Sensor Selection Guide

Sensor Selection for Beginners
Because there are many sensors out there, there are 5 rules that you can use to shortlist the suitable sensors for your application. This is generally a guide which can be used to select any kind of sensors. Not only optical sensors.

Lets say you have a project to do pin counting of integrated chips and you are sourcing for new sensor to complement the project. You might want to start with these:

Target Object
Sensors are all the same in the sense that they all do detection and sensing. However, the stability of the output generated will be different. If your object is as small as a pin size, then it will not be wise to use a general fiberoptic sensor head. The general fiberoptic actually has aperture angle of 60 degree. In this case, we have to select from a range of small beamspot sensors. Some laser sensors in the industry offer extremely small beamspot size such as 70 micron. An optical sensor can also be used to detect small object as certain types produce beam spot of only 0.1mm. That is fine enough for most application.

Detecting Distance
It is very important to know the range of detecting distance which is acceptable. Detecting distance means the distance between the sensor head and the object. The distance should allow the sensor to operate perfectly. As I were saying, both optical sensor and laser sensor can actuall produce small beam spot in order to detect..small pin for example. However, for an optical sensor to achieve such a small beam spot, the distance between the sensor and the object has to be very near. When i say very near, it is like 1/2 inch. If your machine does not allow you to mount your sensor this near, then you already reduce your two options into only one. That is.. Laser sensors. Some known laser sensor in the industry can actually produce a beam spot of 50micron at a distance of 7cm away from the object.

Environment
Is it a dusty environment? Is it high temperature? This is also a very importance thing to take note. Say if your machine produce heat of 500 degree F, your sensor should start to melt the minute you turn on the machine.

Mounting space
Now that you have figured out the beam spot and also the detecting distance, you probably want to have a look at the extra space your machine has. Some small machine are just too compact. Some have no problem at all because of the large free space available for mounting. Some already have mounting bracket ready. It is the most common for people to have L shape bracket ready to be used for mounting purpose. There are a lot of sensor which are designed to match the bracket easily. If you cannot have a sensor that stand vertically, then you probably want to get those that are laying down horizontally. Generally this design is called space saving flat type sensor. Bear in mind that, there will be time tthat not even one sensor will suit perfectly to your mounting requirement. In that case, you will have to customize a moutning bracket and tools to fit it in. It is unavoidable as there are many custom machines around.

Budget
Know how much you have in your pocket so you so you wont end up with costly sensor you can't afford. Bear in mind that, there are more than one sensor which can be used for a single application. Take your time, look for one that is mercy to your pocket. If you are really having budget constraint, please remember that you can try to reduce the cost simply by modification on the mounting and perhaps find a way to reduce the detecting distance.

Now let us see how five of these guides will help you to save time and selecting suitable sensor. With the information you have now, you can simply call up you supplier and just say:

"Hey, I am looking for a 0.1mm beam spot size with detecting distance of at least 5cm detecting distance which can stand high temperature and space saving. I only have $300 to spend on this"

It's as easy as that and it saves you time and energy.

Hope this sensor selection guide helps you in certain ways.