Product Overview
The Bently Nevada 21504-04-36-05-02 7200 Series 8 mm Probe is a non-contact proximity probe designed for rotating machinery monitoring applications. It provides a sensing point for detecting changes in the relative position of a conductive shaft without physically contacting the rotating component.
In turbines, compressors, generators, pumps, and other critical rotating equipment, shaft movement can provide useful information about machine operating condition. Changes in radial or axial shaft position may indicate vibration, mechanical imbalance, misalignment, bearing-related problems, or other developing conditions.
The 21504-04-36-05-02 is part of the Bently Nevada 7200 Series 8 mm probe family and is intended to work with compatible driver and monitoring equipment. The probe performs the sensing function, while the associated electronics supply, condition, and process the measurement signal.
One practical characteristic of this configuration is its 0.5 meter total length. The shorter overall length can be useful where the distance between the probe mounting location and associated connection point is relatively limited. It can also help keep sensor routing compact around machinery assemblies.
The stated weight of the 21504-04-36-05-02 is 0.22 kg. Its compact construction makes it suitable for integration into industrial machinery monitoring installations where reliable shaft displacement measurement is required.
Technical Specifications
| Parameter |
Details |
| Manufacturer |
Bently Nevada |
| Model |
21504-04-36-05-02 |
| Product Series |
7200 Series |
| Product Type |
8 mm Probe |
| Probe Type |
Eddy Current Proximity Probe |
| Measurement Method |
Non-Contact Displacement Measurement |
| Measurement Target |
Conductive Rotating Shaft |
| Main Function |
Shaft Displacement and Vibration Monitoring |
| Application |
Rotating Machinery Monitoring |
| Probe Size |
8 mm Series |
| Total Length |
0.5 meters |
| Weight |
0.22 kg |
| Installation |
Machinery Monitoring System |
| Application Area |
Machinery Protection and Condition Monitoring |
Product Features
The Bently Nevada 21504-04-36-05-02 combines an 8 mm proximity probe configuration with a relatively short 0.5 meter total length.
Key features include:
- 8 mm proximity probe design
- Eddy current sensing principle
- Non-contact shaft displacement measurement
- Suitable for rotating machinery
- Supports shaft vibration monitoring
- Suitable for relative shaft position measurement
- 0.5 meter total length
- Compact installation arrangement
- Designed for integration with compatible monitoring electronics
- Suitable for continuous machinery condition monitoring
The shorter probe length can be useful in installations where the sensor needs to remain close to the monitored equipment and excessive cable routing is undesirable.
Working Principle
The 7200 Series probe operates through an eddy current sensing principle. The probe produces an electromagnetic field around its sensing tip, which interacts with the conductive surface of the rotating shaft.
When the distance between the probe and shaft changes, the electrical response of the sensing circuit also changes. This relationship allows the monitoring system to determine relative shaft displacement.
The general measurement sequence includes:
- Generating an electromagnetic field at the probe tip
- Detecting the conductive shaft within the sensing region
- Monitoring changes in the probe-to-shaft distance
- Producing a corresponding electrical response
- Conditioning the signal through associated electronics
- Sending the resulting measurement to the monitoring system
The non-contact principle allows the probe to monitor shaft movement continuously without physical wear between the sensor and rotating target.
Role in Industrial Monitoring Systems
The 21504-04-36-05-02 functions as the sensing element within a machinery protection or condition monitoring channel.
| Function |
Description |
| Shaft Displacement Measurement |
Detects changes in relative shaft position |
| Vibration Monitoring |
Provides shaft movement information |
| Position Monitoring |
Tracks relative movement between probe and target |
| Non-Contact Sensing |
Measures the shaft without physical contact |
| Condition Monitoring |
Supplies data for machinery condition assessment |
| Protection Input |
Provides measurement information to compatible protection equipment |
The probe is normally connected to additional electronics. It should not be considered a complete vibration monitoring system by itself.
Industrial Applications
The Bently Nevada 7200 Series 8 mm probe can be used in applications where accurate monitoring of rotating machinery movement is required.
| Industry |
Typical Applications |
| Power Generation |
Turbine and generator monitoring |
| Oil & Gas |
Compressor and turbine condition monitoring |
| Petrochemical |
Pumps and rotating process equipment |
| Power Utilities |
Critical machinery protection |
| Manufacturing |
High-speed rotating equipment |
| Mining |
Large machinery monitoring |
| Water Treatment |
Pump and motor monitoring |
| Industrial Facilities |
Continuous machinery condition monitoring |
Proximity measurements can be combined with other machine parameters, such as vibration, rotational speed, temperature, and process conditions, to improve overall equipment assessment.
Installation and System Integration
Proper installation is important because the proximity probe measures changes in a relatively small probe-to-target distance.
Recommended installation steps include:
- Verify the complete model number before installation.
- Confirm compatibility with the associated driver.
- Install the probe in the designated mounting location.
- Establish the appropriate probe-to-shaft gap.
- Align the probe with the intended measurement surface.
- Secure the probe against mechanical movement.
- Route the 0.5 meter assembly without excessive mechanical stress.
- Inspect connectors and cable condition.
- Verify the measurement signal during commissioning.
The probe mounting arrangement should remain rigid while the machine is operating. Any movement of the mounting structure can be interpreted by the monitoring system as shaft movement.
Compatible System Components
The 21504-04-36-05-02 normally operates as part of a complete proximity measurement channel.
| Compatible Component |
Function |
| Proximity Probe Driver |
Supplies and conditions the probe signal |
| Extension Cable |
Provides system connection where required |
| Machinery Monitoring System |
Processes and displays measurement data |
| Machinery Protection System |
Evaluates machine operating condition |
| Rotating Shaft |
Provides the conductive measurement target |
| Probe Mounting Hardware |
Maintains the required probe position |
| Vibration Monitoring Equipment |
Analyzes shaft movement and vibration |
The probe and associated electronics should be evaluated as a complete measurement chain when installing or replacing equipment.
Recommended Alternative Models
| Model |
Type |
Key Feature |
Application |
| Bently Nevada 21504-04-36-05-02 |
7200 Series 8 mm Probe |
0.5 meter total length |
Compact machinery monitoring installations |
| Bently Nevada 21504-04-36-10-02 |
7200 Series 8 mm Probe |
1 meter total length |
Rotating machinery monitoring |
| Bently Nevada 21504-00-48-10-00 |
7200 Series 8 mm Probe |
1 meter total length |
Shaft displacement monitoring |
| Bently Nevada 21504-00-52-10-02 |
7200 Series 8 mm Probe |
1 meter total length |
Machinery vibration monitoring |
| Bently Nevada 7200 Series Probes |
Eddy Current Probe |
Non-contact shaft measurement |
Machinery protection |
The 0.5 meter length should be considered when selecting an alternative. A longer or differently configured probe may require changes to cable routing, mounting arrangements, or the associated measurement system. Probe compatibility should therefore be confirmed before replacement.
Key Advantages
- Non-contact measurement of rotating shaft movement
- 8 mm proximity probe configuration
- Suitable for machinery vibration monitoring
- Supports shaft displacement and position measurement
- Eddy current sensing principle
- 0.5 meter total length
- Compact installation arrangement
- No mechanical contact with the rotating shaft
- Suitable for continuous machinery monitoring
- Can be integrated with compatible monitoring and protection equipment
Technical FAQs
Why can a shorter probe configuration be useful in machinery installations?
A shorter overall length can simplify sensor routing when the probe connection point is close to the monitoring equipment or mounting location. It can reduce unnecessary cable slack and help maintain a more organized installation around compact machinery assemblies.
How does probe mounting rigidity affect vibration measurement?
The probe must remain mechanically stable relative to the machine reference point. If the mounting bracket or probe housing moves independently, the monitoring system may interpret that movement as shaft displacement, producing an inaccurate representation of the actual machine condition.
What is the relationship between shaft radial movement and proximity probe output?
Radial shaft movement changes the distance between the shaft surface and the stationary probe tip. The resulting change in the probe’s electrical response is used to represent the relative displacement of the shaft within the measurement range.
When should an extension cable be considered with a 0.5 meter probe assembly?
An extension cable may be required when the physical distance between the probe and the associated driver exceeds the available probe assembly length. However, the cable and driver should be selected as compatible components because the complete electrical characteristics of the measurement chain affect signal performance.
