Data Translation DT340, Getting Started Manual

Page: 46 / 70

Chapter 5
38
Figure 8: Cascading Counters (Shown for Event Counting Using
Counters 0 and 2 and External Gate 0
Connecting Frequency Measurement Signals
This section shows two examples of how to connect a frequency
measurement application to the STP340 screw terminal panel.
The first configuration uses the same wiring as an event counting
application that does not use an external gate signal (see
Figure 7 on
page 37 ); the software uses the Windows timer to specify the duration
of the frequency measurement. In this configuration, the frequency of
the clock input is the number of counts divided by the duration of the
Windows timer.
If you need more accuracy than the Windows timer provides, you can
connect a pulse of a known duration (such as a one-shot output of
another user counter) to the external gate input, as shown in
Figure 9 .
In this configuration, the frequency of the clock input is the number
of counts divided by the period of the external gate input.
STP340 Panel
TB2
Signal Source
Digital Ground
User Clock Input 0
TB12
TB4
Digital Ground
Gate 0
External
Gating
Switch
Shield
TB1
TB11
TB33
User
Counter
Output 0
User
Clock
Input 2
TB3