Tektronix TCP300A, User Manual

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Reference Notes
The effect of measuring two different noncontinuous current amplitudes, 750 A
and 600 A respectively, with varying duty cycles and levels of continuous current
is illustrated. (See Figure 35 on page 58.) (See Figure 36 on page 58.) The
ambient temperature in these two examples is kept constant at 50 °C.
WARNING.
To prevent injury, keep your hands away from the probe head until it
has had time to cool after disconnecting the probe from the circuit. Because when
using the probe near the upper current limit and maximum ambient temperature
for extended lengths of time, the probe head surface can become hot to the touch.
To see how noncontinuous current amplitude affects measurement time, look at
the curves for measurements of 200 A continuous between the two graphs. (See
Figure 35 on page 58.) (See Figure 36 on page 58.) Compare the maximum
measurement time allowed for a duty cycle of 20%: At 750 A, you have 3 minutes
of safe measurement time, versus 17 minutes for a smaller noncontinuous-current
amplitude of 600 A.
By looking at any of the three graphs, you can also see that when you measure
a noncontinuous current having the same amplitude and duty cycle, the
measurement time decreases as the continuous-current amplitude increases.
Finally, compare the two graphs. (See Figure 35 on page 58.) (See Figure 37
on page 59.) Here, the effect of ambient temperature on measurement time is
illustrated. Given a continuous current of 200 A with a noncontinuous current
of 750 A, and having a 20% duty cycle, a 27 °C increase in temperature yields a
12 minute decrease in maximum measurement time.
Keep these factors into account when taking measurements to ensure accuracy
and to protect both yourself from injury and the equipment from damage.
TCPA300/400 Ampli fi ers and TCP300A/400 Series Current Probes User Manual 31