RU2399047C1 - Multi-channel automated system for control of milk coagulation - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: moment of milk coagulation is detected by instrument through change in its efficient viscosity with the help of one or several sensors. Multi-channel system for control of milk coagulation comprises several groups of analog inputs for sensors of pH measurement and activity of ions with the help of ion-selective electrodes. Besides multi-channel system for control of milk coagulation comprises group of analogue inputs for thermometric sensors of viscosity based on thermocouples, and for sensors of temperature based on silicon thermoresistors. Using several groups makes it possible to conduct simultaneous monitoring of temperature, viscosity, active acidity and activity of calcium ions in process of milk coagulation.

EFFECT: development of automated device for simultaneous monitoring of several physical-chemical parametres of milk in process of its coagulation, having proper accuracy and reliability, and low cost.

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Description

The invention relates to the food industry, namely, it is a device for simultaneous monitoring of several physico-chemical parameters of milk in the process of coagulation, for example, temperature, viscosity, active acidity, activity of calcium ions (or other ions, depending on the choice of ion-selective electrodes). The clotting moment of milk is determined by the device by changing its effective viscosity using one or more sensors.

Currently, a number of physicochemical methods are used to determine the moment of milk coagulation [1]. However, only a few of them are suitable for use in industrial production. The most widely used are special viscometers, the principle of which is based on measuring the resistance to translational or torsional vibrational motion of the sensor.

The disadvantages of viscometers include the presence of internal moving parts and, as a result, the relatively high complexity and cost of construction.

The prototype of the invention is an automated two-channel device for integrated monitoring of the process of coagulation of milk [2]. The principle of its action is based on the simultaneous monitoring of two technological parameters of milk: viscosity and active acidity.

The disadvantages of the aforementioned device include the fact that the device allows measurement of only two parameters of milk (viscosity and pH), requires the use of an external potentiometer to measure active acidity, and, in addition, an additional separate thermometer is required to monitor the temperature of the medium.

The technical task of the invention is the creation of an automated device for simultaneous monitoring of several (up to 16) physico-chemical parameters of milk in the process of coagulation, which has good accuracy and reliability, low cost.

The technical problem is achieved due to the fact that the developed device uses several groups of analog inputs for sensors for various purposes, grouped by the type of signal, its level and input resistance. Four main groups of device inputs can be distinguished.

The first group includes high-resistance inputs of potentiometric sensors used to measure the pH or activity of ions using ion-selective electrodes. As converters for these inputs, precision operational amplifiers with an input impedance of about 1Tom, included in the signal repeater mode, are used. Structurally, all the converters are identical and are based on the relatively inexpensive chip 140UD24 (or its analogue ICL7650). The microcircuit is powered from a bipolar stabilized voltage source of ± 5 V. The sensitivity of the inputs (taking into account the gain of the ADC card) is approximately 10 ^-2 V.

The second group of inputs is intended for thermometric viscosity sensors based on thermocouples. The principle of operation of these sensors is based on measuring the temperature difference between two junctions of a thermocouple placed in milk at a distance of about two centimeters [3]. One of the junctions is heated due to the fact that it is glued to the surface of the resistor through which electric current flows. The power supplied to the resistor is kept constant (P≈1 W). An increase in the viscosity of milk during coagulation decreases the convection heat removal from the heated junction and is reflected in an increase in its temperature. The differential signal converters of thermocouples are based on an inexpensive 140UD6 chip (or its analogue MC1456). The microcircuits are powered from a bipolar stabilized voltage source of ± 12 V, a stabilized voltage of +5 V is used to power the heat source. The sensitivity of these inputs (taking into account the ADC card gain) is approximately 10 ^-6 V.

The third group of inputs is intended for temperature sensors based on silicon thermistors. A temperature sensor based on the LM 335 microcircuit was used as a prototype. It has a transistor type case, is relatively cheap and has quite acceptable characteristics (temperature coefficient of voltage of 10 mV / degree) in the technological temperature range (20-40 ° С). A stabilized voltage of +5 V is used to power the chips. The sensitivity of the inputs is determined by the gain of the card.

The last type of inputs is redundant and represents the direct analog inputs of the ADC card. In principle, any measuring devices having an analog output with a voltage of 0.25 V to 10 V can be connected to them.

All inputs, together with the signal conversion unit, are structurally designed as a device located in a standard PC socket for CD / DVD installation. The device is powered by a standard power bus of a personal computer.

For high-impedance inputs of potentiometric sensors, bayonet connectors are used, for the inputs of thermometric sensors three-element connectors of the “common, signal, power” type are used.

As an ADC, an inexpensive serial 16-channel data acquisition card of type A812 is used, connected to the port of a personal computer. A block diagram of a universal multi-channel automated device for controlling milk coagulation is shown in FIG.

To collect data based on the dynamic libraries supplied with the ADC card, a program has been written to poll all the inputs of the device. The program allows you to select the necessary inputs as active, set the gain, the size of the data array and its time resolution. The received data is automatically saved to a file whose name is set by the user.

The view of the working window of the data acquisition program is shown in figure 2.

The design of the device allows you to use it to monitor the gelation process directly in the cheese bath. The use of sensors of various types allows you to obtain more complete information about the technological parameters during the process of coagulation of milk. The use of several sensors of the same type, installed at different points of the cheese bath, can be useful for studying the homogeneity of the medium during the process or to determine the quality of mixing of raw materials.

REFERENCES

1. Lucey J.A. Formation and Physical Properties of Milk Protein Gels // Journal of Dairy Science, 2002 - V.85 - p. 281-294.

2. RF patent No. 2273023. Automated two-channel device for integrated monitoring of the process of milk coagulation / A.M. Osintsev, S.G. Zinoviev, O.V. Ivanenko.

3. A.M. Osintsev, N. A. Bakhtin, V. I. Braginsky, O. V. Ivanenko. Thermographic method for the study of milk coagulation. Cheese-making and butter-making, 2005, No. 5, p.20-21.

Claims (1)

A multi-channel system for controlling milk coagulation, containing several groups of analog inputs for measuring pH and ion activity using ion selective electrodes, for thermometric sensors based on thermocouples, for temperature sensors based on silicon thermistors for monitoring temperature, viscosity, active acidity and calcium ion activity.

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