How do I use the external trigger on the 85XX series DC electronic loads?

A: The external trigger for the 85XX series DC electronic loads serves two purposes.  One is for triggering a transient operation in transient mode, and one is for initiating the start of a programmed list step.

The trigger has two pin inputs in the rear of the instrument.  It accepts a TTL level signal that must be at least 5ms or longer in width.

When using the external trigger for transient mode, it can be used either in pulse or toggled mode.

In pulse mode, the trigger will set off the current set for level B. Level A width(timing) is ignored. But level B timing (up to 6sec) can be set for the amount time to hold the current transient change.

In toggle mode, level A and B width (timing) is ignored. The toggle will be based on the TTL trigger signal. In this mode, each positive TTL trigger signal will toggle the two values set in level A and level B. This is useful if timing of greater than 6 seconds is required for the transient change. To do this, the TTL external signal must send a positive pulse and define a period of however long is required for the toggle change. Once the period ends, sending another TTL signal will toggle it back to the other level change.

When using the external trigger for dynamic list mode, make sure that the list steps and program have been saved and that the load is in list mode.  This can be determined if the "list" indicator is displayed on the front panel screen.  When list is setup, setting a positive TTL signal to the external trigger will initiate the start of the programmed list.  To stop the list at any time, send another TTL signal to the external trigger port.

Note:  Be sure to turn off the load input either manually or programmatically to prevent unwanted drainage of your DUT because sending trigger to stop the list will leave the list stopped at its current list step value.  If the value is not 0, it could drain your DUT until you have turned off the input terminals.