WZ
JIECHUANG
Overview
Industrial resistance thermometers, used as temperature sensors, are typically paired with display instruments, recording instruments, and electronic regulators. They can directly measure the temperatures of various liquids, steam, and gases, as well as the surface temperatures of solids, within the range of -200°C to 800°C during various production processes.
According to national regulations, our company produces two main categories of assembly-type resistance thermometers: Pt100 platinum resistance thermometers conforming to the IEC international standard tolerance grade, and Cu50 copper resistance thermometers conforming to professional standard tolerance grades. These are designed uniformly.
Product standards: IEC 751, IEC 1515, JB/T 8622-1997, JB/T 8623-1997
l Measurement range and accuracy:
Resistance Thermometer Type | Range (°C) | Index | Allowable deviation △ t℃ |
WZP Type Platinum Resistance Thermometer | -200 ~ 420 | Pt100 | Class B (-200 to 800°C) ±(0.30+0.005|t|) |
Class A (-200 to 650°C) ±(0.15+0.002|t|) | |||
WZC Type Copper Resistance Thermometer | -50 ~ 100 | Cu50 | -50 to 100°C ±(0.30+6.0×10-3t) |
For the resistance temperature sensor, the ratio of resistance at 100°C (R100) to the resistance at 0°C (R0), expressed as (R100/R0), is as follows:
Pt100: class A R0 = R100 = 100 ± 0.06Ω class B R0 = R100 = 100 ± 0.12Ω
R100/R0 = 1.3851 ± 0.0012
Cu50: R0 = 50 ± 0.05Ω R100/R0 = 1.428 ± 0.002
l Response Time:
The time required for the output of a resistance thermometer to change to 5% of a step change in temperature is called the response time, denoted by τ0.5.
l Nominal Pressure of Resistance Thermometer:
Nominal pressure refers to the maximum external pressure (static) that the protective tube can withstand at the working temperature without rupturing. The allowable nominal pressure is not only related to the material, diameter, and wall thickness of the protective tube but also to its structural form, installation method, immersion depth, and the velocity and type of the measured medium.
l Minimum Immersion Depth of Resistance Thermometer:
It is generally not less than 150mm (with exceptions for special products).
l Self-heating Effect:
When the measuring current through the resistance thermometer is 5mA, the temperature value corresponding to the resistance increment should not exceed 0.30°C.
l Insulation Resistance:
For the insulation resistance test, the test voltage can be any DC value from 10 to 100V, with an ambient temperature ranging from 15 to 35°C and a relative humidity not exceeding 80%. The insulation resistance value at room temperature should not be less than 100MΩ.
Working Principle
Industrial resistance thermometers are divided into two main categories: platinum resistance thermometers and copper resistance thermometers. Resistance thermometers measure temperature by utilizing the characteristic of a material to change its resistance with temperature. The sensing element (temperature-sensitive component) of a resistance thermometer is made by evenly winding fine metal wire around a frame made of insulating material. When there is a temperature gradient in the measured medium, the temperature measured is the average temperature of the medium layer where the sensing element is located.
Assembly-type resistance thermometers mainly consist of a junction box, protective tube, terminal block, insulation sleeve, and sensing element, along with various installation and fixing devices.
The sensing element of the WZP platinum resistance thermometer is a platinum wire winding. Dual-support platinum resistance thermometers are mainly used in situations where two sets of display, recording, or control instruments need to simultaneously detect the temperature at the same location. The sensing element of the WZC copper resistance thermometer is a copper wire winding.
l Thermoresistance Junction Box Structure Diagram
