User`s manual

7800 Series Hysteresisgraph System User's Manual
A-2 Glossary of Terminology
bit. A contraction of the term “binary digit”; a unit of information represented by either a zero or a one.
2
CalCurve™ Service. The service of storing a mathematical representation of a calibration curve on an EEEPROM or installed in a
Lake Shore instrument. Previously called Precision Option.
calibration. To determine, by measurement or comparison with a standard, the correct (accurate) value of each scale reading on a
meter or other device, or the correct value for each setting of a control knob.
1
cathode. The terminal from which forward current flows to the external circuit.
2
Anode Cathode
+–
Celsius (°C) Scale. A temperature scale that registers the freezing point of water as 0 °C and the boiling point as 100 °C under normal
atmospheric pressure. Celsius degrees are purely derived units, calculated from the Kelvin Thermodynamic Scale. Formerly known
as “centigrade.” See Temperature for conversions.
cgs system of units. A system in which the basic units are the centimeter, gram, and second.
2
coercive force (coercive field). The magnetic field strength (H) required to reduce the magnetic induction (B) in a magnetic material
to zero.
coercivity. Generally used to designate the magnetic field strength (H) required to reduce the magnetic induction (B) in a magnetic
material to zero from saturation. The coercivity would be the upper limit to the coercive force.
compliance voltage. See current source.
Curie temperature (Tc). Temperature at which a magnetized sample is completely demagnetized due to thermal agitation. Named for
Pierre Curie (1859
– 1906), a French chemist.
current source. A type of power supply that supplies a constant current through a variable load resistance by automatically varying its
compliance voltage. A single specification given as “compliance voltage” means the output current is within specification when the
compliance voltage is between zero and the specified voltage.
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 S
d
= (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 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
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.
electron. An elementary particle containing the smallest negative electric charge. Note: The mass of the electron is approximately
equal to 1/1837 of the mass of the hydrogen atom.
2
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
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.
flux (φ
φφ
φ). The electric or magnetic lines of force in a region.
1
flux density (B). Any vector field whose flux is a significant physical quantity; examples are magnetic flux density, electric
displacement, and gravitational field.
1
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 = 1 Mx/cm
2
= line/cm
2
. 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.