CompactLogix HSC Pulse Interval Method to In/Min

Team,
I have an encoder (Encoder Products TR1)that has a wheel attached to it and rides on material in my machine. I need to calculate In/Min as the material is taken up on a spool.

Encoder wheel diameter= 1.9" @2048PPR circumference=6"
Max material Speed = 25"/min

I am setting up the Pulse Interval Method in my compactlogix. The compactlogix Ctr0PulseInterval provides a microsecond signal

What are the steps to convert Micro seconds to In/Min?

Each encoder pulse corresponds to a specific displacement. In your case it is 6"/2048PPR, or 0.0029297".

Divide the inches/pulse value by the Ctr0PulseInterval, multiply by 1000000 to get inches/sec and multiply by 60 to get inches/min.

Keith

thanks for the direction, it works great!

1 Any idea how to clear Ctr0PulseInterval register?
2 Any idea how to slow the update calculation?

thanks

To the best of my knowledge there is no way to do either of these things. What are you trying to accomplish with either of these?

Keith

1. Have you tried copying 0 into it?

2. I'm guessing you mean increase the time interval between calculations? You could use a timer, and place a .DN XIC in front of the blocks doing the calculations

Originally posted by Dhitzfelder:

1. Have you tried copying 0 into it?

Click to expand...

The data tag he is referring to is a member of a scheduled I/O input group. Any value you write into it won't stay there for long.

Originally posted by Dhitzfelder:

2. I'm guessing you mean increase the time interval between calculations? You could use a timer, and place a .DN XIC in front of the blocks doing the calculations.

Click to expand...

I think what he is really trying to do is decrease the rate at which the module comes up with a new value of pulse interval. There really is no way to decrease that rate since it is effectively driven by the incoming pulse rate. However, as you indicate, just because a new value is there doesn't mean you have to read it. However, I think the OP would be better off averaging multiple values and using that average than to pick single occurrences of the value at a set interval.

Keith

Guys,
Thanks for the feedback, I think if I disable the counter the count interval goes to 0. I am using this is a speed calculation and each time I start up my take up motor I need to zero it out for my PID Instruction to start from a zero state.
To slow the refresh rate I thing the average probably better than the timer, I may try both.

thanks again for the replies.

Any easy ways to do an average calculation?

store the recorded values in an array, then add up the array and divide by the number of elements in the array.

ArrayX[10]
Copy ArrayX[0] to ArrayX[1] length 9
Move new value to ArrayX[0]
ArrayLength <= 10 ArrayLength = ArrayLength + 1

use cmp to add all elements of ArrayX then divide by ArrayLength

Reset ArrayLength whenever you stop

I believe this will all work, I thought AB had a function to take the average of an array but I couldn't find it.

*EDIT: look up AVE function

Why do all that work just use the HSC rate input and then a simple math calculation to in/min