Very High Speed Counter Module - Esco Drives & Automation
Very High Speed Counter Module - Esco Drives & Automation
Very High Speed Counter Module - Esco Drives & Automation
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About the <strong>Very</strong> <strong>High</strong> <strong>Speed</strong> <strong>Counter</strong> <strong>Module</strong>s 1-7<br />
Continuous/Rate Mode<br />
The Continuous/Rate Mode will return an incoming frequency and a<br />
total accumulated count to PointBus, by gating an internal 5MHz<br />
internal clock with an external signal.<br />
Similar to the Period/Rate mode except outputs in this mode are<br />
updated continuously. This mode determines the frequency and total<br />
number of input pulses by counting the number of internal 5MHz<br />
clock pulses over a user-specified number of input signal pulses. Each<br />
output is turned on as soon as the turn-on count is reached, and<br />
turned off as soon as the turn-off count is reached. As the internal<br />
5MHz clock is counted, the outputs dynamically track the 5MHz<br />
count.<br />
EXAMPLE<br />
Example of Continuous/Rate Mode<br />
Encoder / Pulse Generator<br />
A ( Not Used )<br />
B ( Not Used )<br />
Z<br />
(Gate / Reset )<br />
Input A<br />
Input B<br />
Input Z<br />
Scalar<br />
5 MHz Clk<br />
1734-VHSC<br />
Z Input ( Pulse )<br />
5 MHz Internal<br />
Sampling Clock<br />
Accumulated Count<br />
1<br />
10 20<br />
Frequency<br />
Updated Here<br />
Outputs Updated<br />
Continuously<br />
Assumes symmetrical pulse, 50% duty cycle, so Period = Sample Time On X 2 {On & Off}<br />
Frequency = 1 / Period If Count = 20, Scalar = 1, and Clock Period = ( 1 / 5 MHz )<br />
Frequency = 1 / [ ( 20 / 1 ) X ( 1 / 5 MHz ) X 2 ] = 125 kHz<br />
As the frequency of the incoming pulse train at the Z Gate/Reset<br />
terminal increases, the number of sampled pulses from the 5MHz<br />
clock decreases. Since accuracy is related to the number of pulses<br />
received over the sample period, the accuracy will decrease with<br />
increasing frequencies at the Gate/Reset terminal. (Refer to the<br />
“Operation of Scalar” information and table in the Period/Rate Mode.)<br />
Publication 1734-UM003A-EN-P - August 2000