Relative; Front Panel Rel; Enabling And Disabling Rel; Defining A Rel Value - Keithley 2500 User Manual

7-2 Relative, Math, Ratio, and Delta

Relative

The rel (relative) feature can be used to null offsets or subtract a baseline reading from
present and future readings. With REL enabled, subsequent readings will be the difference
between the actual input value and the rel value as follows:
Displayed Reading = Actual Input - Rel Value
Once a rel value is established for a measurement, the value is the same for all ranges. For
example, if 1mA is set as a rel value on the 20mA range, the rel value is also 1mA on the
2mA range.
Selecting a range that cannot accommodate the rel value does not cause an overflow condi-
tion, but it also does not increase the maximum allowable input for that range. For exam-
ple, on 2mA range, the Model 2500 still overflows for a >2.1mA input.
NOTE

Front panel rel

Enabling and disabling rel

Rel can be used to null out zero offsets or to establish a zero baseline on the selected mea-
surement channel by pressing the REL key. The reading (which becomes the rel value) is
subtracted from itself. As a result, a zero reading is displayed. Pressing REL a second time
disables rel.
Defining a rel value
A unique rel value can be established for the selected channel from the front panel as
follows:
1. Press MSR1 or MSR2 to select either channel 1 or channel 2 measurement.
2. Press CONFIG and then REL. The present rel value will be displayed.
3. Set the desired rel value. See
4. With the desired rel value displayed, press ENTER. The Model 2500 will return to the
normal display with rel enabled. The reading will reflect the defined rel value.
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In single-channel display mode, the REL annunciator turns on for the displayed
channel. In dual-channel display mode, the REL annunciator turns on if rel is
enabled for either channel.
Section
Models 2500 and 2502 User's Manual
1, "Rules to navigate menus," for details.