Metrix Seismic Vibration

Metrix Seismic Sensors

The function of a seismic accelerometer is to measure the change in acceleration resulting from the forces that are working on an object, in our case rotating or reciprocating machines. It's designed to measure the casing vibration of a machine or other structures.

A charge is generated that is proportional to the acceleration resulting from the force that is exerted upon the machine or the structure. In rotating and reciprocating machines, the forces are internal, and we measure the casing motion with accelerometers.

Accelerometers can measure either dynamic or static acceleration. Dynamic acceleration is what we measure on a rotating or reciprocating machine that is vibrating. Static acceleration is more predictable and constant. Gravity is an example of a static acceleration.

The three different types of accelerometers are piezoelectric, piezoresistive and capacitive:

• Piezoelectric accelerometer sensors are quite sensitive and most effective in measuring shock or vibration. Metrix uses these types of sensors because it provides an accurate and wide frequency response.

• Piezoresistive accelerometer sensors are less sensitive and raise their resistance in response to the pressure they experience.

• Capacitive sensors measure changes in electrical capacitance to measure the acceleration of an object.

METRIX SEISMIC TRANSMITTERS

Seismic transmitters provide a 4-20mA DC signal output proportional to the vibration amplitude, and are ideal for applications where a PLC, DCS, or other automation system will be used instead of a stand-alone vibration monitor.

Metrix offers seismic transmitters with a wide variety operating temperatures, frequency responses, scale factors, case materials, connector types, mounting options, and hazardous area approvals.

METRIX SIGNAL CONDITIONERS

Seismic signal conditioners are designed to accept an input from (and provide power to) a seismic sensor. They convert the signal to a proportional 4-20mA DC signal that can be used as an input to process control instrumentation such as a PLC or DCS. They provide additional convenience features such as optional displays, BNC connectors to access the dynamic sensor signal, and bandpass filtering.

This process of conversion is called a transfer function. This goal is to make the input signal into a workable output signal. One good example of this is in the case of a temperature gauge for a system. While it measures the temperature of the functioning system, the measurement must be converted to an electrical signal to be input into a control system.

Metrix offers seismic signal conditioners that can accept either acceleration or velocity sensors and are available with or without an integral display.

Seismic Equipment Accessories

Seismic accessories include bushings, mounting adapters, junction boxes, conduit fittings, cable assemblies, and other items used when installing sensors, transmitters, and signal conditioners. These accessories provide environmental protection from dust, moisture, and corrosion, robust mechanical protection from the rigors of industrial use, and facilitate professional installation where wiring can be properly terminated, routed, and labeled.