Ge fanuc 90-30

hi, i have this small task to do which requires me to discuss a little about the range of timers available on the 90-30 plc and talk about the range/accuracy trade off.

I have explained the following: TMR, OFDT, UPCTR, DNCTR, but i have no idea where to start when it comes the the next part of the question range/accuracy trade off. can anybody link me some articles or a pdf file that talks about this ? i have been unable to find anything via google

cheers

Timers in a 90-30 can keep trank of time in increments of tenths, hundredths, or thousndths of a second. The timers themselves are 16-bit integer functions which means they can keep track of values between -32768 and + 32767. Therefore a timer with a timebase of thousandths of a second that starts at zero can keep track of 32.767 seconds. The same time with a timebase of hundredths of a second can keep track of 327.67 seconds and a timer with a timebase of tenths of a second can keep track of 3276.7 seconds.
For longer durations than that you can use a counter that increments at a slower rate or you can cascade the output of one timer as the input to another.

Check out GFK-0467.

A clear description of exactly what you want to do may bring out more possibilities.

...I have no idea where to start when it comes the the next part of the question: the range/accuracy trade-off.

Click to expand...

I think it would be more correct to call it a range/time increment trade-off. A 0.001-second-base timer is maybe no more accurate than a 0.1-second-base timer, for the relative time values that they can time. But if you need a time increment of 0.005 seconds, then it would be difficult to time that with a 0.1 second timer.

In other words, the smaller the time increment of the timer, the smaller the range, so you cannot get a timer with a small increment and a large range. As Steve said, to get a small increment and a large range, you have to cascade a small-increment timer with a second timer, or with a large-range counter.