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Rockwell Automation Publication 1443-TD001D-EN-P - March 2019
1443 Series Accelerometers Specifications
Shield Wire Isolation Sensor and Cable Selection
The 1443 Series include sensor and cable solutions that isolate the shield wire from the sensor or ground the shield wire
to the sensor. For standard sensors, select either shield isolated or shield grounded cables. When a sensor with an integral
cable is required, select a sensor with the shield wire isolated from the sensor or that has its shield wire grounded to the
sensor.
When a shield to sensor isolated solution is required, which is the normal recommended method:
• If a sensor without an integral cable is required, use an accessory cable that has its shield wire isolated from the
sensor connector. Select a cable with ‘IBC’ in its catalog number, for example, 1443-CBL-MS2IBC-32S.
• If a sensor with an integral cable is required, use a sensor with its shield wire isolated from the sensor. Select a
sensor with ‘SI’ in its catalog number, for example, 1443-ACC-GP-T16-SI.
When a shield grounded sensor is required:
• If a sensor without an integral cable is required, use an accessory cable that has its shield wire that is grounded to
the sensor connector. Select a cable with ‘GBC’ in its catalog number, for example, 1443-CBL-MS2GBC-16S.
• If a sensor with an integral cable is required, use a sensor with its shield wire that is grounded to sensor case. Select
a sensor with ‘SC’ in its catalog number, for example, 1443-ACC-GP-T16-SC.
The recommended solution is to connect the shield at the measurement system and leave it isolated at the sensor end. Use
IBC version cables or ‘SI’ version sensors when an integral cable sensor is required. However, when EMI problems are
present or expected, then a shield case grounded solution can prove to be a better design.
When signal noise or interference is a problem or concern, you must understand the source of the problem to resolve it.
Noise can be introduced into signals from accelerometers through these common phenomena:
• Electromagnetic Interference (EMI)
EMI is the introduction of unwanted signals into an electronic device from electromagnetic fields that another
electronic device generated. Televisions, radars, vehicles, variable-frequency drives (VFDs), and other electronic
devices can produce high powered electromagnetic fields. EMI can be introduced into the measurement system via
the signal wiring when that wiring acts as an antenna, which occurs when one end of the wire is ungrounded.
When EMI occurs, it typically results in signals being introduced at discrete frequencies that are related to the
signal source. The impact on measurements is dependent on the magnitude and specific frequency of the signal
that is induced. This occurrence is relative to the measurement systems design signal magnitude and frequency
range and the expected signals that are intended to be measured.
• Ground Loops
In electronics, a ground loop is caused when a device has multiple paths for electricity to flow to ground. In a
measurement system, this scenario commonly occurs when a signal wire is grounded at both ends, with each end
having another potential (resistance) to ground.
The key for accelerometer measurement systems is knowing if the machine case, or bearing housing, to which the
sensor is attached, is grounded or not. While a new machine installation can be isolated, changes are possible over
the life of the machine as wear occurs, maintenance is performed, and other changes are made.
Regardless the source, when present these signals or noise can result in significant error in measurements. The result can
be random and inexplicable machine alarms and trips, erroneous condition assessment / diagnosis, and possible damage
to the instrumentation. If the source of the noise is clear, and there is only one concern, then the corrective action is clear,
depending on the source of the problem, try the following:
