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Chapter 5
Phase Measurements – Tachometer Counter 1
On the DT9837A and DT9837B modules, you can measure the phase of the tachometer input
in relation to the A/D sample by reading tachometer counter 1. To read the value of this
counter, specify channel 5 in the analog input channel list.
An internal 48 MHz clock (with 21 ns resolution) is used to calculate the measurement, which
allows you to precisely correlate tachometer measurements with the analog input data.
You can specify the following parameters for tachometer counter 1 using the Open Layers
Control Panel applet, described on
described in
• The signal that starts the measurement: A/D sample, rising edge of the tachometer input
• The signal that stops the measurement: A/D sample, rising edge of the tachometer input
• The value of the Self-Clear flag, which determines the value that is read between
84
Appendix C
starting on
signal, or falling edge of the tachometer input signal
signal, or falling edge of the tachometer input signal
Note: Note that if you choose to start the measurement using the A/D sample, choose a
tachometer edge to stop the measurement. Likewise, if you choose to stop the
measurement using the A/D sample, choose a tachometer edge to start the measurement.
measurements (either 0 or the previous measurement value)
page
36, or by writing to the registers of the module, as
page
135:
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