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Operating Instructions
57
Soft Limits. The power supply can be sent soft limit values that place maximum limits on the voltage and current
programming values that will be accepted. If the power supply receives a programming value that exceeds the soft limit, it
will ignore the command, turn on the ERROR indicator, and set the ERR bits in the status register and in the serial poll
register. The power supply will not accept soft limit values that are lower than present output values or values that are being
held.
Soft limits are programmed using any of the following codes (the values 15 and 5 are used as examples):
VMAX 15 IMAX 5
VMAX 15 V IMAX 5 A
VMAX 15 MV IMAX 5 MA
The soft limits may be read by sending:
VMAX? IMAX?
and addressing the power supply to talk. The response from the power supply is in this format (using 15 and 5 as examples):
VMAX 15.000 IMAX 5.000
Delay. The power supply may switch modes or be unregulated momentarily after a new output value is programmed or the
output is reset from zero. In most cases this temporary condition would not be considered a fault, and foldback or a service
request would be a nuisance. Delay operates to mask CV, CC, and OR conditions from the fault register for a specific
period after a new output value is implemented. The delay is initiated after the following commands:
OUT ON
RST
T, TRG, or Device Trigger
VSET OR ISET if hold is off
The power supply initializes with a delay of 0.5 seconds, which is appropriate in most cases. In some cases a longer or
shorter delay may be required. For example, when up-programming output voltage with a very low current limit, CC mode
may persist longer than 0.5 seconds.
Factors that influence how long the mode change or unregulated condition may last include: difference between old output
value and new output value, current or voltage limit, and output (load) capacitance (for CV mode) or output inductance (for
CC mode). The delay required must be determined empirically; the programming-response times in the specifications table,
Section I, can be used as guidelines.
Delay can be programmed in 1 ms increments using either of the following codes (31999 used as an example):
DLY 31.999S
DLY 31999MS
Delay value may be read by sending:
DLY?
and addressing the power supply to talk. The response from the power supply is in this format (using 0.5 as an example):