Page 86 - Concise Encyclopedia of Robotics

Differential Transducer
output, place a straight ruler so its edge passes through the two input
points; the output is the point on the center scale through which the ruler
passes. In this example, the circuit has no gain.
Differential amplifiers are sometimes employed in robotic sensing
systems.The output of an amplifier in this situation can be used as an error
signal, which is sent to the guidance system to regulate the movement of
a mobile robot. This can ensure that the robot follows a prescribed route in
its work environment, such as the path along which two reference acoustic
or radio waves are exactly in phase. Compare DIFFERENTIAL TRANSDUCER.
DIFFERENTIAL TRANSDUCER
A differential transducer is a sensing device with two inputs and one output.
The output is proportional to the difference between the input signal
levels. An example is a differential pressure transducer, which responds to
the difference in mechanical pressure at two points.
Any pair of transducers can be connected in a differential arrange-
ment. Usually, this involves connecting the transducers to the inputs of a
differential amplifier.
When the two variables have the same magnitude, the output of the
differential transducer is zero. The greater the difference in the magnitudes
of the sensed effects, the greater is the output. The most output occurs
when one of the sensed effects is intense, and the other is zero or near
zero. Whether the output is positive or negative depends on which of the
sensed effects is greater. Compare DIFFERENTIAL AMPLIFIER.
DIFFERENTIATION
See DERIVATIVE.
DIGITAL IMAGE
A digital image, also called a digitized image, is a rendition of a scene at
visible, infrared (IR), or ultraviolet (UV) wavelengths, or using radar or
sonar, in the form of a rectangular array of tiny squares or dots called pixels.
In a grayscale digital image, each pixel has a brightness level that can
attain any of numerous discrete binary values. Common ranges are from
binary 0000 through 1111 (16 shades of gray) or binary 00000000
through 11111111 (256 shades of gray).
In a color digital image, each pixel has a color value of red, green, or
blue (RGB), and also a brightness level that can attain any of numerous
discrete binary values. Color digital images occupy considerably more
data memory or storage space than grayscale digital images, because the
three color values can vary independently with each pixel.
The number of pixels in a digital image determines the resolution.
This figure is generally represented in terms of the number of pixels in

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