Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module - Manual (Page 37)

Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
Frequency Modes 37
Maximum Frequency
A module is capable of counting up to 16 million counts. However, the
maximum rate at which the counter can accept counts depends on the type of
signal directly connected to the module.
The table lists the acceptable signal levels for the 1756-HSC module..
Outputs in Period Rate and Continuous Rate with Scaler = 4
50 Hz at Z-Input
50% Duty Cycle
Scaler Tag = 4
What the Counter
Sees Internally With
Scaler Tag = 4 Counter Idle
Counter Times
Width of Pulse
4 MHz = 160,000
Output State in Period Rate
4 MHz Count = 160,000 4 MHz Count = 160,000
Output State in Continuous Rate
4 MHz Count
= 20,000
4 MHz Count
= 80,000
4 MHz Count
= 20,000
4 MHz Count
= 80,000
4 MHz Count
= 20,000
12634-I
Scaler Tag = 4
Output OnValue Tag = 20,000
Output OffValue Tag = 80,001
Scaler Tag = 4
Output OnValue = 20,000
Output OffValue = 80,001
Signal Type Source Device Maximum Signal
Rate
HSC Channels
Supporting Signal
Pulse Digital Rulers
PHOTOSWITCH 1 MHz with a pulse
width >500 ns Channel A
Quadrature Quadrature Encoder 250 kHz Channels A and B
Frequency
(Frequency,
Period Rate,
Continuous Rate) Flowmeters 500 kHz with a pulse
width > 1
s
Channel A or Z Input
IMPORTANT
Higher signal rates typically require extra caution in the
installation and compatibility of the pulse generating device. Be
sure to read
Appendix D, ‘Application Considerations’, to verify
your device’s compatibility.