Signal conditioners help bridge the gab between the
monitoring device and the sensor. Ultrasonic Signal Conditioners are
composed of a driver and an amplifier. The driver possesses adequate
strength to excite the transducer. And the amplifier boosts the
amplitude of the returning or received signal, so that it can be
monitored using an ordinary analog to digital converter.
The illustration below shows the basic building blocks
of the Ultrasonic Hexamite Signal Conditioners. Input is fed through a
capacitor and clamped before it is conditioned for amplification.
Amplification is typically about 1000 and the signal is made available
at the output through a capacitor.
Electrical Specification |
Color |
Function |
Parameters |
Red |
Supply |
[ 0 < Vsupply < 16 ] @ 100mA max |
Orange |
Analog Out |
0 < V(p-p) < 16 |
Yellow |
Pulse In |
Low: V < 2.5 * High:
V > 0.8 |
Green |
Return (GND) |
0 |
Tx Wire (shielded) |
Sensor Actuation (drive) |
V(p-p) ~ 6 * Vsupply |
Rx Wire (shielded) |
Sensor Monitor |
Signal input (micro volts) |
The following illustrations show how the Hexamite
signal conditioner can be utilized. A user provided Pulse generator should output a train of pulses of
frequency somewhere within the bandwidth specified for this particular
sensor. If the sensor is a 40Khz sensor then the period between the
components of the pulse train should be around 25 microseconds. The number of pulses
in the train can vary depending on the
application, 20 to 40 pulses at the resonance frequency of the sensor is
usually enough for full excitation of the sensor. After the pulse train has entered the
Power Boost Driver, it may be necessary to wait a few milliseconds for
the result from the pulse train to be echoed back to the sensor. The
sound travels 344m/s hence if the surface creating the echo is 10 m
away, it will take the signal about 60 mS to travel to the surface and
back. Therefore train pulse repetition should not exceed 16 times per
second.
Below the RX and the TX lines are
connected together, here the transducer is a single transceiver. The
excitation is about a million times more powerful than the echo that needs
to be detected. It can take some time for the sensor to settle after
excitation, typically a few milliseconds.
The illustration below does not use a
transceiver like the image above, in this case the transmitter and
receiver are separated.
WARNING if the device is reverse polarized or if
the Absolute Maximum Ratings are violated, device can be damaged.
ABSOLUTE MAXIMUM RATINGS |
Ambient temperature during operation |
-40°C to +125°C |
Storage temperature |
-65°C to +150°C |
Voltage on the Red wire
with respect to the green wire |
-0.2 < V <17V |
Current in or out of all
wires except Red or Green |
< | 20mA | |
|