3.4.5 Duty cycle
Depending on the output current, the compliance voltage setting and the ambient temperature, a duty
cycle smaller than 100 % has to be applied for the current output in order to prevent a protective shut-
down of the current amplifier by the overtemperature protection function.
A duty cycle of 75 %, for example, means that the CMC 430 provides the specified current for 75 % of
the time, and then requires the remaining 25 % of the time to cool down (example: 30 s on and 10 s
off). Continuous operation or 100 % duty cycle means that the CMC 430 is able to provide the
specified current for at least 30 minutes without shutting down due to overtemperature.
The diagrams below illustrate that the compliance voltage should not be selected higher than
necessary for the connected burden. The diagrams show the duty cycles with the output loaded by a
short circuit. The short-circuit case represents the worst case because the power dissipation to be
converted into heat completely arises inside the test set. The power dissipation and thus the amount
of heat arising inside the test set reduce if the output is loaded by a burden with a resistance > 0.
Therefore, the possible duty cycle increases with the resistance of the connected burden.
0
20
40
60
80
100
0 2.5 5 7.5 10 12.5
Duty cycle (%)
Output current (A)
0 % complicance voltage (6 V)
50 % complicance voltage (12 V)
100 % complicance voltage (18 V)
0
20
40
60
80
100
0 2.5 5 7.5 10 12.5
Duty cycle (%)
Output current (A)
0 % complicance voltage (6 V)
50 % complicance voltage (12 V)
100 % complicance voltage (18 V)
Typical duty cycles for an ambient temperature
of 23 °C (output loaded by short circuit)
Typical duty cycles for an ambient temperature
of 50 °C (output loaded by short circuit)
Technical data
OMICRON
23
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