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5-6
"Pressing REL" using rel commands
When the front panel REL key is pressed, the displayed reading is used as the rel value.
Subsequent readings are then the result of the actual input value and the rel value.
The :REFerence:ACQuire and :REFerence:STATe ON commands (in that order) can be used
to "press" the REL key. For example, the following command sequence is the equivalent of
pressing the REL key while on the DCV function:
VOLT:REF:ACQ
VOLT:REF:STAT ON
Setting rel values
The :REFerence <n> command specifies the rel value for the specified function, while the
:ACQuire command uses the input signal as the rel value. The :ACQuire command is typ-
ically used to zero the display. For example, if the instrument is displaying a 1µV offset,
sending :ACQuire and enabling rel (STATe ON) zeroes the display.
The ACQuire command is only functional if the instrument is on the specified function.
For example, if the instrument is on the DCV function, the only valid acquire command is
VOLT:DC:REF:ACQ. Also, if the instrument is overflowed ("OVERFLOW") or a reading
has not been triggered ("------"), an execution error (-200) occurs when :ACQuire is sent.
The :REFerence <n> command is coupled to the ACQuire command. When a rel value is
set using :REFerence <n>, the :REFerence? query command returns the programmed
value. When rel is set using :ACQuire, the :REFerence? query command returns the
acquired rel value.
Rel programming examples
Example #1 — The following command sequence zeroes the display for DCV.
FUNC 'VOLT'
VOLT:REF:ACQ
VOLT:REF:STAT ON
Example #2 — The following command sequence configures channel 101 of the
Model 7702 to enable rel and use a 1V rel value when it is scanned.
FUNC 'VOLT',(@101)
VOLT:REF 1,(@101)
VOLT:REF:STAT ON,(@101)
Example #3 — The following command sequence configures channel 101 of the
Model 7702 to zero correct the DCV input when it is scanned.
FUNC 'VOLT',(@101)
ROUT:CLOS (@101)
VOLT:REF:ACQ (@101)
VOLT:REF:STAT ON,(@101)
Model 2790 SourceMeter
' Acquire reading as rel value.
' Enable rel.
' Select DCV.
' Use input level as rel value for DCV.
' Enable rel.
' Select DCV for channel 101.
' Set 1V rel value.
' Enable rel.
' Select DCV for channel 101.
' Close channel 101.
' Use input to channel 101 as rel value.
' Enable rel.
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