A well-regulated pulse is trapezoidal in its shape, and it should match the parameters that were specified for that pulse. Refer to Pulser Specifications for an example of a pulse waveform.

You can specify the following pulse parameters:
  • Rise time
  • Fall time
  • Dwell time
  • Setpoint
  • Charge voltage

Charge Voltage

The charge voltage is a control parameter for the beginning of a pulse only, so you cannot specify the charge voltage throughout the pulse. The charge voltage is not part of the pulse waveform shape.

The default charge voltage is 15 V. You do not need to set the charge voltage value to perform a pulse. However, you might need to change the default charge voltage for a given test based on the following factors:

  • Electrical characteristics of the pulse path
  • Pulse waveform in a given test

A pulse might only have a single charge voltage, but you can specify a different charge voltage for each pulse.

Note NI recommends changing the charge voltage only if you do not get a well-regulated pulse.
Note When using different charge voltages for different pulses, ensure you adjust the charge voltage at the appropriate time. Refer to Adjusting the Charge Voltage for more information.

If the charge voltage is too high or too low for a given path and waveform combination, the pulser cannot regulate the waveform cleanly.

If the charge voltage is too low, the pulse current waveform might not reach the specified setpoint or sustain the pulse duration. The following figure is an example of a pulse beginning to deteriorate early due to a low charge voltage.
Figure 29. Incomplete Pulse
To correct incomplete pulse waveforms, increase the charge voltage.
If the charge voltage is too high, the pulse current waveform rapidly stops and restarts to bleed off excess power without damaging itself. The following figure is an example of this behavior.
Figure 30. Ringing Pulse
To correct ringing pulse waveforms, decrease the charge voltage.

In general, it is easier to regulate pulses at lower setpoints and with shorter durations. If you are unable to find a suitable charge voltage, modify the waveform.

Adjusting the Charge Voltage

The pulser composite instrument can increase charge voltage between pulses by raising the specified charge voltage between performing pulses.

However, the pulser composite instrument cannot reduce the charge voltage of a pulse while a session is open unless you execute a pulse. If the pulser is charged and ready to pulse when you specify a lower pulse voltage, the pulser remains in a ready state. However, the voltage does not adjust downward until you perform the next pulse. The next pulse charges to the new specified charge voltage. Thus, you can use pulses to lower the charge voltage without closing a session to the pulser.

What Should I Do If the RM-16061 Fails to Charge or Generate a Pulse?

If the RM-16061 fails to charge or generate a pulse, check the S505H fuse on the RM-16061.