EN ISO 7726:2001 pdf download

EN ISO 7726:2001 pdf download.Ergonomics of the thermal environment-lnstruments for measuring physical quantities.
The accuracy of measurement of the mean radiant temperature obtained using this appliance varies considerably according to the type of environment being considered and the accuracy of measurement of the temperatures of the globe and the air and the velocity of the air. The actual measuring accuracy shall be indicated wherever it exceeds the tolerances specified in this International Standard.
The mean radiant temperature is defined in relation to the human body. The spherical shape of the globe thermometer can give a reasonable approximation of the shape of the body in the case of a seated person. An ellipsoid-shaped sensor gives a closer approximation to the human shape both in the upright position and the seated position.
The mean radiant temperature can also be calculated from measured values of the temperature of the surrounding walls and the size of these walls and their position in relation to a person (calculation of geometrical shape factors). (See annex B.)
The mean radiant temperature may also be estimated for the plane radiant temperature in six opposite directions weighted according to the projected area factors for a person. Similarly, it can be estimated from the measurement of the radiant flux from different directions.
Any other measuring device or calculation method which allows the mean radiant temperature to be determined with the accuracy specified in the following subclauses may be used.
4.1.3 The plane radiant temperature is the uniform temperature of an enclosure where the radiance on one side of a small plane element is the same as in the non-uniform actual environment.
The so-called “net” radiometer is an instrument which is often used to measure this quantity (see annex C). With this it is possible to determine the plane radiant temperature from the net radiation exchanged between the environment and the surface element and the surface temperature of the radiometer.
A radiometer with a sensor consisting of a reflective disc (polished) and an absorbent disc (painted black) can also be used.
The plane radiant temperature can also be calculated from the surface temperatures of the environment and the shape factors between the surfaces and the plane element (see annex C).
The radiant temperature asymmetry is the difference between the plane radiant temperature of the two opposite sides of a small plane element (see definition of the plane radiant temperature).
The concept of radiant temperature asymmetry is used when the mean radiant temperature does not completely describe the radiative environment, for instance when the radiation is coming from opposite parts of the space with appreciable thermal heterogeneities.
The asymmetric radiant field is defined in relation to the position of the plane element used as a reference. It is, however, necessary to specify exactly the position of the latter by means of the direction of the normal to this element.
The radiant temperature asymmetry is measured or calculated from the measured value of the plane radiant temperature in the two opposing directions.
Any other device or method which allows the radiant temperature asymmetry or the plane radiant temperature to be measured or calculated with the same accuracy as indicated below may be used.
4.1.4 The absolute humidity of the air characterizes any quantity related to the actual amount of water vapour contained in the air as opposed to quantities such as the relative humidity or the saturation level, which gives the amount of water vapour in the air in relation to the maximum amount that it can contain at a given temperature and pressure.
With regard to exchanges by evaporation between a person and the environment, it is the absolute humidity of the air which shall be taken into account. This is often expressed in the form of partial pressure of water vapour.
The partial pressure of water vapour of a mixture of humid air is the pressure which the water vapour contained in this mixture would exert if it alone occupied the volume occupied by the humid air at the same temperature.