Product Overview
The Bently Nevada 990-10-70-03-01 990 Vibration Transmitter is a critical component for continuous vibration monitoring in rotating machinery. Designed to accept one non-contacting 3300 NSv Proximity Probe and extension cable, this transmitter converts shaft vibration into a 4-20 mA signal. Its built-in NOT OK/signal defeat circuit ensures that when a fault condition occurs—such as probe damage or power loss—the output drops below 3.6 mA within 100 microseconds, alerting operators instantly. This proactive failure response helps prevent catastrophic machine damage and reduces unplanned downtime.
Technical Specifications Breakdown
Key parameters from the datasheet define the 990-10-70-03-01's performance boundaries:
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Power Requirement: +12 to +35 Vdc at the transmitter terminal ensures wide compatibility with existing loops.
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4-20 mA Output: Linear over the selected full-scale range (0-10 mils pp or 0-250 μm pp) with ±1.5% accuracy (additional to Prox Out Incremental Scale Factor).
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Maximum Loop Resistance: 1,000 Ω including cable at 35 Vdc—adequate for long cable runs without signal degradation.
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Frequency Response: 5 Hz to 6,000 Hz ±0, 3 dB captures most common vibration frequencies in industrial machinery.
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Transmitter Weight: 0.43 kg (0.9 lbm)—compact footprint for mounting with DIN clips and screws (Mounting Option 03).
The unit is certified for CSA Division 2 hazardous locations (Agency Approval Option 01), making it suitable for use in potentially explosive atmospheres.
Real-World Applications
Typical installations include pumps, fans, compressors, and turbines where early detection of shaft radial vibration is essential. The 990-10-70-03-01's probe gap requirement of 0.5 to 1.75 mm (20 to 55 mils) from the target must be maintained during setup to ensure full-scale range. In a chemical plant, for example, mounting the transmitter on a centrifugal pump allows continuous monitoring. If the vibration exceeds the setpoint, the 4-20 mA loop reflects the change, and any NOT OK condition (e.g., probe failure) triggers the <3.6 mA signal, prompting immediate inspection.
Installation & Setup Guidance
Proper installation hinges on correct probe gap and secure mounting. Use the DIN clips and screws (included with the 03 mounting option) to attach the transmitter. The maximum cable length from the Proximitor Sensor Output (BNC connector) to the remote indicator is 3 meters (10 feet). For best noise immunity, run the cable separately from high-voltage lines. After mounting, adjust the zero and span using the non-interacting external adjustments while verifying the signal against a known target position. The probe gap must be set within 0.5-1.75 mm; using a feeler gauge or digital gap tool ensures accuracy.
Troubleshooting & Common Issues
When the 990-10-70-03-01 outputs a signal below 3.6 mA, the NOT OK/signal defeat circuit has activated. Common causes include:
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Probe damage or cable break: Inspect the 3300 NSv probe and extension cable for physical wear or corrosion.
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Power supply out of range: Verify that +12 to +35 Vdc is present at the transmitter terminals with a DMM.
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Excessive loop resistance: Ensure total loop resistance (including cable and receiver) does not exceed 1,000 Ω at 35 Vdc.
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Incorrect probe gap: Re-check the gap; if it has drifted, re-adjust using the zero/span adjustments.
If the output remains in defeat mode after correcting these, replace the probe or transmitter module. The 990-10-70-03-01's current limiting (23 mA typical) protects the loop from overcurrent. PLC Source PRO stocks the Bently Nevada 990-10-70-03-01 990 Vibration Transmitter and related accessories for fast replacement.