30/07/2025 11:33 pm
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Is there any problem to measure a transformer with an oscilloscope? I’ve heard that one should take care with short circuits or ground short circuits otherwise the oscilloscope would burn out.
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05/08/2025 4:30 am
Measuring a transformer with an oscilloscope, especially in mains-powered circuits, requires caution to avoid damaging your equipment or risking personal safety.
One major risk comes from grounding. Most benchtop oscilloscopes connect their probe ground clips directly to earth ground through the power cord. If you attach the ground clip to a point in the transformer circuit that isn’t referenced to earth ground—such as a floating secondary—you can unintentionally create a short circuit. This short can damage the oscilloscope, harm the transformer, or even cause electric shock.
To prevent this, always ensure the oscilloscope and the circuit under test share the same ground reference. If that’s not possible, use an isolation transformer to power the circuit. This isolates it from the mains ground, allowing you to safely connect the oscilloscope.
You can also use a differential probe, which measures the voltage between two points without relying on a common ground. This makes it ideal for measuring floating or ungrounded circuits.
You also need to pay attention to voltage ratings. Oscilloscopes and their probes can only handle a limited amount of voltage. If you exceed that limit, you risk damaging both the probe and the oscilloscope.
To stay within safe limits, use attenuating probes like 10:1 or 100:1 when working with high voltages, and always verify the maximum input ratings before connecting anything.
Improper connections can also cause short circuits and overloads. If you connect probes incorrectly or create a ground loop, large currents might flow through unintended paths. This can burn out transformer windings, destroy probes, or even start fires. To stay safe, always double-check your connections before powering the circuit.
Set the oscilloscope’s input impedance correctly to avoid incorrect readings or signal distortion. When working with floating circuits, rely on isolation techniques or differential probes to create a safer test environment.
If you follow these steps you can surely measure a transformer with an oscilloscope but make sure safety first.
lukeluke Topic starter
13/08/2025 1:35 am
@techtalks Thank you for your answer. So could I use two transformers? I´d use one isolation tranformer connected to the mains power and a second transformer connected to the isolation transformer so that I´d connect the oscilloscope probe safely to this second transformer?
