Sensor Technology RWT440, User Manual

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Transducer Control 5 User Manual (RWT3746IM)
Revision 7, September 2020 - Page 22
Limits
The limits feature allows the user to configure the transducer to control external
processes based on predefined operational parameters. Control is accomplished via
an open collector output on the transducers analog connector. There are numerous
ways this feature could be utilised, some examples include, system shutdown on
overload or triggering a conveyor belt when a nut/bolt has been tightened to the correct
torque.
At present there is a single control line, but the limits feature is very flexible, allowing
the user to control the output polarity, high and low limit threshold, samples before
trigger, and an auto reset function which resets the limit out if the control value falls
back between threshold values.
When Limits are enabled the transducer will monitor the selected control channel,
when the value falls below the low limit (if enabled) or exceeds the high limit (if
enabled), an internal counter is started and is incremented every time a new value
meeting the condition is met. The counter will be stopped and reset if the control value
falls back between the low and high limits. When the counter exceeds
the “Samples
Required Before Trigger” parameter, the limit output will be set to the active state (level
configured using the output polarity). If auto reset has not been configured, the limit
output will remain latched irrespective of the control channel value. The limit output
can only be reset via a system reset or peak switch input toggle.
If auto reset is enabled, the limit function will enter a reset state when the control
channel value falls back between the low and high limits. If the reset timeout is enabled,
the limit output will remain latched until the timeout expires, at which point the limit
output will return to its inactive state. The reset stage is cancelled if the control channel
value exceeds the high or low limits during the timeout period, if this occurs the timeout
is disabled and the limit output will remain in an active state. If the reset timeout is
disabled, and the control channel value falls back between the low and high limits, the
limit output will instantly be set to its inactive state.
On transducers with firmware version 3 or 4 the limit output is shared with the
Fail Output pin. When limits are enabled the fail output signal is overridden.
On transducers with firmware version 5 the limit output has been moved to a
dedicated I/O pin, allowing access to both limit and fail signals.
Refer to the Transducer User Manual for more details.