The MMS6210, a core component of the epro MMS6000 system, is a dual-channel monitoring module specifically engineered for shaft displacement measurement in rotating machinery. It is capable of measuring parameters such as axial position, differential expansion, and thermal expansion. The module supports inputs from two independent eddy current sensors (e.g., PR 6422/... to PR 6426/... series), features a differential input design with galvanic isolation from the power supply. In single-channel mode, it can monitor axial displacement, radial shaft position, and shaft bend. In dual-channel combined mode, it enables the measurement of minimum/maximum displacement, differential expansion, and thermal expansion in a series configuration (compliant with API 670 standards). It incorporates built-in linearization functionality, suitable for a frequency range of 0–8 Hz (3 dB cutoff) and complex mechanical structures such as rectangular/tapered discs.
Its output and communication capabilities include two 0–10 V dynamic voltage analog outputs (for indication or linkage control), an RS 232 interface for local configuration and data retrieval, an RS 485 communication interface (supporting connection to the epro MMS 6850 analysis system or host computer with Modbus-compatible protocol), and two independent alarm relays (Alert and Danger levels with contact capacity of 48 VDC/100 mA, supporting normally open/closed mode configuration).
For configuration and diagnosis, parameters such as measurement range and engineering units can be set via the RS 232/RS 485 interface, with support for range multiplication (1.0000–4.4999 times). It has built-in sensor self-testing, module fault detection, and password-protected operation levels. Additionally, it can output three selectable harmonic components and phase angles with an adjustable delay time of 1–6 seconds.
Technical Parameters
Parameter Category Detailed Specifications
Sensor Input - Input resistance: >100 kΩ
- Input voltage range: 0–22 VDC
- Frequency range: 0–8 Hz (3 dB)
Sensor Power Supply-Independent power supply per channel: -26 VDC (nominal), max. 35 mA
- Short-circuit/open-circuit protection
Control Input - 24 V logic level, input resistance >10 kΩ
- Supports range multiplication function
Power Supply - Redundant inputs: 18–31.2 V DC (IEC 654-2, Class DC4)
- Power consumption: Max. 6 W (250 mA at 24 V)
Mechanical Characteristics - Dimensions: 100 x 160 x 30 mm (EURO card format)
- Weight: Net 320 g, Gross 450 g
Environmental Conditions - Operating temperature: 0–65°C
- Storage temperature: -30–85°C
- Humidity: 5%–95% (non-condensing)
- Vibration/shock: Compliant with IEC 68-2 standards
Communication Protocol-RS 232/RS 485, supports Modbus-compatible protocol. Up to 31 modules (62 channels) per bus.
Application Fields
Energy and Power: Axial displacement monitoring, differential expansion, and thermal expansion measurement for steam turbines, gas turbines, and hydroturbines.
Process Industry: Shaft position monitoring for compressors, fans, and centrifuges to prevent mechanical failures caused by abnormal displacement.
Safety Systems: Integration into turbomachine protection systems (e.g., ESD) to provide displacement over-limit alarms and support linkage with DCS/SCADA systems.
Typical Applications
Real-time monitoring of axial displacement at shaft ends to identify risks of rubbing between stationary and rotating components.
Measurement of differential expansion in tapered disc configurations via dual-channel series connection, compliant with API 670 requirements for complex machinery.
Output of data to remote monitoring platforms to support predictive maintenance.
Installation and Interfaces
Physical Installation
Mounting Method: 19-inch rack mounting, with each rack accommodating up to 14 modules (28 channels).
Interface Types:
Front panel: RS 232 interface (for configuration).
Rear panel: Terminal blocks for connecting sensors (SENS1/2±), redundant power supplies (+24V/1, +24V/2), alarm outputs (ALERT/DANGER relays), and communication bus (RS 485).
Wiring Key Points
Sensor Connection: Eddy current sensors connect to terminals via dedicated cables, supporting double-ended shielded grounding.
Power and Grounding: Redundant power supplies must be reliably grounded (GND) to avoid common-mode interference.
Communication Network: RS 485 bus requires terminal matching (e.g., 120 Ω resistor) and supports multi-module cascading, with a maximum of 31 nodes per bus.
Configuration and Maintenance
Software Requirements
Operating Systems: MS DOS 6.22 or higher, Windows 95/98/NT 4.0.
Hardware Requirements: 486 DX processor (33 MHz), at least 620 KB RAM, 5 MB hard disk space.
Maintenance Considerations
Online Replacement: Supports hot-swapping. After replacement, configuration parameters must be re-downloaded, and alarm functions will pause for 15 seconds for initialization.
Periodic Calibration: Recommended to verify sensor linearity using standard calibration equipment every six months.
Redundancy Testing: Regularly verify the switching function of redundant power supplies and communication channels to ensure system reliability.
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