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| Protection Systems |
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| General Resources |
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| XM-120 & 121 Dynamic Measurement Modules |  |
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Introduction |  |
Communications | |
Inputs | |
Tachometer | |
Outputs | |
Indicators | |
Signal Conditioning |  |
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Complex Data | |
Measured Parameters | |
Data Buffers | |
Alarms | |
Relays | |
Max Speed Capture | |
Non-Volatile Configuration | |
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Power | |
Approvals | |
Environmental | |
Physical | |
Ordering Informaton | |
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120 & 121 Dynamic Measurement Modules The XM® series from Rockwell Automation is the world’s first machine monitoring and protection system designed as a distributed network of modules deployed on an open standard industrial bus. The XM-120 (Standard) and the XM-121 (Low Frequency) Dynamic Measurement Modules are intelligent 2-channel general-purpose monitors that support measurements of dynamic inputs such as vibration, pressure and strain. The modules built-in tachometer makes them particularly well suited for monitoring shaft, casing and pedestal vibration in rotating equipment. The two modules are identical except for their high pass filter selections and in that the XM-120 also supports shaft eccentricity monitoring when its alternate XM-120E firmware is loaded. Inputs accepted include eddy current probe, standard integrated Electronics Piezo Electric (IEPE) accelerometer, or any voltage output measurement device such as a velocity or pressure transducer. In addition to vibration inputs, the modules accept one tachometer input to provide speed measurement and order analysis functions. Both modules employ a 24-bit A/D converter which provides unparalleled resolution, making them ideally suited for detecting machinery problems. Virtually any fault that manifests itself through changes in the magnitude or phase of vibration can be detected by the advanced signal processing capabilities of the XM-120 & XM-121 Dynamic Measurement modules. These include most mechanical and electrically induced faults such as unbalance, bearing wear, rotor cracks and rubs, instabilities such as oil whirl, pre-load conditions / misalignment and anti-friction bearing defects. With two 4-20mA outputs and a single onboard relay, expandable to five, and an integral tachometer, the XM-120 and XM-121 modules offer a complete monitoring system in a small, simple, easily installed, easily maintained package. The XM-120 and XM-121 modules can operate stand alone, with no interface to higher-level control systems or interactive user interfaces. They can also be deployed on a standard or dedicated DeviceNet network where they can provide real-time data and status information to other XM modules, PLC’s, DCS and Condition Monitoring Systems. Configuration can be performed either locally or remotely via the DeviceNet network. Local configuration is provided by a simple, intuitive Serial Configuration Utility executing on a PC connected to the modules serial communications port. Remote configuration can be performed from any networked PC executing either any standard DeviceNet configuration software, or the XM specific configuration tool included in RSI’s RSMACC EOL software system. Selecting which module, the XM-120 or XM-121, is appropriate for an application is dependent on consideration of the minimum frequency of interest, the types of sensors applied and any integration requirements. Typically the minimum frequency of interest will be about one third the normal operating speed of the machine, unless it is important to monitor the machines behavior during startup or coastdown. When measuring low frequency vibration it is essential that the sensor used be rated below the minimum frequency of interest. Otherwise the sensor may introduce significant noise possibly resulting in erroneous, or misleading, data. And if the signal must be integrated then special attention to the sensor quality and high pass filter selection must be made to insure the minimum of noise introduced to the system as only a small amount of noise, at low frequencies, can result in a dramatic reduction in the quality and capability of integrated measurements. Specifications
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