Detecting eminent failures in critical machinery in factory and other environments where downtime is costly certainly warrants system design consideration. In addition to downtime costs, repair costs can frequently be minimized if failures are caught early. A compact electronic vibration switch from the IMI Division of PCB Piezotronics simplifies adding this protection capability by proving a number of standard features.
The Series 685B vibration switch has an embedded piezoelectric accelerometer that provides the ability to detect a change in the acceleration, vibration or displacement of a rotating machine. Within the 3.5 x 2.8 x 3.5 inch (90 x 70 x 90 mm) aluminum housing are either two solid state or form C relays for separately indicating alarm and alert situations. The system's frequency response from 2 to 1000 Hz allows setting the alarm from 10 to 100 percent of the vibration range and setting the alert from 10 to 100 percent of the alarm setpoint. The time delay at startup is fixed at 20 sec, but is variable from 0 to 45 sec for both the alert and alarm settings to allow for temporary upset conditions.
The switch provides a raw vibration output signal of 100 mV/g for spectrum analysis, a 4 to 20 mA output signal for vibration trending and a 4 to 20 mA calibration feature that allows a precise threshold setup.
Available as an ac (85 to 245V ac) or dc (24V dc ±10 percent) powered unit, the electronic vibration switch mounts directly to fans, pumps and motors with a four-bolt pattern, but also adapts to existing three-bolt pattern installations.