| 摘要 |
FIELD: instrument making. ^ SUBSTANCE: method involves arrangement of level sensors with sensing elements, each of which is made in the form of heat-insulating substrate with thermal resistor to measure the liquid level at check points in the reservoir, alternate cyclic connection of sensing elements to measurement device simultaneously on four lower or upper level sensors, and bottom-up measurement of parametres of all sensors in each sampling cycle. Measured values are averaged during certain time interval, information signal on the state of sensors is transmitted, neighbouring sensors are connected as parametres of sensors change when they are submerged into liquid or removed from it. At that, moving level of liquid is always located between the second and the third sensors. Change of temperature of surface liquid layer is determined by means of additional thermal resistor located at lower edge of the substrate under thermal resistor for level measurement, and there specified is the threshold value of transient signal characteristic of thermal resistor located in upper part of substrate and changing the resistance value due to the change of temperature and thermal conductivity of medium - liquid or gas. Method is implemented by means of the device containing level sensors with sensing elements, which are connected to measurement device which is connected to information input of level indicator. Sensing element of each sensor is made in the form of heat insulating substrate with thermal resistor for liquid level measurement and contains additional thermal resistor arranged symmetrically under the above thermal resistor for measurement of liquid level in the centre of the substrate at the distance of not more than 2 mm. At that, thermal resistor used to determine liquid level at check point is arranged at upper edge of the substrate, and additional thermal resistor used to determine the temperature change of upper liquid layer is located at lower edge of the substrate. Both thermal resistors are connected to measurement device which together with the level measurement scheme also includes liquid temperature determining scheme and microcontroller with software, which changes threshold voltage according to which liquid - gas boundary of transient characteristic of thermal resistor located in upper part of substrate used for measurement of level at check point is determined. ^ EFFECT: improving accuracy of determining the liquid level at temperature vibrations of surface liquid layer and providing protection against false actuations. ^ 2 cl, 5 dwg |
