Product Overview
When axial thrust monitoring requires high reliability, the Bently Nevada 991-25-70-02-00 Probe Vibration Transmitter delivers precise 4-20 mA output. This industrial automation module is designed for axial position measurement using a 3300 NSv proximity probe. The 991-25-70-02-00 offers a full-scale range of 25-0-25 mils and operates from +12 to +35 Vdc.
Technical Specifications
Key parameters of the Bently Nevada 991-25-70-02-00 include:
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Output Signal: 4-20 mA over full-scale range (2-wire)
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Accuracy: Within ±1.5% of full scale (typical)
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Max Loop Resistance: 1,000 Ω (including cable at 35 Vdc)
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Current Limiting: 23 mA typical
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Operating Temperature: -35°C to +85°C
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Weight: 0.43 kg (0.9 lbm)
Linear range for proximity output is 0.25 to 1.65 mm. Suitable for 0.6-0-0.6 mm or 25-0-25 mils current loop ranges. The unit accepts one non-contacting 3300 NSv probe and extension cable.
Installation & Setup Guidance
Mount the Bently Nevada 991-25-70-02-00 on a DIN rail using bulkhead screws (mounting option 02). Connect the 3300 NSv proximity probe and extension cable. Provide +12 to +35 Vdc at the transmitter terminal. Use non-interacting external adjustments for zero and span. The 4-20 mA output is in 2-wire configuration. Ensure loop resistance does not exceed 1,000 Ω.
Maintenance & Reliability
The 991-25-70-02-00 includes a Not OK/Signal Defeat feature. Signal output drops below 3.6 mA within 100 µs upon a detected fault, and restores within 0.1 seconds after the fault clears. This fail-safe behavior minimizes downtime. For ongoing reliability, verify power supply stability and loop resistance. The transmitter operates reliably from -35°C to +85°C and stores from -51°C to +100°C.
Troubleshooting Common Issues
If output remains below 3.6 mA, check for an active Not OK condition (probe fault, cable break, power loss). Use the test signal input to verify accuracy. Confirm power supply meets +12 to +35 Vdc requirement. Excessive loop resistance (over 1,000 Ω) may reduce output signal swing. Adjust zero and span only with the probe in proper position. The current limiting at 23 mA protects the loop.