Keithley 6485, User Manual

Page: 78 / 115

5-2 Relative, mX+b, m/X+b (reciprocal), and log Mode 6485 and 6487 User’s Manual
Relative
Relative (Rel) nulls an offset or subtracts a baseline reading from present and future read-
ings. When a Rel value is established, subsequent readings will be the difference between
the actual input and the Rel value.
Displayed (Rel’ed) Reading = Actual Input - Rel Value
A Rel value is the same for all measurement ranges. For example, a Rel value of 1E-6 is
1
μ
A on the 2
μ
A range. It is also 1
μ
A on the 20
μ
A range and the 200
μ
A range. Note
changing ranges does not disable Rel.
Front panel relative
From the front panel, there are two ways to set the Rel value. You can either use the input
reading as the Rel value or you can manually key in the Rel value.
To use the present reading, disable zero check, display the reading, then press REL. The
REL annunciator will turn on and subsequent readings will be the difference between the
actual input and the Rel value. To disable relative, press REL again (for the Model 6487,
while zero check is disabled). To enter a reading, press CONFIG then REL, enter the
desired value, then press ENTER. Relative will be enabled after you enter the value.
NOTE For the Model 6487, separate Rel values are stored for the amps and ohms
functions.
SCPI programming — relative
Table 5-1
SCPI commands — relative (null)
Commands Description
CALC2:FEED <name>
CALC2:NULL:ACQ
CALC2:NULL:OFFS <Rel>
CALC2:NULL:STAT <b>
CALC2:DATA?
CALC2:DATA:LAT?
INIT Specify reading to Rel: SENS or CALC1.
Use input signal as Rel value.
Specify Rel value: -9.999999e20 to 9.999999e20.
Enable (ON) or disable (OFF) Rel.
Return Rel’ed readings triggered by INIT.
Return only the latest Rel’ed reading.
Trigger one or more readings.