I have one sensor fitted to machine gear; wired to PLC to monitor the speed of machine. Can anybody help me to make ladder program to have +/- 2parts per min. Max speed of machine is 2000 parts per min. Every parts passing sensor will count one. Speed update speed should be at least 2 sec.
Hope some one can help.

Regards,

Shree

 

count how many parts there are in every 2 second interval and multiply by 30?

use a weighted average if needed.

 

Thanks for the reply. this is what we are using it now. But one count missing or overlapping will cause the machine speed to shift from 1970 to 2030. How can I get more accurate speed?

Shree

 

Any body... please help.

Shree

 

If you trigger your counter on the rising or falling edge of the pulse it will be more accurate.
Another thing you can do is take the average of a number of samples e.g. sum the last 5, 2 second counts and multiply by 6. Every 2 seconds move all the counts down one place.
Roy

 

You said you have 2000 counts per minute and want to work with a 2 second sampling period. This is only 66.66 counts per sampling period. This means the best resolution you can get is 1 part in 66.66.

It sounds like you need probably need a higher resolution sensing system. An encoder connected to a high speed counter might work better.

Another way to do this is to very accurately measure the time between pulses so as to measure the period rather than the frequency. Your gear won't be good enough for this though. You will also need an accurate timing device. A PLC timer is inadequate for this.