Surefire01
Electrical
- Oct 17, 2012
- 23
Hi Chaps
I have a small test rig consisting of an SLC-500 rack, a small three phase motor driven by a VFD, and an optical sensor reading a slot in a disc mounted to the motor shaft. I have written a small ladder program to count the pulses for a period of time using a free running timer then after the time period has expired shift the value into an integer file and multiply it up to get an RPM value.
This works ok but has some draw backs: the updated value takes time to display, when the motor is stopped I get strange values. I am using a fast input card but at full motor speed the values jump around a lot. Can anyone point me to a more stable robust solution.
Thanks.
I have a small test rig consisting of an SLC-500 rack, a small three phase motor driven by a VFD, and an optical sensor reading a slot in a disc mounted to the motor shaft. I have written a small ladder program to count the pulses for a period of time using a free running timer then after the time period has expired shift the value into an integer file and multiply it up to get an RPM value.
This works ok but has some draw backs: the updated value takes time to display, when the motor is stopped I get strange values. I am using a fast input card but at full motor speed the values jump around a lot. Can anyone point me to a more stable robust solution.
Thanks.