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The Influence of Insertion Depth on the Measurement Accuracy of Pipeline Temperature and Humidity Transmitters
Date: 2025-12-19Read: 9
Pipeline type temperature and humidity transmitterBy inserting a probe into an air duct or process pipeline to collect medium parameters, the depth of insertion directly affects the representativeness and response speed of the measurement.
Root cause of the problem: There is a phenomenon of velocity and temperature humidity stratification in the airflow inside the pipeline - the central area has high velocity and uniform mixing, while the area near the pipe wall is easily affected by external environmental heat conduction, forming a "cold boundary layer". If the probe is inserted too shallowly (<1/3 of the pipe diameter), it will mainly sense non representative gases near the pipe wall, resulting in low (winter) or high (summer) readings.
Best practice:
The recommended insertion depth is ≥ 1/2 of the pipeline diameter, ideally at 2/3 to enter the mainstream core area;
For rectangular ducts, the probe should extend to the center area of the section and avoid flow disturbances such as bends and valves (upstream ≥ 5D, downstream ≥ 2D);
Small diameter pipelines (<100mm) can use fully inserted probe rods to ensure that all temperature/humidity sensing components are exposed to the airflow;
In high-temperature or corrosive media, it is necessary to balance the insertion depth with the pressure/temperature resistance limits of the probe.
Actual test case: In a certain HVAC system, when the insertion depth is only 50mm (pipe diameter 300mm), the humidity reading is 8% RH lower than the center value; after adjusting to 180mm, the deviation is reduced to ± 1.5% RH.
In addition, excessive length of the probe may cause vibration resonance, and a support frame needs to be installed. Some transmitters offer an "adjustable insertion depth" design for easy on-site optimization.
Overall, a reasonable design of insertion depth is essential to ensurePipeline type temperature and humidity transmitterThe key installation elements for data authenticity and reliability.