What are the principles and methods for selecting thermal resistors for temperature sensors?

Thermal resistors are mainly classified into:

1) Ordinary type thermistor

According to the temperature measurement principle of thermal resistance, the change in the measured temperature is directly measured by the change in the resistance value of the thermal resistance. Therefore, the change in resistance of various wires such as the lead wires of the thermal resistance body will have an impact on temperature measurement.

2) Armored thermistor

Armored thermistor is a solid body composed of temperature sensing elements (resistors), leads, insulation materials, and stainless steel sleeves. Its outer diameter is generally between 2 and 8mm, and can be as small as 2mm. Compared with ordinary thermistors, it has the following advantages: ① Small size, no air gap inside, low measurement lag in terms of thermal inertia; ② Good mechanical performance, vibration resistance, and impact resistance; ③ Can bend, easy to install, and has a long service life.

3) End face thermistor

The end face thermistor temperature sensing element is made of specially processed resistance wire wound tightly against the end face of the thermometer. Compared with general axial resistance thermometers, it can more accurately and quickly reflect the actual temperature of the measured end face, and is suitable for measuring the end face temperature of bearing shells and other components.

4) Explosion proof thermistor

Explosion proof thermistor uses a special structure of junction box to confine the explosion of explosive mixed gas inside its shell caused by sparks or arcs within the junction box, so as not to cause excessive explosion in the production site. Explosion proof thermal resistors can be used for temperature measurement in areas with explosive hazards within Bla-B3c class zones.

The model of the thermistor is WZ □□ - □□□. The following are the meanings represented by each letter:

W-Temperature instrument

Z - Thermal resistance

□ ---- Thermal resistance materials (P-platinum resistance, C-copper resistance)

□ ---- Number of branches (single branch for empty space, double branch for 2)

□ -- Installation and fixing forms (1. Non fixed device type. 2. Fixed threaded type. 3. Removable flange type. 4. Fixed flange type. 5. Removable flange angle gauge type. 6. Fixed threaded conical protective tube type

□ - Wiring device (0. Armored protective cap with lead wire. 1. Wiring board. 2. Splash proof junction box. 3. Waterproof junction box. 4. Explosion proof junction box. 5. Spray proof junction box. 6. Round connector. 7. Flat connector. 8. Display explosion-proof junction box. 9. Armored handle with wire and plug. R. Protective cap with metal hose.). Z, Simple terminal block. F, Anti corrosion junction box

□ -- Diameter serial number (0- Φ 16mm protective tube). 1- Φ 12mm stainless steel pipe.