Keithley 2002, Getting Started Manual

Page: 38 / 95

Device action
The primary device action is a measurement. However, the device action could include a
function change and a channel scan (if scanner is enabled). A channel is scanned (closed) before
a measurement is made. When scanning internal channels, the previous channel opens and the
next channel closes (break-before-make). Also included in the device action is the internal set-
tling time delay for the relay.
Output trigger
After each measurement (device action), an output trigger pulse occurs and is available at the
rear panel of the Model 2002. When used with an external scanner (such as a Model 7001 or
7002 Switch System), each output trigger would be used to select the next channel in a scan (see
EXTERNAL SCANNING in the MEASUREMENT OPTIONS section of this manual).
Counters
All three layers use programmable counters that allow operation to return to or stay in the re-
spective layer. For example, programming the Measure L
ayer counter to infinite keeps opera-
tion in the Measure Layer. After each device action, operation loops back to the Trigger Layer
control source. A counter resets when operation loops back to a higher layer (or idle).
Bench default trigger model setup
The bench default setup takes the Model 2002 out of idle, sets the control sources of all layers
to Immediate, and sets the Measure Layer counter to infinite. With this trigger model setup, op-
eration simply falls into the Measure Layer (and stays there) to make continuous measurements.
Measurement Options 2-13