The influence of compensation temperature on the measurement accuracy of thermal wind speed sensor

Thermal wind speed sensorIt is a device that measures fluid velocity based on the principle of heat exchange. Its core logic is: the fluid flow will take away the heat of the sensor. The higher the flow rate, the faster the heat loss. The wind speed can be calculated by monitoring the heat changes.
01. Core working principle of thermal wind speed sensor
The core components of a thermal wind speed sensor are a heating element (usually a metal wire, metal film, or semiconductor) and a temperature sensing element. These two elements measure wind speed by measuring the relationship between the rate of heat loss and wind speed. The principle behind this is described by heat dissipation laws (such as King's law): when the sensor is heated to a constant value above the fluid temperature, the heat removed by the fluid flow is quantitatively related to wind speed, i.e., Q = k⋅(Ts−Tf)⋅f(v), where: • Q is the heat loss per unit time of the sensor; • k is the heat exchange coefficient (dependent on fluid properties and sensor geometry); • Ts is the sensor temperature; • Tf is the fluid temperature; • ΔT = Ts – Tf is the temperature difference; and • f(v) is a function of the wind speed v. By measuring the heat loss (or the energy required to maintain the temperature difference), the wind speed can be calculated using a calibration curve.

2. Key components and technologies affecting wind speed measurement accuracy
   1. Sensing Element • Material Selection: The heating element must possess both a high temperature coefficient of resistance and stability. • Structure: Commonly used are "hot wire" or "hot film," with the former offering faster response and the latter providing greater mechanical strength. 2. Temperature Compensation Mechanism: Changes in ambient temperature (Tf) directly affect ΔT, so the sensor requires a built-in temperature compensation circuit or software algorithm: • Hardware includes a reference temperature probe for real-time Tf measurement; • Software corrects the heat transfer coefficient (k) to compensate for temperature-dependent changes in fluid thermophysical properties (thermal conductivity, density, etc.), ensuring stable accuracy over a wide temperature range. 3. Calibration and Calibration: The sensor must be calibrated through wind tunnel testing to establish a calibration curve for wind speed versus output signal. • The relationship between heat dissipation and wind speed is affected by sensor geometry and fluid type (air/gas). • Different application scenarios (e.g., low-speed laminar flow versus high-speed turbulent flow) require segmented calibration to reduce nonlinear errors.

3. The impact of temperature compensation on measurement accuracy
   Temperature compensation significantly impacts the measurement accuracy of hot wire anemometers. Its absence or incompleteness can lead to significant measurement deviations, while effective compensation can keep errors within acceptable limits. 1. Basic error caused by temperature fluctuations. 2. Additional error due to changes in the fluid's thermophysical properties. Fluid parameters such as thermal conductivity, density, and specific heat capacity vary with temperature, further amplifying the error. 3. Accumulated error at extreme temperatures. In environments with drastic temperature fluctuations, the above errors can compound.
4. Accuracy improvement effect after temperature compensation
   Effective temperature compensation (including hardware constant temperature control, software parameter correction, etc.) can significantly reduce the above errors. 1. Improved temperature difference stability 2. Effect of thermophysical property correction 3. Accuracy comparison in actual applications

The impact of temperature compensation on the measurement accuracy of hot wire anemometers can be as high as 10%~50% (without compensation), while effective compensation technology can reduce the error to 1%~8%, and the accuracy improvement generally exceeds 80%. The degree of its impact is positively correlated with the temperature fluctuation amplitude, fluid velocity range, and environmental extremes: the greater the temperature fluctuation and the more complex the scene, the more critical the role of compensation. Therefore, in most practical applications (especially non-constant temperature environments), temperature compensation is the core technology to ensure the measurement accuracy of hot wire anemometers. The lack of compensation will cause the instrument to lose its practical value. Jiantong Technology JT1400 Serieswind speed sensorAll of them are equipped with temperature compensation probes and are individually calibrated and calibrated before leaving the factory. While ensuring measurement accuracy, a pre-aging test is also carried out before calibration to ensure that users will not have large measurement deviations due to probe aging during use. At present, the JT1400 series wind speed sensors have been widely used in many fields such as automotive comfort measurement, building HVAC, clean room laminar flow control, wind speed metering mechanisms, etc., gradually realizing the domestic substitution of high-precision wind speed sensors.