Platinum
30% Rhodium
The platinum-rhodium alloy used as the positive wire in conjunction
with platinum 6% rhodium to form a Type B thermocouple.
Platinum
67
To develop thermal emf tables for thermocouples, the National Bureau
of Standards paired each thermocouple alloy against a pure platinum
wire (designated Platinum 2 prior to 1973, and currently Platinum
67). The thermal emf’s of any alloy combination can be determined
by summing the “vs. Pt-67” emf’s of the alloys, i.e.,
the emf table for a Type K thermocouple is derived from the Chromel
vs. Pt-67 and the Alumel vs. Pt-67 values.
Platinum
A noble metal which in its pure form is the negative wire of Type
R and Type S thermocouples.
Poisson Ratio
The ratio between the strain of expansion in the direction of force
and the strain of contraction perpendicular to that force v = -Et/E1.
Polarity
In electricity, the quality of having two oppositely charged poles,
one positive one negative.
Polarization
The inability of an electrode to reproduce a reading after a small
electrical current has been passed through the membrane. Glass pH
electrodes are especially prone to polarization errors caused by
small currents flowing from the pH meter input circuit and from
static electrical charges built up as the electrodes are removed
from the sample solution, or when the electrodes are wiped.
Port
A signal input (access) or output point on a computer.
Positive Temperature Coefficient
An increase in resistance due to an increase in temperature.
Potential
Energy
Energy related to the position or height above a place to which
fluid could possibly flow.
Potentiometer
1. A variable resistor often used to control a circuit. 2. A balancing
bridge used to measure voltage.
Power
Supply
A separate unit or part of a circuit that supplies power to the
rest of the circuit or to a system......
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