An eclipse of the moon. When the moon enters the shadow of the earth, it appears eclipsed to an observer on the earth. A lunar eclipse is penumbral when it enters only the penumbra of the earth’s shadow, partial when part of its surface enters the umbra of the earth’s shadow, and total if its entire surface is obscured by the umbra.
Related Terms 
OPTICALLY PUMPED MAGNETOMETER
A type of magnetometer that measures total magnetic field intensity by observation of the precession frequency of magnetic atoms, usually gaseous rubidium, cesium, or helium, which are magnetized by irradiation with circularly polarized light of a suitable wavelength.

OPERATOR UTILIZATION
The ratio of working time to total clock time; a ratio of 1.00 (or 100) indicates full utilization of the operator's work time.

NUTATINGDISK METER
An instrument for measuring flow of a liquid in which liquid passing through a chamber causes a disk to nutate, or roll back and forth, and the total number of rolls is mechanically counted.

NUSSELT NUMBER
A dimensionless number used in the study of forced convection which gives a measure of the ratio of the total heat transfer to conductive heat transfer, and is equal to the heattransfer coefficient times a characteristic length divided by the thermal conductivity. Symbolized NNu.

NPK
The code identifying the components in a fertilizer mixture: nitrogen (N), phosphorus pentoxide (P), and potassium oxide (K). Fertilizers are graded in the order NPK, with the numbers indicating the percentage of the total weight of each component. For example, 51010 represents a mixture containing by weight 5% nitrogen, 10% phosphorus pentoxide, and 10% potassium oxide. and a detector downstream measures the amount of decay of the resonance, thereby sensing fluid velocity.

NORMAL TIME
1. The time required by a trained worker to perform a task at a normal pace. 2. The total of all the normal elemental times constituting a cycle or operation. Also known as base time; leveled time.

NONLINEAR DISTORTION
1. Distortion in which the output of a system or component does not have the desired linear relation to the input. 2. [ENG ACOUS] The ratio of the total rootmeansquare (rms) harmonic distortion output of a microphone to the rms value of the fundamental component of the output.

MOLD EFFICIENCY
In a multimold blowmolding system, the percentage of the total turnaround time actually required for the forming, cooling, and ejection of the formed objects.

MAXIMUM BELT TENSION
The total of the starting and operating tensions in a conveyor.

MAXIMAL FLOW
Maximum total flow from the source to the sink in a connected network.
