A person’s health, performance and well-being depend to a great extent on the ambient conditions to which he is exposed. Temperature, humidity, air flow velocity and CO₂ content in the air must be optimally adjusted to each other for ambient conditions to be ideal. This requires careful measurement of the parameters and regulation of the air conditioning and ventilation systems.   

Large-scale air conditioning systems exist in almost all hotels, office blocks and industrial buildings, and controlled ventilation is also becoming more and more important in private houses. To achieve this, air conditioning systems need to be perfectly adjusted, because too little exchange of air means a lack of well-being, whereas an excessive air exchange rate wastes energy. The following parameters are crucial for the right ambient conditions: Air flow velocity, differential pressure between rooms and pressure drop at the filter, air humidity, air temperature and the CO₂ content.

In principle, any measurement parameter can be reliably recorded using individual measuring instruments. Handy multi-function measuring instruments with plug-in probes are convenient and easy to handle. Whichever the case, it is not only important how measurements are made, but also where; because there are more or less suitable measurement sites for every measurement parameter.

Velocity measurement

The air exchange rate is a deciding factor in air conditioning systems. This is calculated from the volume flow and the room size. In order to determine it, the air flow must be determined as a measurement parameter, and optimally set via the flow flaps.

In air conditioning technology, the preference is for thermal or vane probes for measuring flow velocity. Thermal probes are especially suitable for temperatures up to 70 °C and lower flow velocities. Vane probes provide optimum results at velocities of up to 40 metres per second. At very high temperatures and flow velocities, or when particles are present in the flow, Pitot tubes are the appropriate measurement principle. In order to achieve reproducible results on inflow or outflow vents, a measurement with a volume flow funnel and a suitable vane measuring instrument is the best solution. This records the entire volume flow, without the need for the measurer to carry out a conversion calculation based on the flow velocity and the area of the duct.

Differential pressure measurement

Air conditioning systems are equipped with filters which prevent dirt from the outside air entering the room air. Dust collects in these filters – periodic checks are needed to establish whether the filter is functional or needs to be replaced. This is done by measuring the pressure in front of and behind the filter, the result being the so-called differential pressure Δp. If the value measured is above the target value, the filter is blocked and must be replaced.

Humidity measurement

The regulation of relative humidity is important anywhere where humans or humidity-sensitive materials are in a room. Low air humidity manifests itself in humans in the form of irritation to the respiratory tract or voice and causes brittleness and cracking in materials. High humidity and partially cool surfaces can lead to the formation of condensation or even to mould growth. In air conditioning systems, it is important to determine the humidity entering a room. This takes place in a duct humidity measurement. For this purpose too, suitable handy test instruments for monitoring air humidity in ducts are available.

Temperature measurement

In temperature measurement, the measurement task determines the correct probe type, which must be properly handled.

Air temperatures in the ambient air (air flowing into the air conditioning system from outside), the inflow air (air flowing from the air conditioning system into the room, the outflow air (air flowing out of the air conditioned room) and exhaust air (air flowing from the air conditioning system to the outside) are relevant for the optimum adjustment of an air conditioning system. In addition to this, the temperature in front of and behind a heat exchanger should be measured in order to check its efficiency.

Easily operable, portable measuring instruments are available for fast and easy temperature measurement. Instruments which simultaneously measure air temperature and surface temperature by infrared are extremely practical. These allow the surface temperature of a radiator, an air vent or a window to be conveniently compared to the air temperature in the room.    

A further application for special thermometers is U-value determination, in order to find out how much heat a building is losing to the outside through the walls and windows. For this purpose, the room temperature, the outside temperature and the surface temperature on the inside of the building are measured and recorded over a time period.

Measurement of comfort

In spite of a suitable room temperature and the correct humidity in the room, a human being can still suffer from draughts. For this reason, turbulence measurements are often carried out in offices or other rooms in which people are present. Special comfort probes are available for these purposes.

Allrounders: Measurement with one instrument:

From planning to commissioning, certification, service and maintenance – air conditioning and ventilation technology is a demanding field, with widely differing measurement tasks. Energy efficiency, hygiene, operational safety, reliability and comfort requirements all have to be fulfilled. Using multi-function measuring instruments and different probes which can be easily plugged in depending on the task, various parameters such as room temperature, surface temperature, relative humidity, volume flow, absolute pressure, carbon dioxide content and heat transfer coefficient can be easily recorded.

Source: Testo

---