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Lake Shore Model 325 Temperature Controller 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.
silicon diode . Temperature sensor based on the forward voltage drop at constant current through a pn semiconductor junction formed
in crystalline silicon.
SoftCal™ . In Lake Shore instruments, SoftCal™ is used to improve the accuracy of a DT-400 Series silicon diode temperature
sensor. This reduces the error between the sensor and the standard Curve 10 used by the instrument to convert input voltage from
the diode to a corresponding temperature.
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.
superconducting magnet . An electromagnet whose coils are made of a type II superconductor with a high transition temperature and
extremely high critical field, such as niobium-tin, Nb
3
Sn; it is capable of generating magnetic fields of 100,000 oersteds and more
with no steady power dissipation.
1
See electromagnet.
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 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
thermocouple . A pair of dissimilar conductors so joined at two points that an electromotive force is developed by the thermoelectric
effects when the junctions are at different temperatures.
2
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.
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)