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HE240 40kHz
Ultrasonic Sensors
Ultrasonic Sensors, for medium to long range applications
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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
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Size: 0.8" dia x 1.60" -- 1/2"
NPT |
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| HE240-B Button: 0.4 dia. x 0.1" |
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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. |
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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. |
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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.
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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.
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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.
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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 |
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| Protection |
NEMA 12 (IP43) |
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| 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
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