WOODWARD 1680-622 Single coil Reluctance Speed Sensor (MPU)

WOODWARD 1680-622 Single Coil Reluctance Passive Speed Sensor (MPU)

1、 Product basic positioning
Type: Variable Relevance (VR) single coil passive magneto electric speed probe, commonly known as MPU magneto resistive pickup in the industry, does not require external power supply Woodward
Adapter Controller
Woodward 505/505E (9907-163), 2301A (9905-973), ProTech overspeed protection, MicroNet, TG governor; Simultaneously compatible with Bently 3500 system speed channel and GE Mark V/VI turbine control system
Shutdown status (2026)
The original factory of the 1680-6XX standard thread MPU series has gradually reduced production, while the 1680-622 series has been discontinued and there are no new original factory futures; Market source: Overseas inventory of new machines, dismantled spare parts, and brand new replacements of the same specifications and models 1680-631/1680-649
Safety certification: ATEX Zone2, CSA explosion-proof, can be used in hazardous areas of chemical and power plants; Meets IEC61508 SIL3 safety circuit matching (passive Class A devices, low loss efficiency) Woodward
2、 Model Hardware Specifications (1680-622 Exclusive)
1. Mechanical dimensions and threads
Installation thread: 5/8-18 UNF American standard external thread, matched with locking nut
Effective insertion length: standard short rod type
Tail outlet: Bare wire outlet (optional MS aviation plug model 1680-622-M)
Installation clearance standard: 0.25-1.02 mm (0.010-0.040 inch), clearance between tooth tip and probe end face; Radial runout of gear disc ≤ 0.51mm
2. Electrical core parameters
table
Project parameters
Single coil integrated permanent magnet magnetic circuit with coil structure
DC internal resistance 250 Ω± 10%
Output waveform sine AC, frequency proportional to speed
Minimum effective output (minimum speed) ≥ 1.5 Vrms (standard operating condition with a gap of 0.5mm)
Peak output voltage up to approximately 60Vpp (high-speed operating condition)
Frequency range of 0.5Hz to 25kHz, covering 500-15000RPM units
The target material must be ferromagnetic steel; Aluminum, brass, and non-magnetic stainless steel cannot generate signals Woodward
3. Environmental tolerance
Working temperature: -40 ℃~+150 ℃
Storage temperature: -40 ℃~+150 ℃
Vibration/Shock: Meets the IEC60068 industrial unit vibration standard, suitable for strong vibration environments of steam turbine and gas turbine bases Woodward
Protection: IP65 metal stainless steel shell, resistant to oil, water vapor, and dust
3、 Working principle
The probe is equipped with a permanent magnet and a single induction coil; When the spindle speed measuring gear rotates, the magnetic flux at the probe end changes alternately at the tooth tip/tooth valley, and the coil induces an alternating sine voltage signal:
Signal frequency=number of teeth x rotational speed ÷ 60, the controller converts real-time rotational speed through frequency conversion;
The signal amplitude increases with the increase of speed and the decrease of clearance; Low speed is prone to insufficient signal and speed fluctuations;
Passive design, no built-in electronic components, extremely low failure rate, suitable for long-term unit safety protection circuit Woodward
4、 Core advantages
Passive power free: only two signal lines, no need for 24V power supply, simplifying on-site wiring;
High reliability and long lifespan: no active chips, high temperature resistance, vibration resistance, suitable for long-term continuous operation of turbines;
Explosion proof universal: Install directly in Zone 2 hazardous areas without the need for additional isolation barriers;
Full platform compatibility: Woodward’s entire range of speed controllers, Bentley 3500, GE Mark V/VI can all be directly connected;
Fault safety: The disconnection/short circuit controller directly reports zero speed and overspeed alarms, triggering trip protection.
5、 Directly interchangeable models within the same series (with consistent thread and internal resistance, only differentiated by rod length)
1680-622: Standard Short Rod (this version)
1680-631: Extension rod, deep installation hole adaptation
1680-649: Extra long rod, specially designed for thick walled units with box bodies
All 5/8-18 threads and 250 Ω internal resistance are unified, and replacement does not require modification of controller parameters or wiring.
6、 Standard matching complete set of accessories
5/8-18 UNF locking nut (factory standard);
Dual core shielded coaxial speed measuring cable (single ended grounding of shielding layer control cabinet);
Speed measuring gear plate: standard steel gear plate with modulus ≥ 2;
Optional MS aviation plug adapter component, convenient for frequent disassembly and maintenance.
7、 Typical application scenarios
Turbine/gas turbine speed acquisition, 505/505E speed control closed-loop control;
Unit overspeed ETS protection, ProTech two out of three overspeed monitoring;
Parallel load distribution of diesel/gas generator sets (2301A controller);
Compressor, fan, expander speed monitoring, vibration diagnosis;
Speed detection of power equipment installed in the chemical explosion-proof zone.
8、 Key points for on-site installation and operation and maintenance
Gap debugging: After installation, measure the AC voltage at low speed to ensure that the minimum operating speed is ≥ 1.5Vrms. If the gap is too large, it is easy to lose speed at low speed;
Wiring specification: The speed measurement shielded cable should be independently threaded through a conduit, away from the strong electrical cables of servo power and solenoid valves, to avoid interference and speed jitter;
Fault diagnosis:
No speed signal: probe breakage, non-magnetic gear, excessive clearance;
Speed fluctuation: cable shielding damage, excessive gear jumping, loose probe;
Spare parts replacement: When discontinuing production of 1680-622, priority should be given to using 1680-631 as a substitute with the same specifications, with completely identical threads and internal resistance, and no need for recalibration;
It is strictly prohibited to use non-magnetic aluminum/stainless steel gear discs, as there will be no induced voltage and the controller will not be able to recognize the speed.