Overview of the Bently Nevada 990-08-70-03-01 Vibration Transmitter
When vibration monitoring signals fail due to probe faults or power loss, machinery damage can escalate quickly. The Bently Nevada 990-08-70-03-01 Vibration Transmitter is engineered to prevent false readings and protect critical rotating assets. This 2-wire loop-powered transmitter accepts one non-contacting 3300 NSv Proximity Probe and converts shaft vibration into a 4-20 mA signal proportional to the specified full-scale range. With built-in NOT OK/signal defeat circuitry, the output drops below 3.6 mA within 100 µs of a fault, restoring automatically within 2-3 seconds once the condition clears.
Key Technical Specifications
| Parameter |
Value |
| Full-scale option |
08: 0-8 mils pp (0-200 μm pp) |
| System length |
70: 7.0 meters (23.0 feet) |
| Mounting option |
03: DIN clips and screws |
| Agency approval |
01: CSA Division 2 |
| Input |
Accepts 1 non-contacting 3300 NSv Proximity Probe and extension cable |
| Power requirement |
+12 to +35 Vdc at transmitter terminal |
| 4-20 mA output |
Over specified full-scale range, 2-wire |
| Loop accuracy |
Within ±1.5% over full-scale range (from TEST input to 250 Ω) |
| Probe gap |
0.5 to 1.75 mm (20-55 mils) from target |
| Max loop resistance |
1,000 Ω including cable at 35 Vdc |
| Current limiting |
23 mA typical |
| Frequency response |
5 Hz to 6,000 Hz +0, -3 dB |
| Weight |
0.43 kg (0.9 lbm) |
Real-World Applications
The Bently Nevada 990-08-70-03-01 is ideal for continuous vibration monitoring of pumps, fans, compressors, and turbines in oil & gas, power generation, and water treatment plants. Its CSA Division 2 approval allows installation in non-hazardous and Zone 2/Div 2 hazardous areas. In a typical refinery cooling tower fan application, the transmitter's loop accuracy ensures early detection of imbalance or bearing wear, while the NOT OK timeline prevents nuisance trips during momentary probe issues.
Installation and Setup Guide
Mount the 990-08-70-03-01 using the DIN clips and screws (option 03). Connect the 3300 NSv probe and extension cable to the transmitter input. The probe must be gapped between 0.5 and 1.75 mm from the target surface to achieve the full 0-8 mils range. Power the transmitter from a +12 to +35 Vdc supply at the terminal block. Use the non-interacting external zero and span adjustments to calibrate. For maximum loop resistance, ensure total cable impedance does not exceed 1,000 Ω at 35 Vdc.
Troubleshooting and Best Practices
If the output stays below 3.6 mA, verify probe gap and target condition. A NOT OK condition can be caused by broken probe cable or power loss; the signal will recover within 2-3 seconds after the fault clears. To avoid accuracy drift, periodically check the probe gap and clean the target surface. The 990-08-70-03-01's current limiting of 23 mA protects the loop from overcurrent. For extended cable runs, stay within the 3-meter maximum for Proximitor Sensor output (BNC). Ensure the Power Supply is set to 28 V for optimal performance in hazardous locations.