Lake Shore Model 325 Temperature Controller User’s Manual
Glossary of Terminology A-1
APPENDIX A
GLOSSARY OF TERMINOLOGY
absolute zero. The temperature of –273.16 °C, or –459.69 °F, or 0 K, thought to be the temperature at which molecular motion
vanishes and a body would have no heat energy.
1
Alumel™. An aluminum-nickel alloy of which the negative lead of a Type K thermocouple is composed.
ambient temperature. The temperature of the surrounding medium, such as gas or liquid, which comes into contact with the
apparatus.
1
ampere. The constant current that, if maintained in two straight parallel conductors of infinite length, of negligible circular cross
section, and placed one meter apart in a vacuum, would produce between these conductors a force equal to 2 × 10
–7
newton per
meter of length.
2
This is one of the base units of the SI.
ampere-turn. A MKS unit of magnetomotive force equal to the magnetomotive force around a path linking one turn of a conducting
loop carrying a current of one ampere; or 1.26 gilberts.
ampere/meter (A/m). The SI unit for magnetic field strength (H). 1 ampere/meter = 4/1000 oersted 0.01257 oersted.
analog controller. A feedback control system where there is an unbroken path of analog processing between the feedback device
(sensor) and control actuator (heater).
analog output. A voltage output from an instrument that is proportional to its input. For example, from a digital voltmeter the output
voltage is generated by a digital-to-analog converter so it has a discrete number of voltage levels.
anode. The terminal that is positive with respect to the other terminal when the diode is biased in the forward direction.
2
asphyxiant gas. A gas which has little or no positive toxic effect but which can bring about unconsciousness and death by displacing
air and thus depriving an organism of oxygen.
AutoTuning. In Lake Shore temperature controllers, the AutoTuning algorithm automatically determines the proper settings for Gain
(Proportional), Reset (Integral), and Rate (Derivative) by observing the time response of the system upon changes in setpoint.
B. Symbol for magnetic flux density. See Magnetic Flux Density.
bar. Unit of pressure equal to 10
5
pascal, or 0.98697 standard atmosphere.
baud. A unit of signaling speed equal to the number of discrete conditions or signal events per second, or the reciprocal of the time of
the shortest signal element in a character.
2
bel (B). A dimensionless unit expressing the ration of two powers or intensities, or the ratio of a power to a reference power, such that
the number of bels is the common logarithm of this ratio.
1
bifilar windings. A winding consisting of two insulated wires, side by side, with currents traveling through them in opposite
directions.
1
boiling point. The temperature at which a substance in the liquid phase transforms to the gaseous phase; commonly refers to the
boiling point at sea level and standard atmospheric pressure.
CalCurve™ service. The service of storing a mathematical representation of a calibration curve on an EEPROM or installed in a
Lake Shore instrument. Previously called Precision Option.
calibrate. To determine, by measurement or comparison with a standard, the correct 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
Carbon-Glass. A temperature sensing material fabricated from a carbon-impregnated glass matrix used to make the Lake Shore CGR
family of sensors.
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.
Cernox™. A Lake Shore resistance temperature detector based on a ceramic-oxy-nitride resistance material.
CGR. Carbon glass resistor.
cgs system of units. A system in which the basic units are the centimeter, gram, and second.
2
Chebychev polynomials. A family of orthogonal polynomials that solve Chebychev’s differential equation.
1
Chebychev differential equation. A special case of Gauss’ hypergeometric second-order differential equation:
(1 – x
2
) f" (x) – xf' (x) + n
2
f (x) = 0.
1
Chromel™. A chromium-nickel alloy of which the positive lead of Type E and K thermocouples is composed.
closed-loop. See feedback control system.
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