Temperature sensor fault analysis (next)
The temperature sensor is simple and mature, and the temperature sensor has a long service life. Field engineers and technicians occasionally encounter faults when using a temperature sensor.
At present, more temperature sensors are PT100, PT1000 type temperature sensors. PT100, PT1000 type temperature sensors belong to platinum resistance, platinum thermal resistance, thermal resistance type temperature sensor, manufacturers will be tested and checked out of the factory. After a period of time, individual sensor failure, the main performance is: reading, reading, reading is not allowed to infinity, reading, reading about the phenomenon of low. The causes of these phenomena are the lack of contact, short circuit, circuit break, external interference, voltage shock and so on.
(1) the problem of wires and their connection. Screws connecting sensors lead loose, copper wire oxidation, corrosion, fall off, wire insulation, insulation, aging, fall off, and so on;
(2) the problem of external interference. The electromagnetic field or shielding or grounding part of the motor, machine tool, vehicle and other equipments which are not opened or stopped periodically or on the spot or in the vicinity is invalid. The distance between the wire and the power supply line is close, etc.;
(3) the problem of voltage current shock. Power ripple, transient voltage, field environment or equipment static voltage, mechanical switch closed overvoltage, line capacitance, load circuit, overvoltage generated by charging and discharging, overcurrent, etc.;
(4) the quality of packaging. Packaging materials used, processes and other problems, resulting in waterproof, shock, insulation, stability and other performance degradation, but also the above-mentioned problems, these should be carefully analyzed by the temperature sensor manufacturers.
The temperature sensor the problems encountered in the course are not the same, not to enumerate, experienced engineers and technical personnel will be analyzed according to the specific circumstances of the scene, to take measures to effectively.
General PT100 temperature sensor failure, easy detection and judgment, use a multimeter 200&Omega file; direct measurement of the two ends of the wire resistance, then according to the value judgment table, conditional can also use the standard platinum resistance and high precision multimeter under constant temperature judgment.
Digital temperature sensor, DS18B20 is the most used, DS18B20 is generally not easily appear problem, if there are problems, in addition to the above reasons, as well as the value of the pull-up resistor in the circuit board does not match the base program timing is not set correctly, the general performance for the circuit driving ability is weak, or even incorrect display garbled etc..