Lakeshore 332 User Manual page 170

National Institute of Standards and Technology (NIST) . Government agency located in Gaithersburg, Maryland and
Boulder, Colorado, that defines measurement standards in the United States.
noise (electrical). Unwanted electrical signals that produce undesirable effects in circuits of control systems in which they
2
occur.
normalized sensitivity . For resistors, signal sensitivity (dR/dT) is geometry dependent; i.e., dR/dT scales directly with R;
consequently, very often this sensitivity is normalized by dividing by the measured resistance to give a sensitivity, s
percent change per kelvin. s
normally closed (N.C.) . A term used for switches and relay contacts. Provides a closed circuit when actuator is in the
free (unenergized) position.
normally open (N.O.) . A term used for switches and relay contacts. Provides an open circuit when actuator is in the free
(unenergized) position.
O.D. Outer diameter.
oersted (Oe) . The cgs unit for the magnetic field strength (H). 1 oersted = 10¾ π ampere/meter ≈ 79.58 ampere/meter.
ohm (Ω) . The SI unit of resistance (and of impedance). The ohm is the resistance of a conductor such that a constant
current of one ampere in it produces a voltage of one volt between its ends.
open-loop . A control system in which the system outputs are controlled by system inputs only, and no account is taken of
1
actual system output.
pascal (Pa) . The SI unit of pressure equal to 1 N/m
–3
4.191 × 10 inches of water, or 1 × 10
permeability . Material parameter which is the ratio of the magnetic induction (B) to the magnetic field strength (H):
µ = B/H. Also see Initial Permeability and Differential Permeability.
platinum (Pt) . A common temperature sensing material fabricated from pure platinum to make the Lake Shore PT family
of resistance temperature sensor elements.
polynomial fit . A mathematical equation used to fit calibration data. Polynomials are constructed of finite sums of terms
of the form a , where a
x
i i
positive temperature coefficient (PTC) . Refers to the sign of the temperature sensitivity. For example, the resistance of
a PTC sensor increases with increasing temperature.
pounds per square inch (psi) . A unit of pressure. 1 psi = 6.89473 kPa. Variations include psi absolute (psia) measured
relative to vacuum (zero pressure) where one atmosphere pressure equals 14.696 psia and psi gauge (psig) where
gauge measured relative to atmospheric or some other reference pressure.
ppm . Parts per million, e.g., 4 × 10
precision . Careful measurement under controlled conditions which can be repeated with similar results. See repeatability.
Also means that small differences can be detected and measured with confidence. See resolution.
prefixes . SI prefixes used throughout this manual are as follows:
Factor Prefix
24
10 yotta
21
10 zetta
18
10 exa
15
10 peta
12
10 tera
9
10 giga
6
10 mega
3
10 kilo
2
10 hecto
1
10 deka
probe . A long, thin body containing a sensing element which can be inserted into a system in order to make
measurements. Typically, the measurement is localized to the region near the tip of the probe.
proportional, integral, derivative (PID) . A control function where output is related to the error signal in three ways.
Proportional (gain) acts on the instantaneous error as a multiplier. Integral (reset) acts on the area of error with respect
to time and can eliminate control offset or droop. Derivative (rate) acts on the rate of change in error to dampen the
system, reducing overshoot.
quench . A condition where the superconducting magnet goes "normal," i.e., becomes non-superconductive. When this
happens, the magnet becomes resistive, heat is generated, liquid cryogen is boiled off, and the magnet power supply is
shut down due to the sudden increase in current demand.
rack mount . An instrument is rack mountable when it has permanent or detachable brackets that allow it to be securely
mounted in an instrument rack. The standard rack-mount is 19 inches wide. A full-rack instrument requires the entire
width of the rack. Two half-rack instruments fit horizontally in one rack width.
A-6
Lake Shore Model 332 Temperature Controller User's Manual
= (100/R) (dR/dT) %K, where T is the temp. in kelvin and R is the resistance in ohms.
T
2
. Equal to 1.45 × 10
–5
bar.
th
is the i fit coefficient and x
i
–6
is four parts per million.
Symbol
Y
Z
E
P
T
G
M
k
h
da
2
–4
psi, 1.0197 × 10
is some function of the dependent variable.
i
Factor Prefix
–1
10 deci
–2
10 centi
–3
10 milli
–6
10 micro
–9
10 nano
–12
10 pico
–15
10 femto
–18
10 atto
–21
10 zepto
–24
10 yocto
–5 2
kg /cm , 7.5 × 10
f
Symbol
d
c
m
µ
n
p
f
a
z
y
Glossary of Terminology
, in
T
–3
torr,