When the Leakage sensor at work can achieve the best measurement results
When the Leakage sensor is used, there are often problems with this or that, once the problem will affect the accuracy of the instrument, then when the Leakage sensor at work can achieve the best measurement results, then the Leakage sensor When used, should pay attention to the following matters to ensure the best measurement results:
At high temperatures, such as the protection of a layer of coal ash, dust attached to the above, then the thermal resistance increases, hinder the heat conduction, then the temperature value is lower than the true value of the measured temperature. Therefore, should be kept outside the thermocouple protection tube to reduce the error.
Such as thermocouple insulation, protective tube and cable plate dirt or excessive salt residue caused by thermocouple between the furnace and the insulation between the furnace, more serious at high temperatures, which will not only cause the loss of thermoelectric power but also the introduction of interference, The resulting error is sometimes up to Baidu.
Such as the location of the thermocouple device and the depth of insertion can not reflect the true temperature of the furnace, etc. In other words, the thermocouple should not be placed too close to the door and heated place, insert the depth of at least 8 to 10 times the diameter of the protective tube ; Thermocouple protection between the casing and the gap between the wall did not fill the thermal material caused by the furnace heat overflow or cold air intrusion, so the thermocouple protection tube and the gap between the furnace wall hole refractory mud or asbestos rope and other insulating material block to avoid cold Hot air convection and affect the accuracy of temperature measurement; thermocouple cold side too close to the furnace so that the temperature exceeds 100 ℃; thermocouple device should avoid as far as possible strong magnetic field and strong electric field, so should not thermocouple and power cable The thermocouple can not be placed in the area where the measured medium is rarely flowing. When measuring the temperature of the gas in the tube with a thermocouple, it is necessary to make the thermocouple against the flow velocity direction and fully cooperate with the gas contact.
Leakage sensor is a typical temperature also has a temperature sensitivity of the semiconductor resistance, we can use two f temperature detection, temperature control, temperature compensation, microwave power measurement and regulation to control, and then we must be selected in accordance with the The need to select the appropriate type and type of application circuit, but also need to pay attention to NTC Leakage sensor temperature control range has been in line with the application circuit requirements. Although the thermistor is able to withstand a certain temperature of the thermal shock, but because of its packaging material is glass, because in order to try not to heat the semiconductor aging, we must as much as possible to avoid rapid temperature changes. The current flowing through the thermistor also causes the component itself to heat itself, resulting in a temperature difference, so we have to take this factor into account before choosing it. And because of the use of circuit insulation and electrostatic induction, the wrong wiring will lead to flow through the thermal semiconductor current is too large to damage the thermistor, where you need to pay attention to the wiring method do not have over current through the thermistor. After 5T (seconds), preferably 7T (seconds) above the time to start measuring. For systems that require high accuracy or do not want the thermal resistance of the thermal semiconductor to be aged, then we are highly reliable thermally sensitive semiconductors that have been identified by high temperature tests. The circular thermistor, which is often used as a circuit for temperature compensation, can not be used in systems where the allowable characteristics vary year by year because it is not manufactured as a component of temperature measurement and should be avoided Reliability of the system and the requirements of high-precision measurement of the meter.
Leakage sensor should be around to set some "baffle", even with a thin metal plate to cover the sensor. This prevents the debris from defusing the sensor and some of the movable parts, and this "contamination" tends to cause the movable part to be unhappy and affect the weighing accuracy. The system has no movement of the phenomenon, you can use the following methods to determine. That is, on the scale platform plus or minus about one thousandth of the rated load to see if the temperature display is reflected, there is a reflection that the movable part of the "pollution."