• Ultraschallsensoren Füllstandsmessungen

Operating modes

Different operating modes and device configurations enable microsonic sensors to be used in all conceivable automation applications.

A sensor´s blind zone

determines its smallest permissible detection range. No objects or disturbing reflectors should be placed in the blind zone because this can lead to incorrect measurements.

The detection range

is measured by different standard reflectors.

The operating range

is a sensor´s typical area of operations.

The sensor can also be employed for distances up to its maximum range in the case of good reflectors.

All sensors comply with the requirements of German national (DIN) and European (EN) standards.

DIN EN 60947-5-2 Low-voltage switchgear and control gear: control circuit devices and switching elements; proximity switches
DIN EN 61000-4-2 Electromagnetic compatibility: testing and measurement techniques; electrostatic discharge immunity test
DIN EN 61000-4-3 Electromagnetic compatibility: testing and measurement techniques; radiated, radio-frequency electromagnetic field immunity test
DIN EN 61000-4-4 Electromagnetic compatibility: testing and measurement techniques; electrical transients/burst immunity test
EN 55011 Limits and methods of measurement of radio disturbance characteristics of ISM radio-frequency equipment
IEC 60068-2-6 Environmental testing – test Fc: vibration
IEC 60068-2-27 Environmental testing – test Ea and guidance: shock
EN 60529 Degrees of protection provided by closures (IP code)

The ultrasonic sensor in reflective mode (proximity switch)

represents the classic method of operation. It exploits its background interference suppression which is superior to other sensing principles. Here, the switch is activated as soon as the target is located within the preset detect point. The detect point is coupled with a hysteresis. This operating mode is suitable for, e.g. counting items on a conveyor belt or for presence detection. The overview table for distance measurement sensors lists all the sensor types that can work in reflective mode.

The window mode

is an extension of the reflective mode. In this case the switch is only activated when the target is located within a window defined by two window limits. This can be used to monitor, for example, correct bottle sizes in a crate - taller and shorter bottles are rejected. Window mode and also two-way or reflective ultrasonic barriers can be based on all ultrasonic sensors that support microsonic teach-in.

The two-way or reflective ultrasonic barrier

operates in a similar way to a photoelectric barrier. However, in contrast to the photoelectric barrier, no special triple reflector or similar device is needed. Any reflector, e.g. a metal flag, is adequate. In this case the ultrasonic sensor is set up in window mode in such a way that the fixed reflector lies within the window. The reflective ultrasonic barrier supplies a signal as soon as an object completely obscures the reflector. It does not matter whether the target absorbs all the sound or even 'deflects' it. Therefore, this operating mode is used for foams and other materials difficult to detect and for scanning objects with irregular surfaces.

The ultrasonic sensors with analogue output

transmit the measurement as a proportional voltage (0-10 V) or current (4-20 mA). For ultrasonic sensors with analogue output, the near and far window boundary of the analogue characteristic and also whether the characteristic is rising or falling can be configured. Depending on the sensor type and window width, resolution lies between 0.025 and 0.36 mm.

Ultrasonic sensors with IO-Link

permit continuous communication on all levels of the system architecture, from the sensor to the upper fieldbus level. The distance value measured is transmitted to the controller in bit serial form.

Ultrasonic double sheet controllers

operates as a one-way barrier and detects two or more sheets inadvertently stuck together. The transmitter-receiver arrangement can scan papers, films, cardboard and thin sheet metal. Signal outputs are available for indicating double and missing sheets.

double-sheet control dbk+4

The through beam barrier

consists of two units which operates as a transmitter and a receiver similar in fuction to a photoelectric barrier. The emitter sends cyclic sound impluses received by the receiver. If an object interrupts the pulses between the transmitter and the reciever, the switching output of the receiver is set.

Ultrasonic label and splice sensors

work on the same principle as ultrasonic double sheet controls. Since the interior adhesion of the labels to the backing material represents a joint without a separating air layer, label sensors must be calibrated to the backing material and the labels.

Ultrasonic edge sensors

are designed as fork sensors and also work as one-way barrier. They are used for path control and emit an analogue signal of 0–10 V or 4–20 mA which is proportional to the orientation of the path edge.