Vibration sensors (AC accelerometers)
Vibration sensors - also called AC accelerometers - are used to measure vibrations on rotating machinery such as motors, pumps, gears and fans. The sensors are a central part of modern condition monitoring and predictive maintenance, where vibrations are analysed to detect incipient faults in machines.
At TME Solutions we supply industrial accelerometers from Hansford Sensors, known for their robust construction and reliability in demanding industrial and maritime environments.
Typical applications include monitoring of:
- electric motors
- pumps
- gear
- fans
- compressors
- marine equipment
By installing vibration sensors, faults can be detected early and maintenance can be planned before unplanned downtime occurs.
HS-150 vibration sensor
At TME Solutions, we often use HS-150 accelerometers, which is a shear-type vibration sensor developed for industrial vibration measurements.
The shear design provides a very stable measurement and reduces the influence of temperature variations and mechanical deformation in the machine structure.
Advantages of the HS-150:
- Stable and accurate vibration measurement
- Low sensitivity to temperature changes
- Robust stainless steel construction
- Suitable for permanent installations
- Wide frequency range for vibration analysis
The sensor is typically used for vibration measurement on:
- engines
- pumps
- fans
- gear
IEPE accelerometers (constant current)
AC accelerometers are typically IEPE sensors (Integrated Electronics Piezo Electric).
This means that the sensor is powered via a 2-wire constant current system, where both signal and power are delivered through the same cable.
Typical specifications:
- Power supply: 2-10 mA constant current
- output signal: AC voltage proportional to vibration
- Low impedance output
This makes IEPE accelerometers suitable for:
- portable vibration instruments
- Online monitoring systems
- vibration analysis
Sensor sensitivity (mV/g)
The sensitivity of a vibration sensor is specified in mV/g and describes how much electrical signal the sensor delivers for a given vibration.
For most industrial machines, the following are used 100 mV/g accelerometers, as they provide a good compromise between signal strength and measurement range.
Sensitivity:
Typical application:
10 mV/g
High vibrations
50 mV/g
General machine monitoring
100 mV/g
Motors, pumps and fans
500 mV/g
Very low vibrations
Correlation between mV/g and frequency range
There is often a correlation between Sensor sensitivity and frequency range.
High sensitivity sensors typically contain a larger internal mass, resulting in a lower resonance frequency and thus a lower usable frequency range. Sensors with lower sensitivity, on the other hand, can measure higher frequencies.
That's why we provide 100 mV/g sensors A good compromise between:
- signal strength
- frequency range
- measuring range
This is one of the reasons why this type of accelerometer is standard in many condition monitoring systems.
Top exit and side exit
Vibration sensors can be delivered with different cable outputs depending on the installation conditions.
Top exit
- Cable outlet at the top
- most used solution
- Suitable for motors and pumps
Side exit
- Cable exit on the side
- Used where space above the sensor is limited
Cable or connector
Sensors are available with both Integrated cable or plug connection.
Integrated cable
- robust installation
- High IP protection
- Suitable for permanent installations
Sensor with connector
Typical connector types:
- 2-pin MIL connector
- 4-pin connector
- M12 Industrialisation
Benefits:
- Easy sensor replacement
- Flexible cable length
Sensors can come with different cable types depending on the environment:
- PUR cable
- FEP cable
- silicone cable
- armoured cables
Temperature
Temperature conditions are important when choosing a vibration sensor.
Sensor type:
Temperature:
Standard accelerometer
up to approx. 120°C
High temperature sensor
up to 180-200°C
For high temperature installations, sensors are supplied with Specialised cables and high-temperature designs.
ATEX and IECEx sensors
For installations in explosive environments, accelerometers come with ATEX and IECEx certification.
These sensors are typically used in:
- Oil and gas industry
- chemical industry
- offshore installations
- Dust-filled environments
Installation of vibration sensors
Correct mounting is essential for accurate vibration measurements.
The most commonly used mounting methods are:
Stud mount
The best solution for permanent installations.
Typical mounting threads:
- M8
- M10
- ¼-28 UNF
Other options:
- magnet (temporary measurements)
- mounting pads
- glue
The sensor should be mounted as close to the bearing as possible.
The mounting method has a major impact on the frequency response of the accelerometer.
If the sensor is not mounted rigidly to the machine, a mechanical resonance can occur between the sensor and the mounting. This resonance can amplify vibrations at certain frequencies while reducing the usable frequency range.
That's why we provide stud mounting typically provide the best frequency response and the most accurate measurement result, while magnet mount or handheld probes have a more limited frequency range.
Advice on vibration sensor selection
Choosing an accelerometer depends on a number of factors:
- vibration level
- frequency range
- Temperature
- Mounting
- cable routing
Hos TME Solutions we are happy to help you choose the right vibration sensor for your installation.
- Vibration sensors for industry and marine
- Professional accelerometers from Hansford
- Advice on installation and assembly
Contact us if you need help choosing a vibration sensor.
