WR
JIECHUANG
Overview
Industrial assembly-type thermocouples serve as temperature measurement sensors, typically used in conjunction with display instruments, recording instruments, and electronic regulators. They can directly measure the temperature of various liquid, steam, and gas media, as well as solid surface temperatures, within the range of 0 ℃ to 1800 ℃ in various production processes. According to national regulations, all types of thermocouples produced by our company meet relevant standard requirements.
Technical Parameters
Temperature Measurement Range and Allowable Range | ||||
Thermocouple Types | Code | Index | Range (℃) | Allowable Deviation (Δt℃) |
Platinum Rhodium30 — Platinum Rhodium6 | WPR | B | 600 ~ 1700 | ±1.5℃ or ±0.25%t |
Platinum Rhodium10 — Platinum | WRP | S | 0 ~ 1600 | ±1.5℃ or ±0.25%t |
Nickel Chromium — Nickel Silicon | WRN | K | 0 ~ 1200 | ±2.5℃ or ±0.75%t |
Nickel Chromium — Copper Nickel | WRE | E | 0 ~ 800 | ±2.5℃ or ±0.75%t |
Copper — Copper Nickel | WRC | T | -40 ~ 350 | ±1℃ or ±0.75%t |
Iron — Copper Nickel | WRF | J | 0 ~ 800 | ±2.5℃ or ±0.75%t |
Nickel Chromium Silicon — Nickel Silicon | WRM | N | 0 ~ 1200 | ±2.5℃ or ±0.75%t |
Note: "t" refers to the actual measured temperature of the sensing element. | ||||
l Thermal Response Time
The time required for the output of a thermocouple to change to approximately 5% of the step change in temperature is called the thermal response time, represented by τ1.5
l Nominal Pressure of Thermocouple
Nominal pressure refers to the static external pressure that the protection tube can withstand without rupturing at the operating temperature. In reality, the allowable working pressure depends not only on the material, diameter, and wall thickness of the protection tube but also on its structural form, installation method, insertion depth, as well as the flow rate and type of the measured medium.
l Thermocouple Minimum Insertion Depth
n It should be no less than 8-10 times the outer diameter of its protection tube, except for special products.
l Insulation Resistance of Thermocouple (at Room Temperature)
n The test voltage for room temperature insulation resistance is DC 500V ±50V. The atmospheric conditions for measuring room temperature insulation resistance are as follows: temperature 15-35℃, relative humidity 45%, atmospheric pressure 86-106kPa.
n a. For thermocouples longer than 1 meter, the product of the room temperature insulation resistance and its length should not be less than 100MΩ.m, i.e., Rr.L > 100MΩ.m (L > 1m), where:
l Rr - room temperature insulation resistance of the thermocouple, in MΩ
l L - length of the thermocouple, in meters.
n b. For thermocouples equal to or shorter than 1 meter, the room temperature insulation resistance should not be less than 100MΩ.
Upper Limit Temperature Insulation Resistance Table | ||
Upper limit temperature (tm℃) | Test temperature (t℃) | Resistance value (MΩ) |
100 ≤ tm < 300 | t=tm | 10 |
300 ≤ tm < 500 | t=tm | 2 |
500 ≤ tm < 850 | t=tm | 0.5 |
850 ≤ tm < 1000 | t=tm | 0.08 |
1000 ≤ tm < 1300 | t=tm | 0.02 |
tm > 1300 | t=1300 | 0.02 |
Working Principle
A thermocouple works by welding two different conductors at both ends to form a loop. The measuring end is exposed to the temperature to be measured, while the reference junction remains at a known temperature. A temperature difference between these ends generates a thermoelectric potential, which is displayed on an instrument as a corresponding temperature value.
The thermoelectric potential increases with the temperature of the measuring end and depends only on the materials of the conductors and the temperature difference, not on the length or diameter of the electrodes.
An assembled thermocouple includes a junction box, protective tube, insulating sleeve, terminal blocks, and electrodes, along with various mounting and fixing devices.
“Thermocouple working principle diagram”
“Waterproof Junction Box Diagram”
“Basic Structure of a Thermocouple”
