Banner U-Gage Ultrasonic Sensor Manual de usuario descargar pdf (Pagina 2)

LIGHT GAUGING

ULTRASONIC

MEASURING

ARRAYS

RADAR

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Photoelectrics

Sensors

Fiber Optic

Sensors

Special Purpose

Sensors

Measurement &

Inspection Sensors

Vision

Wireless

Lighting &

Indicators

Safety

Light Screens

Safety

Laser Scanners

Fiber Optic

Safety Systems

Safety Controllers &

Modules

Safety Two-Hand

Control Modules

Safety Interlock

Switches

Emergency Stop &

Stop Control

Light Gauging Sensors

Light gauging sensors utilize either “Time of Flight” or triangulation technology to

detect the presence and position of targets.

Time of Flight: Measurement of the amount of time that emitted light takes

to travel to the target and return to the sensor. This technology is used in

long-range sensing applications.

Triangulation: An emitter transmits visible light through a lens, towards a

target. The beam bounces off the target, returning some light to the sensor’s

Position Sensitive Device (PSD) receiver element. The target’s distance from the

receiver determines the angle at which the light travels to the receiver element.

This angle, in turn, determines where the received light will fall along the PSD

receiver element. The position of the light on the PSD receiver element is

processed through analog and/or digital electronics to calculate the appropriate

output value.

Surface Reﬂectivity and Texture

Triangulation sensors depend on the diffuse reections of light from the target. A

diffuse reection is one in which the light tends to scatter equally in all directions

from the target. If the target surface is mirror-like, then light will tend to reect in

only one direction (If this target is not perpendicular to the sensor, the light will be

reected away from the sensor).

Triangulation sensors also require a non-porous, opaque surface for accurate

operation. Measurement errors will result from semi-transparent targets such as clear

plastic, or from porous materials such as foam.

Best Worst Typical

Specular targets

(e.g., a mirror) reect

light in only one

direction

Mixed targets (most

objects) display traits

of both diffuse and

specular targets

Diffuse targets (e.g.,

matte nish white

ceramic) reect light

consistently in all

directions

Color Effects

The color of the object being measured can affect the resolution and accuracy of the

readings. White, red, yellow and orange targets will reect more light than green, blue

or black targets. The resolution for dark targets may be up to four times less than for

white targets.

The graph below shows the relative amount of received light that is reected from

various target colors, using visible red light. The resolution is roughly affected according

to the square of the received light. For example, reducing the amount of light by a factor

of nine will degrade the resolution by a factor of three.

Metal Surfaces

Bare metal surfaces do not exhibit consistent reectivity across their surfaces. As a

result, the repeatability from one point on a metal surface to another, even at the same

distance from the sensor, will degrade. This effect varies from metal to metal and is

dependent upon surface nish.

Total Expected Measurement Error

Keep in mind that the overall expected accuracy of an analog sensor is the combination

of several performance parameters, not simply the sensor’s resolution. Linearity and

temperature effect can also affect accuracy.

Programmed

Sensing Window

Lenses

Laser

Emitter

Near

Limit

Far

Limit

Object Movement

PSD

Receiver

Element

Signal

Conditioning

Circuitry

Output

Circuitry

Emitter

Circuitry

Microprocessor

Triangulation Technology

Programmed

Sensing Window

Lenses

Laser

Emitter

Near

Limit

Far

Limit

Object Movement

PSD

Receiver

Element

Signal

Conditioning

Circuitry

Output

Circuitry

Emitter

Circuitry

Microprocessor

More light is reected in the

y-direction than the x-direction

Courtesy of Steven Engineering, Inc.-230 Ryan Way, South San Francisco, CA 94080-6370-Main Office: (650) 588-9200-Outside Local Area: (800) 258-9200-www.stevenengineering.com

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