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Period / Rate Mode
The Period/Rate Mode will return an incoming frequency and a total
accumulated count to the POINTBus, by gating an internal 5MHz
internal clock with an external signal.
This mode determines the frequency and total number of input pulses
by counting the number of internal 5MHz clock pulses over a
user-specified number of input signal pulses. At the end of the
specified number of pulses, the module returns the frequency
(0 - 1 MHz).
EXAMPLE
Example of Period/Rate Mode
Encoder / Pulse Generator
Z Input ( Pulse )
5 MHz Internal
Sampling Clock
Accumulated Count
Assumes symmetrical pulse, 50% duty cycle, so Period = Sample Time On X 2 {On & Off}
Frequency = 1 / Period
If Count = 20, Scalar = 1, and Clock Period = ( 1 / 5 MHz )
Frequency = 1 / [ ( 20 / 1 ) X ( 1 / 5 MHz ) X 2 ] = 125 kHz
As the frequency of the incoming pulse train at the Z (Gate/Reset)
terminal increases, the number of sampled pulses from the 5 MHz
clock decreases. Since accuracy is related to the number of pulses
received over the sample period, the accuracy decreases with
increasing frequencies at the Gate/Reset terminal. Refer to the
following Scaling table.
AB Drives
A ( Not Used )
B ( Not Used )
Z
(Gate / Reset )
1
10
Publication 1734-UM006B-EN-P - August 2005
About the Modules
1-5
Input A
Input B
Input Z
Scalar
5 MHz Clk
1734-IJ/IK
20
Frequency
Updated Here
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