Overview
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | Bently Nevada 3500/50M (3500/50) |
| Brand | Bently Nevada |
| Product Type | 2-Channel Tachometer Module |
| Series | 3500 Series Machinery Protection System |
| Operating Temp | -30 deg C to +65 deg C with standard I/O modules |
| Storage Temp | -40 deg C to +85 deg C |
| Relative Humidity | Up to 95%, non-condensing |
| Power Consumption | 5.8 W typical |
| Channels | 2 |
| Transducer Types | Proximity probes or passive magnetic pickups |
| Input Signal Range | +10.0 V to -24.0 V |
| Input Impedance | 20 kOhm standard; 40 kOhm TMR; 7.15 kOhm internal barrier |
| Transducer Supply | -24 VDC, 40 mA maximum per channel |
| Maximum Input Frequency | 20 kHz |
| Full-Scale Speed Range | Up to 99,999 rpm |
| RPM Accuracy | <100 rpm: +/- 0.1 rpm; 100 to 10,000 rpm: +/- 1 rpm; >10,000 rpm: +/- 0.01% of true shaft speed |
| Rotor Acceleration Accuracy | +/- 20 rpm/min |
| Recorder Outputs | +4 to +20 mA proportional to full-scale range |
| Active Load Resistance | 0 to 600 Ohm |
| Buffered Outputs | Front-panel coaxial connector for each channel |
| Output Protection | Short-circuit and ESD protected |
| Output Impedance | 550 Ohm |
| Monitoring Functions | Speed, speed band, zero speed, rotor acceleration, reverse rotation |
| Peak Capture | Maximum operational speed, maximum reverse speed, or total reverse rotations |
| Keyphasor Function | Conditioned Keyphasor signal supplied to rack backplane |
Bently Nevada Mechanical Signal Processing
The 3500/50M processes rotational signals from proximity probes or passive magnetic pickups. Therefore, correct transducer signal amplitude and installation geometry directly affect speed calculation.
For eddy-current probe applications, technicians should verify the probe gap voltage before commissioning. A typical Bently Nevada installation uses a -10 VDC gap-voltage target as a field reference when applicable to the probe and monitor configuration. The actual target must follow the applicable probe system documentation.
The module supports rotor-speed calculations up to 99,999 rpm and accepts input frequencies up to 20 kHz. It also provides rotor acceleration monitoring with an accuracy specification of +/- 20 rpm/min.
Furthermore, the module conditions Keyphasor-related signals and distributes them through the 3500 rack backplane. This allows other rack functions to receive the conditioned timing signal without requiring a separate Keyphasor module for this function.
Frequently Asked Questions (FAQ)
Q: What transducers can the 3500/50M accept?
A: The module accepts proximity probe signals and passive magnetic pickup signals within the specified +10.0 V to -24.0 V input range.
Q: Does the 3500/50M provide a Keyphasor output?
A: Yes. The module conditions Keyphasor signals and supplies them to the 3500 rack backplane for use by other rack monitors.
Q: What should be checked before commissioning a proximity probe input?
A: Verify probe wiring, polarity, signal amplitude, shielding, and physical gap. For applicable Bently Nevada eddy-current systems, technicians commonly validate the gap voltage against the specified installation target.
Field Installation Guidelines
- Install the module in the designated 3500 rack position according to the rack configuration documentation.
- Verify the transducer type before connecting field wiring.
- Maintain correct polarity for proximity probe and magnetic pickup connections.
- Route probe signal cables separately from high-voltage power and high-current switching conductors.
- Use appropriate cable shielding and terminate the shield according to the system grounding scheme.
- Avoid unnecessary cable loops and parallel routing with high-noise electrical circuits.
- For eddy-current probes, verify mechanical clearance and electrical gap voltage before applying operational setpoints.
- Confirm that the transducer supply does not exceed the specified -24 VDC and 40 mA maximum per channel.
- Check buffered-output coaxial connections for secure mechanical engagement.
- After installation, verify measured speed against an independent reference before enabling protection setpoints.
- Confirm recorder-output loop loading remains within the specified 0 to 600 Ohm active-load range.
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