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Bently Nevada 990-08-XX-03-00 Vibration Transmitter

The Bently Nevada 990-08-XX-03-00, also cataloged as the 990 2-Wire Vibration Transmitter, operates as a dedicated hardware component for converting raw eddy-current proximity probe signals into a proportional 4-20 mA current loop output within machinery protection and control systems.

Suffix Breakdown & Model Matrix

Suffix Position	Value	Description
990	Series	2-Wire Vibration Transmitter
08	Full-Scale Option	0-8 mils pp (0-200 um pp)
XX	System Length Option	50 (5.0 meters) or 70 (7.0 meters) depending on exact probe and cable assembly length
03	Mounting Option	35 mm DIN rail clips
00	Agency Approval Option	No approvals (Standard / Non-hazardous area)

Hardware Specifications

Parameter	Specification
Model Brand	Bently Nevada 990-08-XX-03-00
Origin	USA
Weight	Approx. 0.43 kg (0.9 lbm)
Dimensions	Not specified in source documentation
Operating Temp	-35 degC to +85 degC (-31 degF to +185 degF)
Power Consumption	12 to 35 VDC (at the transmitter terminal)
Input Signal	Accepts 1 non-contacting 3300 NSv Proximity Probe and extension cable
Output Signal	4 to 20 mA DC, proportional to full-scale peak-to-peak vibration
Full Scale Range	0 to 8 mils pp (0 to 200 um pp)
Accuracy	Within +/-1.5% over specified full-scale range
Frequency Response	5 Hz to 6,000 Hz (+/-3 dB)
Incremental Scale Factor (ISF)	7.87 mV/um (200 mV/mil) +/-6.5% typical at the Prox Out port
Current Limiting	23 mA typical
Not OK Circuit Response	Drops loop current to < 3.6 mA within 100 us of a fault
Housing Material	Aluminum (Potted construction for high moisture protection)
Mounting	35 mm DIN rail mount (via option 03)
Adjustments	Non-interacting external Zero and Span potentiometers
Storage Temperature	-51 degC to +100 degC (-60 degF to +212 degF)
Relative Humidity	Up to 100% condensing, non-submerged (potted construction)

Eddy-Current Probe Scaling and Gap Voltage Validation

The 990 series integrates the proximitor sensor driver directly into the transmitter housing, conditioning the raw eddy-current signal from the 3300 NSv probe. The Incremental Scale Factor (ISF) is specified at 7.87 mV/um (200 mV/mil) with a typical tolerance of +/-6.5% at the Prox Out port. Gap voltage can be validated at the COM terminals, where a healthy probe gap typically presents a DC bias target of approximately -10 VDC. The transmitter provides dynamic vibration data extraction via a coaxial connector and dedicated PROX OUT / COM terminals for diagnostic verification using standard oscilloscopes or analyzers.

Frequently Asked Questions

Q: What is the probe length configuration for the XX suffix?

A: The XX system length option must be specified at time of order as either 50 (5.0 meters) or 70 (7.0 meters), corresponding to the total probe and extension cable assembly length in the 3300 NSv system.

Q: How does the Not OK circuit behave during probe failure?

A: Upon probe disconnection or failure, the Not OK circuit forces the loop current below 3.6 mA within 100 microseconds, preventing false 4-20 mA alarm conditions in the downstream PLC or DCS.

Q: Can the zero and span be adjusted in the field?

A: Yes, the transmitter features non-interacting external Zero and Span potentiometers accessible without disassembling the potted housing.

Field Installation Guidelines

Mount the transmitter to a standard 35 mm DIN rail using the supplied clips (option 03). Ensure the aluminum housing is seated firmly to maintain mechanical stability. Route the 3300 NSv proximity probe cable and extension cable with proper shielding, grounding the shield at the transmitter end only to prevent ground loops. The 4-20 mA output loop requires 12-35 VDC power supply at the transmitter terminals; verify polarity before connection. For dynamic diagnostic access, connect a coaxial cable to the PROX OUT connector or use the COM terminals for gap voltage measurement. The potted construction allows operation in 100% condensing humidity environments, but the unit must not be submerged.

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