Prefabricated thermal resistance
Description
Assembled thermal resistance temperature sensor is equipped with display instrument to measure the temperature of liquid, gas medium and solid surface in the range of -200-600℃. It is widely used in petroleum, chemical industry, machinery, metallurgy, electric power, textile, food, atomic energy, aerospace and other industrial sectors and scientific and technological fields. Prefabricated thermal resistance usually consists of temperature sensing element, mounting fixture and junction box.
Optional model
Pt100, Pt1000, Cu50
Main technical index of assembly thermal resistance
| Thermal resistance type | Temperature range: ° C | Dividing sign | Allowable deviation △t℃ | WZP type platinum resistor | - 200 ~ 420 | Pt100 | Grade B (-200~800℃) tolerance ± (0.30+0.005/t/) |
| Grade A (-200~650℃) tolerance ± (0.15+0.002/t/) | |||||||
| WZC type copper resistance | - 150 ~ 100 | Cu50 | Tolerance of -50~100℃ |
Working principle of assembly thermal resistance
Thermal resistance measures temperature by using the property that the resistance of a substance changes as its temperature changes. The heated part of the thermal resistance (temperature sensing element) is double wound evenly on the skeleton made of insulating material with fine metal wire. When there is a temperature gradient in the measured medium, the measured temperature is the average temperature in the medium layer within the range of the temperature sensing element.
Assembly thermal resistance characteristics
| Assembly type structure, parts decomposition is good, easy maintenance; |
| Low cost to replace wearing parts; |
| Complete specifications, stable and reliable performance. |
| Insulation resistance |
The room temperature insulation resistance of platinum thermal resistance should be no less than 100MΩ The normal temperature insulation resistance of the copper thermal resistance should be no less than 50MΩ. The test voltage of the normal temperature insulation resistance should be 10-100V DC. Autothermal effect: Platinum resistance allows a very large current of 5mA to pass through, resulting in a temperature rise of no more than 0.3℃. Thermal response time: when there is a step change in temperature, the thermal resistance output change to equal to 50% of the step change, the time required, called thermal response time, expressed by τ0.5. |
Thermal resistance time constant
| Thermal inertness class | Time constant (seconds) | Thermal inertness class | Time constant (seconds) |
| Ⅰ | 90-180. | Ⅲ | 10 to 30 |
| Ⅱ | 30-90. | Ⅳ | 10 |
| Nominal pressure of thermal resistance: generally refers to the static external pressure that the protective tube can withstand at working temperature without cracking. |
| Very small thermal resistance Insertion depth: should not be less than 8-10 times the outer diameter of its protective casing. |
| Insulation resistance: When the ambient air temperature is 15-35℃ and the relative humidity is < 80%, the insulation resistance is 20 megohm (voltage 100V). |
| . Insulation resistance with splash-proof junction box shall be 2 megohm (voltage 100V) |
| The resistance value (R0) of the thermal resistance sensing element at 0℃ and its ratio to that at 100℃ : |
| The ratio is equal to R100 over R |
| When the indexing number is Pt10 or Pt100; R100 /R0 =1.3850±0.001 |
| When the index is Cu50, Cu100; R100 /R0 =1.3850±0.002 |
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