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The 991-01-XX-01-00 serves as a thrust transmitter within the Bently Nevada 991 series, built on modification 288865-01. This loop-powered unit converts eddy-current probe signals into a standardized 4–20 mA output. Plant engineers use it for axial position monitoring on steam turbines and compressors.
Technical Specifications
| Parameter | Value |
|---|---|
| Model | 991-01-XX-01-00 |
| Modification | 288865-01 |
| Category | Thrust Transmitter |
| Input Signal | Eddy-current proximity probe |
| Output | 4–20 mA, loop-powered |
| Frequency Range | 0 to 100 Hz |
| Measurement Range | 0 to 1.0 mm (typical thrust window) |
| Supply Voltage | 12 to 30 Vdc |
| Operating Temperature | -40°C to +85°C |
| Storage Temperature | -55°C to +100°C |
| Weight | Approx. 0.5 kg |
| Dimensions | 110 mm × 55 mm × 35 mm |
| Mounting | DIN rail or panel mount |
| Connector | Screw terminal block |
| Enclosure Rating | IP65 |
| Part Count | Single-channel module |
Signal Path and Interface Details
The transmitter accepts a raw proximity probe signal from the thrust bearing location. Next, it filters noise and converts the result into a proportional current loop. Because the design draws power from the same two wires, field wiring stays simple. The 991-01-XX-01-00 supports long cable runs without extra supply conductors.
Energy Storage and Power Draw
No internal battery or supercapacitor resides inside this module. The unit relies entirely on the external loop supply for operation. Consequently, power loss immediately interrupts the output signal. System designers should therefore provide an uninterruptible 24 Vdc source.
Installation Notes
Operators mount the housing on a standard DIN rail inside a control cabinet. Shielded twisted-pair cable minimizes electromagnetic interference over distance. Meanwhile, the IP65 enclosure tolerates dust and water spray in industrial settings. Always verify loop polarity before energizing the circuit.