Goniometers are devices that measure angles or allow objects to be rotated in a certain direction. It is an angle-measurement instrument like a protractor, but more particularly built for measuring the angles of bodily joints, faces of crystalline structures and assessment of a wide range of motions and interactions. This article will explore the types and industrial applications of goniometers.
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What are Goniometers?
Goniometers are devices that may either measure an angle or move an item along a fixed point to that angle. Numerous industries rely on goniometers for a variety of purposes. The size and motion range of an object can be measured using goniometers.
Working Principle of Goniometers
Several types of goniometers are now available in the market, and each one has its own working principle depending upon the application.
A typical goniometer comprises two limbs, generally made of plastic or wood, which are joined by a joint and usually linked to a circular piece of the same material, labeled with different angular measurements.
A measurement is shown when one limb moves closer or farther away from the other limb on the circular piece. Depending on the use, goniometers may be built from a variety of materials and have a wide range of sizes.
Types of Goniometers
There are different types of goniometers available for different applications. Their working principle depends on the application for which they are designed.
Universal Goniometers
There are two types of universal goniometers named short arm and long arm. The short arm goniometer is used for smaller joints such as the wrist, elbow, or ankle, while the long arm goniometer is used for joints with long levers such as the knee and hip joints.
Twin Axis Electro Goniometer
Electro goniometers measure joint range of motion or angular displacement electronically. Electro goniometers have one or two potentiometers or strain gauges between two end-blocks.
The potentiometer's voltage output varies with the joint's angle of motion. With the cable connected to compact data-loggers, electro goniometers are portable for data collecting in the workplace or other areas. These data loggers can store a day's worth of data. Electro goniometers are flexible and lighter than accelerometers and gyroscopes.
Inclinometer
A gravity goniometer or inclinometer features one arm with a vertical weighted pointer. It is a sensor that measures the magnitude of an inclination angle or structural deformation. Both percentages and degrees of gravity are used to represent the bend.
When tunneling, excavating, or dewatering, inclinometer sensors are used to gauge the slope's gradient.
Software-based Goniometers
A smartphone as a digital goniometer offers various advantages, including availability, the convenience of measurement, application-based measurement tracking, and one-handed usage. The accelerometers in phones are used in these apps to determine joint angles.
Arthrodial Goniometer
The Arthrodial Goniometer is used for measuring cervical spine rotation, anteroposterior flexion, and lateral flexion.
Applications
Medical experts use goniometers to compare the range of motion in a patient's limb before and after therapy to see whether the treatment is helping the patient's condition.
In painting, goniometers are used to draw a straight line or a completely round circle. Furthermore, goniometers measure the angle of each face in a crystalline structure, which has led to a greater understanding of the atomic structure of a crystal. The industrial applications of goniometers are discussed below.
Crystallography
Goniometers are used in crystallography to measure the angles between crystal faces, to rotate samples in X-ray diffraction, and are used to study the atomic structure of different crystals.
Medical Industry
Goniometers are used by medical professionals to measure the joint’s range of motion. A goniometer is used to determine the presence of muscle, tendon, or joint dysfunction, develop a diagnosis, create therapeutic objectives, evaluate progress or lack thereof, and modify treatment depending on progress.
Smartphone Industry
Smartphone app-based goniometers (SG) are replacing Universal Goniometers (UG) in measuring joint range of motion. SGs are quite accurate in measuring knee flexion and knee error regardless of examiner competence level, hence making it the preferable tool for analyzing knee range of motion in clinical practice.
Material Engineering
Portable PC-based ultrasonic goniometers are used to study the characteristics of a material using ultrasonic waves. Researchers published an article IOP Conference which presents a novel specific software package that can manage a scanner's operation, display the data and evaluate material properties.
Optical goniometers are also used for the optical characterization of materials. Goniometric optical scatter instrument GOSI can be used to analyze low scatter surfaces, including smooth optical mirrors and silicon wafers, using ultraviolet and visible laser light sources.
Future Outlook
Over time, there have been tremendous advancements in the types, working principles and applications of goniometers. Each application requires goniometers to be very accurate in their function.
Lately, smartphone application developers have built mobile applications that provide the features of a goniometer. These applications (such as Knee Goniometer and Goniometer Pro) employ the accelerometers in phones to calculate joint angles.
A recent study certifies these applications and their devices as trustworthy and valid instruments with as much accuracy as a universal goniometer. Advancements in the working principle of goniometers needs to be looked up to make goniometers more reliable to use in medical and other industries.
References and Further Reading
Choi, K.-B., et al. (2021) ‘Kinematic Analysis of a Parallel Manipulator Driven by Perpendicular Linear Actuators’, MDPI [Preprint]. doi.org/10.3390/act10100262.
Du, X & Chen, Q (2021) ‘Dual-Laser Goniometer: A Flexible Optical Angular Sensor for Joint Angle Measurement’, IEEE Transactions on Industrial Electronics, 68(7), pp. 6328–6338. doi.org/10.1109/TIE.2020.2996141.
Mehta, S.P., et al. (2021) ‘Smartphone goniometer has excellent reliability between novice and experienced physical therapists in assessing knee range of motion’, Journal of Bodywork and Movement Therapies, 25, pp. 67–74. doi.org/10.1016/j.jbmt.2020.11.021.
Milani, P., et al. (2014) ‘Mobile smartphone applications for body position measurement in rehabilitation: A review of goniometric tools’, PM and R, 6(11), pp. 1038–1043. doi.org/10.1016/j.pmrj.2014.05.003.
Rezende, A., et al. (2018) ‘Polymer optical fiber goniometer: A new portable, low cost and reliable sensor for joint analysis’, Sensors (Switzerland), 18(12), pp. 1–9. doi.org/10.3390/s18124293.
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