Rockwell Automation 57C421B Pulsetach Input Module/DCS 5000/AutoMax - Manual (Page 42)

4Ć20
4.6.2 Use in Remote I/O Racks
32Ćbit register references should be used with cautionwhenthis
module is placed ina remote rack. The remote I/O system does not
always transfer registers greater than 16 bits as a unit. As a result, it
is possible for anapplicationtask to read the least significant 16 bits
of a new value and the most significant 16 bits of the previous value.
Interrupts cannot be used with Pulsetach Input modules in remote
racks.
WARNING
IF YOU USE DOUBLE INTEGER VARIABLES IN THIS INSTANCE, YOU MUST
IMPLEMENT A SOFTWARE HANDSHAKE BETWEEN THE TRANSMITTER AND
THE RECEIVER TO ENSURE THAT BOTH THE LEAST SIGNIFICANT AND MOST
SIGNIFICANT 16 BITS HAVE BEEN TRANSMITTED BEFORE THEY ARE READ BY
THE RECEIVING APPLICATION PROGRAM. FAILURE TO OBSERVE THIS
PRECAUTION COULD RESULT IN BODILY INJURY OR DAMAGE TO EQUIPMENT.
4.6.3 Pulsetach Feedback Precautions
WARNING
LOSS OF, OR AN OTHERWISE IMPROPER, PULSETACH SIGNAL CAN RESULT IN
UNCONTROLLED MOTOR SPEED. PROVIDE AN INDEPENDENT METHOD OF
SHUTTING DOWN THE EQUIPMENT IF THIS SHOULD OCCUR. FAILURE TO
OBSERVE THIS PRECAUTION COULD RESULT IN BODILY INJURY AND IN
DAMAGE TO, OR DESTRUCTION OF, THE EQUIPMENT.
Whenthis module is used with a pulsetach ina drive control system,
you must incorporate an independent method of determining that
this module is actually reading proper motor RPM. It is necessary to
determine this because the Pulsetach Input module is not capable
of detecting a loss of feedback in all situations, such as, for
example, whena coupling breaks betweenthe motor and the
pulsetach.
WARNING
THE USER IS RESPONSIBLE FOR ENSURING THAT DRIVEN MACHINERY, ALL
DRIVE TRAIN MECHANISMS, AND THE WORKPIECE IN THE MACHINE ARE
CAPABLE OF SAFE OPERATION AT MAXIMUM SPEEDS. FAILURE TO OBSERVE
THESE PRECAUTIONS COULD RESULT IN BODILY INJURY AND IN DAMAGE TO,
OR DESTRUCTION OF, THE EQUIPMENT.
You must also determine the maximum safe operating speed for the
motor, connected machinery, and material being processed. Then,
either verify that the system is incapable of reaching that speed, or
else incorporate the necessary hardware/software to ensure that this
limit will never be exceeded.