Inside a “Budget” Current Probe

Current measurements are not as handy as voltage measurements. You typically need to either measure the voltage across something and do some math or break the circuit so a known resistor in your instrument develops a voltage your meter measures and converts for you. However, it is possible to get non-contact current probes. They are generally pricey, but [Kerry Wong] shows us one under $200 and, thus, budget compared to similar probes. Check out the review in the video below.

The OWON unit has three ranges: 4 A, 40 A, and 400 A. It claims a resolution of 10 mA and a bandwidth of 200 kHz. It requires a 9 V battery, which [Kerry] suspects won’t last very long given the rated power consumption number, although the measured draw was not as high as claimed. The specs aren’t great — this seems to be little more than a current probe meter with a connector for an oscilloscope, but if it meets your needs, that could be acceptable.

Stay tuned for the end if you want to see the insides. There’s not much on the PCB’s top side. There’s a hall-effect sensor, some adjustment pots, and an op amp. The other side of the board has many more components, but the circuit is purely analog.

It made us wonder if we should nip down to the local cheap tool store and buy a $40 meter with similar specs. It seems like you could find a spot to tap a voltage from that and save quite a bit of money.

It is possible to create a probe that doesn’t break the bank and manages at least 2 MHz of bandwidth. Or, make your own for about $25, although we can’t vouch for the specs on that one.