High Current Measurement Probe at Low Cost

While a voltage waveform is easy enough to measure with an oscilloscope, current behavior is a bit more elusive. There are a number of commercial current probes on the market, but according to “undersilicon” they tend to be expensive. In order to make such measurements easier for those on a hobbyist budget, this electronics researcher came up with a device that uses an ACS730 Hall effect transducer to output a voltage signal proportional the current input.

Along with its transducer, the design employs a pair of AD823ARZ op-amps to scale the signal to a nice human-readable 100mV/A. The system can measure up to around 25A of current continuously, with transient peaks possible to greater than 40A. It can handle bandwidths of up to 1 MHz with a -3 dB signal attenuation, but it would likely be safer to keep it at under 500 kHz where this value will be under 1 dB. Power is supplied by a LiPo battery, allowing it to operate continuously for 15-20 hours.

According to the project write-up, the probe costs about 30 euros, or about 35 USD, and build files are available there. If you’re on a budget and/or looking for a new project, and would like a good way to measure current waveforms, this looks like a great place to start!