Page 55 - FoodFocusThailand No.158 May 2019

SCOOP

buttons are pressed simultaneously, the system will automatically readjust the mathematical
equation inside the microcontroller. This helps save time and cost as there is no need to
send the device back to its manufacturer.
Using the salt meter is easy. Dip the probe’s golden metallic tip into liquid food, long
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press the power button, the %NaCl and face symbol will be shown on the display. They
will disappear if the power button is released. After each use, the device should be cleaned
and dried or wiped with wet tissue paper. If fat stain remains, dishwashing liquid may be
used to clean the probe’s tip. The device should not be left dipped in food, nor is it
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recommended to be used with hot food as it is suitable for room temperature only.

voltage converter so that the voltage can be read ข้อมูลเพิ่มเติม/Additional Information
by the microcontroller using an analog-to-digital 1 เครื่องวัดความเค็มในอาหาร CHEM meter พัฒนาโดยคณะวิศวกรรมศาสตร์ มหาวิทยาลัยมหิดล
converter (ADC). The read voltage will then be Salt meter, named CHEM meter, is developed by the Faculty of Engineering, Mahidol University
converted back to show the electrical current
volume that flows from the anode to the cathode,
which will then be used to calculate the sodium
chloride percentage (%NaCl). The microcontroller
then sends the calculated value to the 128x64
pixels OLED display. The circuits mentioned here
are battery-powered, and the voltage is controlled
by an integrated circuit.
The microcontroller is embedded with a
mathematical equation that calculates sodium
chloride percentage (%NaCl) from conductivity. A
vital step, therefore, is to collect data to formulate
the equation for such correlation. This can be done
by preparing sampling saline solutions with known
concentration such as 0.1%, 0.3%, 0.6%, 0.9%
and 1.5%. The data of electrical charge flowing
through the probe dipped in each sampling solution
will then be collected. The result shows that there
is a linear correlation between the measured
electrical current and the sodium chloride
percentage (%NaCl). The variable of the linear
equation from the data collection experiment will
then be recorded in the microcontroller and later
be used in the calculation for salinity in a food
sample. At present, the formulated equation is
based on sodium chloride solutions, which are
different from real food matrix. The formulation of
the mathematical equations that are suitable for
each type of food involves the collection of a lot of
data. This system is flexible and can be further
improved in the future, thus enabling the processing
program to be uploaded continuously.
Apart from displaying salinity in sodium chloride
percentage (%NaCl), a salt meter can also display
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symbols that facilitate easy understanding such as
a smiley face when there is low salinity (less than
0.7 %NaCl), a normal face for medium salinity
(between 0.7-0.9 %NaCI), and an unhappy face
for high salinity (more than 0.9 %NaCl). The
percentage; however, does not indicate a
consumption unit. Even with a low percentage of
sodium, if a higher amount of food is consumed,
the amount of sodium intake into the body will also
increase. Therefore, consumption unit should also
be taken into consideration together with the
displayed sodium chloride percentage.
Continuous use of the device during a
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prolonged period of time may wear away or damage
the probe. Impurities may intervene in the reading
of electrical conductivity, leading to inaccurate
results. In this system, user can calibrate the
device by referring to the standard saline solution
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(0.9 %NaCl). When the calibration and power
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