Sensor designed to sustain frequent cleaning

By Jane Byrne, 13-Feb-2009

Source of Article:

A new inductive proximity sensor designed for metal object and machine part detection is high temperature, washdown and detergent resistant and is targeted specifically at applications in the food and beverage industry, claims Omron.

Tom Kahn, product marketing manager for proximity sensors, Omron USA, said that the company’s new E2EH sensor can be used with bottling and filling machines, dairy industry clean-in-place applications, bakery ovens and other food and drink handling applications that require a wide temperature range.

He said the sensor has an in-built amplifier and can deliver maximum sensing capability in the 110-120°C range, as compared to the industry standard inductive proximity sensor range of 60-70°C.

Detection method

Kahn explained that the E2EH, like most inductive proximity sensors, uses the eddy current kill oscillator method to detect metal objects: "The sensor core induces a magnetic field above the sensing face that a passing metal object causes to collapse. This change of state is detected as a signal that an object is present."

Speaking to, Kahn said that the design of the new sensor was customer led, with requests from food and beverage industry clients for improvements to the company’s previous version, which was high temperature resistant but had a separate amplifier and was not designed for the rigours of detergent washdown.

“That sensor was designed primarily for embedding in mould halves for plastics fabrication and use detecting objects entering/leaving conveyor ovens,” explained Kahn.


He said that Omron studied what caused failures in fully-potted sensors exposed to cycles of extreme heat and cold in both air and water to find a more efficient way to build a reliable proximity sensor:

“Potted sensors fail most often due to thermal shock caused by the expansion and contraction that occurs as a sensor cycles between high and low temperatures. It can allow condensation to be sucked inside when temperature drops quickly.

“As a by-product of this research, Omron formulated a potting resin and special production technique that smoothly filled the internal cavity without voids, which had been a source of cracking, causing a seal failure point and eventually permitting ingress of washdown liquid,” continued Kahn.

Material selection

He said that the E2EH’s 316L stainless steel shell, plastic face, potting compound and wiring termination were all selected for their ability to protect the sensing core and electronics against the corrosive effects of washdown with high concentration detergents at elevated temperature and pressure over a long exposure time.

“The formulation of 316L stainless steel offers an extended range of corrosion resistance to the aggressive detergents and disinfectants used in food and beverage processing such that the E2EH exceeds IP69K rating requirements and carries an ECOLAB certification.”

Kahn added that the sensing range of its new tool is slightly longer than the industry standard 10mm range for a 30mm diameter sensor: “The important difference is that the E2EH does not need to shorten the sensing range due to use at high temperatures or exposure to thermal swings, in comparison to conventional sensors.”


He maintains that the E2EH has other uses besides metal object and machine part detection in that it has been used successfully in packaging applications to detect the foil layer in a tamper-evident seal lid under a plastic cap, such as those in use on cylinders of grated Italian-style.

And he said that the sensor is available in three different sizes to accommodate the various food and drink industry applications and the space available in any given sensing site.

In terms of cost, Kahn said that the E2EH will be priced higher than a conventional inductive proximity sensor in the US market:

“The cost difference is easily justified by the sensor’s ability to offer reduced labour and parts costs arising from less frequent replacement. Other sensors fail and need to be replaced often due to their inability to sustain long exposure to temperature extremes and corrosive chemicals,” he claims.

The E2EH sensor is available through Omron Europe as well, said the company.



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