Resistance type temperature sensor classification description
Resistance type temperature sensor is also called contact thermometer. The material is divided into:
Platinum thermal resistance,
Copper heat resistance,
Thermistors, (NTC and PTC)
1. Contact resistance type temperature sensor temperature measurement principle:
By the heat balance principle, the two objects in contact, After a sufficient time to reach thermal equilibrium, Then their temperature must be equal. At this time through the temperature sensing element A measurement and conversion of physical parameters, Whereby the parameter values corresponding thereto, This is the contact temperature sensor temperature measurement principle. Therefore, when the specific heat capacity of the measured object is large, Contact temperature measurement of temperature measurement accuracy is relatively high, In this way it measures the actual temperature of the object. The prerequisite is that the specific heat capacity of the measured object is larger than the temperature sensor. Contact temperature sensor detection part and the measured object has good contact, Also known as the thermometer. If one of them is a thermometer, You can use it to achieve temperature measurement of another object, This temperature measurement method is called contact method.
2. What is platinum resistance temperature sensor:
Platinum resistance temperature sensor is the use of metal platinum changes in temperature when the resistance itself also changes the characteristics of the temperature to measure. Since the characteristic curve of the platinum resistance is non-linear,The standard resistance versus temperature relationship is given in the form of indexing tables,While the resistance - temperature polynomial function R (t) said.
RTD is the most accurate and stable temperature sensor,Its linearity is better than thermocouples and thermistors. But RTD is also the slowest and most expensive temperature sensor. Therefore, the most suitable for precision RTD has strict requirements,
While the speed and price are not critical application areas.
Platinum resistance temperature sensor is used to measure the air, soil and water temperature sensor. Widely used in meteorological and environmental protection departments.
3. What is the copper heat resistance temperature sensor:
Copper RTD temperature sensor is the use of metal at different temperatures for different resistance measurements. In addition to copper,Commonly used for industrial thermal resistance of metal and metal platinum. A metal wire around the bracket made of metal thermal resistance (sensor), Place it at the location where the temperature is to be measured, And then measuring its resistance. and then control temperature - resistance relationship, You can know the temperature measurement point.
Common metal thermistor temperature sensor indexing number are:
Pt100 (0 ℃ when the resistance is 100Ω platinum thermal resistance)
Pt10 (platinum resistance value of 10Ω at 0 ℃)
Cu100 (0 ℃ when the resistance is 100Ω copper thermal resistance)
Cu50 (0 ℃ when the resistance is 50Ω platinum thermal resistance)
Copper thermal resistance as a measure of temperature sensor,Usually and display instruments, recording instruments and electronic regulator supporting the use. It can directly measure the various production processes from -200 ℃ ~ 420 ℃ range of liquid, vapor and gas media and solid surface temperature.
Copper thermal resistance WZC-200, WZC-201 Model parameters
|Protection of pipe materials
|Pipe thread G1/2
|Pipe thread M27X2
4. What is the thermistor temperature sensor (NTC and PTC)
NTC temperature sensor
NTC thermistor in the use of a certain measurement power, The resistance decreases rapidly with increasing temperature (ie negative temperature coefficient). With this feature, the NTC thermistor can be measured by measuring its resistance to determine the corresponding temperature, So as to achieve the purpose of detection and control of temperature.
Usually by the NTC thermistor, probe (metal shell or plastic shell, etc., to extend the lead, and the metal terminal or connected device composition.
Ntc temperature sensor usually consists of 2 or 3 metal oxides, is manganese, cobalt, nickel and copper and other metal oxides as the main material, Using ceramic technology made of. These metal oxide materials are of semiconducting nature, Because in the conduction mode is completely similar to germanium, silicon and other semiconductor materials.When the temperature is low, the oxide material has a small number of carriers (electrons and holes)So its resistance value is higher; As the temperature increases, the number of carriers increases, so that the resistance value decreases. Ntc temperature sensor at room temperature in the range of 10O ~ 1000000 ohms, Temperature coefficient -2 [%] ~ -6.5 [%].
PTC temperature sensor
PTC is the abbreviation of Positive Temperature Coefficient, that is, positive temperature coefficient. Is a type of thermistor, It is a type of thermistor whose resistance value increases with temperature. This type of thermistor in the protection circuit has a wide range of applications. Such as in the protection circuit to install a PTC thermistor, When the temperature of the thermistor is raised to a certain temperature, The resistance value of the thermistor becomes large, thereby blocking the circuit. When the temperature drops will automatically resume is sleeping, So as to protect the entire circuit from damage.
Overheat protection of the motor is commonly used in the stator winding of the motor buried in a very small sensor with a PTC thermistor sensor. Under normal circumstances the motor thermal protection temperature sensor in a low resistance state, Does not affect the normal operation of the motor. When the internal overheating of the motor due to failure, Motor overheat protection temperature sensor with thermal resistance jump, With the relay power loss release, Motor to stop running, Wait for troubleshooting before re-running. The advantage of this method of protection is to directly monitor the temperature changes within the winding, The motor is protected before the superheat temperature breaks through the insulation level of the motor. At the same time as the motor overheat protection with the temperature sensor can be restored, It is not necessary to replace the fuse resistor.
5. Contact resistance type temperature sensor advantages and disadvantages
Contact resistance type temperature sensor The main advantage of temperature measurement is intuitive and reliable, Thermometer structure is simple and the price is relatively low. Contact temperature sensor shortcomings are:
In the contact process may damage the measured object temperature field distribution, So as to affect the thermal state of the measured medium,
Resulting in measurement error;
② Some measuring components can not fully meet with the measured object, Can not achieve sufficient heat balance, So that the temperature measurement components and the measured temperature is inconsistent, Will also bring measurement error;
③ because it takes some time to achieve heat balance, So there is temperature delay phenomenon;
④ In contact with the process, Some of the measured object has a strong corrosive and in the case of high temperature will seriously affect the performance of temperature sensing components and life.