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As always, different types of timers are available with different manufacturers. Here are most of them:
Let's now see how to use them. We typically need to know 2 things:
When the instructions before the timer symbol are true the timer starts "ticking". When the time elapses the timer will automatically close its contacts. When the program is running on the plc the program typically displays the elapsed or "accumulated" time for us so we can see the current value. Typically timers can tick from 0 to 9999 or 0 to 65535 times.
Why the weird numbers? Again its because most PLCs have 16-bit timers. We'll get into what this means in a later chapter but for now suffice it to say that 0-9999 is 16-bit BCD (binary coded decimal) and that 0 to 65535 is 16-bit binary. Each tick of the clock is equal to x-seconds.
Typically each manufacturer offers several different ticks. Most manufacturers offer 10 and 100 ms increments (ticks of the clock). An "ms" is a milli-second or 1/1000th of a second. Several manufacturers also offer 1ms as well as 1 second increments. These different increment timers work the same as above but sometimes they have different names to show their timebase. Some are TMH (high speed timer), TMS (super high speed timer) or TMRAF (accumulating fast timer)