Specifications

Measurement Examples
17
MEASUREMENT EXAMPLES
Example 1: Internally Triggered Gate Mode
This example, described under the heading “QUICK TEST” on page 59 of this manual, is easy to perform and
will quickly acquaint the user with the basic operation of the SR400.
Example 2: Externally Triggered Gate Mode
In this example, the SR400 is programmed to make 10 counting measurements of a 10 kHz pulse train. For
each measurement, a gate will be delayed 500 ms from an external trigger pulse and will open of 500 ms
duration. Following the gate, there will be a 6 second dwell period* during which the counter will be
disarmed. After the dwell period, the counter will reset to 0 counts, re-arm and repeat the measurement. After
10 measurement cycles, the SR400 will stop counting and disarm. You will need a 10 kHz signal source and a
0.5 Hz square wave generator for this example.
*It is important to note that the dwell period begins at the first external trigger pulse arriving after the
gate is closed. Thus, even though there is only one gate opened for each measurement cycle, a minimum
of two external triggers are needed: one to trigger the gate and another to begin the dwell period.
The following timing diagram illustrates this example.