Spectrum Controls 1746sc-CTR4 - Manual (Page 59)

Floating Point Rate Mode
Read this appendix to:
• configure rate for floating point mode
• read input words to get data
• use ladder logic to create floating point value
Overview The floating point rate mode allows the user to monitor rate to a higher
degree of accuracy. The default mode for the counter module provides
1Hz rate resolution. The floating point mode allows the module to report
rate resolution of up to 0.0001Hz. The rate resolution is dependent on the
input signal speed. Low speed signals will provide the highest resolution.
As rate increases the frequency accuracy will decrease.
Configuring Each Input
Channel for Floating Point
Rate
The Data Register format for floating point is different that the default
register mode. The data words have been moved to accommodate the
floating point rate value. Your ladder logic must be modified to support
this new word format. In order to activate the floating point mode you
must set the Rate Factor to a value of -1.
The following steps are necessary to accomplish this:
1) Load the value (-1) into the Rate Limit / R Factor
2) Toggle the Program Scale Factors configuration bit (Bit 15) to write the
configuration to the module.
3) Create ladder logic to join the two input works to create your floating
point value.
Appendix A