Diff Probe

Overview #

The goal of this project was to create a relatively cheap and simple differential probe, intended mostly for hobbyists and makers.

Specification #

This probe has a voltage rating of ±500V on each input, which means a differential rating of ±1000V.
Depending on the opamps the usable bandwith can be in excess of 10 MHz.

The power supply is done via a USB-C connector and a DC/DC converter for galvanic isolation.

I’ve tried two different opamps, with whom the Diff-Probe can reach the following bandwidths:

Opamp	Opamp bandwith	Probe bandwidth	Cost per opamp
TL072	3MHz	~1MHz	<0.20$
AD8039	350MHz	~18MHz	~2.50$

Cost #

All the components cost about 20 to 25 USD with the more expensive opamp option. The other option is obviously quite a bit cheaper.

Housing #

This housing is printed in ABS for durability, but can easily be printed in PLA. It is held together with two M3x10 and one M2x12 screw, which are all screwed into heat set inserts. The M2 screw can be omitted, but the housing will probably not fully close on that side and leave a small gap.

Assembly of the Diff-Probe:

Files #

All the sources and output files can be found on my Github page.