Projects / Measurements, sensors and data acquisition
Laboratory analog adapter with a low-value shunt and OPA320 amplifiers for observing microamp and milliamp current dynamics on an oscilloscope.
During electronics debugging, it was necessary to see current waveform over time: startup, transients, sleep modes, pulsed loads and slow sensor dynamics. A multimeter was not enough and a dedicated current probe was not always available.
A practical bench adapter was built for observing small currents. It is inserted in series with the load, amplifies the voltage across a low-value shunt and outputs a scaled voltage signal to an oscilloscope.
Project materials
Engineering context
For debugging, current waveform shape can be more important than only average current.
Separate or isolated supply for the measurement circuit helps reduce influence from the tested bench.
Several outputs with different gain make it easier to choose a useful oscilloscope scale.
The device is intended as a practical engineering adapter, not as a closed metrology instrument.
Work done
Analog measurement-adapter circuit.
Low-value shunt current sensing.
OPA320 operational-amplifier stages.
Intermediate outputs with different scaling.
Coaxial outputs for oscilloscope connection.
Battery or isolated supply option for the analog part.
Assembly and bench validation.
Details
The adapter is a practical engineering tool for quickly seeing current-consumption dynamics on an oscilloscope screen. It is useful when a current changes with time and a multimeter hides the relevant behavior.
Load current flows through a low-value shunt. The voltage drop across the shunt is amplified by operational-amplifier stages and converted into an oscilloscope voltage signal proportional to current.
The adapter is suitable for debugging low-power devices, sensors, analog front ends, microcontroller sleep modes, power rails and other circuits where current changes over time. It was especially useful for low-power sensors with periodic wake-up and transmission cycles.
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