User`s manual

Lake Shore MTD Series Cryotest System User’s Manual
A-2 Glossary of Terminology
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 a 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
+–
Carbon-Glass™. A temperature sensing material fabricated from a carbon-impregnated glass matrix used to make the
Lake Shore CGR family of sensors.
Caution. An operation or maintenance procedure, practice, condition, statement, etc., which, if not strictly observed,
could result in damage or destruction of equipment, or loss of effectiveness.
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
Chromel™. A chromium-nickel alloy which comprises the positive lead of Type E and K thermocouples.
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.
cold finger. A cryogenically cooled component incorporated into the dewar of an infrared detector assembly in order to
maintain the sensing elements at the proper temperature (77 K or colder).
compliance voltage. See current source.
Constantan. A copper-nickel alloy which comprises the negative lead of Type E, J, and T thermocouples.
cryogen. See cryogenic fluid.
1
cryogenic. Refers to the field of low temperatures, usually –130 °F or below, as defined by 173.300(f) of Title 49 of the
Code of Federal Regulations.
cryogenic fluid. A liquid that boils at temperatures of less than about 110 K at atmospheric pressure, such as hydrogen,
helium, nitrogen, oxygen, air, or methane. Also known as cryogen.
1
cryostat. An apparatus used to provide low-temperature environments in which operations may be carried out under
controlled conditions.
1
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.
curve. A set of data that defines the temperature response of a temperature sensor. It is used to convert the sensor's
signal to temperature.
Curve 10. The voltage versus temperature characteristic followed by all DT-400 Series Silicon Diode Temperature
Sensors.
decibels (dB). A unit for describing the ratio of two powers or intensities, or the ratio of a power to a reference power;
equal to one-tenth bel; if P
1
and P
2
are two amounts of power, the first is said to be n decibels greater, where
n = 10 log
10
(P
1
/P
2
).
1
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.
deviation. The difference between the actual value of a controlled variable and the desired value corresponding to the
setpoint.
1
Dewar. A vacuum-insulated bottle used to contain cryogenic fluid.
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.