seismic vibration transmitter
990, 991 series



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The 991 Thrust Transmitter is intended primarily for the original equipment manufacturers (OEMs) of centrifugal air compressors or small pumps, motors, or fans who prefer to provide a simple 4 to 20 mA proportional axial displacement (thrust) signal as the input to their machinery control system. The transmitter is a 2-wire, loop-powered device that accepts input from our 3300 NSv* proximity probe and its matching extension cable (available in 5 m and 7 m system length options). The transmitter conditions the signal into appropriate engineering units proportional to the shaft’s axial position1, and provides it as a 4 to 20 mA industry-standard signal for input to the control system where machinery protection alarming and logic occurs2.

The 991 transmitter provides the following notable features:

Integrated Proximitor Sensor requires no external unit
Non-isolated "PROX OUT " and "COM" terminais plus a coaxial connector provide a dynamic vibration and gap voltage signal output for diagnostics3. Non-interacting zéro and span potentiometers under the Transmitter label supports loop adjustment.
Test Input pin allows quick vérification of loop signal output, using a variable DC voltage source as the input.
A Power-up Inhibit circuit éliminâtes signal errors due to line voltage transients.
A Not OK/Signal Defeat circuit prevents high outputs or false alarms due to a faulty proximity probe or loose connection.
Choice of DIN-rail clips or bulkhead mounting screws as standard options simplifies mounting.
Potted construction for high humidity lup to 100% condensingl environments.