Directed Energy, Inc.

            Current monitoring for the PCO-7115

            There's an easy way to see an accurate rendition of the output pulse from a PCO-7115 on your oscilloscope.


            The PCO-7115 includes a circuit that works with the optional PCA-9245 cable. For the PCO-7115-5-1, the scale factor is 2 A per V into 50 Ω, which means the input impedance of the scope should be set to 50 Ω (or a 50 Ω terminator should be used). The displayed waveform is scaled to 1 V of amplitude for every 2 A of output current.


            How does the monitor work? The driver contains a resistance in series with the output that converts the laser diode current to a small voltage. The current monitoring resistors in the driver, combined with the scope's 50 Ω input impedance, yields the scale factor.


            Compared with a standard scope probe, you'll see much less noise with this low-impedance system. The combination of a standard probe's long ground lead and the scope's high input impedance results in significant noise pickup from the high currents being switched nearby.


            Updated: 31 Jan 2019 07:35 AM
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