Force And Torque Measuring Devices Pdf
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Measurement of Force and Torque and pressure Standards www. This reaction may be in the form of a tensile force pull or it may be a compressive force push. Force is represented mathematically as a vector and it has a point of application. Therefore the measurement of force involves the determination of its magnitude as well as its direction. The measurement of force may be done by any of the following two methods.
Any unknown force may be compared with the gravitational force ma on the standard mass 'm'. The values of 'm' and 'a' should be known accurately in order to know the magnitude of the gravitational force. The other masses can be compared with this standard with a precision of a few parts in On the other hand, 'a' is a derived quantity but still makes a convenient standard. Its value can be measured with an accuracy of 1 part in Therefore any unknown force can be compared with the gravitational force with an accuracy of about this order of magnitude 6.
The direction of force is parallel to that of the gravitational force, and hence only its magnitude needs to be determined. The constructional details of an analytical balance is as shown in Fig. W1 is an unknown force and W2 is the known force due to a standard mass.
Point G is the center of gravity of the balance arm, and WB is the weight of the balance arm and the pointer acting at G. The above figure shows the balance arm in an unbalanced position when the force W1 and W2 are unequal. This unbalance is indicated by the angle which the pointer makes with the vertical. Therefore, the weight of the balance arm and the pointer do not influence the measurements. Analytical Balance: Equal arm balance 8. It requires a set of weights which are at least as heavy as the maximum weight to be measured.
An unequal arm balance is used for the measurement of heavier weights with the help of lighter weights. The unequal arm balance uses two arms. One is called the load arm and the other is called the power arm. The load arm is associated with the load i. This force acts as counterpoising force against the load which may be a test force Ft.
When measurement of large weights. When measurement of large weights is involved, multiple lever systems shown in Fig. In these systems, a large weight W is measured in terms of two smaller weights Wp and Ws. Contnd… Platform Balance Multiple Lever System The system is provided with an adjustable counterpoise which is used to get an initial balance. Before the unknown load W is applied to the platform, the poise weight Wp is set at zero of the beam scale and counter piece is adjusted to obtain initial zero balance.
In order to simplify the analysis it is assumed that the weight W can be replaced by two arbitrary weights W1 and W2. Also it is assumed that the poise weight Wp is at zero and when the unknown weight W is applied it is entirely balanced by the weight, Ws in the pan A proving ring is a circular ring of rectangular cross section as shown in Fig.
D is the outside diameter of the ring, y is the deflection. The above equation is derived under the assumption that the thickness of the ring is small compared to the radius. And also it is clear that the displacement is directly proportional to the force.
Contnd… Since the deflection obtained is very small, the usefulness of the proving ring as a calibration device depends on the accuracy with which this small deflection is measured. This is done by using a precision micrometer shown in the figure. In order to obtain precise measurements one edge of the micrometer is mounted on a vibrating reed device which is plucked to obtain a vibratory motion.
The micrometer contact is then moved forward until a noticeable damping of the vibration is observed. Such a turning effect is called torque or couple. Torque measuring devices used in this connection are commonly known as dynamometers.
They are, therefore, useful in determining performance characteristics of devices such as pumps, compressors etc. They neither add nor subtract the transmitted energy or power and are sometimes referred to as torque meters.
Mechanical Dynamometer Prony Brake These dynamometers are of absorption type. The most familiar and simple device is the prony brake as shown in Fig. Two wooden blocks are mounted diametrically opposite on a flywheel attached to the rotating shaft whose power has to be measured. One block carries a lever arm, and an arrangement is provided to tighten the rope which is connected to the arm. The rope is tightened so as to increase the frictional resistance between the blocks and the flywheel.
L where force F is measured by conventional force measuring instruments, like balances or load cells etc Hydraulic Dynamometer Fig.
This is a power sink which uses fluid friction for dissipation of the input energy and thereby measures the input torque or power. The capacity of a hydraulic dynamometer is a function of two factors, speed and water level. The power consumed is a function of cube of the speed approximately. The torque is measured with the help of a reaction arm. The power absorption at a given speed may be controlled by adjusting the water level in the housing.
This type of dynamometer may be made in considerably larger capacities than the simple prony brake because the heat generated can be easily removed by circulating the water into and out of the housing. As shown in the Fig. The rotor and stator are fitted with a system of cup-shaped pockets, those on each half of the stator being of opposite pitch to those which they face on the rotor and thus forming spherical chambers when they match.
The stator and rotor pockets are so shaped that when the dynamometer is in action the path of the water is a helix as shown in Fig. The vortex produced gives rise to a braking effect between rotor and stator, the stator tending to turn in the direction of rotation of the rotor. The tendency of the stator rotation is taken as a means of measuring the torque with the help of a torque arm on the outer circumference of the stator and a force measuring device. The arms carry the plates which are fixed normal to their direction of motion as shown in the Fig.
On rotation of the brake a resisting torque is produced which is proportional to the area of the blades, the square of the speed, the density of the ambient air and cube of the blade radius arm.
Torque measurement device ME5000
When connected to a measurement reading transducer, every DEPRAG torque measuring instruments of the ME Measuring Electronic series provides precise and highly dynamic measurements of torque values. Using a fast and high resolution AD converter the torque value is displayed and that accurately and digitally even at a highly-dynamic tightening process. Naturally, all relevant measuring metrics are traceable to national standards. We offer an extensive calibration service for the regular checkup of your measuring instrument. Depending on the instrument design, the values can additionally be sent to one of our printers large line of accessories or to a primary host computer.
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Force and Torque Measurement Engineered Better Integrated Manufacturing Mark Corporation is a designer and manufacturer of force and torque measurement products. Since our founding in , our products have proven themselves in numerous applications in virtually every industry around the globe. With our roots as an engineering consultancy, Mark has focused on better engineering from our very beginning.