How to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors?

The temperature and humidity sensor of the air-conditioning box should clearly define the measurement range, allowable error, installation environment, calibration basis and maintenance method. The instrument capabilities need to match the control objectives and acceptance methods. Sensor nominal accuracy, controller display resolution and final system control accuracy are not the same indicators.

Specify the complete measuring chain during the selection phase

The probe, transmitter, controller input and display scaling may affect the results. Make sure the model, range and signal are consistent. Calibration should cover the actual range of use and describe reference equipment and recording requirements. If the probe is close to saturated air, may condense, or come into contact with cleaning agents, you need to check the applicable conditions and avoid just looking at the indicators in a dry environment at normal temperature.

The performance conditions should include range, error, response and actual temperature and humidity environment; the connection conditions should include power supply, signal, scaling and controller input matching; the management conditions should include calibration basis, records, review and confirmation after replacement. The three items correspond to different links, and you cannot give just one sensor model. How to avoid the influence of local airflow on the air supply temperature sensor of air conditioning box, please refer toHow should the air supply temperature sensor of the air conditioning box avoid the influence of local airflow?。

The measurement range and control objectives must match

The measurement range of the sensor should cover the actual possible temperature and humidity. If you select based on the normal operating range only, the range may be exceeded during dehumidification startup or winter preheating. The allowable error should match the control accuracy requirements, but the sensor nominal accuracy cannot be directly regarded as the system control accuracy. The sampling period, filter settings and actuator response of the controller will also affect the final control effect.

What control objectives should be clarified when selecting a constant temperature and humidity air conditioning box? Please refer toWhat control objectives should be clarified when selecting a constant temperature and humidity air conditioning box? . Please refer to how the allowable fluctuations of constant temperature and humidity units should be written into the technical requirements.How should the allowable fluctuations of constant temperature and humidity units be written into the technical requirements?。

Installation location affects reading representativeness

Temperature and humidity sensors should be installed at a location that can represent the target air state and avoid hot and cold stratification, coil local jets, direct humidification steam, and wall effects. If the supply air temperature probe is installed in a local cold air flow, the reading may be low; if the return air humidity probe is close to a wet surface, the reading may be high. Depending on the installation location, the representativeness of the readings is different.

Mixing section length and air flow uniformity, please refer toHow long is the air mixing distance required in the mixing section of the air conditioning box? . For the influence of wind speed facing the coil, please refer toWhat impact does the coil head-on wind speed have on heat exchange and water entrainment in the air conditioning box? . The location of the measuring points should be clearly marked on the system diagram and box structure diagram.

Condensation and environmental pollution should be checked separately

The humidity inside the air conditioning box may be close to saturation, and condensation may form on the surface of the probe. Some sensors may drift or be damaged in long-term high-humidity environments. If the probe may come into contact with cleaning agents, disinfectants or process gases, its material compatibility and protection level also need to be checked. Sensors with capacitive, resistive or other principles may behave differently in high humidity.

Whether chemical filter materials and on-site cleaning agents need to be confirmed for compatibility, please refer toDo chemical filter media and on-site cleaning agents need to be confirmed for compatibility? . Why water sealing is often needed for negative pressure drainage of air conditioning boxes? Please refer toWhy does negative pressure drainage of air conditioning boxes often require water sealing?。

Calibration requirements should be written to be executable

Calibration requirements should specify the calibration basis, reference equipment, calibration points, allowable deviations, recording format and calibration cycle. Calibration points should cover the common operating range, rather than just calibrating one point. Calibration records should be traceable to the equipment number, sensor number, date and calibrator. Whether recalibration is required after sensor replacement should also be stated in the maintenance documentation.

Please refer to the table of points that need to be provided before the air-conditioning box is connected to the building automation system.What point tables need to be provided before the air-conditioning box is connected to the building automation system? . For condition checks before starting the machine for the first time, please refer toWhat conditions need to be checked before the air conditioner is turned on for the first time? . During debugging, the consistency of the sensor readings with the reference instrument should be checked.

What to check first when a deviation is found on site

First confirm the comparison instrument and installation status, and then check the wiring, scaling and the effects of contamination and condensation. You cannot just adjust the controller bias to make a certain point look consistent when the cause is unknown. After the probe is replaced, the measuring range and program configuration should be confirmed, a review should be arranged according to project requirements, and the old and new numbers and change records should be kept.

For the relationship between control logic and measuring points, please refer toHow to change the debugging sequence of air conditioning box from stand-alone unit to system linkage? . How temperature and humidity sensors affect dehumidification and humidification control, please refer toWhy do we need to consider the temperature when selecting an air-conditioning box based on relative humidity?。

Aili industrial supporting equipment

Aili Industrial can check the measurement link interface in combination with the control configuration, and the project party will explain the acceptance and calibration requirements in advance, which will help select the appropriate sensor and data range. Aili's industrial manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The sensor installation position, control interface and box structure can be matched in the same package; non-standard configurations can be installed according to the measurement point requirements.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. Specific sensor selection, calibration requirements and delivery scope still need to be verified based on the corresponding configuration data and on-site working conditions. Actual results are subject to on-site calibration and performance test results.

Submit project parameters:https://ailigy.com/contactus.html

Related questions and answers

Is the sensor nominal accuracy the system control accuracy?
no. System control accuracy is also affected by installation position, controller sampling, actuator response and load changes, of which sensor accuracy is only one part.

How often do sensors need to be calibrated?
The calibration cycle should be determined based on the use environment, sensor type and project requirements. High humidity or polluted environments may require more frequent inspections and calibrations.

Can Aili Industries assist in determining sensor installation and calibration requirements?
The sensor selection and interface can be checked based on the control objectives, measuring point locations and acceptance methods. Specific calibration requirements need to be confirmed based on project conditions and product data.

Related articles

1. How should the air supply temperature sensor of the air conditioning box avoid the influence of local airflow?

2. What control objectives should be clarified when selecting a constant temperature and humidity air conditioning box?

3. What point tables need to be provided before the air-conditioning box is connected to the building automation system?

4. Why do we need to consider the temperature when selecting an air-conditioning box based on relative humidity?

Key points for selection and acceptance inspection