Lake Shore Model 321 Autotuning Temperature Controller User’s Manual
Glossary of Terminology
A-3
degree
. An incremental value in the temperature scale, i.e., there are 100 degrees between the ice point and the boiling
point of water in the Celsius scale and 180 degrees between the same two points in the Fahrenheit scale.
demagnetization
. when a sample is exposed to an applied field (H
a
), poles are induced on the surface of the sample.
Some of the returned flux from these poles is inside of the sample. This returned flux tends to decrease the net
magnetic field strength internal to the sample yielding a true internal field (H
int
) given by: H
int
= H
a
– DM ,where M is
the volume magnetization and D is the demagnetization factor. D is dependent on the sample geometry and
orientation with respect to the field.
deviation
. The difference between the actual value of a controlled variable and the desired value corresponding to the
setpoint.
1
differential permeability
. The slope of a B versus H curve: µ
d
= dB/dH.
differential susceptibility
. The slope of a M versus H curve:
χ
d
= dM/dH.
digital controller
. A feedback control system where the feedback device (sensor) and control actuator (heater) are joined
by a digital processor. In Lake Shore controllers the heater output is maintained as a variable DC current source.
digital data
. Pertaining to data in the form of digits or interval quantities. Contrast with analog data.
2
dimensionless sensitivity
. Sensitivity of a physical quantity to a stimulus, expressed in dimensionless terms. The
dimensionless temperature sensitivity of a resistance temperature sensor is expressed as Sd = (T/R)(dR/dT) which is
also equal to the slope of R versus T on a log-log plot, that is S
d
= d lnR / d lnT. Note that the absolute temperature
(in kelvin) must be used in these expressions.
drift, instrument
. An undesired but relatively slow change in output over a period of time, with a fixed reference input.
Note:
Drift is usually expressed in percent of the maximum rated value of the variable being measured.
2
dynamic data exchange (DDE)
. A method of interprocess communication which passes data between processes and
synchronized events. DDE uses shared memory to exchange data between applications and a protocol to
synchronize the passing of data.
dynamic link library (DLL)
. A module that contains code, data, and Windows resources that multiple Windows programs
can access.
electromagnet
. A device in which a magnetic field is generated as the result of electrical current passing through a helical
conducting coil. It can be configured as an iron-free solenoid in which the field is produced along the axis of the coil,
or an iron-cored structure in which the field is produced in an air gap between pole faces. The coil can be water
cooled copper or aluminum, or superconductive.
electrostatic discharge (ESD)
. A transfer of electrostatic charge between bodies at different electrostatic potentials
caused by direct contact or induced by an electrostatic field.
error
. Any discrepancy between a computed, observed, or measured quantity and the true, specified, or theoretically
correct value or condition.
2
excitation
. Either an AC or DC input to a sensor used to produce an output signal. Common excitations include: constant
current, constant voltage, or constant power.
Fahrenheit (°F) Scale
. A temperature scale that registers the freezing point of water as 32 °F and the boiling point as
212 °F under normal atmospheric pressure.
See
Temperature for conversions.
four-lead
. measurement technique where one pair of excitation leads and an independent pair of measurement leads are
used to measure a sensor. This method reduces the effect of lead resistance on the measurement.
GaAlAs
. Gallium-aluminum-arsenide semiconducting material used to make the special Lake Shore TG family of diode
temperature sensors.
gamma
. A cgs unit of low-level flux density, where 100,000 gamma equals one oersted, or 1 gamma equals 10
–5
oersted.
gauss (G)
. The cgs unit for magnetic flux density (B). 1 gauss = 10
–4
tesla. Named for Karl Fredrich Gauss (1777
–
1855)
a German mathematician, astronomer, and physicist.
gaussian system (units)
. A system in which centimeter-gram-second units are used for electric and magnetic qualities.
general purpose interface bus (GPIB)
. Another term for the IEEE-488 bus.
germanium (Ge)
. A common temperature sensing material fabricated from doped germanium to make the Lake Shore
GR family of resistance temperature sensor elements.
gilbert (Gb)
. A cgs electromagnetic unit of the magnetomotive force required to produce one maxwell of magnetic flux
in a magnetic circuit of unit reluctance. One gilbert is equal to 10/4
π
ampere-turn. Named for William Gilbert
(1540
-
1603), an English physicist; hypothesized that the earth is a magnet.
gilbert per centimeter
. Practical cgs unit of magnet intensity. Gilberts per cm are the same as oersteds.
