8. Technical notes for the product performance
8.1 Measurement principle
The products utilize the Company’s proprietary micro-machined
(MEMS) thermal calorimetric sensing technology. A thermal signal
generator (microheater) is placed on a thermally isolated membrane
where two thermistors are placed symmetrically concerning the
microheater. The flowing fluid carries away the heat from the
microheater causing a re-distribution of the temperature field which is
registered by the thermistors. The amount of heat carried by the
flowing fluid is dependent on the fluid’s mass as well as its thermal
properties. By precisely gauging the changing of the temperature field
with a metrological reference standard, the fluid’s mass flow rate can
be established and reproduced.
After the circuitry temperature compensation, and with the proper design of the MEMS sensing chip
by adding the pressure balancer that allows the flatness of the membrane at various fluidic pressure
conditions. the calorimetric thermal sensing will guarantee a pressure and temperature independent
mass flow data acquisition. The MEMS technology also allows the mass production of the sensing
elements that significantly reduces the cost compared to a traditional thermal mass flow sensing
element. It enables the current offer with superior value to the users. For additional information,
please refer to the company’s US patents and other publications made available to the public.
8.2 Precautions for the best performance of the product
8.2.1 Comparison with a third party reference meter
It is very common that a user may compare the data from the product with a third-party reference
meter, and in many cases, there could be some discrepancies.
When performing such a comparison, please note that the reference meter should have a better-
specified accuracy (about 1/3 of the product), and pay special attention to the differences in the
reading accuracy and full-scale accuracy.
A full scale accuracy = reading accuracy x (full scale flow rate/ set point (current) flow rate)
approach illustration.
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