Overview
Configured for multi-channel machinery vibration and position monitoring in the Bently Nevada 3500 Machinery Protection System, the Bently Nevada 3500/42M (3500/42 Proximitor / Seismic Monitor) accepts proximity, velocity, or acceleration transducer signals. It conditions the inputs, calculates configured measurement values, and compares active static values against programmable Alert and Danger setpoints.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | 3500/42M |
| Base Model | 3500/42 |
| Brand | Bently Nevada |
| Product Type | Proximitor / Seismic Monitor |
| System | 3500 Machinery Protection System |
| Channel Count | 4 channels |
| Input Signals | Proximity, velocity, or acceleration transducers |
| Input Quantity | 1 to 4 transducer signals |
| Standard I/O Input Impedance | 10 kOhm for proximitor and acceleration inputs |
| TMR I/O Input Impedance | 50 kOhm effective impedance for three channels wired in parallel |
| Transducer Power Supply | -24 VDC nominal |
| Buffered Transducer Outputs | 1 coaxial connector per channel |
| Buffered Output Protection | Short-circuit protected |
| Buffered Output Impedance | 550 Ohm |
| Recorder Output | +4 to +20 mA proportional to monitor full-scale |
| Recorder Load | 0 to 600 Ohm |
| Recorder Voltage Compliance | 0 to +12 VDC |
| Power Consumption | 7.7 W typical |
| Alert Setpoints | User-programmable for each active static value |
| Danger Setpoints | User-programmable for any two active static values |
| Alarm Adjustment Range | 0 to 100% of full-scale |
| Alarm Accuracy | Within 0.13% of desired value |
| Module Format | Standard 3500 rack module |
| Rack Occupancy | 1 monitor slot plus associated I/O slot |
| Operating Temp | -30 deg C to +65 deg C |
Machinery Signal Processing and Rotor Monitoring
The 3500/42M processes four transducer channels and supports configurable measurement functions through 3500 Rack Configuration Software. Channel pairs can be configured for radial vibration, thrust position, differential expansion, eccentricity, REBAM, acceleration / velocity, shaft absolute, or circular acceptance region measurements.
For proximity-based measurements, the monitor processes the transducer signal according to the configured channel function. Therefore, correct probe type, signal scaling, polarity, and mechanical target relationship must be established before commissioning.
The proximity signal also requires appropriate gap voltage verification. For Bently Nevada eddy-current systems, technicians commonly validate the probe operating point against the specified installation target, including a -10 VDC nominal gap target where applicable to the installed transducer system.
The monitor provides buffered transducer outputs through front-panel coaxial connectors. Consequently, technicians can access the conditioned transducer signal for measurement verification without changing the primary monitoring path.
The monitor also provides recorder outputs from +4 to +20 mA. These outputs represent the configured monitor full-scale range and support connection to external recording or indication equipment within the specified load range.
Frequently Asked Questions (FAQ)
Q: How many transducer channels does the 3500/42M support?
A: The module provides four channels and accepts 1 to 4 proximity, velocity, or acceleration transducer signals.
Q: What alarm parameters can the 3500/42M configure?
A: The module supports programmable Alert levels for each active static value and Danger levels for any two active static values. Alarm adjustment ranges from 0 to 100% of full-scale.
Q: Does the 3500/42M provide direct access to transducer signals?
A: Yes. Each channel provides one front-panel coaxial buffered transducer output with a specified 550 Ohm output impedance.
Field Installation Guidelines
- Install the monitor in the designated 3500 rack monitor slot with its associated I/O module.
- Verify that the installed I/O module matches the required transducer type and system configuration.
- Confirm transducer wiring polarity and signal identification before applying system power.
- Route transducer cables separately from high-voltage power conductors and high-current switching circuits where practical.
- Maintain cable shielding and grounding practices specified for the installed Bently Nevada transducer system.
- Verify the proximity probe mechanical gap and electrical gap voltage before enabling vibration or position alarm functions.
- Confirm the configured measurement range and scaling against the installed transducer characteristics.
- Check buffered transducer outputs during commissioning to verify signal continuity and conditioning.
- Verify recorder output polarity, scaling, and external load before connecting the output to downstream equipment.
- Confirm Alert and Danger setpoints against the approved machinery protection configuration before placing the monitor into service.
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