Conventional photoelectric sensors for detecting PET bottles depend on refraction and the attenuation of light intensity caused by surface reflection. However, it is difficult to attain a sufficient level of excess gain with these methods. The E3ZM-B PET optimised models utilise the birefringent (double refraction) property of PET bottles to significantly increase the level of excess gain. The polarization component that is disturbed by the PET bottles as they pass along the line is cut by a special and unique Omron polarization filter. This greatly lowers the intensity of the received light level and provides enhanced stability compared to conventional sensors.

Enhanced detection stability with E3ZM-B using the double refraction property

Conventional PET detection sensor

The E3ZM-B PET optimised models use automatic light adjustment to compensate for soiling or temperature fluctuations. With conventional sensors, parameters may require resetting when the sensor or reflector becomes contaminated with dust or dirt. Temperature fluctuations may also lead to detection errors, as this can effect the performance of the LED. Original Omron light emission control technology greatly reduces the resetting work required.

The IP69k test according to DIN 40 050 part 9 is intended to simulate high pressure / steam cleaning. During the test 14-16 l/min water at 80ºC is sprayed onto the sensor from different angles with 8000-10000 kPa. The sensor may not suffer any damaging effects from high pressure water in appearance and functionality.

The detergent resistant sensors are tested on alkaline and acid based detergents commonly used in the food industry. In comparison to conventional metal or plastic housing sensors, longer sensor lifetimes of 20 times or more can be achieved.

Issue 1: Increasing the difference between usable signal and noise

Issue 2: Compensating for optical effects

As light travels through differing transparent materials (glass/PET) the following detection errors can occur:

• Lens-effect: transparent objects with convex shapes (e.g. shower gel bottles) can perform like a lens and allow too much light to be received by the sensor. This can result in a false reading that no object is present or it can cause a so-called double-triggering (2 signals for only one object).
• Total reflection: if the emitted light meets the surface of a transparent object at a certain angle, the light can be totally reflected instead of going through the transparent object. If the totally reflected beam hits the receiver, it can falsely result in a "no object" reading.

Issue 3: Process related requirements

In order to select the correct transparent detection sensor taking also machine and process related issues into consideration is very important:

• Minimal space between bottles
• Conveying speed of the bottles/containers
• Object size or shape (miniature objects, flat glass, etc)
• Limited mounting space or long distances
• Hot, wet or hygienic environments
• Detection of container and content at the same time (e.g. vial and plug, vial and lyo cake, glass syringe with or without protective cover,…)

Best choice in value for money

E3Z-B:

• For standard applications
• All transparent objects
• Excellent value for money

Best choice in reliability, flexibility, stability

E3ZM-BT:

• The "All-rounder"….stable detection of transparent objects in a wide range of applications
• All transparent objects
• Excellent chemical resistance

• The "M18 cylindrical brother" of E3ZM-BT
• Position independent detection due to co-axial optics

Best performance for dedicated applications

E3ZM-B:

• The "PET-Specialist"
• Advanced reliability due to special polarization and automatic threshold control

• Best detection performance for transparent film, flat glass in hot or wet environments or longest lifetime for frequently cleaned environments