EPRO PR6423/000-000 contact displacement transducer (vibration sensor)​

Description

1. Core Overview & Working Principle

• Probe (Sensor):​ Contains a coil energized by a high-frequency current from the oscillator module.
• Extension Cable:​ Connects the probe to the oscillator.
• Oscillator/Converter Module​ (e.g., CON0x1): Provides power to the probe and converts the gap distance between the probe tip and the observed metallic surface (the shaft) into a proportional DC voltage​ signal.

1. DC Gap Voltage:​ A negative DC voltage (typically -2 to -18 V DC) proportional to the average distance between the probe and the shaft (for position monitoring, e.g., thrust position).
2. AC Vibration Voltage:​ A superimposed AC voltage (typically 0-20 V AC peak-to-peak) proportional to the dynamic movement of the shaft (for vibration monitoring).

2. Key Features & System Components

• Non-Contact Measurement:​ No physical contact with the rotating shaft, allowing high-speed and high-fidelity measurement.
• High Frequency Response:​ Capable of measuring vibrations from 0 to 10 kHz or higher, suitable for detecting high-speed phenomena.
• Robust Design:​ Probe is designed to withstand harsh industrial environments (temperature, pressure, oil, steam).
• System Components (Typical):
  • Probe:​ PR6423 (The sensor itself).
  • Extension Cable:​ Specific length cable (e.g., 5m, 9m) with connectors.
  • Probe Tip / Sensing Area:​ Must be selected based on the material of the target shaft. Different materials (e.g., steel, stainless steel) require different probe types for proper calibration.
  • Oscillator/Driver:​ A separate module (e.g., CON0x1, PR6426) required to power the probe and generate the standard signals.

3. Common Technical Specifications

• Probe Diameter:​ Typically 8 mm​ (common standard) or 5 mm, 11 mm.
• Sensitivity:​ Standard sensitivity is 8.0 mV/µm​ (or 200 mV/mil). This means for every micron of shaft movement, the output AC voltage changes by 8.0 mV.
• Linear Range:​ The distance over which the output is linear to the gap change. For an 8mm probe, a common linear range is approximately 2.0 mm​ (e.g., from 1.0 mm to 3.0 mm from the probe tip).
• Gap Voltage (Static):​ Typically -2 V DC at the near end of the linear range and -18 V DC at the far end.
• Temperature Range:​ Probes can typically operate from -35°C to +150°C​ (or higher with special versions).
• Output:​ Requires connection to a compatible oscillator/driver​ and then to a monitoring system​ (e.g., EPRO MMS6000, Bently 3500/3300).

4. System Integration & Setup

• Installation:​ The probe is mounted in a threaded or flanged holder, rigidly installed on the machine casing, aimed perpendicular to the shaft surface. The initial gap​ (distance between probe tip and shaft at rest) must be set within the specified linear range, typically at the mechanical midpoint​ (e.g., -10 V DC).
• Calibration:​ The entire chain (Probe + Cable + Oscillator) is calibrated as a single unit. Replacing any part requires re-calibration or system re-scaling in the monitor.
• Connection:​ The oscillator’s output (Gap DC and Vibration AC) is wired to a vibration/position monitoring module​ in a rack system. This module provides scaling, alarms, and 4-20 mA outputs.

5. Typical Applications

• Radial Vibration Monitoring:​ Two probes installed 90 degrees apart (X and Y direction) on each bearing to measure shaft vibration orbit.
• Axial (Thrust) Position Monitoring:​ One or two probes observing the thrust collar to monitor rotor axial movement.
• Differential Expansion:​ Measuring the differential growth between the rotor and casing in steam turbines.
• Eccentricity (Slow Roll) Monitoring:​ Measuring shaft bow during low-speed rotation (turning gear operation).
• Keyphasor® Reference:​ A dedicated probe observing a keyway or notch on the shaft provides a once-per-revolution timing pulse for phase analysis.