A Portable Electronic System for in-situ Measurements of Oil Concentration in MetalWorking Fluids

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A Portable Electronic System for in-situ
Measurements of Oil Concentration in
MetalWorking Fluids
Marco Grossi, Bruno Riccò Department of
Electrical Energy and Information
Engineering University of Bologna, Italy
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MetalWorking Fluids (MWFs) oil in water
emulsions used for machine cooling and
lubrication during different finishing processes,
because of their good thermal conductivity and
lubrication properties.
The oil concentration (in the range 1 to 10)
should be kept (approximately) constant during
the MWFs lifecycle in order to optimize emulsion
and machine performance.

• The oil concentration should be measured at
  regular intervals
• Manual titration reference laboratory method
• Refractometer industry standard

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A new instrument is presented to measure the oil
concentration in MWFs

• the method is based on the measure of the sample
  viscosity

• the viscosity is measured using the falling ball
  principle

• the ball falling time is measured by two
  proximity sensors

• a PT100 thermistor is used to compensate
  viscosity variations due to temperature

• the instrument is battery-operated for in-situ
  measures

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• automated system based on the µ-controller
  STM32F103R6

• power supply by four 1.5V AAA alkaline batteries

• 2x8 monochromatic LCD and four buttons for user
  interaction

• low power consumtion average current drawn 28mA

• on-board EEPROM to store calibration files for
  different products

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The instrument is filled with the sample under
test
PT100
The ball is allowed to fall under its gravity
Top proximity
When the ball exits the top-proximity active area
the counter is activated
When the ball enters the bottom-proximity active
area the counter is deactivated
Bottom proximity
The oil concentration is calculated from the
measured falling time
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Measures carried out at temperature of 25 C
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The ball falling time is function of both oil
concentration and temperature
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For a given concentration it is
where the parameter b is also function of Coil
an iterative algorithm is used to compensate for
temperature variations using the PT100 thermistor
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MWFs prepared with different oil products are
characterized by different calibration equations
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IF YOU WANT TO KNOW MORE AND SEE A VIDEO OF THE
INSTRUMENT PLEASE READ
Marco Grossi, Bruno Riccò. A portable electronic
system for in-situ measurements of oil
concentration in MetalWorking fluids. Sensors
and Actuators A Physical, 243, 2016, 7-14.