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The electronics for a complete system include the following
parts: The D-Flow UFO ASIC as described above, a microprocessor,
a power supply, an excitation stage, a communication interface
and a temperature sensor.
Power supply
The D-Flow UFO ASIC requires 5V for the analogue component and
2.7 - 5.5 V for the digital component. The ASIC also needs a
2.5 V reference. The microprocessor should preferably have the
same voltage as the digital component of the ASIC. Depending
on the transducers to be used, another voltage may be required
for the excitation.
In its electronic evaluation platforms, D-Flow uses a single
3.6 V supply voltage together with voltage step-up circuits.
Microprocessor
The UFO ASIC can be considered a standard I/O module that must
be controlled by a microprocessor. The processor calculates
the measured sing-around time data into flow data in a manner
that suits your needs. It also controls the communication to
you as a user, via a display or computerized control system.
D-Flow has worked with Hitachi H8 and later Mitsubishi M16C
microprocessors. If you have a preferred processor family you
will certainly find one that is suitable for your application,
although using the Mitsubishi M16C will save you time in designing
the software. The system normally needs an 8-bit or a 16-bit
processor with at least 5 kB RAM. The size of the software used
in D-Flow prototypes is about 10 kB. The ASIC requires a reference
clock. It is often suitable to use the internal clock of the
processor. The clock shall have a frequency of 1 - 16 MHz. For
minimum power consumption, 1 MHz is recommended.
Excitation stage
Since D-Flow technology is very versatile and fits many applications,
there are some components that need to be adapted in each case.
One is the excitation stage that powers the pulse to be sent
by the transducers. The type of excitation stage differs for
liquid applications and gas applications. The big difference
in acoustic impedance between the transducer and the gas makes
it harder to transmit a pulse in a gas than in a liquid. D-Flow
has developed a few excitation stages for 5V up to 200V and
from 250 kHz to 4 MHz of frequency.
Receiving electronics
Since we use the same transducers to both transmit and receive
the pulses, the electronics for transmission and reception of
the pulses are connected to one another.
Filter
Another component that needs to be adapted is the filter. The
filter is a band-pass filter that must be adapted to the frequency
of the transducer. In liquid applications, we normally use a
frequency of 4 MHz, and in gas the frequency is 250 - 1000 kHz.
Communication interface
To communicate with the outside world, the system needs a communication
interface. D-Flow uses an RS232 port that communicates with
a PC via optic fibre. D-Flow has also developed a pulse output
and a display. Depending on your requirements, you need to develop
an appropriate communication system. For example: 4 –
20 mA, 0 – 5 V, CAN-bus, LON Works, Bluetooth etc. |
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