Lake Shore 625, User Manual

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Lake Shore Model 625 Superconducting MPS User’s Manual
A-6 Glossary of Terminology
Seebeck effect . The development of a voltage due to differences in temperature between two junctions of dissimilar metals in the
same circuit.
1
self-heating . Heating of a device due to dissipation of power resulting from the excitation applied to the device. The output signal
from a sensor increases with excitation level, but so does the self-heating and the associated temperature measurement error.
sensitivity . The ratio of the response or change induced in the output to a stimulus or change in the input. Temperature sensitivity of a
resistance temperature detector is expressed as S = dR/dT.
setpoint . The value selected to be maintained by an automatic controller.
1
serial interface . A computer interface where information is transferred one bit at a time rather than one byte (character) at a time as in
a parallel interface. RS-232C is the most common serial interface.
SI . Système International d'Unités. See International System of Units.
stability . The ability of an instrument or sensor to maintain a constant output given a constant input.
strain relief . A predetermined amount of slack to relieve tension in component or lead wires. Also called stress relief.
susceptance . In electrical terms, susceptance is defined as the reciprocal of reactance and the imaginary part of the complex
representation of admittance: [suscept(ibility) + (conduct)ance].
susceptibility (

) . Parameter giving an indication of the response of a material to an applied magnetic field. The susceptibility is the
ratio of the magnetization (M) to the applied field (H).

= M/H. In both SI units and cgs units the volume susceptibility is a
dimensionless parameter. Multiply the cgs susceptibility by 4

to yield the SI susceptibility. See also Initial Susceptibility and
Differential Susceptibility. As in the case of magnetization, the susceptibility is often seen expressed as a mass susceptibility or a
molar susceptibility depending upon how M is expressed.
temperature scales . See Kelvin Scale, Celsius Scale, and ITS-90. Proper metric usage requires that only Kelvin and degrees Celsius
be used. However, since degrees Fahrenheit is in such common use, all three scales are delineated as follows:
Boiling point of water
Freezing point of water
Absolute zero
kelvin Celsius Fahrenheit
0 K
273.15 K
373.15 K
–273.15 °C
0 °C
100 °C
–459.67 °F
32 °F
212 °F
Triple point of water 273.16 K
To convert Kelvin to Celsius, subtract 273.15.
To convert Celsius to Fahrenheit: multiply °C by 1.8 then add 32, or: °F = (1.8 × °C) + 32.
To convert Fahrenheit to Celsius: subtract 32 from °F then divide by 1.8, or: °C = (°F – 32 )/1.8.
temperature coefficient, measurement . The measurement accuracy of an instrument is affected by changes in ambient temperature.
The error is specified as an amount of change (usually in percent) for every one degree change in ambient temperature.
tesla (T) . The SI unit for magnetic flux density (B). 1 tesla = 10
4
gauss
thermal emf . An electromotive force arising from a difference in temperature at two points along a circuit, as in the Seebeck effect.
1
tolerance . The range between allowable maximum and minimum values.
torr . Unit of pressure. 1 torr

1 mm of mercury. 1 atmosphere = 760 torr.
two-lead . Measurement technique where one pair of leads is used for both excitation and measurement of a sensor. This method will
not reduce the effect of lead resistance on the measurement.
Underwriters Laboratories (UL) . An independent laboratory that establishes standards for commercial and industrial products.
unit magnetic pole . A pole with a strength such that when it is placed 1 cm away from a like pole, the force between the two is 1
dyne.
volt (V) . The difference of electric potential between two points of a conductor carrying a constant current of one ampere, when the
power dissipated between these points is equal to one watt.
2
volt-ampere (VA) . The SI unit of apparent power. The volt-ampere is the apparent power at the points of entry of a single-phase, two-
wire system when the product of the RMS value in amperes of the current by the RMS value in volts of the voltage is equal to one.
2
watt (W) . The SI unit of power. The watt is the power required to do work at the rate of 1 joule per second.
2
References:
1 Sybil P. Parker, Editor. McGraw-Hill Dictionary of Scientific and Technical Terms: Fifth Edition .
New York: McGraw Hill, 1994 (IBSN 0-07-113584-7)
2 Christopher J. Booth, Editor. The New IEEE Standard Dictionary of Electrical and Electronic Terms:
IEEE Std 100-1992, Fifth Edition. New York: Institute of Electrical and Electronics Engineers, 1993
(IBSN 1-55937-240-0)
3 Nelson, Robert A. Guide For Metric Practice, Page BG7 - 8, Physics Today, Eleventh Annual Buyer’s Guide,
August 1994 (ISSN 0031-9228 coden PHTOAD)