Author Topic: Best way to MOD banana jacks on to a SparkFun/JYEtech Cap meter?  (Read 1160 times)

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Offline rwgast_lowlevellogicdesin

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Best way to MOD banana jacks on to a SparkFun/JYEtech Cap meter?
« on: December 31, 2015, 02:31:05 am »
Ok so I keep buying UNI-T DMM's and breaking them! I have a few Klein meters that just keep on going. I love these meters for industrial but they suck when it comes to low capacitance and resistance. I went looking in to LCR meters, but most of them didn't meet my needs for low measurement values either, unless they were 500+!! I got this this little kit, guess I could have just built it on prefboard but I didn't expect it to work so well, and thought I would be wasting my time doing it from scratch, especially since there is a HEX only and they wont release source which I desperately want so I can move to a 328 and add more capability.

https://www.sparkfun.com/products/9485

So this thing is pretty cheap! The cool thing is it goes all the way down to 1pf-500uf. When doing RF and filters a meter that can read a 1-10pf cap is pretty darn handy. That one detail makes this a much better option than one for the cheap0 e-bay MK LCR/Transistor tester. It has been nice to test my trimmer caps and old AIR bread cutters!

So here is the deal I want to mount this in one of those cheapo RatShack aluminium boxes, it is basically the only enclosure I have it will fit in that is made of metal. I also want to add banna jacks so I can use my short test clips and probe master leads, when called for.

Here is a close up of the kit built,


You stick the DUT in that SIP header to the right of the ATMega48. The first 3 holes are Positive and the next three holes are Ground/Negative. Above that is J3 which is also a breakout for +/- of the DUT. I had planned to stick the PCB inside the aluminium enclosure with the LCD popping out then break all the headers out taller than the AVR chip so they will be accessible while PCB is in the enclosure.

Now my question is if I want to tap banana plugs in to J3 and then mount them in the enclosure to the right of the PCB what is the best way to go about this??? It seems like a silly question but all meter jacks are built on to the PCB, in this instance you plug the cap in to a header on the PCB which is about the same technique. In order to mount the jacks to the right side my wires from J3 will have to be about 3.5 inches long. Im also going to have to modify the LCD to stand a bit higher etc, etc.

My real question is about the wires I would be connecting to J3 or the first port for the DUT. I know you do not want to add any extra capacitance inductance, or resistance that you do not need to. So what would be the best way to wire j3 to the jacks? Should I use thick or thin wire? Does it need to be shielded, would coax impeadence cause issues? I plan to connect enclosure to ground in order to shield it, should I use DC iron toriods or ferrites on the signal test wires? I was thinking of running solid #12 and twisting it tight then wrapping around an iron toroid but im not sure if that would skew the test pulsing.

I know this is no agilent meter or anything but I want to get the best accuracy I can at the 1pf range, I really bought it to help me design fixed and adjustable filters.


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