Hexamite

HE240TR 40Khz Low Cost

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HE240 40kHz Ultrasonic Sensors

Ultrasonic Sensors, for medium to long range applications

  • Precision Positioning

  • Wind speed Monitoring

  • Doppler Applications

  • Echo Ranging 

  • Level Measurements (Solids and Liquids)

HE240TX. is an Ultrasonic Ceramic Transmitter, it can produce wide beam up to 120db output SPL (Sound Pressure Level) at 40 kHz in air.  Single conductor shielded cable extends from the back of this sensor for connection to a driver circuit.

HE240RX is an Ultrasonic Ceramic Receiver.  It can pick up 40kHz vibration or sound waves with sensitivity of up to -53dB/V/microbar.  Single conductor shielded cable extends from the back of this sensor.

The HE240 series sensor is protected by a heavy duty chromed brass housing with 1/8" (3mm) thick walls.  The American standard NPT configuration, 1/2" pipe size, and readily available mounting accessories, make this sensor easy to apply and install.  The sensor can withstand rain; however, water film can block the pores of the protective screen, reducing its sensitivity until the water has evaporated or been wiped off.  It should be shielded from rain.  HE240TX-B and HE240RX-B are button versions of the HE240,   With a 0.4" diameter and 0.1" height, it can be glued on objects.

SENSOR APPLICATION EXAMPLES

 

Size: 0.8" dia x 1.60" -- 1/2" NPT

he240 transmitter receiver
HE240-B Button: 0.4 dia. x 0.1" ceramic button sensor
In the following a HE240RX receiver is placed opposite a HE240TX transmitter at a fixed distance.  The transmitter, referred to as T1, is excited with various voltage levels.  The opposite receiver, referred to as T2, is used to receive the signal.  The graphs below plot the output from T2.

 

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 Above: T1 is excited with a 5Vp-p CMOS square wave oscillating at 40kHz.  100 waves are transmitted.  The response as amplitude builds inside the T2 crystal is plotted above.
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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

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Above: Continuous excitation voltage oscillating at 40kHz  is applied to T1.  The T2 resulting amplitude is plotted above.
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The above illustrates how the output of T2 decays as distance increases between T1 and T2.  T1 is excited with oscillating voltage, amplitude 28V. 
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Above: T1 was excited with a 30Vp-p 40kHz step input using signal conditioner HE40SCR.  The illustration above shows how long it takes the system to settle on 40kHz.  Distance between T1 and T2 is1.5m.
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Above: T1 excitation using HE40SCR 30Vp-p FSK (Frequency Shift Keying) signal, low frequency 38647Hz (duration 26 waves) and high frequency 40201Hz (duration 26 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 schematic on the right shows how the PIC16C622 and the PIC16C71 can be interfaced to the HE2XX series transducers.  For 40kHz transducers, C1 and C2 should be about 2nF, R1 about 3Kohms, and R2 about 5Kohms.  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. 

ATMEL AVR interface suggestions

The schematic on the right  shows how the AT90S2313 microcontroller can be interfaced to the HE2XX series transducers.  For 40kHz transducers, C1 and C2 should be about 2nF, R1 about 3Kohms, and R2 about 5Kohms.  R3 sets the level for the internal analog comparator of the AT90S2313, and should be high, say 50Kohm.

 

INTEL 8051 interface suggestions

The schematic on the right shows how the INTEL 8051 microcontroller can be interfaced to the HE2XX series transducers.  For 40kHz transducers, C1 and C2 should be about 2nF, R1 about 3Kohms, and R2 about 5Kohms.  R3 sets the level for the analog comparator, and should be high, say 50Kohm.

 

Cable length between the HE240 series transducers and a signal conditioner is left to the user's discretion.  At 10m lengths, the added environmental noise and signal reduction at 40kHz is insignificant.

Beam Pattern

The sensor is located in the locus of the polar plot (shown right) facing north.  Maximum signal strength is along the 0 degree axis.  As the observer with the measuring instruments moves east and west, that is, perpendicular to the 0 line, signal strength degrades. The beam pattern character line represents observation angles where signal has degraded by 6 decibels. 

 

Electrical Specifications HE240TX

Parameters Values Units
Operating Frequency 40 kHz
Input Voltage 25 (max) Volts (RMS)
Output (SPL) 115 db
Input Impedance 300 ohm
Beam Spread 12 degrees
Bandwidth 2 kHz
Temperature -40 to 100 C

Electrical Specifications HE240RX

Parameters Values Units
Operating Frequency 40 kHz
Receive (Sensitivity) -53 dB/V/Ubar
Output Impedance 300 ohm
Reception Angle 12 degrees
Bandwidth 2 kHz
Temperature -40 to 100 C

Housing HE2XX Series

Housing Description Units
Material Type Brass  
Protection NEMA 12 (IP43)  
Diameter 0.8 In
Diameter 20  mm
Length 1.6 In
Length 41 mm
Leads Length (attached) 0.3 meters
Panel Nut Threads 1/2" - 20

NPT