| Measurement
of nominal flow or ultra low flow for chemical
applications medical purposes and wafer fab
related oem flow sensors is demonstrated by
a non intrusive, non fouling sensor set using
piezo ceramic crystals. Using a patented measurement
technique system , the sensor measures the flow
rate of a fluid using a concurrent transit time
technique. The entire assembly can be manufactured
from materials such as PFA or other sonically
conductive materials.
Fluid analysis is essential in a wide range
of current applications including flowrate for
medical analysis, wafer fab ,corrosive chemicals
and many other fields rely on fast, precise,
and reproducible analyses. Tools that automate
the dosing and analysis of fluid samples are
essential for affordable performance.
Highly specialized electronic sensors have
been designed to automate sample analysis, but
the dosing of liquids – still a prominent
issue – must be done physically. This
operation is usually accomplished with specialized
micro-syringes driven by stepper motors. It's
easy to imagine the difficulty and expense associated
with such setups.
In a unique approach to this problem, EESITEC
Technologies developed a non-contact sensor
that can be used for dosing as part of a toolkit
for experiments or measurement of flow or ultra
low flow in various applications. As described
in the following, a key element of that design
was a non intrusive sensor device. Requirements
were:
- Small size
- Non contact with chemical media
- Temperature stability
- Long-term stability
- Simple, easy, and fully automated recalibration
- Linear output
To insure that the sensor is not affected
or altered by chemically aggressive fluids,
the piezo ceramic crystals are permanently fixed
into plastic wedges which in turn are clamped
onto the sensor tube ends.
This flow sensor design is not only highly
accurate but affordable. The ability to measure
extremely low flow rates by the manufacturing
of small line flow sensors and the sensor being
non contact with the process fluid enables measurement
of ultrapure or toxic chemicals. As mentioned
previously, the flow sensor wetted parts can
be manufactured out of PFA and the sensor cell
. The sensor path lengths are extended because
several traverses of the ultrasonic signal are
impractical using more popular methods of non-intrusive
sensor design. The comple flow sensor systems
consists of flow detector and signal converter.
The flow sensor elements are designed to fit
unique applications where the piezoelectric
arrangements need to be made out of standard
pieces, while the range and the resolution of
the flow sensor system is determined by a combination
of sensor frequency, sensor length of interrogation
of the tube. Standard flow sensor bore diameters
are 6,8 and 12mm. The flow sensor technology
even allows the measurement to continue even
with a high degree of bubbles in the liquid.
The flow sensor interrogation is conducted in
such a way that flow profile averaging is achieved
since the signals pass through all of the fluid
media and not only one portion.
Typical accuracy of the standard flow sensor
offering is +/- 0.3% of reading. The flow sensor
is contamination free from ions, particles,
corrosion resistant, no metal parts or mechanical
elements in contact with the fluid. The flow
sensor is easy to install with standard tube
size and threads.
Minute measurements even down to a fraction
of a mL/minute are possible over long periods
of time without needing to change sensors.
Some typical features are :
- Resolution 0.3mL/M (flight path dependant)
- 4-20mA analog output
- Binary open collector: 24 V/4 mA reed contact:
48 V/0.1 A
- as state output: limit, sign change or
error
- as pulse output: Pulse value: (0.01...1000)
units
- Width: (80...1000) ms
Work Modes :
- High Resolution Flow Meter (Mono or Bi-Directional)
- Liquid detector (alarm when no liquid in
sensor)
- Flow switch (fully programmable)
For more information contact EESITEC Technologies
or visit their website http://www.eesitec.com
Electrical :
- Power Supply: 12-36VD
- Power Consumption: 120mA (24VDC)
- Ambient Condition: 0 to 50C/30 -80% RH
- Installation: Panel Mounting (1/8 DIN)
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