Failsafe Object Detection

In applications where we want to set an alarm when an object appears, we normally program a switch to close when a target is closer than some setpoint.   This problem becomes difficult when we don’t know in advance what the target will look like, or what its position will be, with respect to the sensor.

If sound strikes the object of interest at an oblique angle, the reflection can go away from the sensor, rather than return to be detected.  This can make the application unreliable.  However, there IS a way to improve the situation.

Example:  Detecting a truck backing up to a loading dock.

The objective is to either open the door when a truck backs up, or sound an alarm, so personnel can receive the truck.  What if the truck is small or odd shaped and there is no good target for sound to bounce off from?FailSafe-Graphic

The solution?  Don’t try to detect the truck, instead, detect the ground!  Since the ground is a stable target, program the sensor to switch the alarm off when it sees the ground, and turn the alarm on when it sees anything else.

If a truck pulls up that has no good surfaces for bouncing sound from, the sensor will lose the target and not detect anything.   To make this technique failsafe, we have to manage the situation where a truck DOES produce a useful reflection.   To do this, simply set the minimum range close to the ground.   If the distance to the ground is 150″, you could set the sensor to close when an object is detected closer than 130″.   Any object greater than 20″ tall would open the door or trigger the alarm.

We still have to manage variations due to temperature swings (1% for every 10 degrees F). By setting the switch to window mode, and enabling it for a range of 130” to 170”, we should eliminate the impact of seasonal temperature variations.

You may still see false triggers due to animals or people in the bay area.  SenixVIEW software will allow you to experiment with sensor gain and power, and apply filtering such that a vehicle or other interrupting target will have to be present for a specified period of time before the alarm is set.  This should permit you to minimize, if not fully eliminate, false triggering.


Whether used indoors or out, ToughSonic sensors can take abuse. Rugged electronic components are epoxy potted into small stainless steel housings, and there are no mechanical parts to break. IEC compliant electrical interfaces are protected from reversed connections and overvoltages.

These proximity sensors easily connect with all common automation equipment. Applications range from simple ON/OFF switches to relay connections, PLC inputs and multi-sensor detection networks. They are cost effective, with many user-adjustable features built into the sensor’s software – power that you can unlock with our SenixVIEW PC software.

Object Detection Applications
Ultrasonic proximity sensors are found in applications where the presence or absence of a material, object or person is important in the control of a machine or process. They are commonly found in printing, converting, robotics, material handling and transportation industries.

Senix Toughsonix 3
Senix Toughsonix 12
Senix Toughsonix 14
Senix Toughsonix 30
Senix Toughsonix 50