595 Old Willets Path, Hauppauge NY. 11788 - Ph: 631 582 5600 Fax: 631 582 5671 - info@spectronsensors.com
Home | Company Profile | Inclinometers | Tilt Sensors | Signal Conditioners | Tilt Switch | Gyro Erection Switches | Contact

Tilt Sensor Primer

Glossary of Engineering Terms


NEW - Low Cost - 3 Axis Iclinometer


Spectron shares in success as Huygens probe makes triumphant landing on Titan!


Tilt Sensor and Inclinometer Primer, September 2004
Magazine Archive


Man Lifts
More Applications

Spectron FTP Site
Target Applications
Man Lifts
Crane Safety Systems
Wheel Alignment Systems
Crawler Drills - Mining
RV (Motorhome) Leveling Systems
Standby Instrument Systems
Boom Lifts
Telescoping Handlers (Telehandlers)
Satellite Antennas
Construction Lasers
Automobile Security Systems
Geotechnical - Soil Subsidence
Motor Graders (Road Graders)
Passenger Boarding Bridges (Jetways)


Manlifts, Scissor Lifts, and Aerial Work Platforms

Manlifts, Scissor Lifts, and Aerial Work Platforms are used to perform numerous tasks, both indoors and outdoors. The come in various sizes and configurations, in both electric and fuel powered versions. What they all have in common is that they use a Tilt Sensor or Tilt Switch (commonly referred to as a 'level sensor' in this industry) as part of their safety system to prevent 'tip-over'. This can occur when the equipment is not on level ground and/or is supporting a heavy load.

Traditionally, this application has been served by companies who produce crude electro-mechanical switches. This technology utilizes a pendulum, whose movement is damped by silicon fluid. This approach is antiquated, and only signals once an unsafe condition has been reached. In addition, they also incorporate a delay function to prevent false triggering. This has prompted the manufacturers to place a sticker on the outside of the device to avoid liability in case of an accident.
This application can be readily satisfied by either of three superior Spectron products:

  • TAD II Threshold Angle Detector
  • SPECTROTILT™ Dual Axis Inclinometer
  • SP Series Dual Axis Electrolytic Tilt Sensor

    The TAD II provides switching (open collector) type outputs, and readily replaces the electro-mechanical pendulum devices commonly used. The SPECTROTILT™ II Dual Axis Inclinometer, which has variable DC outputs, has more distinct advantages. The DC output can be interpolated to not only alarm when required, but to also indicate approaching unsafe conditions. The SP Series Dual Axis Electrolytic Tilt Sensor can also serve this application well, and is the obvious choice for the OEM.
  • Crane Safety Systems
    (Boom Angle Measurement, Safe Load Indicators, Load Moment Indicators)

    Cranes of various types and sizes are employed daily, to accomplish numerous lifting jobs worldwide. Unfortunately innumerable accidents have occured, many of which were fatal, which involved the crane falling or tipping over under load. Subsequent investigations into the root cause of these accidents have yielded various conclusions. Regardless of the actual cause, it is generally acknowledged that if the
    operator had received some type of warning of the impending accident, the majority of them could and would have been avoided.

    To eliminate these types of accidents from occurring, manufacturers developed safety systems. Known in the industry as 'safe load indicators' or 'load moment indicators', these sophisticated systems are capable of monitoring numerous crane variables. One of the most essential and critical measurements required to make these systems
    effective is boom angle, which typically has a range of 0-90 (+/-45) degrees maximum. This is accomplished using an inclinometer (or tilt sensor), and is a classic application for these devices.
    The majority of other manufacturers' inclinometers commonly used to measure boom angle, fall into one of the following categories. Some perform well in terms of linearity, but have relatively large temperature coefficient errors (silicon based). Others perform well in both linearity and temperature, but have poor repeatability and/or hysteresis (potentiometer / pendulum technology), or vice versa. The typical stated accuracy's of these type sensors range from +/-1.5 to over +/-3 degrees.

    With boom angle changes in the fractions of a degree equating to dramatic changes in the actual working load on the crane, the need to reduce or eliminate these errors is apparent. Spectron recognized this need in the industry for a rugged, cost effective, high performance tilt sensor, and developed the SPECTROTILT™ RS232 Electronic Inclinometer. By employing on-board linearity correction and temperature compensation, intrinsic errors have been eliminated, thereby improving accuracy to < +/-0.3 degrees over a +/-60 degree angular sensing range. The SPECTROTILT™ also features a proprietary, glass/ceramic hybrid sensing element, full ESD and EMI protection, an aluminum housing, and a fully potted electronics to provide superior environmental protection.
    Back to Top

    Wheel Alignment Systems

    In its most basic form, a wheel alignment consists of adjusting the angles of the wheels so that they are perpendicular to the ground and parallel to each other. The terns used in the automotive industry to describe the angular position of the wheels are Camber, Caster and Toe-in. The camber and caster angles are referenced to the gravity vector, which makes them an ideal application for measurement using a tilt sensor or inclinometer.

    The required angular measurement range for both camber and caster in most wheel alignment systems is normally +/-7 degrees (+/-10 degrees maximum). With these angles being perpendicular to each other, and the limited angular sensing range, this is an ideal application for the SP Series Dual Axis Tilt Sensor, and/or the SPECTROTILT™ IIDual Axis Electronic Inclinometers. For manufacturers who require higher accuracy, the SPECTROTILT™ (single axis) Electronic Inclinometer is the logical choice. The variety of input/output options and mechanical configuration will allow easy interface/retrofit into most existing systems, while durable construction completes the overall package.
    Back to Top

    Crawler Drills - Mining

    Crawler Drills, also known as Blast Hole Drill Rigs, are used extensively in the mining, quarry and construction industries. They are primarily employed for surface drilling and/or 'drill and blast' tunneling tasks, usually through solid rock. Working under a Geologists direction, these rig operators drill blast holes up to 100 feet deep, at precise coordinates, to accept explosive charges. If the charge is not properly positioned, the rock which is separated is either too large (thereby requiring secondary processing), or worse yet, fragments into small unusable pieces.

    Regardless of the exact application, the need to precisely position the drill mast, and hence the blast hole, is paramount. Where the bottom of the blast hole will end up inside the rock face, is a function of the angle of the drill mast (X and Y) and the depth from the surface. The drill mast angle is normally measured using two single axis inclinometers, mounted perpendicular to each other. The required measurement range is typically +/-45 degrees maximum, with an accuracy of less than 3 degrees acceptable. Although dual axis inclinometers are available which can meet the angular measurement range, few if any can meet the accuracy requirement, particularly at the measurement range extremes.
    This is an excellent application for the SPECTROTILT™ Electronic Inclinometer. Not only can it meet the measurement range and accuracy requirements, its rugged packaging, hermetically sealed sensing element and potted electronics are an attractive feature, considering the working environment.

    One big concern in this type application is vibration, which can be severe during the actual drilling process. This will cause large sensor output variations. Although most operators simply set the drill mast angle prior to drilling (little or no vibration present), some prefer to do active monitoring during the drilling process, as the drill may tend to 'walk'. Increasing the viscosity of the electrolyte in the sensing element will dampen vibration sensitivity, and most readily solves this problem.
    Back to Top

    RV (Motorhome) Leveling Systems

    Recreational Vehicles (RV's) have evolved from mere family vacation transportation, into virtual 'homes-away-from-home' on wheels. They are fully equipped with the latest in creature comforts for short trips, lengthy vacations and full timing. Once the final destination has been reached, it is important that the RV be leveled for safety and functionality.

    A number of companies have emerged over the years, which design and manufacture 'leveling systems'. These systems consist of hydraulically actuated jacks positioned near the front and rear corners of the body, a level sensing unit and a display/controller. Models span the range from manual operation, to fully automated systems that level the RV at the touch of a button.
    Regardless of overall system complexity, in order to perform the leveling task consistently, it is imperative to accurately measure the attitude of the vehicle. This is achieved using a dual axis tilt sensor, and is a classic application.

    Spectron serves this application with the SP Series Dual Axis Electrolytic Tilt Sensor. The SP sensor meets or exceeds all the application and specification requirements, is very cost competitive and generally performs better than comparably priced devices. The fact that the sensor is hermetically sealed eliminates any fluid leakage concerns. The 5-pin interface facilitates easy mounting/soldering to the host circuit board, while the peripheral conditioning circuitry required is very inexpensive to add to the host circuit board.
    Back to Top

    Standby Instrument Systems

    Electronic Standby Instrument Systems are an integral part of aircraft safety systems. In case of an electronic or mechanical failure of the primary instruments, these standby systems provide the necessary information to help the pilot navigate and safely land the aircraft.

    Originally, these standby systems utilized mechanical spinning gyro attitude indicators, which required regular overhauls by skilled technicians. As airlines and airframe manufacturers looked to reduce maintenance costs, they turned to the avionics manufacturers to develop a more costeffective alternative. The result was the emergence of standby instrument systems that use internally mounted solid state rate sensors and accelerometers, which virtually eliminate all regularly scheduled maintenance. Compact, light, repeatable and reliable, these standby systems are capable of displaying such data as airspeed, altitude, heading and other navigational information, as well as attitude.
    Like their predecessor, these standby attitude indicators must go through an 'initial alignment' when the aircraft is first powered up. This is an internal calibration process involving the rate sensors and accelerometers. In order for this calibration to be accurate, the attitude (pitch and roll) of the aircraft during alignment must be precisely measured and accounted for. This is typically done with a tilt sensor, and is an excellent example of an application where accuracy and high reliability are paramount.

    Spectron currently serves this market with the SH50056 Series Ceramic Electrolytic Tilt Sensor. For many avionics manufacturers it has become the sensor of choice. The accuracy and long-term stability provides unrivaled performance. The compact size is ideal for this space restrictive application, while the factory 'reference surface' eases installation alignment concerns. The extended operating temperature range of -54 to +125 degC, and hermetically sealed construction afford superior environmental protection.
    Back to Top

    Boom Lifts

    Boom lifts, both telescopic and articulating, are primarily used for jobs that require high reach capability, or for reaching up and over machinery, equipment, and other obstacles. Able to extend up to 150 feet high and rotate a full 360 degrees, these versatile machines enable the operator to maneuver forward or backward, steer, raise/lower or extend the boom arm, all from the work platform (basket) itself. This is all done while keeping the work platform level and stable.

    While in service, these boom lifts will be required to carry various payloads in all types of terrain. The actual working load on the boom itself is dependent upon the angle of the boom, and how far it is extended (telescoped). The attitude of the chassis is also relevant.

    This gives us three distinct applications for an inclinometer and/or tilt sensor;

  • work platform angle
  • boom angle
  • chassis attitude

    The work platform angle does not require a large angular measurement range being a leveling application, but does require high accuracy. The SPECTROTILT™ Electronic Inclinometer is a great choice for this application. The various input/output configurations offer numerous interface options. The SPECTROTILT™ having a hermetically sealed sensing element, full ESD and EMI protection, an aluminum housing, and a fully potted electronics also provides exceptional environmental protection

    The boom angle application is virtually the same as in a Crane Safety System, whereas changes in the fractions of a degree can equate to dramatic changes in the actual working load, leading to a 'tip-over' situation. This application is best served by the SPECTROTILT™ RS232 Electronic Inclinometer. Please see the 'Crane Safety Systems' Applications Note for further details. The chassis attitude application is nearly identical to a manlift, whereas the exact angle of the chassis is not important, only that it remains within a certain angular limit from level. This application can be readily satisfied by either of three Spectron products:

  • TAD II Threshold Angle Detector
  • SPECTROTILT™ II Dual Axis Inclinometer
  • SP Series Dual Axis Electrolytic Tilt Sensor.
  • Back to Top

    Telescoping Handlers (Telehandlers)

    Telescoping Handlers (aka 'telehandlers'), are a workhorse of the construction industry. The compact nature of these machines, combined with their lifting capacity/versatility and rough terrain capabilities, also makes them ideal for countless other duties outside of the construction realm.

    A telehandler is basically a small mobile crane with a telescopic boom, designed to operate on rough terrain. Hence, the familiar problem of 'tip-over' is a fundamental concern. Many manufacturers use weighted (filled) tires to provide ballast, which helps combat the issue. However, this will not give a warning, nor prevent an accident from occurring if the conditions are present. Some manufacturers have acknowledged the severity of this problem, and introduced safety systems into their telehandlers.

    Two factors, which can contribute to 'tip-over' are cab attitude and boom angle. Both of these variables are most easily measured using an inclinometer. For cab attitude, both the pitch and roll axis' (X and Y) will need to be monitored, typically not exceeding a +/-30 degree maximum range. This a near ideal application for the SPECTROTILT™ II Dual Axis Electronic Inclinometer. Where the daily working environment and the packaging are a concern, the SPECTROTILT™ Ratiometric Electronic Inclinometer (single axis) will do the job.
    The boom angle has the same characteristic effect as it does on a normal crane, whereas fractional changes of a degree can equate to dramatic changes in the actual working load. The relatively long reach of the boom (when extended) compounds this effect, especially at or near level. The normal working range of the boom is 0-90 degrees. This is an excellent application for the SPECTROTILT™ Electronic Inclinometer. The packaging features such as a hermetically sealed sensing element, full ESD and EMI protection, an aluminum housing and fully potted electronics provide superior environmental protection. With the long-term exposure to the elements that a sensor in this type application will have to endure, these features are significant.
    Back to Top

    Satellite Antennas

    The systems used to broadcast and receive signals from and to satellites are both complex and impressive. Depending upon the exact application, the type of antenna system needed, can vary widely. For fixed earth station applications, the antenna is simply pointed at the appropriate satellite, and locked in place. However, for mobile applications such as Satellite News Gathering (Vans) and Flyaway systems, the dynamic of accurately aligning the antenna with the appropriate satellite each and every time becomes critical. Errors in the order of fractions of a degree can cause signal degradation, loss, or failure to acquire a signal. To accomplish this task reliably, companies have developed what are known as antenna positioner/controllers. These are electronic devices, which use various sensors to measure, then automatically adjust the antenna to the proper azimuth (deviation from true north) and elevation (slope angle) positions required. The elevation angle is normally measured using an electronic inclinometer, with a minimum measurement range of 0-90 (+/-45) degrees. Spectron proudly serves this market with the SPECTROTILT™ Electronic Inclinometer. The SPECTROTILT™ has distinct advantages over the electronic inclinometers from other manufacturers who have traditionally supplied this market. They use plastic housings, and do not have sealed sensors and/or electronics, leaving them vulnerable to the environment. The SPECTROTILT™ on the other hand has a rugged aluminum housing, ermetically sealed sensor, and fully potted electronics providing superior protection. In addition, the RS232 version provides an absolute accuracy of +/-0.3 degrees, which is typically 10X more accuate than competing devices.
    Back to Top

    Construction Lasers

    Construction Lasers are used extensively in the building, general construction and civil engineering industries. They are the perfect tools for leveling, grading, aligning and positioning for exterior, interior and underground work. For layout, these devices allow workers to accurately measure and align forms, footers and foundations. For building construction, interior lasers allow for the positioning of ceilings, finished floors and interior walls accurately and quickly. And for underground utilities, pipe lasers allow for the accurate alignment of pipe work even in the harshest of environments.

    In order for these lasers to produce a properly positioned beam/target, they must first have an accurate reference to true level. Realizing that these lasers are used to project beams over long ranges, relatively minute leveling errors at the instrument will equate to large absolute beam positional errors, which will continue to increase with distance (example: 5 arc-seconds = 1/32" error @100 ft.). Hence the need for an accurate, repeatable and reliable true level reference. This application is commonly fulfilled by use of a high accuracy 'tilt sensor'
    Depending on the exact type of laser, the quantity of tilt sensors required will vary. For pipe lasers, which simply project a beam in one plane for sloping purposes, only one is needed. For interior (rotating) lasers, which can project a 360o beam, two are required. Some lasers combine multiple functions, and will require three.

    Spectron proudly supplies this market with both the RG Series and SH Series Electrolytic Tilt Sensors. The RG Series sensor is by far the best performing, providing repeatability, and stability, which exceeds industry requirements. The SH50054 or SH50055 Ceramic Sensors are a cost effective alternative, and offer easy mounting.
    Back to Top

    Automobile Security Systems

    Automobile theft is an everincreasing problem worldwide. In the United States alone, a reported 1.3 million vehicles were stolen in 2002, according to FBI statistics. To combat this trend, automobile manufacturers and after-market suppliers have developed sophisticated anti-theft systems.

    When first introduced, these systems consisted of mostly electro-mechanical 'deterrents', many of which were easily bypassed or disabled. As technology advanced, they evolved into fully integrated microprocessor based systems, using multiple electronic sensors for event detection. These sensors range from ultrasonic intrusion (glass breakage), to motion detectors (internal and external), to tilt sensors. The tilt sensor is used to detect whether the vehicle is either being jacked up, towed, or somehow disturbed.
    A tilt sensor, which will be successful in supplying this type application, must meet specific performance and 'other' criteria. In terms of performance, it must be dual axis, have a measurement range of +/-30 degrees minimum, an operating temperature range of -40 to +85 degC, and have a relatively stable output when in a static state.

    Spectron can supply this market with the SP Series Dual Axis Electrolytic Tilt Sensor. The SP sensor meets all the normal application/specification requirements, and is extremely cost competitive. The fact that the sensor is hermetically sealed eliminates any fluid leakage concerns, which is of prime importance to manufacturers. The 5 pin interface facilitates easy mounting/soldering to the host circuit board, while the viscosity of the fluid inside the sensor can be altered to eliminate false alarms due to passing trucks, thunder, and other benign disturbances.
    Back to Top

    Geotechnical - Soil Subsidence

    The use of tilt sensors and electronic inclinometers within the geotechnicalmonitoring world has existed for many years. These applications range from bridge structural monitoring, to measuring dam deformation, to building monitoring during adjacent construction. Many other specific applications also exist, all centered around structural, foundation and/or ground stability monitoring.

    One application, which utilizes electronic inclinometers extensively, is known as soil subsidence. This involves monitoring slopes and landslides to detect zones of movement, and to provide settlement profiles. This will require the inclinometers to be mounted in both the vertical and horizontal planes respectively. This is how it works.

    Once the area to be monitored is identified, an inclinometer casing is installed. This is a special purpose, grooved pipe used to properly locate the inclinometer to obtain subsurface measurements. It is typically installed in boreholes, but can also be embedded in fills, cast into concrete, or attached to structures. These casings provide not only access, but also accurate reference surfaces for probe type (portable) and for in-place (permanent) inclinometers.
    Once the casing is installed, an initial survey is taken, which establishes the profile of the casing. Subsequent surveys reveal changes in the profile of the casing if movement has occurred. These movements, which are typically minute, require highly accurate and repeatable measurements.

    Most companies involved in the geotechnical monitoring market prefer to construct their own electronic inclinometers, as the physical shape, packaging, and cost are of prime importance. However they still require tilt sensors to make them work. Spectron has proudly served this market successfully for many years with the SH50056 and SH50058 Series Ceramic Electrolytic Tilt Sensors. These tilt sensors provide the accuracy, resolution and long-term stability required for this demanding application, while costing considerably less than competing technologies such as vibrating wire and force balance based devices. In addition, the compact size and hermetically sealed construction are a big plus, and will be key selling points when speaking with the customer.
    Back to Top

    Motor Graders (Road Graders)

    Motor Graders (aka Road Graders) are widely used in the construction of roads, railway beds, airport runways and commercial building sites. They are instrumental in producing smooth consistent surfaces, either level or graded. Highways which appear level to the naked eye, are actually graded at a slight angle, to promote and guide 'runoff'.

    The uniformity and slope of the finished surface relies solely upon the systems used to control the angle of the blade on the Motor Grader. These are known as 'automatic blade controllers', During the grading process these systems monitor the blade angle, and make corrections by actuating hydraulic cylinders. The angle of the blade has traditionally been measured using a single axis inclinometer, with an angular measurement range not exceeding +/-45 degrees.
    Spectron can exceed all the requirements of this application with the SPECTROTILT™ Ratiometric Electronic Inclinometer. The wide single ended DC voltage input range, and output, make it ideal for interface into most existing systems. The packaging features such as a hermetically sealed sensing element, full ESD and EMI protection, aluminum housing and fully potted electronics provide superior environmental protection. With the longterm exposure to the elements that a sensor in this type application will have to endure, these features are vital.

    With vibration being a major concern in this type application, Spectron provides a big advantage. The viscosity of the fluid within the sensing element can be altered to dampen the response, virtually eliminating vibration sensitivity. This feature, coupled with the exceptional packaging makes the SPECTROTILT™ a natural choice.
    Back to Top

    Passenger Boarding Bridges (Jetways)

    Air travel, whether for business or pleasure, is something the majority of us will do numerous times in our lives. While most of us will remember details of the actual flight, few will remember boarding the aircraft. As you descend down the ramp to board, you are on what is known in the industry as a 'passenger boarding bridge', or 'jetway' as they are commonly referred to.

    In recent years, the airline industry has become extremely competitive, forcing airlines to utilize every asset to their fullest. To make full utilization of an individual terminal, these jetways must be able to service different types and sizes of aircraft, which in turn gives the airlines maximum scheduling flexibility. In order to do this, the jetway must be able to adjust to different aircraft heights, while keeping the mating floor area level for safety purposes.
    Flight 'turn around time' is also another area of concern. To deplane and board passengers as quickly as possible, 'dual boarding bridges', also known as 'over the wing' bridges, are becoming more commonplace. These allow passengers to board from the front and rear simultaneously. Although much quicker for boarding purposes, they present a two-fold challenge in terms of keeping the mating floor areas level.

    The sensor of choice for this application is the Spectron TADII - Threshold Angle Detector. When installed into a jetway system, it detects whether the floor is level within a predetermined limit (normally +/-1 degree). If in excess, the output triggers the system to automatically adjust the level of the floor in the proper direction, via hydraulic or electro-mechanical actuators. The open collector outputs of the TADII are easily interfaced into most PLC based systems, or can be used to directly drive solenoids and/or relays.
    Back to Top
    Home | Company Profile | Inclinometers | Tilt Sensors | Signal Conditioners | Tilt Switch | Gyro Erection Switches | Contact