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

Marco Grossi, Bruno RiccòDepartment of Electrical Energy and Information Engineering

University of Bologna, Italy

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 MWF’s lifecycle in order to optimize emulsion and machine performance.

The oil concentration should be measured at regular intervals:1. Manual titration: reference laboratory method2. Refractometer: industry standard

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

•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

Top proximity

Bottom proximity

PT100The instrument is filled

with the sample under test

The ball is allowed to fall under its gravity

The oil concentration is calculated from the

measured falling time

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

Measures carried out at temperature of 25 °C

The ball falling time is function of both oil concentration and temperature

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

MWFs prepared with different oil products are characterized by different calibration equations

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.