Description
Bently Nevada 3300/20 Dual Thrust Position Monitor
Configured for thrust position monitoring in the Bently Nevada 3300 Series Machinery Protection System, the Bently Nevada 3300/20 (base model 3300/20) provides direct measurement and processing of dual-channel axial displacement signals from eddy-current proximity probes.
Hardware Specifications
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Parameter
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Specification
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Model Brand
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Bently Nevada 3300/20
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Origin
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United States
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Weight
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1 kg
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Dimensions
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1-slot 3300 rack module
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Operating Temp
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0 degC to +65 degC
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Power Consumption
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1.5 W nominal / 7.7 W max
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Input Signal
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0 to -10 Vdc from proximity probes
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Input Impedance
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10 kOhm nominal
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Transducer Supply
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-24 Vdc (programmable to -18 Vdc)
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Accuracy
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±0.33% FS typical, ±1% FS max @ +25 degC
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Display Resolution
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±1.6% of monitor full scale
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Sensitivity Settings
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200 mV/mil (8 V/mm), 100 mV/mil (4 V/mm)
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Recorder Outputs
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+4 to +20 mA, 0 to -10 Vdc, +1 to +5 Vdc
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Buffered Outputs
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100 Ohm output impedance, short-circuit protected
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Alarm Relays
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Configurable Alert/Danger, epoxy or hermetic seal
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Eddy-Current Probe Scaling and Gap Voltage Validation
The 3300/20 supports programmable scaling factors aligned to standard eddy-current probe response curves. Gap voltage validation targets a nominal -10 Vdc baseline for static probe positioning, ensuring linear displacement measurement range and minimizing rotor dynamics interference. Cross-talk suppression between Channel A and Channel B is implemented via isolated input conditioning circuits.
Frequently Asked Questions
Q: Does the 3300/20 support hot-swap replacement without system shutdown?
A: No. The module must be installed or removed only when the rack power is disabled to prevent backplane transient damage.
Q: What is the switching delay for AND voting logic in alarm relays?
A: Alarm relay activation occurs within one system update cycle after both channels meet their respective setpoints.
Q: Are buffered transducer outputs electrically isolated from recorder outputs?
A: Yes. Buffered outputs are isolated to prevent ground loops affecting measurement accuracy.
Field Installation Guidelines
Mount the 3300/20 in any available standard slot of a powered-down 3300 rack, avoiding reserved slots 1 and 2. Use shielded twisted-pair cable for probe wiring, grounding the shield at the rack end only. Maintain separation of probe cables from high-voltage wiring to reduce electromagnetic interference. Verify gap voltage at installation using front-panel test points before enabling machinery operation.
