Both flat-surface platinum resistance thermometers and screw-in platinum resistance thermometers are widely used in industrial temperature measurement, but they differ fundamentally in structural design, installation mechanisms, performance parameters, and application scenarios. The following systematically distinguishes between the two from five dimensions: core structure, installation method, performance characteristics, application suitability, and selection considerations, combining key parameters and examples.
I. Core Structural Design and Contact Mechanism
Flat-surface Platinum Resistance Thermometer:
Sensing Element Packaging: Platinum wire or film is directly embedded in a rigid end face (thickness usually <1mm), forming a flat contact surface. High-density magnesium oxide insulation is used internally to enhance thermal conductivity and mechanical strength. The protective sheath is often made of stainless steel or ceramic to ensure resistance to contamination and corrosion.
Contact Method: The end face is a fixed planar structure, achieving heat conduction through direct contact with the measured surface, reducing thermal resistance errors.
Screw-in Platinum Resistance Thermometer:
Sensing Element Packaging: The sensing head is placed inside a threaded protective tube (such as stainless steel or alloy), fixed by screwing it in. The internal structure is similar to traditional axial thermal resistors, but with added threading for easier installation.
Contact Method: The sensing point is located at the tip or side of the probe and needs to be inserted into the measured medium (such as liquid or pipe) through a threaded hole; it is not optimized for surface contact.
Core Difference: Flat-surface type uses direct contact with the surface, emphasizing low thermal resistance; screw-in type relies on threaded installation, and the sensing point may not be directly exposed to the surface.
II. Installation Method and Fixing Mechanism
Flat-surface Type:
Requires precise alignment with the measured surface, commonly using threaded compression (such as M8×1) or flange fixing, with thermal conductive grease to enhance contact; after installation, it is necessary to verify that there are no gaps in the end face, suitable for flat or slightly curved surfaces.
Caution: Forcing the protective tube to bend will cause measurement distortion; the installation torque is usually ≤5 N·m.
Screw-in Platinum Resistance Thermometer:
Screwed into a pre-reserved hole in the equipment (such as a pipe or cavity), without the need for additional fixing parts; installation is simple, but it is necessary to ensure thread matching (such as G1/2 or NPT standard).
Precautions: Loose threads or poor sealing can easily lead to media leakage; a thermal insulation gasket is required in high-temperature environments.
Key Differences: Flat-type sensors require high-precision contact to reduce heat loss; screw-type sensors prioritize quick threaded installation and are suitable for insertion-type measurements.
III. Performance Parameters and Measurement Characteristics Comparison
|
Parameter |
Flat-Type Surface Sensor |
Screw-Type Platinum Resistance Thermometer |
|
Response Time |
Milliseconds (τ63%) (Thin surface, low thermal resistance) |
Seconds (Threaded structure increases heat conduction path) |
|
Accuracy Class |
Class A (±0.15°C) or higher |
Class B (±0.30°C), affected by threaded installation gap |
|
Temperature Range |
-200°C~850°C (Ceramic encapsulated type) |
-50°C~400°C (Thread material limits high temperature) |
|
Vibration Resistance |
Excellent (Rigid encapsulation reduces resonance) |
Medium (Threaded connection is prone to loosening) |
|
Long-Term Stability |
High (Magnesium oxide filling prevents contamination) |
Medium (Thread sealing affects reliability) |
IV. Application Scenarios and Adaptability Differences
Flat-Type Surface Sensor Application Scenarios:
High-precision surface temperature measurement: Such as bearing shells, reactor sealing surfaces, or semiconductor wafer carriers, requiring close contact to capture the true temperature.
Harsh environments: Chemical pipeline corrosion monitoring (Hastelloy casing for corrosion resistance), or vibration areas of nuclear power equipment.
Example: Motor bearing housing temperature measurement, fixed by threaded compression, with a response time as fast as milliseconds.
Screw-Type Platinum Resistance Thermometer Application Scenarios:
Insertion-type measurement: Such as pipeline fluid and storage tank liquid temperature monitoring, the threaded design facilitates screwing into standard interfaces.
General industrial applications: Lower cost, suitable for non-corrosive environments such as food processing and HVAC systems.
Example: Condenser outlet water temperature monitoring, long-rod threaded structure enables long-distance temperature measurement. Key Differences: Flat-type sensors are optimized for surface contact; screw-type sensors are suitable for insertion into media for measurement, offering high flexibility but lower accuracy.
V. Purchasing Considerations and Summary Recommendations
Material Selection:
Flat-type sensors prioritize stainless steel or ceramic packaging (corrosion resistance); screw-type sensors should use 316L threaded tubes to suit fluid environments.
Accuracy and Cost:
Flat-type sensors with A-grade accuracy have a higher unit price (200–300 RMB) and are suitable for precision applications; screw-type sensors with B-grade accuracy are more economical (100–200 RMB) and suitable for budget-constrained projects.
Installation Assessment:
Choose flat-type sensors for flat surfaces; choose screw-type sensors if a standard threaded interface is available. Custom requirements (such as ultra-thin end faces or special threads) require prior communication with the manufacturer.
Recommended Brands:
Wuxi Zhongce Sensor Technology Co., Ltd. offers high-precision flat-type sensors (nuclear power certified); Anhui Tiankang Group's screw-type products offer excellent cost-effectiveness.
Summary: Flat-type platinum resistance thermometers achieve high-precision, fast-response surface temperature measurement through direct contact with the surface, suitable for demanding environments; screw-type platinum resistance thermometers simplify insertion measurement through threaded installation, offering lower cost but limited response and accuracy. When choosing, prioritize matching the application requirements: flat-type for surface monitoring, screw-type for media insertion.
