UT203 With Oscilloscope Output

So, you have a UT203 and don't want to buy another clamp multimeter with oscilloscope output.

Here is the instructables for creating one.

Unfortunately you can't directly connect UT203 to scope. The voltage output from "clamp" is only in mV.

You have to use op-amp to boost mV. Op-amp design must be dual rail voltage because you can have
positive and negative voltage output from "clamp".

First you need to open UT203 and connect to "clamp" output..

Open UT203 casing and connect to "cn2" like on the picture.

Red wire is (+) positive and brown wire is ground.

You can add DC male plug, for quick connection of external op-amp,

or you can permanently connect it to op-amp.

Op-amp circuit is rely simple. You can use any op-amp. Because you can have positive and negative

current flow through "clamp" you have to build dual rail op-amp circuit. When there is 10A current flowing trough

test wire, there is only 10mV output from "clamp". Op-amp will boost that voltage by factor 10x (or by factor 100x)

and you will have 0.1V. In case current is flowing in opposite direction output from "clamp" will be -10mV, and op-amp will also boost that voltage by factor 10x (or 100x), and the output will be -0.1V.

The gain factor is controlled by switch "S2". When the switch is in OFF position gain is 100x. When switch "S2"

Is in ON position gain factor is 10x

The red LED is only there so you don't forget to switch off op-amp power supply.

And here is the completed op-amp in white box and with BNC connector. Just for test I have connect it to

universal multimeter. Current flowing through test wire is 2.9A. Gain factor in Op-amp is 10x and multimeter is

measuring 0.02V. The last picture is scope output from UT 203 measuring relative compression on Golf MK3 1.4i