PCB Piezotronics IMI SENSORS 686 Series Installation And Operating Manual page 23

Using the Switch and External Latching for Automatic Machinery Shutdown
Figure 21 – Using the Switch and External Latching for Automatic Machinery Shutdown
The Smart Switches are hooked up for automatic motor shutdown in case of high vibration levels on critical
machinery. Since RL2 contacts are normally closed, pushing the Start pushbutton closes the M contact and
starts the motor. If the start-up delay option for the switches is enabled, the Smart Switches will not trip during the
specified startup delay time, regardless of the vibration level. After this delay, the switch relay will be activated if
the vibration level of either switch exceeds the alarm threshold for a period greater than the specified operational
delay time. This action will close the contacts and send a voltage to the RL relay coil. This will open the RL2
contacts and shut down the motor.
Since the LA (latching) option is specified, the RL1 contacts are used for external latching. Closing of RL1
provides constant coil energizing after the shutdown event. Therefore, when the vibration level drops below the
alarm threshold level after shutdown, the closed RL1 contacts still energize the RL coil and keep RL2 in the open
position. The Reset pushbutton should be pushed to reset the 2-wire switch, close the RL2 contacts and open
the RL1 contacts before restarting the motor.
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