Pulse_Fall - Keithley 4200A-SCS Reference Manual

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Section 13: LPT library function reference

pulse_fall

This command sets the fall transition time for the pulse output.

int pulse_fall(int instr_id, long chan, double fallt);

Rise and fall transition time can be set independently for each pulse card channel. There is a

minimum slew rate for both the rise and fall transitions. For the fast speed range, the minimum is

362 µV/µs, or 1 V/2.7 ms. For the high voltage range, the minimum slew rate is 1.8 mV/µs, or

1 V/500 µs. The pulse_range command is used to set pulse speed.

As shown below, the pulse fall time occurs between the 100 percent and 0 percent amplitude points

on the falling edge of the pulse, where the amplitude is the difference between the V High and V Low

pulse values.

The pulse fall time setting takes effect immediately during continuous pulse output. Otherwise, the fall

time setting takes effect when the next trigger is initiated. The pulse_trig command is used to

trigger continuous or burst output.

For slow speed, note that the minimum transition time for pulse source only (no measurement) on the

40 V range is 50 ns for the 4225-PMU and 4220-PGU.

Use the pulse_source_timing command to set the pulse fall time for the 4220-PGU and 4225-

The instrument identification code of the pulse card, such as VPU1 or VPU2

Channel number of the pulse card: 1 or 2

Pulse fall time in seconds (floating point number):

Fast speed: 10e-9 to 33e-3

Slow speed: 4220-PGU and 4225-PMU: 50e-9 to 33e-3

Default: 100e-9

Model 4200A-SCS Parameter Analyzer Reference Manual

4200A-901-01 Rev. C / February 2017