marco: Ultrasonic Sensors

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"Modular Sensor"

The new marco ultrasonic family

Introduction

Ultrasonic sensors can be used for a large range of applications, from the measuring of distances and room surveillance, to online monitoring of liquids and position detection of objects in space.

Standard ultrasonic sensors are resonance-operated, i.e. the connecting body oscillates in the resonance of its diameter to match its impedance. The result is a set relation between frequency, diameter (= size), beam characteristic and the dead range of the sensor due to the swing-out characteristic.

The Modular Transducer Principle, developped by marco using piezo wafers to actively control the connecting body. This principle, patented by marco (German patent DE 195 12 417 A 1), allows extremely small construction sizes with very high echo amplitudes; it enables unrestricted shapes of the sound field (even fan-shaped beams are possible!) and the smallest dead range ever obtained.

Manufacturing these transducers is as a rule more cost efficient than making traditional resonance oscillators; the geometrical adaptability opens the way for many new applications.

marco has created a completely new product family, the "Modular Sensor" including transducers and electronic drives.

Ultrasonic transducers in M8 housing

Housing: threaded tube M8 x 1; 14 mm long, (incl. 3mm at the front for mounting with O-ring)

Nominal frequency: 420kHz

Band width (referred to -6dB): ±30kHz

Beam angle (referred to -6dB): ±12°

Coverage: 20-80mm in transmit+receive operation, 5-100mm with two transducers operating as transmitter and receiver.

Operating temperature: -20 to +75°C

Directional characteristic in transmit-receive mode

Application examples:

Level measuring in test tubes
Distance measuring, even of very short distances, or in restricted mounting space

Ultrasonic sensors for flow measuring - measuring of current velocity

Two sensors are mounted for flow measuring, here in a plexiglas tube; the evaluation of the signals, partly very complex, is done by a digital signal processor combined with the electronic drive.
Fan-shaped ultrasound beam

The "Modular Transducer Principle" allows the formation of a sonic beam, in this case with a different beam angle in vertical and in horizontal direction. The transducer transmits and receives as a "radiating line".
Dimensions: 8 x 32 x 20 mm
Nominal Frequency: 50 kHz
Echo Amplitude: 500 mV_pp when driven: 180 V_pp, Reflector 100 x 100 mm², Distance 1 m
Feasible Range: up to 7m
Band Width (Referred to -3dB): 3 kHz
Beam Angle (Referred to -3dB) vertical: ±5°
Beam Angle (Referred to -3dB) horizontal: ±20°
Dead Range: approx. 25cm
Operating Temperature: -20 to +75 °C

vertical and horizontal directional characteristic
Application examples:
Surveillance of fork lifts and similar
Reverse sensors (sensor triangulation)
Protection of safety standards at work: surveillance of access rooms to machines
Surveillance of conveyors and assembly lines
Ultrasonic measuring in liquids
Ultrasonics in air and in liquids are distinguished by the different impedance matching depending on the medium, and by the frequency range that is used depending on the transmission properties of the medium through which sound will travel.

The ultrasonic transducer has integrated reference measuring in the housing so that temperature differences in the liquid have no influence on the measuring signal.
Measuring range (calculated from the reference surface): 10-5000mm (up to 10 000 with a very homogenous medium)
Medium: 1-component hydraulic medium
Pressure (static): up to 1000bar
Pressure (dynamic): up to 350bar in 10msec
Temperature of the medium: -45 to +95°C
Precision: 1%, 0.5% with an extremely homogenous medium
Frequency: 480kHz ultrasound; no low frequency

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Piezo Fundamentals

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marco Systemanalyse und Entwicklung GmbH
Hans-Böckler-Str. 2 . D-85221 Dachau
Tel (+49) [0] 8131 5161 0 . Fax (+49) [0] 8131 5161 66