Key Technical Specifications

• Probe Diameter: 8mm (0.315 in), standard for general-purpose vibration monitoring.
• Sensitivity: 3.94 V/mm (100 mV/mil), industry-standard scaling for 3300 XL systems.
• Linear Range: Typically 2mm (80 mils) total, with optimal linear region 0.25–2.3mm.
• Frequency Response: 0–10 kHz, captures sub-synchronous through blade-pass frequencies.
• Temperature Rating: Probe/Cable -51°C to +177°C; Pre-driver -35°C to +85°C.
• Thread Size: 1/4-28 UNF (verify with your mounting bracket; some use M10x1).
• Cable Type: Standard (non-armored) with ClickLoc connector; 5.0m length indicated by “50”.
• Target Material: Must be ferromagnetic or conductive; non-conductive coatings cause signal loss.
• Gap Voltage: Target -10.0 VDC ±0.2V at static installation (50 mils / 1.27mm gap).
• Shielding: Triple-shielded cable to reject EMI from VFDs and motor leads.

 

Product Introduction

I’ve replaced more Bently probes than I can count, and the 330104-00-02-50-02 is the bread-and-butter sensor for turbine and compressor monitoring. It’s an 8mm eddy current probe that measures shaft motion without touching it, converting the gap change into a voltage the 3500 rack can interpret. When this probe fails, you get false alarms or, worse, miss a real bearing wipe.Engineers trust this specific 330104 configuration because the 3.94 V/mm sensitivity matches the factory calibration on most 3300 XL pre-drivers. But don’t get complacent. I’ve seen techs install these with the wrong thread adapter and strip the housing, or ignore the gap voltage and wonder why the vibration reading drifts in summer. This probe is precise, but it demands respect for installation torque, target surface finish, and proper grounding. Do it right, and it’ll outlast the machine.

Quality SOP & Tech Pitfalls

The Lab Report:
We don’t just eyeball these. Every 330104-00-02-50-02 gets the full workup:

1. Visual & Connector Check: Inspect the ClickLoc connector for bent pins or corrosion. A single bad contact causes intermittent signals.
2. Gap Voltage Test: Mount on a calibrated test stand, set to 50 mils, verify output is -10.0 VDC ±0.2V. Anything outside that range is out of spec.
3. Linearity Sweep: Move the probe in 0.1mm increments across the linear range. Plot voltage vs. gap; deviation >1% means the coil is damaged.
4. Cable Continuity & Shield: Megger the shield to ground. High resistance or opens = EMI pickup in the field.
5. ESD & Clean Packaging: Sealed in anti-static bag with desiccant. Moisture in the connector is a silent killer.

The Engineer’s Warning:
Never use Teflon tape on the probe threads. I’ve seen it shred and jam in the housing, making removal a nightmare. Use only the specified thread sealant or dry-fit with proper torque. Also, always verify target surface condition. A scratched, pitted, or coated target will cause signal distortion that looks like vibration but is actually measurement error. And don’t forget the locknut. I’ve had a probe back out during startup because someone hand-tightened it and called it good. Torque to 1.7–2.3 N·m with a calibrated wrench.

 

Installation & Configuration Guide

1. Pre-Installation: ⚠️ LOCKOUT/TAGOUT. Verify shaft is stationary. Take photos of the old probe’s orientation, cable routing, and gap voltage reading. Clean the mounting hole with compressed air; no metal shavings allowed.
2. Removal: Disconnect the ClickLoc connector before unthreading. Use two wrenches: one on the probe body, one on the locknut, to avoid twisting the cable.
3. Installation: CRITICAL: Set the gap voltage to -10.0 VDC ±0.2V before locking. Thread the probe in until it touches the shaft, then back out while monitoring the pre-driver output. Stop at -10.0 VDC. Torque the locknut to spec while holding the probe stationary. Recheck voltage after tightening; if it shifts >0.2V, redo it.
4. Power-On & Testing: Restore power to the 3300 XL pre-driver. Verify gap voltage is stable. Run the machine at low speed and check the vibration waveform for symmetry. Asymmetry indicates improper gap or target damage.

Compatible Replacement Models

• 330104-00-02-50-02: ✅ Drop-in Replacement. Exact match for 8mm, 3.94 V/mm, 5.0m cable. Verify thread size (1/4-28 UNF vs M10x1).
• 330104-00-02-10-02: ⚠️ Cable Length Difference. 1.0m cable instead of 5.0m. Only use if cable run is short; longer cables add noise.
• 330105-00-02-50-02: ❌ Reverse Thread. Left-hand thread for specific mounting brackets. Do not interchange unless your bracket explicitly requires it.

 

Frequently Asked Questions

Can I use this probe with a non-Bently pre-driver?
Technically yes, if the pre-driver accepts -24VDC input and 3.94 V/mm sensitivity. But I’ve seen mismatched pre-drivers cause offset errors or saturation. Stick with 3300 XL pre-drivers unless you’ve validated the entire signal chain.Why is my gap voltage drifting with temperature?
Eddy current probes are temperature-sensitive. The -10.0 VDC setpoint is for 25°C. At 100°C, the voltage may shift by 0.5–1.0 VDC. This is normal; the 3500 system compensates via zero-shift. But if the drift is erratic, check for cable damage or connector corrosion.How do I know if the target is bad?
Run a slow-roll plot. If the waveform shows consistent spikes at the same shaft position, the target is likely damaged or has a keyway/phasing mark in the sensing area. Also, check for non-conductive coatings; paint or rust will kill the signal.Can I extend the cable with a standard extension?
No. Bently cables are impedance-matched and shielded. A generic extension will cause signal reflection and noise. Use only Bently-approved extension cables with ClickLoc connectors.What’s the max cable length?
Standard is 5.0m for this model. You can extend to 9.0m total with an approved extension cable, but beyond that, signal degradation becomes a real risk. If you need longer runs, consider a 330180 pre-driver mounted closer to the probe.Is the 330104-00-02-50-02 still manufactured?
Yes, but Bently has introduced the 330104-00-02-50-02-A revision with improved shielding. The -A is backward compatible and recommended for new installations in high-EMI environments. Always verify the exact suffix when ordering.