Maynuo / BK Precision DC Power Supplies

[metalphreak]

Dave, have you asked BK Precision (or perhaps Maynuo) if they'd send you one of their power supplies for review?

I'm very tempted to get a Maynuo M8811 ( http://www.maynuo.com/english/pro.asp?tid=32 ). Waiting to see how decent the DC load I have on the way is (and how reliable the seller out of hong kong is too).


Specs look pretty decent. Set values in 0.5mV, 0.1mA steps.

Setting Value Accuracy: 0.01%+2mV, 0.05%+1mA
Readback Value Accuracy: 0.02%+5mV, 0.1%+5mA

Not really sure how the readback accuracy is less than the set value? The maynuo has a 5 1/2 digit DC voltmeter as well which the BK Precision doesn't. Clearly its the same designer who has progressed the design further with the new company.

[cosmos]

I was also tempted ... so much that I now have both their M9712C DC load and the M8811 PSU.

For anyone interested:
Things I like and notes of special things.

Having 10uA and 100uV  resolution readbacks is a treat and the reason I bought the M8811, I love it and it looks to be very accurate.
Dialling goes in steps of 100uV but it actually only moves every 5th step (as it also says in data sheet) , fine with me.
After calibration (see more below) the readback and DMV matches to about 0.15mV vs the Keithley 2000.
Set and readback matches to about 500uV (looks like a fixed offset) this is after my recalibration, it was about the same before too.
Settings to 0.001V works, readback says it is 2.5mV vs DVM 1.8mV vs Keithley 1.15mV (flickering +/-50uV), setting 0.0015V increases all by close to the expected 500uV.

The DVM is no direct replacement for a multimeter, the input impedance is well under 1 Meg ohm.
The DVM can not do negative voltages.
The DVM terminals are std types, shrouded test leads will not fit.
The DVM seems internally coupled to the negative output terminal , I only need to connect the two red terminals to get exactly the same reading as the readback.
DVM goes at least to 60V.
Having DVM terminals sitting next to the PSU terminals is risky, I fried a circuit when I forgot where the wires where going and "measured" with 30V at 0.1A current limit     


It is quiet, no noticeable fan noise as I can tell but I have other units with fans here so YMMW.
I have asked Maynuo if they would consider making the DVM readout optional (in a FW update) and instead have a PSU power reading there. no reply to that yet.
The user interface works for me, most menus and functions looks and works the same on the DC load and the PSU, they keypad was strange at first but now I stopped thinking about it.


Calibration issue:
I am (finally) completely happy with the M8811 after a bit of noise to get the DVM part to not be at the edge of specs.

The M8811 came with very good matching for setting vs readback (inside a few counts)
The DVM part however was off over 100 counts (but that is still just inside spec)
I mailed Maynuo a request to get the calibration procedures to fix it.
I got back a description showing how to calibrate the readback, (V and I)  and the remote sense, but nothing on what I needed and requested (DVM).
It was also clear that they thought the DVM was inside the spec so why would I not just be happy with it and go away.
I requested the DVM info a few more times then gave up, I was not even able to get it into the calibration mode following the description I got (partly my own fault, "press shift UP,DOWN" I missed that "shift" referred to a button and of course the omitted info that you have to press ENTER to get to the next step).

After getting access to a better multimeter (Keithley 2000) I tried again and figured out what was missing in the calibration description.
I could then also figure out the missing part about the DVM (educated guess as there was only one remaining button of 4 not already mentioned) .. it was following the same procedure as the others and was dead simple...nothing special and nothing to keep secret...i don't get it that I could not be told that.


I have not yet used the PC interface, or the milliohm meter function.

All in all I would buy it again. 
M8811 was 468USD incl shipping

[metalphreak]

M8811 was 468USD incl shipping

Where from? Did it include the USB to TTL RS232 cable? I'd be very interested at that price but can't find any decent suppliers.

[cosmos]

I am not sure if it was with the USB cable or not, I can only find one cable here so I guess that means it was not included with the 8811 but came with the 9712C

I got it from here but they no longer list it: http://www.aliexpress.com/store/907896
these have it at about the same price: http://www.aliexpress.com/item/Maynuo-M8811-Programmable-DC-Power-Supply-0-1mV-0-01mA-5A-30V/880317013.html

I will PM you some details. 

[metalphreak]

Just realised this isn't the M8831 thread. Doh    From what info I got from Maynuo and cosmos, the M8831 should only be ~$100-150 more than the M8811.

[JMcC]

Sorry for re-opening an old thread, but I was wondering if you still have that M8811 calibration procedure along with the corrections you found out about.

Thanks,

JMcC