Ultrasonic Proximity Sensors

Light and sound are two natural phenomena, which let every living being recognize their environment without physical contact and over widely varying distances.  Ultrasonic proximity sensors use reflected or transmitted ultrasonic waves to detect the presence or absence of a target component. The output is Boolean, that is, the sensor merely detects whether the target is or is not within the design detection range. The measurement of proximity, position and displacement of objects is essential in many different applications: valve position, level detection, process control, machine control, security etc. Proximity sensing is the technique of detecting the presence or absence of an object using a critical distance. A position sensor determines an object's coordinates (linear or angular) with respect to a reference, displacement means moving from one position to another for a specified distance (or angle). In effect, a proximity sensor is a threshold version of a position sensor.

Proximity sensors, ultrasonic can be a sensor element or chip, a sensor or transducer, an instrument or meter, a gauge or indicator, a recorder or totalizer, and a controller.  A sensor element or chip denotes a "raw" device such as a strain gage, or one with no integral signal conditioning or packaging.  A sensor or transducer is a more complex device with packaging and/or signal conditioning that is powered and provides an output such a dc voltage, a 4-20mA current loop, etc.  An instrument or meter is a self-contained unit that provides an output such as a display locally at or near the device. Typically also includes signal processing and/or conditioning.  A gauge or indicator is a device that has a (usually analog) display and no electronic output such as a tension gage.  A recorder or totalizer is an instrument that records, totalizes, or tracks force measurement over time.  Includes simple datalogging capability or advanced features such as mathematical functions, graphing, etc.  Controllers are devices that accept sensor input and provide control function (limits, PID, logic, etc.) via one or more control signal outputs.  The body style of proximity sensors, ultrasonic can be barrel, limit switch, rectangular, slot, or ring.  Electrical connections can be fixed cable, connector(s), or terminals.  Intrinsically safe ultrasonic proximity sensors are incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most ignited concentration.

Important performance specifications to consider when searching for ultrasonic proximity sensors include maximum operating distance, repeatability, sonic cone angle, impulse frequency, and transmitter frequency.  Load configurations are also important parameters to consider.  Proximity sensors, ultrasonic may switch an AC load or a DC load.  DC load configurations can be NPN or PNP.  NPN is a transistor output that switches the common or negative voltage to the load; load connected between sensor output and positive voltage supply.  PNP is a transistor output that switches the positive voltage to the load; load connected between sensor output and voltage supply common or negative.  Wire configurations are 2-wire, 3-wire NPN, 3-wire PNP, 4-wire NPN, and 4-wire PNP.

Additional parameters that are important to consider when searching for ultrasonic proximity sensors include switch types, housing materials, dimensions, and environmental operating parameters.

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Part Numbers for Ultrasonic Proximity Sensors