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Bently Nevada 990-05-XX-03-05 990 Series Vibration Transmitter

The Bently Nevada 990-05-XX-03-05, also cataloged as the 990 Vibration Transmitter, operates as a dedicated hardware component for processing raw proximity probe signals into a standardized 4-20 mA current loop output within condition monitoring networks.

Suffix Breakdown & Model Matrix

Suffix Position	Value	Description
990	Base	Vibration Transmitter
05	Full-Scale Range	0-5 mils pp (0-125 um pp)
XX	System Length	50 (5.0 m) or 70 (7.0 m)
03	Mounting	DIN-rail clips and bulkhead mounting screws
05	Agency Approval	CSA Class I Div 2, ATEX Zone 0/2, ABS maritime

Hardware Specifications

Parameter	Specification
Model	990-05-XX-03-05
Brand	Bently Nevada
Origin	USA
Weight	0.96 lbs (0.43 kg)
Dimensions	100 x 74 x 53.3 mm (3.9 x 2.9 x 2.1 in)
Operating Temp	-35 degC to +85 degC
Power Consumption	+12 to +35 VDC input, 4-20 mA loop
Input Compatibility	1 x 3300 NSv Proximity Probe & extension cable
Output Signal	4-20 mA DC proportional to full-scale vibration
Full-Scale Range	0 to 5 mils peak-to-peak (0 to 125 um peak-to-peak)
Loop Accuracy	Within +/-1.5% over specified full-scale range
Max Loop Resistance	1,000 ohms (including cable resistance at 35 VDC)
Frequency Response	5 Hz to 6,000 Hz (+/-0.3 dB)
Probe Gap Requirement	0.5 mm to 1.75 mm (20 mils to 55 mils)
Diagnostic Output (Prox Out)	Non-isolated BNC and terminal connection (7.87 mV/um / 200 mV/mil nominal)
Storage Temperature	-52 degC to +100 degC
Humidity Limits	100% condensing, non-submerged (potted construction)
Mounting Type	35 mm DIN-rail or standard bulkhead screw-mounting

Eddy-Current Probe Scaling & Gap Voltage Validation

The 990 series integrates an internal Proximitor sensor calibrated specifically for 3300 NSv proximity probes. The transducer converts the raw eddy-current probe signal into a linearized 4-20 mA output with a nominal sensitivity of 200 mV/mil at the Prox Out diagnostic port. Gap voltage must be validated to maintain the probe tip within 20 to 55 mils (0.5 to 1.75 mm) from the target surface to ensure linear operation. The Not OK / Signal Defeat circuit clamps the output to less than 3.6 mA within 100 microseconds upon detecting a faulty probe state or loose connection, preventing false machine trips during signal degradation events.

Frequently Asked Questions

Q: What is the maximum cable resistance allowed in the 4-20 mA loop?

A: The maximum loop resistance is 1,000 ohms total, including cable resistance, at 35 VDC supply voltage.

Q: Does the transmitter support hot-swap replacement on DIN rail?

A: The 2-wire loop-powered design requires loop power to be disconnected before removal or installation. The Power-Up Inhibit circuit clamps the output below 3.6 mA for 2 to 3 seconds upon startup to block line voltage transients.

Q: What probe gap voltage range is required for linear operation?

A: The probe gap must be maintained between 20 and 55 mils (0.5 to 1.75 mm) from the target surface for correct linear measurement.

Field Installation Guidelines

Mount the transmitter to a 35 mm DIN rail or use the supplied bulkhead mounting screws. Connect the 3300 NSv proximity probe and extension cable to the input terminals, ensuring the shield is properly grounded at the transmitter end. Wire the 4-20 mA output loop to the PLC, DCS, or SCADA analog input card, observing polarity. Adjust the Zero and Span potentiometers externally to calibrate the output against the 0-5 mils full-scale range. Verify the gap voltage is within the 20-55 mil window before commissioning. The potted construction tolerates 100% condensing humidity, but the unit must not be submerged.

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