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Wide Beam 25KHZ Ultrasonic Sensors for Air and Gasses

miniature ultrasonic sensor

ultrasonic sensor

HX25TRM Miniature

HX25TRC Aluminium Can

HX25TRE British pipe threads


  • Precision Positioning

  • Wind speed Monitoring

  • Doppler Applications

  • echo Ranging 

  • Level Measurements (Solids and Liquids)

The HX25TR is designed for applications in air and gasses. It transmits 118db signal Wide Beam 23 degrees at 25.7khz. Reception sensitivity level is -56db/V/microbar.  Range from 0m to 100m transceiver to transceiver operation, and echoes from 0.1m to 50m are achieved with conventional low cost circuitry. When applying this transducer for echo analysis, the crystal settling rate is a limiting factor as to how close an object can be. 

The HX25TRE series sensor is protected by a heavy duty chromed brass housing, with 1/8" or 3mm thick walls. It is a hex nipple 1/2 inch British Pipe Threads. The sensor can withstand rain, but water film can block the pores of the protective screen, reducing it's sensitivity until the water has evaporated or been wiped off. It should be shielded from rain. 

In the following, two HE225TR transceivers are placed facing each other at a fixed distance. One transceiver referred to as T1 is exited with various voltage levels, and the opposite transceiver referred to as T2 is used to receive the signal. The graphs below plot the output from T2

Above: T1 is exited with a 5Vp-p CMOS square wave oscillating at 25.7Khz, 70 waves are transmitted. The response as amplitude builds inside the T2 crystal is plotted above.

Above: 5Vpp CMOS/TTL square wave is applied to T1 at various frequencies. The frequency response is measured across the output wires of T2, and plotted above

graphical image 3 28khz
Above: Continuous excitation voltage oscillating at 25.7Khz  is applied to T1. The T2 resulting amplitude is plotted above.

The above illustrates, how the output of T2 decays as distance increases between T1 and T2. T1 is exited with oscillating voltage, amplitude 20V @ 25.7khz. 

Above: T1 was excited with a 30Vp-p 25.7Khz step input at using signal conditioner HES025, the illustration above shows how long it takes the system to settle on 25.7Khz. Distance between T1 and T2 is 1.5m.

Above: T1 excitation using HES025 30Vp-p FSK (frequency shift keying) signal, low frequency 26936hz (duration 20 waves) and high frequency 27800hz (duration 20 waves). The response was monitored across output pins of T2, placed 1.5m apart from T1, and plotted as shown above. Note that the ripples are digitization errors. 

Microchip PIC interface suggestions

The following example, shows how the PIC16C622 and the PIC16C71 can be interfaced to the HE2XX series transducers. For 25Khz transducers C1 an C2 should be about 2nF, R1 about 5Kohms and R2 about 7Kohms. R3 sets the level for the analog comparator of the PIC16C622 and should be high, say 50Kohm. If the A/D converter of the PIC16C71 is being used, R3 should be removed. 

There is an error in the schematic on the right, capacitors marked 2.2pF on the input and output of the operational amplifier, should be marked C1 and C2 respectively. The 4.7k ohm resistor at the input of the opAmp should be marked R1.

schematic PIC

ATMEL AVR interface suggestions

The following example, shows how the AT90S2313 microcontroller can be interfaced to the HE2XX series transducers. For 25Khz transducers C1 an C2 should be about 2nF, R1 about 5Kohms and R2 about 7Kohms. R3 sets the level for the internal analog comparator of the AT90S2313 and should be high, say 50Kohm.

There is an error in the schematic on the right, capacitors marked 2.2pF on the input and output of the operational amplifier, should be marked C1 and C2 respectively. The 4.7k ohm resistor at the input of the opAmp should be marked R1.

Schematic AVR

INTEL 8051 interface suggestions

The following example, shows how the INTEL 8051 microcontroller can be interfaced to the HE2XX series transducers. For 25Khz transducers C1 an C2 should be about 2nF, R1 about 5Kohms and R2 about 7Kohms. R3 sets the level for the analog comparator and should be high, say 50Kohm.

 

Electrical Specifications HE225TR

Parameters Values Units
Operating Frequency 25.7 kHz
Input Voltage 20 (max) Volts (RMS)
Output (SPL) @20V 118 db
Receive (Sensitivity) -56 db/V/Ubar
Impedance 300 ohm
Beam Angle 23 degrees
Bandwidth 2 kHz
Settling Decay 6 mS
Temperature -40 to 100 C
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Copyright 1999 [Hexamite]. All rights reserved. Revised: .

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