Measurement Basics
Commerce, process control and understanding the world
What are three reasons a measurement might be done?
...taking the fixed numerical value of the speed of light in vacuum c to be 299,792,458 when expressed in the unit m s^−1, where the second is defined in terms of ∆νCs.
What is a meter?
A PMD that uses a c-shaped hollow tube that uncoils as pressure increases.
What is a Bourdon Tube gauge?
Two TMD that use two different metals to create a detectable signal.
What are a thermocouple and a bi-metallic thermometer?
A flow sensor that uses a floating element inside a tapered tube to measure volumetric flow rate visually
What is a rotameter?
The stage of a measurement system might amplify, attenuate, filter, or change one type of signal to another to optimize the signal for the digitizer
What is the signal conditioning stage?
...by taking the fixed numerical value of the cesium frequency ∆νCs, the unperturbed ground-state hyperfine transition frequency of the cesium-133 atom, to be 9,192,631,770 when expressed in the unit Hz, which is equal to s^−1.
What is a second?
A PMD that usually relies on a (variable) gap between two parallel plates.
What is a capacitive pressure tranducer?
Platinum
Two flow sensors that rely on creating a pressure drop in the flow
What are a venturi and orifice meter?
A basis for quantifying a measured quantity
What is a unit?
...by taking the fixed numerical value of the elementary charge e to be 1.602176634 × 10^−19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆νCs.
What is a Ampere?
A PMD includes a coil and a magnet to create a detectable signal.
What is an inductive pressure transducer?
A TMD that has a non-linear relationship between temperature and resistance.
What is a thermistor?
What is a hotwire anemometer?
Get your calculator out!
What is the voltage resolution of a 12 bit digitizer set to a range of 0 to 10 V?
by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 ×10−23 when expressed in the unit J K^−1, which is equal to kg m2 s^−2 K^−1, where the kilogram, meter and second are defined in terms of h, c and ∆νCs.
What is a Kelvin?
Two PMDs that rely on measuring a difference in height of a liquid.
What are a u-tube and inclined manometer?
A TMD that senses the thermal radiation emitted from a body.
What is an infrared thermometer?
What is PIV?
200 kHz, for a 100 kHz signal.
What is the minimum sampling rate needed to reliably capture the 100 kHz signal.
...by taking the fixed numerical value of the Planck constant h to be 6.62607015 ×10^−34 when expressed in the unit J s, which is equal to kg m^2 s^−1, where the meter and the second are defined in terms of c and ∆νCs.
What is a kilogram?
A PMD relies on a material which can develop a voltage difference just by mechanically stressing it.
What is a piezoelectric pressure transducer?
The part of a liquid-in-glass thermometer acts as a mechanical amplifier of the detectable signal
What is a the stem or capillary tube or just tube?
This flow measurement listens for an acoustical echo with a frequency different than that of the outgoing sound.
What is a doppler flow meter?