Measurements and Mathematics Terms

The inverse of a number; the reciprocal is formed by inverting the numerator and the denominator of a fraction.

A four-sided figure that has four lines at 90 degree angles.

The opposite sides are parallel to each other and are equal in length, but are not equal in length to the lines that run perpendicular to them.

A solid that has four sides, with each junction at 90 degree angles.

The opposite sides are equal in length and parallel to each other, but they are not equal in length to the sides that run perpendicular to them

To give a close approximation of a number by dropping the least significant numbers; for example, a number can be rounded up or down to the nearest whole number, 78.7 can be rounded up to 79, and 77.4 can be rounded down to 77.

You can get the same sum of 1,089 every time you add certain numbers together:

1. Take any three-digit number in which the first digit is larger then the last digit (654).
2. Reverse the number and subtract the smaller number from the larger one (456; 654 - 456 = 198).
3. Reverse the result and add this number to the result (198 reversed = 891 + 198 = 1,089)
4. As shown above, the answer is 1,089 every time you use the procedures as indicated.

A set of marks on a measuring instrument; usually, with numbers in increments from low to high values.

Any real number, or any quantity that can be measured using a single real number.

Temperature, length, and mass are all scalars and it is said that a scaler has magnitude, but no direction.

A quantity with both direction and magnitude; such as, force or velocity, is called a vector.

An object with three dimensions: length, width, and height.

A solid that is bounded by a curved surface.

Any point measured from the outside of the sphere to the center of the sphere is equal in distance.

An instrument used to measure weight.

The object is placed on a hook attached to a spring and the weight is read on a scale.

A four-sided figure that has four lines arranged at 90 degree angles.

The opposite sides are parallel to each other and all sides are of equal length.

A measured unit that is used as the basis for measuring other things; for example, a foot and a meter are standards of length.

Devices, or telemeters, used for transmitting signals over great distances.

Telemetry measurements are made and other data collected at remote or inaccessible points and transmitted to receiving equipment for monitoring, display, and recording.

Originally, the information was sent over wires, but modern telemetry more commonly uses radio transmission.

Basically, the process is the same in either case. Among the major applications are monitoring electric-power plants, gathering meteorological data, and monitoring manned and unmanned space flights.

Aerospace telemetry for rockets and satellites was inaugurated with the Soviet satellite Sputnik, launched in 1957, and systems have grown in size and complexity since then.

Observatory satellites have performed as many as 50 different experiments and observations, with all data telemetered back to a ground station.

The techniques developed in aerospace have been successfully applied to many industrial operations, including the transmission of data from inside internal-combustion engines during tests, from steam turbines in operation, and from conveyor belts inside mass-production ovens.

The SI unit of magnetic flux density (field intensity) for magnetic fields.

The intensity of a magnetic field can be measured by placing a current-carrying conductor in the field. The magnetic field exerts a force on the conductor, a force which depends on the amount of the current and on the length of the conductor.

One tesla is defined as the field intensity generating one newton of force per ampere of current per meter of conductor.

One tesla represents a magnetic flux density of one weber per square meter of area. A field of one tesla is quite strong: the strongest fields available in laboratories are about 20 teslas, and the earth's magnetic flux density, at its surface, is about 50 microteslas (µT); and one tesla equals 10,000 gauss.

Magnetic fields are measured in units of tesla (T). The tesla is a large unit for geophysical observations, and a smaller unit, the nanotesla (nT; one nanotesla equals 10⁻⁹ tesla), is normally used.

A nanotesla is equivalent to one gamma, a unit originally defined as 10⁻⁵ gauss, which is the unit of magnetic field in the centimeter-gram-second system. Both the gauss and the gamma are still frequently used in the literature on geomagnetism even though they are no longer standard units.

The tesla, defined in 1958, honors the Serbian-American electrical engineer Nikola Tesla (1856-1943), whose work in electromagnetic induction led to the first practical generators and motors using alternating current.

An instrument that converts the physical stimulus to be measured; such as, temperature, vibration, or pressure, into an electrical signal and therefor operates as the actual measuring instrument.

Transducers can take many forms and they can be self-generating or externally energized.

An example of the self-generating type is a vibration sensor based on the use of a piezoelectric material; that is, one that produces an electrical signal when it is mechanically deformed.

Many externally energized transducers operate by producing an electrical signal in response to mechanical deformation. Typical physical inputs producing such deformations are pressure, mechanical stress, and acceleration.

A simple mechanical transducer-sensing device is a strain gauge based on the change in electrical resistance of a wire or a semiconductor material under strain. Another externally energized transducer, called the variable-reluctance type, is one in which the magnetic circuit is broken by an air gap.

The mechanical movement to be measured is used to change this air gap and so it changes the reluctance, or opposition, to the production of a magnetic field in the circuit. The change in reluctance is then translated into an electrical signal.