Decay Time Constant (Current Probes); Direct Current (Current Probes); Frequency Derating (Current Probes); Insertion Impedance (Current Probes) - Tektronix PRIMER P6101B Manual

Primer

Decay Time Constant (current probes)

The decay time constant specification indicates a current
probe's pulse supporting capability. This time constant is the
secondary inductance (probe coil) divided by the terminating
resistance. The decay time constant is sometimes called the
probe L/R ratio.
With larger L/R ratios, longer current pulses can be
represented without significant decay or droop in amplitude.
With smaller L/R ratios, long- duration pulses will be seen as
decaying to zero before the pulse is actually completed.

Direct Current (current probes)

Direct current decreases the permeability of a current probe's
coil core. This decreased permeability results in a decreased
coil inductance and L/R time constant. The result is reduced
coupling performance for low frequencies and loss of
measurement response for low-frequency currents. Some
AC current probes offer current-bucking options that null the
effects of DC.

Frequency Derating (current probes)

Current probe specifications should include amplitude
versus frequency derating curves that relate core saturation
to increasing frequency. The effect of core saturation with
increasing frequency is that a waveform with an average
current of zero amps will experience clipping of amplitude
peaks as the waveform's frequency or amplitude is increased.

Insertion Impedance (current probes)

Insertion impedance is the impedance that is transformed
from the current probe's coil (the secondary) into the current
carrying conductor (the primary) that's being measured.
Typically, a current probe's reflected impedance values are in
the range of milliOhms and present an insignificant effect on
circuits of 25Ω or more impedance.
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Input Capacitance (universal)

The probe capacitance measured at the probe tip.

Input Resistance (universal)

A probe's input resistance is the impedance that the probe
places on the test point at zero Hertz (DC).

Maximum Input Current Rating (current probes)

The maximum input current rating is the total current (DC
plus peak AC) that the probe will accept and still perform as
specified. In AC current measurements, peak-to-peak values
must be derated versus frequency to calculate the maximum
total input current.
Maximum Peak Pulse Current Rating
(current probes)
This rating should not be exceeded. It takes into account
core saturation and development of potentially damaging
secondary voltages. The maximum peak pulse current rating is
usually stated as an amp-second product.

Maximum Voltage Rating (universal)

Voltages approaching a probe's maximum rating should be
avoided. The maximum voltage rating is determined by the
breakdown voltage rating of the probe body or the probe
components at the measuring point.

Propagation Delay (universal)

Every probe offers some small amount of time delay or phase
shift that varies with signal frequency. This is a function of the
probe components and the time it takes for the signal to travel
through these components from probe tip to oscilloscope
connector.