Testing Room Atmosphere

The Control Of The Testing Room Atmosphere

• The THERMOSTATS and HYGROMETER CONTROL VALVES operates by compressed air.
• The air input to the conditioning plant may come from outside or be recirculated air, or a mixture of both.
• In all instance it is filtered before heating and conditioning.
• A fan blows the conditioned air in to the laboratory through special ducts with lowered outlets in the ceiling.
• All the windows are double glazed used to prevent unwanted air coming in from the corridor when people pass in and out of the laboratory.
• Automatic two "towers" are used, one for adding moisture and one for subtracting moisture from the air.

Measurement of Moisture Regain

By oven dry method (Direct)

• It contains the fiber sample in a mesh container.
• The container is suspended inside the oven from one pan of balance, the mechanism of which is outside the oven.
• This ensures that the weight of the sample can be monitored without disturbing the system.

ADVANTAGE

• All the weighing is carried out inside the oven.
• The use of the conditioning oven to dry a sample is correct standard procedure; any other method of sample drying has to be checked for accuracy against it.
• The use of the conditioning oven to dry a sample is correct standard procedure; any other method of sample drying has to be checked for accuracy against it.

Measurement of Atmospheric Moisture

Wet & Dry Bulb Hygrometer

• This is an instrument equipped with two thermometers, side by side.
• The bulb of one of the thermometers is covered with a muslin wick dipping into water.
• The water is absorbed up the muslin and evaporates, cooling.
• The difference between the wet and dry bulb temperatures is called the wet bulb depression.
• If the air is fully saturated (100% relative humidity) the water cannot evaporate, so both the wet and dry bulb temperatures are the same.

                                                            

Hair Hygrometer

• These devices use a human or animal hair under tension.
• The hair is hygroscopic (tending toward retaining moisture); its length changes with humidity, and the length change may be magnified by a mechanism and indicated on a dial or scale.

• The traditional folk art device known as a weather house works on this principle. Whale bone and other materials may be used in place of hair.
• This instrument uses strands of human or horse hair with the oils removed attached to levers that magnify a small change in hair length.