A heating, ventilation and air-conditioning (HVAC) system typically has one key function: maintaining a comfortable temperature for an indoor climate. Regardless of the system's other properties (e.g., humidity control or pollutant monitoring), people will notice if the temperature inside a room is too warm or cold.
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Temperature control is one of the oldest automated processes for HVAC units. It relies on keeping temperatures in check. Alongside the growing interest in improving energy efficiency, automation and real-time responses to ambient conditions have become more important in HVAC systems.
Advanced temperature sensor technology, strategically integrated throughout the system, keeps HVAC performance unnoticeable.
Temperature Sensor Types
Any system is only as good as its parts. Four sensor types monitor and maintain temperature, the most notable metric of HVAC system function.
Thermistors, the most common sensors used in HVAC units, are known for their accuracy and rapid response and are the backbone of many HVAC systems. Thermistors alter resistance alongside temperature fluctuations, offering high sensitivity. They are perfect for general climate control and ensure reliable indoor temperatures.
Non-contact infrared sensors assess temperature without direct contact. Their infrared technology detects thermal radiation, making them suitable for monitoring difficult-to-reach areas or those where traditional sensors might be obstructed. Thus, they augment the HVAC system's adaptability.
Resistance temperature detectors (RTDs) are favored for their accuracy over a wide range of temperatures. Metal's resistance changes with temperature, and RTDs are thus classically used in industrial settings for their durability and reliability.
Thermocouples are vital in high-temperature applications. They work by measuring the voltage difference created at the place where two different metals meet. This makes them suitable for harsh conditions where other sensors might fail, guaranteeing that HVAC systems function optimally even in extreme environments.
Source: Amphenol Advanced Sensors
| Temperature Sensor Type |
Function |
Ideal Application |
| Thermistors |
Change resistance with temperature fluctuations, offering high sensitivity. |
General climate control in HVAC systems. |
| Resistance Temperature Detectors (RTDs) |
Measure temperature by detecting changes in the resistance of metal. |
Industrial settings for accurate temperature monitoring. |
| Thermocouples |
Measure the voltage difference created at the junction of two different metals, responding to temperature changes. |
High-temperature environments in HVAC systems. |
| Non-Contact Infrared Sensors (NCIR) |
Detect thermal radiation without direct contact using infrared technology. |
Monitoring difficult-to-reach or obstructed areas in HVAC systems. |
HVAC Temperature Sensor Integration
Modern HVAC systems are sophisticated and require intelligent design for the system and its setup. In both cases, ensuring the system is working at peak performance means finding a balance between its performance, the functionality of its sensor technology, and the environment.
Choosing HVAC Temperature Sensors
There are a range of options for the type of temperature sensor needed for an HVAC unit, but there are some universal considerations for the system and its performance:
- Response time: A sensor that is slow to respond when ambient conditions go outside preset parameters will make a space uncomfortable and increase utility bills due to system inefficiency.
- Long-term accuracy: HVAC temperature sensors should always take accurate and repeatable readings. Sensor drift should not be a concern for consumers.
- Robustness: HVAC sensors must endure the rigors of consistent use without premature failure. Temperature sensors should be made to last, which could mean investing in a customized sensor solution.
- Reliability against moisture ingress: Moisture can create a range of problems (such as shorts, corrosion, and loss of accuracy) for an inadequately protected sensor. The system must have the appropriate IP rating for the sensor’s application and environment.
Sensor Sensitivity for Testing Coordinate Measuring Machines (CMMs)
CMM accuracy can be significantly influenced by temperature due to thermal expansion and temperature gradients. When exposed to temperature alterations, materials may expand or contract, affecting both the object under measurement and the CMM.
HVAC temperature sensors must be sensitive, responsive, and accurate to alleviate such effects. This will create an indoor environment with consistent temperatures within a specified tolerance range.
HVAC Design Considerations versus Temperature Sensor Function
Even very simple HVAC systems are multifaceted.
A range of external factors can affect the capabilities of HVAC air temperature sensors if they are not accounted for in HVAC system design (particularly for HVAC air temperature sensors).
The surrounding environment will significantly affect performance, whether an HVAC temperature sensor is in an interior or exterior system. Placing a temperature sensor too close to heat sources or other equipment can result in inaccurate readings.
Similarly, installing the sensor near a window or door can affect immediate ambient conditions.
The elevation of the system itself can influence temperature sensor function. For example, in a high-rise building with a rooftop HVAC system, strategic sensor placement should account for air stratification and ensure precise temperature control across different floors.
HVAC systems may need zoning or varied setpoints for sensors at various heights to preserve reliable indoor comfort.
It is important to find the perfect ratio between the size of the HVAC system and the area it is responsible for. A system that is too small will need to work much harder than a larger one, while a system that is too big will waste energy and money.
HVAC systems need proper airflow to work efficiently. A temperature sensor in an area with poor air circulation may lead to false readings and the system working harder than necessary.
Dead air spaces with minimal or nonexistent circulation make it harder to maintain consistent temperatures because the lack of movement prevents the effective allocation of heated or cooled air.
Maintenance and Calibration
For some sensors, upkeep and regular calibration are a normal part of operation. However, HVAC ambient temperature sensor maintenance should not always be necessary.
Advanced HVAC temperature sensors are usually pre-calibrated by their manufacturer to meet operational requirements, removing the need for consumer maintenance in most applications.
Such systems are intended to withstand consistent, long-term use and the effects of environmental variables without compromised precision or reliability.
In some situations, routine calibration will need to occur. For applications where temperature must stay within a finite range, calibration can be vital for preserving ambient conditions.
The location of temperature sensors in an HVAC system can also determine whether routine calibration is necessary. For example, if a temperature sensor is close to an evaporator core or an air discharge, it may need more regular recalibration than an HVAC duct temperature sensor.
Conclusion
Temperature sensors are the pillars of any HVAC system. Their careful incorporation into system design is essential for optimal performance, whether the system focuses on maintaining comfortable climates or meeting energy efficiency standards (usually both).
Accuracy and reliability are not the only factors to consider regarding temperature control in an HVAC system. The ability to adapt quickly to changing ambient conditions is just as crucial. This is where high-quality, advanced HVAC temperature sensors make all the difference.
This information has been sourced, reviewed and adapted from materials provided by Amphenol Advanced Sensors.
For more information on this source, please visit Amphenol Advanced Sensors.