Commonly used thermal resistance temperature measuring components

External wound integral sintered platinum resistance element

Platinum resistance operating temperature
When producing platinum resistors, the temperature measuring elements are mainly configured based on the temperature measurement range and on-site vibration conditions. Generally, platinum resistors are produced using externally wound sintered platinum resistor elements and mica platinum resistor elements. In theory and textbooks, it is often described that the range of use for industrial platinum resistors is -200~850 ℃. However, the maximum actual temperature for industrial platinum resistors is not more than 500 ℃. Due to the higher insulation resistance requirements for measuring high temperatures with thermal resistors than thermocouples, and the difficulty in ensuring the high-temperature insulation stability of platinum resistors, thermocouples should be used for temperature measurement above 300 ℃. Thermoresistors measure low temperatures, while thermocouples measure high temperatures.

Regarding the price of platinum resistors
The price of platinum resistors is also a topic of concern for everyone. Taking the most commonly used assembled thermoelectric resistors as an example, let's have a clear understanding of the reasons for the price differences of the same model of platinum resistors. When it comes to the price of platinum resistors, it is necessary to first understand the composition of platinum resistors. Prefabricated platinum resistors consist of six components:
1. Protection tube
Platinum resistance protection tubes are usually made of 304 or 1Cr18Ni9Ti according to national standards, with a wall thickness of 2mm. By reducing the thickness of the protective tube wall and changing the material to stainless iron, production costs can be reduced. Thin walled tubes are lightweight, while stainless iron tubes have a magnetic affinity.

2. Platinum resistance element
Platinum resistor manufacturers usually configure the platinum resistor components in the above table based on user usage, and platinum resistors have inherent quality and cost differences in the production process. The inner wound ceramic platinum resistance element and mica platinum resistance element are both made by winding pure platinum wire. The cost reduction method is to reduce the diameter of the platinum wire used to make the element, reducing the element cost to 1/4 to 1/6 of the original product. However, this method has a fatal impact on the service life and temperature measurement of the platinum resistance.

3. Platinum resistance element lead
The lead wire of platinum resistance element is made of pure silver wire with a diameter of 0.4mm -0.6mm according to national standards. Generally, the higher the temperature and the longer the length, the thicker the lead wire diameter. At present, low-priced platinum resistors on the market mostly replace pure silver leads with silver plated alloy leads or reduce lead diameter to minimize the use of precious metals, and the cost can be reduced to 1/4 of the cost of silver leads. But doing so has a significant impact on the accuracy and service life of platinum resistance temperature measurement.

4. Insulated magnetic beads
Platinum resistance insulated magnetic beads are threaded on the component leads to insulate the leads from each other and from the protective tube. Reducing costs usually involves using inferior ceramic materials, while good ceramics are white and shiny, distinguishable by the naked eye.

5. Wiring board
The platinum resistance terminal block is used to fix external cables and component leads. Reducing costs usually involves using inferior ceramic materials, while good ceramics are white and shiny, distinguishable by the naked eye.

6. Platinum resistance junction box
Platinum resistance junction boxes are usually made of precision die cast aluminum alloy, with requirements for thickness and strength. Reducing costs usually involves reducing the thickness of the junction box and using recycled aluminum die-casting. The strength, thickness, weight, and precision of the junction box vary greatly, and the cost can be reduced to 1/2 to 1/3 of the original product.

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