Glossary

distance of the righting arm.

a phenomenon that occurs in semiconductor diodes when the electric field across the space-charge region becomes high enough to produce a form of field emission that suddenly increases the number of carriers in this region. This breakdown is typically several hundred to several thousand volts, depending on the semiconductor’s construction, and is not destructive. Also called reverse breakdown, Zener effect.

a solid-state diode that uses Zener breakdown to regulate voltage in a circuit in which it is installed. It operates on the principle that the voltage that occurs during breakdown is relatively constant and therefore can be used to regulate voltage. See Zener breakdown.

see Zener breakdown.

hydrated silicates of aluminum with alkali metals.

a special fitting on equipment that accommodates a similar fitting on a grease gun. The zerk allows grease to be injected, but forms a seal to prevent the entry of dirt into the equipment when the gun is removed.

to bring a differential pen to the zero point on an orifice chart.

in process control, a procedure in process transmitters that establishes the minimum, or zero, level of measurement in a process variable.

the output of a transducer with zero measurand applied.

on an orifice chart, the point at which no differential pressure is exerted on the differential pen.

the actual potential of the surface of the earth taken as a point of reference. See electric potential.

a condition wherein the drilling fluid fails to form measurable gels during a quiescent interval (usually 10 minutes).

electrokinetic potential of a particle as determined by its electrophoretic mobility. This electric potential causes colloidal particles to repel each other and stay in suspension.

in process control, a method used to establish the optimum performance of a closed-loop automatic control system. It uses an experimental procedure to establish system gain and time constants within proportional (P), proportional-plus-reset (PI), and proportional-plus-reset-plus-rate (PID) systems.

a very soluble salt used to increase the density of water to points more than double that of plain ­water. Normally added to a system first saturated with calcium chloride.

a relatively small inflatable boat, usually equipped with an outboard motor, which is mainly used for recreation and transporting marine scientists and divers. The boat is named after the Canadian firm Zodiak that makes them. Although the Zodiac brand is synonymous for these small inflatable boats, other brands, such as Eagle, are available. Also, Zodiak makes rescue boats, life rafts, and other inflatable products.

a rock stratum that is different from or distinguished from another stratum (e.g., a pay zone).

the practice of separating producing formations from one another by means of casing, cement, and packers for the purposes of pressure control and maintenance, as well as the prevention of mixing of fluids from separate formations.

a formation that contains holes or cracks large enough to allow cement to flow into the formation instead of up along the annulus outside of the casing.