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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Channels | 6 |
| Input Types | RTD or Thermocouple (or mixture on non-isolated I/O) |
| Input Impedance | >10 MΩ per lead |
| Power Consumption | 9 W nominal |
| TC Types Supported | E, J, K, T |
| RTD Types Supported | 100 Ω Pt (α=0.00385 or 0.00392), 120 Ω Ni, 10 Ω Cu |
| Recorder Outputs | 4–20 mA per channel (proportional to full scale) |
| Load Resistance (Recorder) | 0–600 Ω |
| Voltage Compliance | 0 to +12 Vdc |
| Front-Panel LEDs | OK, TX/RX, Bypass |
| Typical Accuracy | ±1 °C or better (depends on sensor and range) |
| Operating Temperature | –30 °C to +65 °C |
| I/O Options | Non-isolated RTD/TC or Isolated TC; Internal/External terminations; Internal barriers available |
4. Product Introduction
The Bently Nevada 3500/61 is a six-channel temperature monitor for the 3500 Series Machinery Protection System. It accepts Resistance Temperature Detector (RTD) and Thermocouple (TC) inputs, conditions the signals, and compares them against user-programmable alert and danger setpoints.
Unlike the 3500/60, the 3500/61 provides individual 4–20 mA recorder outputs for each of its six channels. The module is configured via the 3500 Rack Configuration Software and supports mixed RTD/TC inputs on non-isolated I/O modules or channel-to-channel isolated TC inputs. It is the standard temperature monitoring solution for bearings, windings, lube oil and process temperatures on turbines, compressors and other critical machinery.
- 3500/61
- 3500/61
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Channel Not OK | Open or shorted sensor / wrong wiring | ✅ High | Measure sensor resistance or millivolt at I/O terminals | Verify field wiring and sensor type first |
| Incorrect temperature reading | Wrong sensor type configured (RTD vs TC or wrong TC type) | ✅ High | Check channel configuration in rack software | Match software setting exactly to installed sensor |
| All channels high or drifting | Common-mode noise or ground loop (non-isolated I/O) | ✅ Medium | Compare readings with isolated I/O or portable thermometer | Consider TC Isolated I/O module if noise is present |
| Recorder output incorrect | Load >600 Ω or open circuit | ❌ Low | Measure 4–20 mA into known 250–500 Ω load | Check external wiring before replacing module |
| Module will not communicate | Backplane contact or power issue | ❌ Low | Reseat module; verify power supply OK LEDs | Confirm both power supplies online if redundant |
| Intermittent readings after install | Loose Euro-style connector or ESD damage | ✅ High | Reseat connector; inspect for bent pins | Always use ESD strap; torque terminals per manual |
If symptoms persist, capture front-panel LED status, a full diagnostic log from the 3500 Rack Configuration Software, and photos of the I/O module face, then contact technical support.
6. Frequently Asked Questions (FAQ)
Q: What is the difference between the 3500/60 and 3500/61? A: Functionality is identical except the 3500/61 provides individual 4–20 mA recorder outputs for all six channels. The 3500/60 does not.
Q: Can I mix RTD and thermocouple inputs on the same module? A: Yes, on the non-isolated RTD/TC I/O modules. The isolated TC I/O modules accept only thermocouples.
Q: Does it support hot-swap? A: The monitor can usually be removed and inserted with the rack powered, but always follow plant lockout procedures and the specific I/O module guidelines.
Q: Why is the price lower than a factory-new unit from Baker Hughes? A: This is New Original / New Surplus stock—genuine Bently Nevada parts that have never been installed in a running system. Units ship with a 1-year warranty after functional verification.
Q: Will my existing configuration file work after replacement? A: Yes, provided the sensor types and full-scale ranges match. Always back up the current configuration and note the exact firmware revision before swapping.
Q: What accuracy can I expect? A: Typically ±1 °C or better for platinum RTDs over limited ranges. Accuracy depends on sensor type, wiring and full-scale range selected—consult the datasheet for exact figures.
Q: What is the typical lead time and warranty? A: Units are normally in stock for same- or next-day shipment. All modules carry a 1-year warranty against defects in materials and workmanship.
