HE240 Sensor 40Khz Low Cost

Main Index

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, with sensitivity 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" or 3mm thick walls. The American standard NPT configuration and 1/2" pipe size, readily available mounting accessories make this sensor easy to apply and install. 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. HE240TX-B and HE240RX-B are button version of the HE240, 0.4" diameter and 0.1 height it can be clued on objects.

Microchip PIC interface suggestions

The following example, shows how the PIC16C622 and the PIC16C71 can be interfaced to the HE2XX series transducers. For 40Khz transducers C1 an 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. 

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.

ATMEL AVR interface suggestions

The following example, shows how the AT90S2313 microcontroller can be interfaced to the HE2XX series transducers. For 40Khz transducers C1 an 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.

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.

INTEL 8051 interface suggestions

The following example, shows how the INTEL 8051 microcontroller can be interfaced to the HE2XX series transducers. For 40Khz transducers C1 an 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.

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.

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 below facing north, maximum signal strength is along the 0 degree axis. As the observer with the measuring instruments moves east and west i.e. perpendicular to the 0 line signal strength degrades. The beam pattern character line shown below represents observation angles where signal has degraded by 6 decibels.