Correct method of measuring a pulse

1. Jan 4, 2009

James G Deye

I am currently working a project to evaluate the power output of a single pulse through an air core transformer. Using a scope to measure the secondary output and I am confused on what voltage to use. Scope shows DC voltage, peak voltage, drop Voltage differntial of peak and drop voltage. Would a current probe also be advantages for these measurements. The single pulse we capture is about 26 microseconds from peak to end. We hope to calculate though these measurements the forcast of different wire guages and number of turns on the secondary.

Jamie

2. Jan 5, 2009

Staff: Mentor

Welcome to the PF, Jamie. To get a clear picture of the power in the pulse, you will need to measure the instantaneous voltage and current, and calculate the product P(t) = V(t) * I(t).

If you have a good (high-bandwidth) current probe, then you can put that on Ch2 of your 'scope, and use the math function to give you the product to display the P(t) graph.

If you're current probe is not of high enough bandwidth, you could put a low-resistance shunt at the low-side of the coil that you are driving (with one side of the resistor to ground), and measure that voltage to get a picture of what the current is. This is slightly more invasive as measurements go, but as long as you keep the voltage drop across the shunt small compared to the total coil voltage, you should get a pretty accurate measurement.