Biomedical Engineering Reference
In-Depth Information
Frequency measurement is required as part of those devices that convert the
measured physical quantity into a frequency change, such as the variable-reluc-
tance velocity transducer, stroboscopes, the vibrating-wire force sensor, the res-
onant-wire pressure sensor, the turbine flow meter, the Doppler-shift ultrasonic
flow meter, the transit-time ultrasonic flow meter, the vibrating level sensor, the
quartz moisture meter, and the quartz thermometer. In addition, the output rela-
tionship in some forms of AC bridge circuit used for measuring inductance and
capacitance requires accurate measurement of the bridge excitation frequency.
Frequency is calculated in units of hertz (Hz). The digital counter timer is the
most common instrument for measuring frequency. The oscilloscope is also
commonly used for obtaining approximate measurements of frequency.
Appendix A: Definitions of the SI Base Units
kilogram
The mass of a piece of platinum-iridium alloy held in reserve under standard
conditions near Paris
second
The duration of 9192613770 periods of radiation equivalent to the transition between
the two hyperfine levels of the ground state of the caesiurn-133 atom
metre
Distance traveled in 1/299792458 of a second by plane EM waves in a vacuum
Ampere
The electric current which, if maintained in two straight parallel conductors of infinite
length and negligible circular cross-section, when placed one meter apart in a
vacuum would produce, per meter of length, a force of 2 9 10
7
N between the two
conductors
Kelvin
The fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
mole
A mole the amount of substance of a system which contains as many molecules,
atoms, or elementary entities as there are carbon atoms in 0.012 kg of carbon-12
References
1. Yang Huang, Yani Xu, Yijia Guan, et. al. Quelle : RUDAR - Roskilde University Digital
2. The International System of Units (SI): Bureau international des Poids et Measures (2010),
http://www.bipm.org/en/si/
, 30 Nov 2010
3. The International System of Units from NIST: National Institute of Standards and Technology,
http://physics.nist.gov/cuu/Units
, 30 Nov 2010
4. B.C. Nakra, K.K. Chaudhry, Instrumentation Measurement and Analysis (Tata McGraw Hill,
NY, 1985)
5. E.O. Doebelin, Measurement Systems: Application and Design, 5th edn. (McGraw Hill, NY,
2003)
6. A.S. Morris, Measurement & Instrumentation Principles (Elsevier, London, 2001)
7. L.F. Adams, Engineering Measurements and Instrumentation (Hodder & Stoughton Ltd,
London, 1975)
8. J.J. Carr, Elements of Electronics Instrumentation and Measurement, 3rd edn. (Prentice Hall,
NJ, 1996)
9. B.A. Gregory, An Introduction to Electrical Instrumentation and Measurement Systems, 2nd
edn. (McMillan Press, NY, 1981). (ELBS Edition)
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