Suppress (N) - Keithley 595 Instruction Manual

IEEE-488 PROGRAMMING
4.9.7 Suppress (N)
Purpose
Serves as a means of baseline suppression by subtracting a stored offset value from
subsequent readings.
Format Nn
Parameters
n = 0 Suppress off.
n = 1 Suppress on using new value.
Description
When Suppress is enabled (Nl), the instrument will store the next reading as the
baseline value. All subsequent readings will be the difference between this stored
baseline value and the actual capacitance or current measurement (applicable only
to capacitance and current, even if Q/t-is "on").
Suppress reduces the dynamic range of the measurement. For example, assume that
1OnA is applied to the input of the instrument; If the stored baseline value is 1OnA
on the 2OnA range, the display will read zero. In addition, input capacitance of -IonA
would overrange the instrument, even though current measurements to -19.999nA
are normally within the capabilities of the 2OnA range.
To use~~suppress, perform the following steps:
1. Cancel Suppress, if on, by sending NO over then bus.
2. Select a range and function consistent with- the expected measurement.
3. Connect the signal to be used as a baseline to the instrument input (perhaps the
strays of an "opened" fixture).
4. Turn on Suppress by sending NlX over the bus and wait for the baseline to be
stored.
5. Add the signa to be measured. Subsequent~ readings will be the difference be-
tween the baseline and the applied signal.
NUKE If the instrument is waiting for a trigger ("triG" message displayed), sending
Nl will turn on the SUPPRESS indicator light, but a basetie value cannot be stored
until the proper trigger occurs. See paragraph 4.9.19 for trigger information.
Default
Reference
Upon power up or after receiving a DCL or SDC co mmand, Suppress will be off (NO).
The equivalent front panel control for the N command is the the SUPPRESS button.
See paragraph 3.3.4 for complete information on using Suppress.
Example
From the front~panel, torn off Si~ppress if it is on. Enter the following statements
to turn Suppress on:
NOTE: After FND LINE is pressed the second time, Suppress will turn on and blank
the display. The last statement turns Suppress off. Setting the range lower than the
stored baseline value may overrange the instrument since, for example, 1OnA is over-
range on the 2nA range. Function changes cancel baseline suppress.
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