The document discusses the electrical interface of sensors, dividing it into power (operating voltage) and output signal type. It describes discrete outputs like PNP and NPN transistors that function like a switch, and analog outputs that can represent measurement or position as a varying voltage, current, or digital pulse width. Discrete sensors are generally preferred over 2-wire AC/DC types. The document provides examples of analog applications and reviews the key aspects of a sensor's electrical interface.

1. Level I
1
Training Series: Level I

2. 2
Electrical InterfaceElectrical Interface
The Back-end

3. 3
Electrical InterfaceElectrical Interface
Divided into 2 areas:
◦ Operating voltage
◦ Output signal type
Electrical Interface
PowerPower
SignalSignal

4. 4
OUTPUT SIGNAL TYPES
 Discrete
 ON or OFF
 YES or NO
 Analog
 Speed control
 Position information
MIN MAX
Electrical Interface
SignalSignal

5. 5
OPERATING VOLTAGE
 Direct Current (DC)
 Current flows in only
ONE direction
 Safe, easy-to-handle
power source
 Alternating Current (AC)
 Current changes direction 60
times a second
 Readily available
Electrical Interface
PowerPower

6. 6
A DISCRETE
SENSOR IS A SWITCH
Electronics
Sensing Side
Front-end
Electronics
Power Wires
Switch
Electrical Interface

7. 7
Electronics
BASIC SENSOR CIRCUIT
Sensors with relay output
+
-
Unlike a switch,
sensors require
power to operate
Electrical Interface

8. 8
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
Electrical Interface

9. 9
THE NPN & PNP OUTPUT
Functions similar to a switch,
But current only flows in one direction
PNP
Transistor Mechanical
Switch
Electrical Interface

10. 10
THE DIFFERENT TRANSISTORS
What direction do you want current to flow?
NPN
Also called Sinking
Electrical Interface
PNP
Also called Sourcing
+--+

11. 11
PNP, 3-WIRE
1
4
+
PNP Output
3 -
Load
Standard diagram form
As shown in our catalog
The Sensor
The Load
Connector
Pins
Electrical Interface

12. 12
PNP, 3-WIRE
1
4
+
PNP Output
3 -
Load
Watching the current flow
Sensors Power
Output Signal
Electrical Interface

13. 13
1
4
+
NPN Output
3 -
Load
NPN, 3-WIRE
Watching the current flow
Sensors Power
Output Signal
Electrical Interface

14. 14
1 ~
3 ~
Load
THE 2-WIRE AC/DC OUTPUT
Functions similar to a switch,
But with a small leak
Sensors Power
Supply from leakage current
Output Signal
Triac
Electrical Interface

15. 15
QUICK REFERENCE:
WIRING PNP & NPN
N P N
P N P
+
-
Load
First side of load
Second side of load
Switched side
Positive
Negative
Sensor is PNP
Electrical Interface

16. 16
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
1
4
+
3 -
Load
1 ~
3 ~
Load
Electrical Interface

17. 17
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)?
Electrical Interface

18. 18
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
Electrical Interface

19. 19
ANALOG OUTPUTS
Unlike a discrete output with two defined states,
analog signals have an infinite number of states.
Discrete
Analog
On
Off
Voltage
Time
Max
Min
Voltage
Time
Electrical Interface

20. 20
ANALOG USES
To provide absolute measurement or position
information
Measurement
Position
Electrical Interface

21. 21
ANALOG APPLICATIONS!
 Spool diameter
 Rotational position
 Liquid level
 Sort parts
 Determine part orientation
 Measure vibration
 Measure straightness
 Hydraulic or pneumatic
cylinder position
Expanding
possibilities
Expanding
possibilities
Electrical Interface

22. 22
ANALOG DATA
0 10987654321
Measurement
Panel meters Control systems
Electrical Interface

23. 23
ANALOG INFORMATION
 The many forms for representing measurement or
position information
10
0
10
-10
5
-5
20
0
20
4
Voltage
Current
Digital Pulse
Electrical Interface

24. 24
ANALOG VOLTAGE
Information contained in varying voltage
Maximum Voltage
0 10
987654321
Measurement
Half VoltageNo Voltage
0 10
987654321
Measurement
0 10
987654321
Measurement
Water Analogy Volt Meter
Electrical Interface

25. 25
ANALOG CURRENT
Information contained in varying Current
0 10
987654321
Measurement
0 10
987654321
Measurement
0 10
987654321
Measurement
Maximum CurrentHalf CurrentNo Current
Water Analogy Current Meter
Electrical Interface

26. 26
DIGITAL PULSE
Information contained in digital pulse timing
100.00
Maximum measurementHalf wayMinimum measurement
50.000.00Pulse Width
Meter
Start/Stop
Electrical Interface

27. 27
ELECTRICAL INTERFACE REVIEW
 Operating voltage: Sensor Power
DC: Safest
AC: Most available
 Output signal types
Discrete
 PNP, 3-wire
 NPN, 3-wire
 AC/DC 2-wire
Analog
 Voltage
 Current
 Digital pulse
Electrical Interface
PowerPower
SignalSignal