GE Bently Nevada 1900/27 Operation And Maintenance Manual page 8

1900/27 Vibration Monitor Operation and Maintenance Manual
Relay BYPASS - A relay BYPASS switch lets you disable both relays while you
adjust the relay setpoints or maintain the machinery. This feature prevents
false alarms or undesired machinery shutdowns. When the monitor is
bypassed, the red BYPASS LED is on.
Coaxial connector - A coaxial connector on the front of the monitor
provides a buffered velocity signal (500 mV/in/s or 20 mV/mm/s) for locally
sampling dynamic data. The connector provides direct access to the
integrated transducer signal which can be used to diagnose and analyze
machinery.
Two alarm relays - The monitor has two single-pole, double-throw relays
(Type 2 FORM C). Use these relays as inputs to the machinery control
circuits, or to drive alarm annunciators such as a bell or light on an alarm
panel. You can also wire these relays together with other relays into an
AND or OR voting logic scheme. Although typically used as an Alert relays,
you can reconfigure the Alert relay to become a NOT OK relay, an Alert
logically OR'ed with NOT OK relay, or an auxiliary Danger relay. The relay
circuits include arc suppressors to increase relay contact life expectancy
and reduce arcs in hazardous locations.
4 to 20 mA Intereface - Systems set up to collect data usng a 4 to 20 mA
communications system can access the peak velocity data through this
interface.
True peak measurements - The 1900/27 Vibration Monitor uses an analog
peak-to-peak detector to determine the peak vibration amplitude. This
method is more accurate than methods which measure the RMS level and
attempt to convert it to peak value. The RMS method is poor because it
applies the conversion factor for pure sinusoidal signals even though
machinery vibration is rarely a pure sine wave (see Appendix B).
Timed OK/Monitor Defeat - This special proprietary circuit minimizes the
possibility of false alarms caused by a defective transducer, transducer
wiring, or transducer power supply.
Power-up Inhibit - This feature minimizes false alarms caused by a
transient power surge or interruption of power.
Monitor Self Test - The monitor conducts a self test which checks the
monitor's power supply voltages and verifies the signal path when you
power up the monitor or when you initiate a self test during operation of
the monitor.
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