Relative, Math, And Db; Relative; Basic Front Panel Operation Procedure - Keithley 3700 series Reference Manual

Relative

The REL (relative) function can be used to null offsets or subtract a baseline reading from
present and future readings. When REL is enabled, subsequent readings will be the difference
between the actual input value and the REL value.
You can define a REL value for each function. Once a REL value is established for a
measurement function, the value is the same for all ranges. For example, if 50V is set as a REL
value on the 100V range, the REL is also 50V on the 1000V, 10V, 1V, and 100mV ranges.
Therefore, when you perform a zero correction, the displayed offset becomes the reference
value. Subtracting the offset from the actual input zeros the display, as follows:
A REL value can be as large as the highest range.
Selecting a range that cannot accommodate the REL value does not cause an overflow
condition, but it also does not increase the maximum allowable input for that range. For
example, on the 10V range, the Series 3700 still overflows for a 12V input.
NOTE

Basic front panel operation procedure

1. Select the desired measurement function and an appropriate range setting.
2. Apply the signal you wish to REL to a switching channel input or to the Series 3700 inputs.
3. If using a switching module, close the input channel.
4. Press the REL key to acquire the REL value. The REL annunciator will turn on, but the
display will not zero until a new reading is triggered.
In this section:
Relative .......................................................................................................... 5-1
Math ............................................................................................................... 5-3
dB commands ................................................................................................. 5-7
The various instrument operations, including REL, are performed on the input signal in
a sequential manner.

Relative, Math, and dB

Section 5