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DIY milliohm/volt meter kit

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iloveelectronics:
Inspired by another discussion about milliohm meters on the other forum (EEVBlog) a few weeks ago, I went searching for one and found a Chinese designed DIY kit. Seeing that it's all 0805 and 0603 SMD components and quite a few IC's with small pin pitches I was initially a bit hesitant (as I failed miserably before with another DIY kit with a MCU in a LQFP package) but thought I would give it a go anyway.

The soldering job is a bit rubbish but at least this time no chips get killed and it works!

Besides the PCB and components the kit also comes with a lot of documentation (in Chinese), a pair of Kelvin clips and leads, an acrylic case, a lithium rechargeable battery, a programmer (for uploading the firmware), and even the source code of the firmware.

I took the attached pictures before I attempted to calibrate it but I was already quite impressed with its resolution and stability in the readings. It has 2 ohm ranges (0.2 and 20) and in the 0.2 ohm range it offers resolution all the way down to 1 micro ohm!

I have since done some not-so-precise calibration with the gear I have and compared the results against the HP3457A and this little device is tracking very well with the HP across the ranges. I will post more pictures in this thread later on as I'm trying to order some resistance standards for calibration.

The device also doubles as a 5.5 digit volt meter by changing some jumpers on the back side and I have played around with that a little bit today. Initial impression is that it has great accuracy but seems to drift a bit over time. I will also update on that later.

SeanB:
What is the price of the kit? If you stock it will you be giving a translation better than the poor results often seen as to assembly and test? You probably would have to ship these without the batteries though, unless you have a giant pile of them and want to send them by surface mail to me ;) or Martin to test to destruction.

iloveelectronics:

--- Quote from: SeanB on November 13, 2013, 12:26:48 PM ---What is the price of the kit? If you stock it will you be giving a translation better than the poor results often seen as to assembly and test? You probably would have to ship these without the batteries though, unless you have a giant pile of them and want to send them by surface mail to me ;) or Martin to test to destruction.

--- End quote ---

I will stock some (I already talked to the author and got permission) and I will personally translate the documentation to English, but it will take me some time. In terms of pricing I haven't worked it out yet but I think it's safe to say that it will at least be about the price of a UT61E.

iloveelectronics:
I'm still waiting for some resistance standards to arrive but I went ahead and did some calibration using my 0.5%/2% tolerance (in the x1/x0.1 ohm ranges respectively) decade resistance box. I calibrated the device against my HP3457A on 18 ohms on the 20 ohm range and 0.1 ohms on the 0.2 ohm range.

Here are a few pictures of how the measurements taken by this little DIY device compare to the HP3457A. In the pictures they are measuring 10 ohms and 0.2 ohms. The HP measures 10.0140 ohms and 0.2102 ohms (with some jumping around on the least significant digit), while the milliohm meter measures 10013.90 mOhms and 210.213 mOhms (with actually less jumping on the LSD even though the resolution is higher than the HP).

I'm happy  :)

iloveelectronics:
A couple more pictures to show where I put the battery inside the case, and a hi-res photo if anyone's interested in seeing the actual part numbers and so on.

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