The Dry Heat Loss Transducer MM0057 enables you to simulate the human body thermally while it measures the Equivalent Temperature. With this transducer the integrated effect on the body of the air temperature, the mean radiant temperature and the air velocity can be evaluated. The human body's senses are only able to feel heat loss from the body.
The dry heat loss transducer is able to measure part of this basic parameter directly, the other part of the heat loss is the evaporative heat loss. This can be estimated by measuring the humidity of the air. By measuring these two parameters it is enough for a thermal comfort evaluation according to ISO 7730 – normally four measurement parameters are required.
The term "Equivalent Temperature" is often used instead of Dry Heat Loss. Equivalent temperature, which can be calculated from the dry heat loss, is by definition the uniform temperature of a radiant black enclosure with zero air velocity in which an occupant would have the same dry heat loss as the actual non-uniform environment.

Evaluating Thermal Comfort
The heat loss value from this transducer enables you to evaluate the thermal comfort and calculate PMV values according to ISO7730 (PMV values are calculated using dry heat loss, humidity, Clo. and Met. rates). The Equivalent Temperature is also able to be calculated.

Thermal Mannequin
For thermal comfort evaluations in non-uniform conditions, for example in vehicles, measurements in several positions maybe necessary. A number of MM0057 transducers (between 8 and 10)and the "FLATMAN ", a simple thermal mannequin can be used for this application.


Transducer Design
The Dry Heat Loss Transducer is an ellipsoidal device designed to simulate the human body thermally. It contains a surface temperature sensor and surface heating element. The power to this element is adjusted automatically to bring the surface to a temperature similar to that of a human clothed as specified in the Thermal Comfort Data Logger 1221. The rate of heat production needed to reach this temperature is used as a measurement of the environmental conditions. The operative temperature is derived from the surface temperature sensor of the unheated transducer. Four major factors were taken into consideration during the design of this transducer:

Size
The size has been chosen so that the ratio between heat loss by radiation and by convection is similar to that of the human body. The human body has an effective radiation area of only 0.7 times its surface area (due the insides of the arms and legs radiating against the body). If the transducer had the same surface area as the human body, its simple shape would lose 1.4 times more heat by radiation than a human body. However, the convection heat loss per unit surface area increases as the size of an object is reduced. By reducing the size of the transducer, the mean radiant temperature and air temperature have the same weighted influence on the transducer as on a person.

Shape
The shape of the transducer is determined by the need to obtain the same angle factor to the individual room enclosures as for a human being. This has been achieved by using an ellipsoid shape.

Color
The transducer's color and emission coefficient have been chosen so that the long-wave radiation absorbed by the transducer is the same as that of both a naked and a dressed person. It is not possible to simulate people in both dark and light colored clothing for short-wave radiation. The grey color chosen simulates both naked people and people dressed in light colored clothing.

Orientation
People do not maintain the same posture. For this reason, the transducer has three settings: vertical, 30° from the vertical, and horizontal, which represent the body in the standing, sitting and lying positions respectively.

Cable Connections
The integral cable supplied with the transducer is fitted with a standard 7-pin DIN plug. Electrically, the temperature registration part of the transducer is equivalent to a Ni1000 resistor in a four-wire configuration. This means, extension cables can be used without a loss of accuracy.