This web site covers just part of Monitran's product range, so if you don’t see what you require please talk to a member of our sales team for details of other Monitran products or our custom build service.
Contact DetailsSome answers to the questions we are often asked -
An accelerometer is an electromechanical device that will measure acceleration forces. These forces could be static, like the constant force of gravity pulling at your feet, or they could be dynamic - caused by moving or vibrating the accelerometer. Accelerometers can be used to measure vibration on cars, machines, buildings, process control systems and safety installations. They can also be used to measure seismic activity, inclination, machine vibration, dynamic distance and speed with or without the influence of gravity.
Mechanical failures may occur without motors and pumps becoming overloaded – hence there may not be a significant rise in temperature or current. However, as most of us know from years of driving, the earliest indication of a problem with a vehicle tends to be audible.
Hence, noise and vibration monitoring are starting to play increasingly important roles in predictive maintenance.
On machine vibration is simply the back and forth movement of machines or machine components. Any component that moves back and forth or oscillates is vibrating. Essentially vibration (whether audible or not) is a form of energy loss, so, if a pump, motor, gearbox, drive train or servo-valve vibrates more than usual then the component is either being overloaded or its sub-components such as bearings and teeth, are probably failing.
Monitoring vibration (this ‘leakage of energy’) is neither as difficult nor as costly as most assume, as vibration sensors and associated signal conditioning hardware are an extremely cost-effective alternative to having equipment fail.
Vibration causes the mass to accelerate
In this type of accelerometer the piezoelectric crystal produces an electrical charge which is connected directly to the measurement instruments. The charge output requires special accommodations and instrumentation most commonly found in research facilities. This type of accelerometer is also used in high temperature applications (>120C) where low impedance models can not be used. This robust device has no moving parts and offers long term stability and reliability. It has a wide frequency and dynamic ranges and signals can be integrated to give velocity and displacement values
The piezoresistive accelerometer similarly depends on the change of an electrical property when a crystal is subjected to a force These tips will help you isolate the most effective sensor types for your task but with such a wide and varied offering we welcome your enquiry to our technical sales team who will enable you to pinpoint the perfect match for the task in hand. On this site we provide one or more icons to indicate the most suitable applications.
What do you need to do?
For vibration analysis and condition monitoring, look to those sensors with an AC or charge output, and for continuous monitoring and machine protection look to those sensors with a DC output.
Which Application are the sensors going to be used in?
Against each accelerometer we provide one or more icons to indicate the most suitable applications.
How will you connect the accelerometer to your measuring system?
Monitran’s sensors either have ‘plug and socket’ connections or are supplied with integral cables.
For many models there is a choice of Top or Side Entry, with the latter having a lower profile and therefore ideal for use when space is at a premium.
Many of our accelerometers are ATEX- or IECEx - approved versions and are suitable for use in flammable gas or dust hazard areas, both in petrochemical and underground environments.
We can supply top or side entry ATEX or IECEx Group 1 sensors for mining or tunnelling environments.
The mounting method will typically be governed by the nature of the machine or structure to which the sensor will be and the permanence of its installation. Bearing this in mind, mounting methods include male studs, female threads, epoxy adhesive or magnetic attachment. The quickfit option ( with a wide range of adapters available ) is particularly useful for sensors with stiff integral cables.
The Graph below gives examples of the different reading you will achieve with various mountings:-
For any given application you need to select a suitable sensitivity and output range. Most sensors have standard sensitivities and ranges, which are given on this site and , but please refer to our datasheets ( which you can download on this site ) for other sensitivity/range options.
Most of our sensors operate in the range 1Hz to a few kHz but if you need to measure seismic vibrations or movements within large structures you will need a low frequency sensor which measures, and produces an output, down to DC (0Hz). For very high speed machines, consider a charge output sensor which, with the right charge amplifier, will respond at very high frequencies.
All sensors have high resistance to liquid penetration with fully submersible to IP68 versions available for deep water applications.
Which temperature range do you need?
Most sensors will work in sub-zero temperatures and most can handle any heat generated by the machinery to which they are attached. For hotter environments we can supply sensors which will operate in temperatures as high as 250°C.
During the past 20 years condition monitoring has evolved as a significant opportunity to make an industry run in a more cost effective way. Vibration Analysis is one the effective condition based maintance technologies. Our sensors can be used to monitor vibration levels on pumps, motors, fans and all other types of rotating machinery. This will in turn enable you to use the data for troubleshooting and fault diagnosis.
In our sensor guide, which you can request by emailing our offices; we have labelled each sensor with an industry symbol to help you identify the best sensor for your particular application. Whilst this list is not conclusive – and your industry requirement may not be ‘featured’ it gives a guide to the full range of applications our sensors could be used,
For further information on the different applications please go through to our Application Page.
All standard monitran accelerometers come with integral stainless steel over braided PTFE twin core cable . This cable has two conductors, (power/signal & common), which are twisted together and provide degree of difference in order to reduce the electrical energy interference. Because we feel this cable offers a good projection from radio frequency interference we feel this, in most applications is the best suited for the sensors connectivity and in particular sensors that are in a permanent situation.
The other main type of cable is a coaxial – this works on an inner conductor and have a shield which acts as the common seal. These cables work well with BNC and Microdot connectors and are recommended for sensors not used in permanent installations.
Please note we do not recommend you use a cable length of more than 10M for charge output sensors (1100 series )
Environment:
Another important consideration is the type of coating the cable. You must be aware of the type of environment you plan to use the sensor in. The jacket material used can project from high and low temperatures, chemicals, radiation and moisture.
To withstand the rigours of internal and external factory and works environments with elevated temperatures, humidity, oil and other chemicals plus rain and cleaning down with high pressure hoses requires a robust cable construction. Monitran’s standard cables use ETFE insulation for high temperature resistance and chemical inertness plus overbraiding with stainless steel mesh to protect against abrasion and wear.
The above cables are used up to 140ºC while perfluoroalkoxyethylene (PFA) insulation allows operation to 260ºC.
For long periods of immersion and operation down to 100m depth an external polyurethane coating over ETFE insulated cores with optional stainless steel overbraiding exhibits excellent water resistance and long life.
For lower temperature operation and less demanding environments like testing laboratories PVC insulated cables are acceptable and economical.
In the above examples the sensors are usually permanently mounted to machinery such that flexibility is not the most important criterion. However, for measurements with portable vibration analysers coiled, stretchable cable with PVC insulation offer convenience and economy.
The performance and reliability of results from vibration sensors depends critically on their electrical connection to the measuring system. Connectors and cables must be selected carefully to ensure optimum data collection, minimum signal interference and suitability for the working environment. Cables may be directly connected to the sensor or via a plug-in connector.
Construction:
Factory environments demand cabling with high levels of noise rejection, protection from external electrical fields and radiofrequency interference. Where possible, cables will be twin-core shielded. The twin cores will be twisted together and carry the power/signal and return signals. However, where cable dimensions are too large to allow connection to small and miniature sensors then single core, screened (coaxial) cables are supplied.
Extension:
Cables to constant current and 4-20mA output sensors can be extended over long distances with no significant effect on signal quality. When connecting large numbers of sensors to a remote control room it is convenient and economic to combine the cables at a junction box and make the onward connection with multi-core cables. Each sensor needs its own pair while a common shield is acceptable.
Charge output sensors, however, have very low level signals and 10m should be regarded as a normal maximum length. Following charge amplification, though, extension may proceed as above.
Connectors
Again monitran accerelerometers are normally supplied with a common 2 – pin military connector. ( MIL-C-5015 ). This is because it has been proofed to be a rugged ,simple and cost effective means of connectivity and is available with a variety of boots and sealing methods for different methods. However we can supply connectors on the end of the cable to work with any electrical connector that your acquisition equipment uses. These include BNC and Microdot.
Monitran can recommend cables/connectors to match the sensor to data collectors - please use the Contact Form and select the correct sensor/datacollector.
To use vibration as a trending tool for condition monitoring a regular programme of data collection is necessary. In order to interoperate and analysis this data some form of acquisition equipment is required ( data collector ).
A data logger is an electronic instrument that records measurements (acceleration, temperature, relative humidity, light intensity, on/off, open/closed, voltage, pressure and events) over time. Typically, data loggers are small, battery-powered devices that are equipped with a microprocessor, data storage and sensor. Most data loggers utilise turn-key software on a personal computer to initiate the logger and view the collected data.
Monitran do not manufacture data collectors – but have built an in-house database that will allow you to select the correct cable and connector in order for you to use our sensors with most collectors on the market. Please use this form to identify the collector you are currently using and the sensor you wish to use and then email the form to us. We will be pleased to advise you on the most suitable cable/connector for this use.
We pride ourselves on manufacturing to order as many items we produce are built to customers’ specific requirements. We also offer a custom-design service where we will construct products that meet the required performance specifications and the environmental conditions. This means it is impossible to carry all our lines at one time in stock so we manufacture every product to order. However, e recognise that many projects require our products quicker than our quoted delivery time ( between 2 – 4 weeks ) and we will always endeavour to help where ever possible.
How an LVDT works The LVDT, Linear Variable Differential Transformer is a well established transducer design which has been used through out many decades for the accurate measurement of displacement and within closed loops for the control of positioning.
In its simplest form, the design consists of a cylindrical array of a primary and secondary windings with a separate cylindrical core which passes thought the centre. (Fig A)
The primary windings (P) are energized with a constant amplitude A.C. supply at a frequency of 1to10kHz.
This produces an alternating magnetic fielding the centre of the transducer which induces a signal into the secondary windings(S&S )depending on the position of the core.
Movement of the core within this area causes the secondary signal to change (Fig B ) .As the two secondary windings are positioned and connected in a set arrangement (push-pull mode), when the core is positioned at the centre, a zero signal is derived.
Movement of the core from this point in either direction causes the signal to increase (Fig C). As the windings are wound in a particular precise manner, the signal out put has a linear relationship with the actual mechanical movement of the core.
The secondary output signal is then processed by a phase-sensitive demodulator which is switched at the same frequency as the primary energizing supply. This results in a final output which after rectification and filtering gives D.C. or 4-20m. A proportional to the core movement and also indicates its direction, positive or negative form the central zero point (Fig D).
The distinct advantage of using an LVDT displacement transducer is that the moving core does not make contact with other electrical components of the assembly, as with resistive types, as so offers high reliability and long life. Further, the core can be so aligned that an air gap exists around it, ideal for applications where minimum mechanical friction is required.
The LVDT design lends it self for easy modification to fulfil a whole range of different applications in both research and industry.
Complete sealing for part or full submersion in liquids and gases, Heavy construction build for tough industrial areas, Miniature and low cost models for price- conscious OEM usage, Internal electronic circuitry eliminating the need for additional instrumentation equipment.
When an AC current flows in a coil in close proximity to a conducting material the magnetic field of the coil will induce circulating (eddy) currents in the material Cracks in a material are one example of a factor that can affect the magnitude of eddy currents and which are therefore detectable by this method. Other factors include:
Conductivity Calibration is conducted at our factory using a ‘back-to-back’ reference accelerometer with a traceable performance to UK National Standards. Both devices are fitted to an electromagnetic vibration system and excited at various frequencies. The accelerometer sensitivity figure is calculated from the measurement of amplitude of vibration and of its output and is specific to the frequency at which measurement is made. If required, we can provide a plot showing the frequency at which measurement is made.
A typical response frequency graph
If required, particularly for research and scientific applications where absolute acceleration intervals. For industrial use, generally changes in vibration level trends are required and recalibration is normally unnecessary. However, with the portable Vibration Meter (VM110/115 ) because of the typical exposure to irregular use and rough handling, we recommend you have this checked and recalibrated annually.
