://www.ebay.com/itm/TekPower-3711A-TP3711A-Programmable-DC-Electronic-Load-0-360V-300W-/290771559411?pt=LH_DefaultDomain_0&ssPageName=RSS:B:SHOP:US:101&hash=item43b355e3f3&nma=true&si=4%2FoYUNwtxMPRuUXZmUBrIJTg4og%3D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
If its you, its in good hands.
I wonder if the 150W, which is really 200W, is just crippled in firmware and is in hardware a 300W. Much of its components suggest it is. A photo of your PCB and your comparison would clear it up easily, when you've time to get to it.
--- Quote from: free_electron on September 20, 2012, 06:20:23 pm ---ah , good. i just bought a 'out-of-spec' 3711 for cheap on fleabay. so i can compare.
--- End quote ---
LaurenceW:
Greetings all,
I've just posted a rather wordy initial impression of my Maynuo electronic load, here
https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/30/
I'll get the lid off this weekend, and grab some pictures.
saturation:
Excellent review, must read for anyone considering an eload. Please keep it up, and as many pictures as you can! I'll post comments on that thread rather than here.
--- Quote from: LaurenceW on September 20, 2012, 11:50:30 pm ---Greetings all,
I've just posted a rather wordy initial impression of my Maynuo electronic load, here
https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/30/
I'll get the lid off this weekend, and grab some pictures.
--- End quote ---
free_electron:
Yep. Me. Snatched it for less than that :)
I have some 'reverse engineering ' info.
The meanders on the pcb are there for a purpose. The two powerfets at the back have their own 0.1 ohm sense resistor to close the loop. These two resistors share a single trace on the board that is via-stitched between top and bottom layer and comes to the front of the board. The meanders on the front resistors inject the same trace length to the star point. The reason is load balancing. The pcb trace resistance would be different between front and back and the front fets woul pull more current than the back. Deliberate operation. Good design.
The bank of 6 mosfets on the main board is for range switching.
The use either 0.2 ohms for current measuring , in series with 0.02 ohms ( five 0.1 in parallel ). At high current they turn on the bank of six mosfets to short the 0.2 ohms out.
A relay toggles between the sense points. ( strange.. No analog mux ... Probably because there is a post divider protecting against large voltages.. )
My machine is off in the voltage measuring department. The programmed and measured currents are correct. The voltage measured on the terminals is wrong , so it probably needs adjustment.
The sticker said. Cannot adjust , but they didnt even try.... None of the pot seals are broken and this machine has no electronic calibration.... Lazy callabs...
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