Rockwell Automation 57C421B Pulsetach Input Module/DCS 5000/AutoMax - Manual (Page 60)

EĆ2
Appendix E
(Continued)
In addition to these programming changes, input
impedances have changed from the 57421Ć1 module
to the 57C421A module. Be sure to checkthe external
5V pulse input circuitry.
D Note that if you are replacing a 57421Ć1 module with a 57C421A module,
you must add the three jumpers shown in figure 3.4 to the terminal strip of
the 57C421A module in order for the module to operate properly if the
original module was used with 12 V optoĆisolated inputs.
Module 57C421B differs from module 57C421A as follows:
D The 2 kHz timer has been replaced by a 200 kHz timer in 57C421B.