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Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • Tek A6302 Current Probe Derating

    Most currents around here come in tens-of-milliamps, maybe a few hundred, tops, but it’s worth noting some curves from the Tektronix AM503 current amplifier manual for A6302 Hall effect probes:

    Tek A6302 Calibration Setup
    Tek A6302 Calibration Setup

    The maximum current drops from 20 A for frequencies above 20 kHz:

    Tek A6302 Current Probe - Max Current Frequency Derating
    Tek A6302 Current Probe – Max Current Frequency Derating

    There’s a 100 A·μs pulse charge limit:

    Tek A6302 Current Probe - Specified Operating Area
    Tek A6302 Current Probe – Specified Operating Area

    Because the probe is actually a pulse transformer, its internal termination imposes a (small) load on the input circuit:

    Tek A6302 Current Probe - Insertion Impedance
    Tek A6302 Current Probe – Insertion Impedance

    The specs are 100 mΩ at 1 MHz and 500 mΩ at 50 MHz, which means the load is essentially zilch for the circuits and signals I deal with.

    The Tektronix Probes for Current Measurement Systems has some useful descriptions.

    Memo to Self: Should any of those limits matter, rethink what you’re doing.

    An interesting story about the AM503 design from someone who lived through it.