Advantech PCM-3780 manual Period Measurement, Using Advantech 32-bit DLL Driver, Using Direct I/O

3.5 Period Measurement

3.5.1Using Advantech 32-bit DLL Driver

This approach is for a low frequency signal.

We recommend you to perform period measurement through our 32-bit DLL driver because it is the simplest way for both programming and wiring. Just connect the unknown single to Gate and the duty cycle will be measured by the software.

3.5.2 Using Direct I/O

This approach is for a low frequency signal.

Figure 3.4: Period Measurement

Implementing this measurement needs two counters, one for the up cycle period and another for the down cycle period. These added together gives the total period. The duty cycle can also be calculated by dividing the up period with the total period. Connect the unknown signal to each counter's gate.

Apply a standard clock pulse to each counter. Counter 0 counts the up cycle, while Counter 1 counts the down cycle. In PCM-3780, wiring is simple. Just connect the unknown signal to Counter 0, and use the regis- ter to select the gate source. Counter 0 selects "Gate N". Counter 1 selects "Gate N-1".

Apply the standard clock to both counters with the clock source selection register. It can change the clock for different measurement ranges. Counter 0 set as "Mode O" will make gate polarity positive. Counter 1 set as "Mode O" will make gate polarity negative.

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