Introduction to sensors

transcript

Level I Level I

Training Series: Level ITraining Series: Level I

Electrical InterfaceElectrical Interface

The Back-end

Divided into 2 areas:◦Operating voltage

◦Output signal type

PowerPower

SignalSignal

OUTPUT SIGNAL TYPES

Discrete ON or OFF YES or NO

Analog Speed control Position information

MIN MAX

SignalSignal

OPERATING VOLTAGE

Direct Current (DC) Current flows in only

ONE direction Safe, easy-to-handle

power source

Alternating Current (AC) Current changes direction

PowerPower

A DISCRETE SENSOR IS A SWITCH

Electronics

Sensing SideFront-end

Electronics

Power WiresSwitch

Electronics

BASIC SENSOR CIRCUIT

Sensors with relay output

Unlike a switch, sensors require power to operate

TYPES OF DISCRETE ELECTRICAL OUTPUTS

Sensors of today use Solid-State outputs, not mechanical relays

Today Yesterday PNP, 3-wire Relay NPN, 3-wire AC/DC, 2-wire

THE NPN & PNP OUTPUT

Functions similar to a switch,But current only flows in one direction

PNPTransistor Mechanical

Switch

THE DIFFERENT TRANSISTORS

What direction do you want current to flow?

NPNAlso called Sinking

PNPAlso called Sourcing

PNP, 3-WIRE

PNP Output3 -

Standard diagram formAs shown in our catalog

The Sensor

The LoadConnector

PNP, 3-WIRE

PNP Output3 -

Watching the current flow

Sensors Power

Output Signal

NPN Output3 -

NPN, 3-WIRE

Watching the current flow

Sensors Power

Output Signal

THE 2-WIRE AC/DC OUTPUT

Functions similar to a switch,But with a small leak

Sensors Power Supply from leakage current

Output Signal

QUICK REFERENCE:WIRING PNP & NPN

N P NP N P

First s

ide of load

Second side of lo

Switched sid

Positive

Negative

Sensor is PNP

IF GIVEN A CHOICE, WHICH DISCRETE SENSOR TYPE SHOULD I CHOOSE?

PNP or NPN, 3-wire

- Fewer interface problems

- Largest selection- Lowest unit costs

AC/DC, 2-wire- Many interface

issues- Smaller selection- Susceptible to noise

1st CHOICE

2nd CHOICE

NORMALLY OPEN (NO)VS. NORMALLY CLOSED (NC)

Identifies the non-active state (target not present) of the sensor

Electronics

Normally Open

Is it off (open)?

Is it on (closed)?

NORMALLY OPEN (NO)VS. NORMALLY CLOSED (NC)

Identifies the non-active state (target not present) of the sensor

Electronics

Is it off (open)?

Is it on (closed)?

Electronics

Normally Closed

ANALOG OUTPUTS

Unlike a discrete output with two defined states, analog signals have an infinite number of states.

Discrete

Analog

Voltage

ANALOG USES

To provide absolute measurement or position information

MeasurementPosition

ANALOG APPLICATIONS!

Spool diameter Rotational position Liquid level Sort parts Determine part

orientation Measure vibration Measure straightness Hydraulic or pneumatic

cylinder position

Expandingpossibilitie

ANALOG DATA

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Measurement

Panel meters Control systems

ANALOG INFORMATION

The many forms for representing measurement or position information

Voltage

Current

Digital Pulse

ANALOG VOLTAGE

Information contained in varying voltage

Maximum Voltage

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Measurement

Half VoltageNo Voltage

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Measurement

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Measurement

Water Analogy Volt Meter

ANALOG CURRENT

Information contained in varying Current

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Measurement

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Measurement

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Measurement

Maximum CurrentHalf CurrentNo Current

Water Analogy Current Meter

DIGITAL PULSE

Information contained in digital pulse timing

100.00Maximum

measurementHalf wayMinimum

measurement50.000.00Pulse Width

Start/Stop

ELECTRICAL INTERFACE REVIEW

Operating voltage: Sensor PowerDC: SafestAC: Most available

Output signal typesDiscrete

PNP, 3-wire NPN, 3-wire AC/DC 2-wire

Analog Voltage Current Digital pulse

PowerPower

SignalSignal

Introduction to sensors

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