Basic Timer Setup

[pstephens]

Thanks, you guys!

 

[Tom Jenkins]

Eric nailed it, Paula. You can set the retentive ranges for the counters and V-memory. I don't always have the timers retentive, but I make sure my counters are in the set retentive range.

A self re-setting timer is one that uses it's own timer done contact to reset itself. Below is an example that will trip the hour meter at 0.1 hour increments, and uses two registers. One is for 0-999.9 hours and the other for 0-9999 thousand hours.

A word of caution here. The timer could loose up to 0.1 hour if you power cycle, and the resetting could cause you to loose an amount equal to your scan time on every cycle on some PLCs. For an hour meter used to track preventive maintenance this is no big deal. If you are using it for billing or custody transfer of a fluid or a similar hyper-critical function then an external hour meter or pulse counter is better.

P.S. Sorry about the resolution. I was expirementing with a graphics editor, and the expirement was a success because I learned about another thing that doesn't work like I wanted.

 

[pstephens]

Hi Tom,

Thanks for the diagram. That was more or less how I set it up, but you filled in some blanks for me. I knew that the timer settings were not retentive, but I wasn't sure if/how they could be made so. I did notice that the counters always seem to retain their setting.

Good point about the inherent inaccuracies of this method. I'm not even sure if this feature will be useful to the customer, I just thought it would come in handy for timing maintenance intervals and such. A reasonably close approximation is fine in this case. Thanks again.

Paula