How to Test Proximity Sensor with a Multimeter

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Proximity sensors sense the absence or presence of objects using an electromagnetic field, sound, and light. You will find many different types, each fitted to particular environments and applications. 

In today’s post will talk about proximity sensors and how you can test them with a digital multimeter. 

What is a Proximity Sensor? 

Keep in proximity sensor is an electric device that can sense the object’s presence within its vicinity without any physical contact. To sense such objects, the proximity sensor discharges or produces a beam of electromagnetic radiation, normally in the form of infrared light, and locates the reflection to identify the object’s distance or proximity from the sensor. 

Keep in mind that proximity sensors are normally utilized in industrial applications, from recycling to food production and manufacturing. They are also utilized in vehicles for locating the proximity of other vehicles relative to one’s vehicle and parking-assist functions. 

In mobile devices, particularly phones, the proximity sensor is utilized to locate whether the user’s face is close to the phone during a phone call, prompting the screen to turn off to avoid false touches on the touchscreen. 

You will find many types of proximity sensors, and they utilize numerous ways of sensing. For instance, photoelectric and capacitive sensors are more suitable to organic and plastic targets, while the inductive proximity sensors can only sense metal targets. 

Some of the typical types of proximity sensors are the following:

  • Photocell
  • Infrared
  • Hall effect
  • Sonar
  • Radar
  • Doppler effect
  • Inductive 
  • Capacitive

Just remember that proximity sensors are sensors detecting the presence or movement of objects without any physical relay or contact that information captured into an electrical signal. It can also be categorized as a proximity switch, a definition provided by the Japanese Industrial Standards (JIS) to every contactless detecting sensor. 

Does everything sound complicated? Proximity sensors suggest a sensor detecting, capturing, and relaying information without any physical contact. 

What are the Features of a Proximity Sensor?

For you to understand more about proximity sensors, we will take a closer look at their features. 

  • High-speed response rate

Proximity sensors provide a high-speed response rate, unlike switches where contact is needed for sensing. 

  • Longer service life

A proximity sensor utilizes semiconductor outputs. That means there are no moving parts depending on the operating cycle. Hence, its service life is more likely to be longer than traditional sensors.

  • Suitability for a wide array of applications

Proximity sensors are ideal for damp conditions and wide temperature range usage compared to your conventional optical detection. Did you know that proximity sensors are also ideal in phones, too, be it iOS or Android devices? 

It is composed of basic IR technology that switches off and on display based on your use. For instance, it turns off the display when a phone call is continuous, like you would not accidentally activate something while putting it close to your cheeks. 

  • Not affected by surface conditions

Further, proximity sensors are also almost not affected by surface colors of objects, as it normally detects physical changes. 

  • Contactless sensing

The good thing about having contactless proximity sensing is that it enables detection even without touching the object. That guarantees the object remains well-conditioned. 

How Does a Proximity Sensor Work?

In the most basic terms, proximity sensors work by sending data about the motion or presence of an object into an electrical signal. They output an ON signal when a certain object enters their range. You will find more variances in the way that numerous proximity sensors work, as discussed below:

  • Working principle of magnetic proximity switches 

These are switches that are straightforward and easy. The reed end of the switch is run by a magnet. When the reed switch is activated, and ON, the sensor will turn ON as well. It’s also worth mentioning that proximity sensors aren’t influenced by the color’s surface of the object detected. They depend on physical movement and the object’s motion. Hence, its colors don’t play a crucial role in the sensor’s efficacy. 

  • Working principle of inductive proximity switches 

These sensors work by sensing eddy currents, which causes magnetic loss produced by external magnetic fields on a conductive surface. The detection coil produces an AC magnetic field, and impedance changes are sensed due to produced eddy currents.

  • Working principle of a capacitive proximity sensor 

Capacitive proximity sensors work by sensing changes in capacitance between an object and sensor. Factors like the object’s size and distance will impact the amount of capacitance. Moreover, the sensor only senses any changes in capacity produced between the two. 

How Do You Test a Proximity Sensor? 

How do you test a proximity sensor? One of the most practical tools you can use is a digital multimeter. A multimeter is a mix of a multi-range DC voltmeter, multi-range ohmmeter, and multi-range ammeter, in case you didn’t know.

It is packed to the brim with all the needed parts of this configuration. When we talk about an analog multimeter, DC voltage is measured with a set of resistors attached between the circuit under test or the meter movement. 

A switch which is normally a rotary type—that enables higher resistance to be inserted—is in series with the meter movement to read greater voltages. The full-scale voltage for the whole range is performed by measuring the product of the full-scale deflection current of the movement and the total of the movement’s resistance and the series resistance. 

Here are the steps you need to do to test a proximity sensor:

  1. Set your digital multimeter to 20V DC. 
  1. Connect the red probe to the sensor signal. 
  1. Connect the black probe to Sensor GND. 
  1. Let’s say your proximity sensor signal voltage should be 12V, but it’s not detected. It means you have a bad proximity sensor.
  1. Now, let’s check for a good proximity sensor. If you receive a 0v, it means you have a bad proximity sensor. 

There you have it! We hope you are now aware of the steps you need to take on testing a proximity sensor with a digital multimeter. Are you now ready to test? If yes, share your thoughts with us by leaving your comments below!

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