Watlow F4T • 203 • Chapter 5 Function Reference
Retentive
A retentive timer is used to keep track of how much cumulative time the input has been ac-
tive. For example, it can be used to time how long an alarm is on over the course of a day.
The output can be used to trigger an event if the elapsed time is considered excessive.
To understand the timer’s behavior consider these scenarios illustrated in the timing diagram
below
1. While the RUN input is active, the elapsed time counts up. Whenever RUN is inactive, the
elapsed time holds. When the elapsed time reaches the specified time, the output be-
comes active and remains active until the timer is re-
set. When the RST input becomes active, the output
becomes inactive and the elapsed time is reset to zero.
2. If RST becomes active while the timer is running, the
timer stops and the elapsed time is reset to zero.
Note:
The elapsed time increments whenever the input is ac-
tive and the reset is not, even if it exceeds the Time
parameter setting.
Note:
The active and inactive states are user configurable with the parameters described below.
Therefore, the description of the timer’s behavior for its inputs and outputs refers to the
active and inactive states for each rather than on or off. For example, if the input’s ac-
tive state is set to High, the timer starts running (becomes active) when the input changes
from low (off to high (on). However, if the input’s active state is set to Low, the timer
starts running (becomes active) when the input changes from high (on) to low (off).
Signals
Direction Label Type Function
Receivers
RUN Digital
Run signal. As long as RST is inactive, the timer runs when
this input is active and holds when this input is inactive.
RST Digital
Reset signal. The output becomes inactive and the elapsed
time is reset to zero when this input becomes active.
Transmitter - - - - Digital
Active whenever the elapsed time is greater than the
specified time. Once on, the output remains on until the
timer is reset.
Function
To measure how long the input is active and trigger the output when the cumulative time
reaches a specified duration, set Function to Retentive.
Time
Set the cumulative amount of time the input must be active before the output becomes ac-
tive.
Range: 0 to 30,000.0
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