FAQ

What are the most common sensor outputs?

Four of the most common sensor outputs are NPN current sinking, PNP current sourcing, Two-wire DC/AC and Relay.

NPN Current Sinking



One simple way to understand NPN wiring is to look at the following simple electrical circuit.

The positive side of the battery is attached to the load. The negative side of the load is switched.


PNP Current Sourcing



One simple way to understand PNP wiring is to look at the following simple electrical circuit.

The negative lead of the battery is attached to the load. The positive side of the load is switched.


Two-Wire Sensor

How do you know which sensor you need if you aren’t sure whether it is NPN or PNP?

One good question is to ask whether or not the common of the PLC is connected to + voltage or 0 voltage.
If the DC voltage PLC has a positive voltage common, an NPN output sensor is required.
If the DC voltage PLC has a 0v common, a PNP output sensor is required.

Response time requirement for rotating targets.

In order to calculate response time of a rotating target we have to convert rotational speed to linear speed.

Target length/Linear Speed = required response time

For example: The rotating part has a 15mm long piece of reflective tape attached to 50mm diameter shaft.
The maximum speed of the shaft is 6000 revolutions per minute = 100 revolutions per second.



Converting rotating speed to linear velocity:
Circumference of shaft PI (π) * diameter= π * 50mm= 157mm

Linear velocity of the shaft circumference = 100revolutions per Second * 157mm/revolution = 15,700 mm/second.

Target length/linear speed = 15mm/15,700 mm/sec = .000955seconds = .955milliseconds required response time.

This is assuming that the sensor’s effective beam is small. The larger the effective beam the faster the response time needs to be.

Calculating Response Time Requirements

Response time of a sensor is the maximum amount of time it takes for the sensor to detect a target object and change the state of the output signal.

Calculating response time is an important component in specifying a sensor especially when the application is very high speed or when detecting very small objects.

The following information is required in order to determine response time:
1.) Size of the target object
2.) Distance or space between target objects
3.) Speed





1.) 7mm wide registration mark
2.) 160mm spacing between marks
3.) 300 ft/minute

300ft/minute = 5ft/second
5ft/second = 60"/second
60"/second x 25.4 = 1524mm/second



1.) 12,000 parts per minute
2.) 20mm wide target object
3.) Parts equally spaced 5mm apart

12,000 parts/min. = 200 parts/second
Each part is 22mm wide + 3mm spacing = 25mm of linear travel
Speed of the parts = 25mm/part x 200 parts/second = 5000mm/second

IP69K Protection

IP69K is a rating of German standard DIN 40050-9 extending the IEC 60529 rating system for high-pressure, high-temperature wash down applications.

Test Condition:
A sensor on the turn table that rotates 5 times per minutes.
Pressure: 80~100 bar
Flow Rate: 14~16 liter/minute
Temperature: +80°C / -5°C
Distance from Nozzle: 100~150mm
Nozzle Angle: 0°, 30°, 60°, 90°
Testing Period: 30sec per angle

IP69K does not guarantee the sensor's working condition under the test condition example given above. The sensor will not work properly when the lens is wet and the light is refracted.