Model 2701 User’s Manual Scanning 7-23
Manual/external trigger scan
The only difference between a manual/external trigger scan and the basic scan is control.
The basic scan runs as soon as the STEP or SCAN key is pressed. The manual/external
trigger scan is controlled by the front panel TRIG key or by triggers received from another
instrument.
NOTE For the following procedure, the Model 2701 can be triggered by pressing the
TRIG key or by receiving a trigger pulse from another instrument. Section 8
provides details on triggering.
1. If the scanner is presently enabled (STEP or SCAN annunciator on), press SHIFT
and then HALT to disable it.
2. Press the EX TRIG to place the instrument in the external triggering mode. The
TRIG annunciator turns on and the reading is blanked (-------).
3. Press STEP or SCAN to enable the scan (STEP or SCAN annunciator turns on).
4. The TRIG key or input triggers control the scan as follows:
STEP operation — In general, each time the Model 2701 is triggered, one channel
is scanned. When the STEP key is pressed to enable the scan, the first channel in
the scan list closes. When the first trigger occurs, a measurement is taken, the
channel opens, and the next channel closes. This process continues for each
channel in the scan. After the last channel in the scan list is scanned, the first
channel in the scan list closes.
The reading count determines how many channel measurements will be performed
during the scan sequence. If the reading count is greater than the scan list length,
operation loops back to the beginning of the scan list and continues.
After a scan sequence (as determined by the reading count) is completed, the scan
remains enabled (STEP annunciator on), but the Model 2701 goes into the idle
state. If you wish to repeat the scan sequence, you will have to first take the
Model 2701 out of idle. This can be done by pressing the STEP (or TRIG) key.
SCAN operation — In general, when the Model 2701 is triggered, a complete
scan of all the channels in the scan list is performed. When the SCAN key is
pressed to enable the scan, the first channel in the scan list closes. When a trigger
occurs, one scan of the scan list channels is performed. After the last channel is
scanned, the first channel in the scan list will close.
Reading count determines how many scans will be performed (see “Trigger
models,” page 7-4). If programmed for another scan, it will start when another
trigger occurs.
After the last scan is completed, the scan remains enabled (SCAN annunciator on),
but the Model 2701 goes into the idle state. If you wish to repeat the scans, you will
have to first take the Model 2701 out of idle. This can be done by pressing the
SCAN (or TRIG) key.
5. When finished, press SHIFT and then HALT to disable the scan, and press EX
TRIG to take the Model 2701 out of the external triggering mode.
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