3500/42M (Bently 4-channel vibration/ displacement monitoring module with 4-20mA output)

Model: 3500/42M (Common spare part number: 176449-02, Backplane 128229-01)

Brand: Bently Nevada (Bently Nevada)

Series: 3500 Mechanical Protection System (TSI)

Location: Full-height 4-channel multi-function monitoring card, the core vibration/ displacement monitoring unit of the 3500 system, supporting electrical eddy current, speed, and acceleration sensor inputs, with 4-20mA analog output, can be directly connected to DCS/PLC, widely used in turbine, compressor, fan and other rotating machinery protection.

I. Basic Parameters

1. Electrical and Power Consumption

Power Supply: 3500 rack backplane + 5 VDC

Power Consumption: 7.7 W (typical)

Sensor Power Supply: -24 VDC (for eddy current probes)

Input Impedance: 10 kΩ (eddy current / acceleration input)

Analog Output: 4-20 mA (per channel, load 0–600Ω)

2. Measurement Accuracy (Full Scale)

Radial Vibration / Displacement: ±0.33%

1X/2X Vector: ±1%

Thermal Expansion / Thrust: ±0.33%

3. Environmental and Mechanical

Operating Temperature: -30 °C ~ +65 °C

Storage Temperature: -40 °C ~ +85 °C

Relative Humidity: 5%–95% (no condensation)

Dimensions (Height × Width × Depth): 241.3 × 24.4 × 241.8 mm (full-height module)

Weight: Approximately 0.91 kg

Installation: Any full-height slot of 3500 rack (slots 3–15)

4. Status Indicator Lights (Panel)

OK (Green): Module Normal

CH1–CH4 (Yellow): Channel Alarm / Fault

II. Core Functions (4 Channels, Paired Programming)

Can simultaneously monitor 2 sets of parameters (channels 1/2 as one set, 3/4 as another set), supporting:

✅ Radial Vibration (X/Y axis, eddy current probes)

✅ Axial Displacement / Thrust (rotor runout)

✅ Thermal Expansion / Cylinder Thrust: ±0.33%

✅ Eccentricity (shaft bending)

✅ REBAM (bearing wear monitoring)

✅ Acceleration / Velocity (shell vibration, piezoelectric / velocity sensor)

✅ Absolute Shaft Vibration (shaft vibration + shell vibration)

Key Capabilities

Dual-mode Monitoring: Output both steady-state values (peak-to-peak / RMS) and transient waveforms / spectra (for System 1 diagnosis).

4-20mA Output (Core Difference): Each channel independently 4-20mA, corresponding range can be set (e.g. 0–250 μm), directly connected to DCS without additional conversion module.

Programmable Alarms:

Warning (Alert): Can be set for each channel

Danger: Can be set for each channel

Sensor Failure (Not OK): Automatic detection of probe breakage / short circuit

Filtering and Vector Processing: Built-in 1X/2X tracking filtering, notch filtering (filters out power frequency interference), accurately extracting vibration components.

III. Model Code (3500/42M-XX-XX) Table

Section Code Explanation

1 01 Standard input (Eddy Current / Speed / Acceleration)

2 00 Standard logic (no special function)

IV. Differences from 3500/40M

3500/42M: With 4-20mA output, full functionality, 7.7W, for scenarios requiring hard-wired DCS.

3500/40M: Without 4-20mA, basic vibration monitoring, 5.8W, only for System 1 network monitoring scenarios.

V. Installation and Wiring

1. Sensor input (backplane)

Eddy Current probe: Connect CHx IN (+/-), -24V power supply

Speed / Acceleration: Connect CHx IN (+/-), passive

Shielding: Single-ended grounding, away from strong electricity

2. 4-20mA output (backplane)

CHx OUT +/-: Connect DCS analog input card (positive / negative)

Load: ≤ 600Ω, single-ended grounding of shielded line

VI. Configuration Points

Channel pair configuration: 1/2 same function, 3/4 same function (such as 1/2 axis vibration, 3/4 thrust).

Range setting:

Axis vibration: 0–250μm (peak-to-peak)

Thrust: ±2mm

Shell vibration: 0–10mm/s (effective value)

Alarm threshold:

Warning: 70% of the range

Danger: 90% of the range (adjustable)

4-20mA mapping: 4mA = 0%, 20mA = 100% of the range, reversible.

VII. Common Faults

OK light off: Poor contact (plug and unplug clean the gold fingers), configuration error, hardware damage.

Channel failure (CHx flashes yellow): Probe disconnection / short circuit, wiring error, sensor power abnormal.

4-20mA no output: Reverse output wiring, load exceeds limit, output configuration not enabled.

Vibration value drift: Probe gap not appropriate, shielding grounding， strong electromagnetic interference.