Hyde Park & Telemecanique …… sensing using a “background”
In industrial automation applications, often the task of a sensor is to continually and reliably sense the presence of an object from leadin- edge to trailing-edge. Even though the object itself may have an ideal, flat surface, for some applications, it may be presented in a random, unpredictable orientation, resulting in an unfavorable angle with respect to the sensor. Unfavorable incident angles to objects may return little or no signal back to the sensor.
One of the most popular modes of sensing is the Proximity mode. By definition, in the Proximity mode, the sensor emits a signal, the signal is reflected off the surface of the object, and the sensor confirms object presence if the return signal is sufficient to be detected by the sensor’s receiver. While the Proximity mode has its advantages for simplicity, and in some applications, it is the only feasible mode due to other constraints, it is challenged when the object is presented in any manner that has an unfavorable incident angle or angles.
The Hyde Park/Telemecanique line of ultrasonic sensors have a unique way of dealing with such objects. With the Hyde Park ultrasonic sensors, it is referred to as “using a background”, and with the newer Telemecanique XX Configurable ultrasonic sensors, it is called the “Reflex” mode.
With both of these Hyde Park/Telemecanique sensors in their respective modes, the window of sensing (from near limit to far limit) is intentionally installed around a “background”, and interestingly, not around the object to be sensed. In this mode, the sensors make their decision as to whether the object is present, not based on whether they receive a return echo from the object itself, but rather if the echo is received from the background. The advantage is that sensing the sensor performance is totally independent of the incident angle of the object to be sensed, as well as distance to the object. Even if the object returns no echo, the sensor determines the object is present. This distinction between echoes returned from the background or from anywhere else, is due to its ability to reliably measure the travel time of the sound to the background, and only accept echoes returning from that distance. In this mode, the independence of distance to the object is derived from a fixed distance to the background, so the object can be anywhere between the sensor and it the background. The sensor’s decision is also independent of the amplitude of the return signal, as the determination is strictly time-based, not amplitude-based.
The background can be any material from which the sensor can receive a sufficient signal. In some applications, the background can be an existing part of the machinery itself, or even the building’s floor or wall.
The Hyde Park / Telemecanique ultrasonic sensor can either switch ON or OFF its output when the object is present, to satisfy the respective needs of the electrical controls.
The background should preferably be slightly smaller in size than the object to be sensed, so that the object will block the ultrasonic signal from reaching the background when the object if fully in view.
Since 1995 & 2017 respectively, Excel Automation/Eagle Sensors & Controls have been Authorized Distributors of the Hyde Park/Telemecanique line of sensors. Contact us for technical, application, or sales support.