0 Types Of Chambers Climatic simulation Used to test the reliability & performance of components and assemblies under various conditions of temperature, humidity, altitude, vacuum and vibration. Thermal stress/shock screening Used to produce rapid changes in temperature to screen out potentially faulty components and sub- assemblies. Plant growth test chambers/rooms Used in horticultural research labs to set standard growing conditions for testing fertilizers etc. Environmental Chambers

1 Related applications Brick and ceramic drying rooms Mushrooms farms Cheese maturing rooms Incubators - eggs, antibiotics Fruit and meat storage rooms Environmental Chambers These all involve the control of temperature, humidity and sometimes CO2, solar energy. They are really all environmental chambers. Environmental Chambers

2 Typical Chamber. Temp probe Humidity probe Water Spray Humidification Compressor Cooling/dehumidify Heating Heaters X26 By-pass Cooling/dehum coils Environmental Chambers

3 Example plant growing chamber. Control & Data Acquistion of: Temp, %RH, CO2 and day/night simulation Recor der Temp PID Loop Humidity PID loop _ _ Temp _ C02 PID loop %RH C02 Control OP Toolkit Blocks Light SP Temp SP %RH SP C02 SP Time Plant Growth Chamber 26/2704 Example plant growing Chamber

4 Brick, tiles drying room The purpose of drying is to extract water so that the product does not crack during the firing process. The aim is to achieve this as quickly as possible without cracking the product during the drying process. Typically both temperature and humidity are controlled. This process can take from 3 days to 3 weeks depending upon the product type Bricks & Ceramics Example - brick or tile drying room 2 weeks Temp Humidit y 30C 20C Example Brick Drying Room

5 Humidity measurement Definition Relative humidity is the ratio (in %) of the pressure of water vapour actually present, to the saturation pressure at the same air temperature. Methods of measurement Capacitive sensors - best for measurements below 90%RH Wet and dry bulbs - best above 90% RH Humidity Measurment

6 Capacitive sensor: Humidity measurement The sensor is a capacitor with a dielectric which absorbs or releases water vapor as the relative humidity of the ambient air rises or drops. The dielectric is typically a thin film of polymer. The capacitance depends on the amount of water contained in the film. The electronics in the sensor head measure the capacitance of the sensor and convert it into a humidity reading. The sensors typically require a 24vdc supply and deliver and output signal of 0 to 1 volt. Suppliers: Vaisala from Finland Rotronics from the US Humidity Measurment

7 Wet and dry bulbs Humidity measurement Humidity is determined by measuring the temperature difference between a ‘Dry’ bulb and a ‘Wet’ bulb. The bulbs are typically Pt100 sensors. The wet bulb is fitted with a ‘sock’ one end of which sits in a reservoir of water at the temperature of the chamber. The sock siphons water out of the reservoir. This evaporates keeping the wet bulb at a lower temperature to the dry bulb. The rate of evaporation is a function of the %RH. The %RH is a function of this temperature difference and the dry bulb temperature. The value is looked up in PSYCHROMETRIC tables. E.g. Dry bulb temp Difference20C30C 0.596%97% 1.091%93% Humidity Measurment

Humidity function block Humidity measurement Humidity Block % RH Psychometric Constant Wet RTD Dry RTD Altitude Compensation Humidity Measurment

9 What is dewpoint? Dewpoint measurement Dewpoint is the temperature at which air becomes saturated with water and begins to condense - forming dew. Therefore at 100 % relative humidity the process temperature equals the dewpoint temperature. The lower the dewpoint temperature, the smaller is the risk of condensation and the drier the gas or air stream. Dewpoint is preferred for humidity measurement in dry conditions as changes in the dewpoint are easier to measure. Dewpoint Measurment

10 Control methods Heating is usually electrical Cooling and dehumidification is normally performed using compressors Fast cooling is typically provided by liquid nitrogen Humidification is achieved using either steam or atomised water sprays Environmental Chambers Recorder Values Temperature, Humidity, Dewpoint, Atmosphere, Light, Vibration

11 Environmental Chambers Temp Humidit y Water Spray Humidification Compressor Cooling/dehu m Heaters X26 Cooling/dehum coils Using cooling coils to dehumidify will cool at the same time. This can be compensated for by, for example, applying a little more heat when de-humidifing - either via an auxiliary heater or by using feed forward in the controller - some experimentation is necessary Control issues Temperature and humidity interact e.g. If the temperature is increased without adding or removing water, the %RH will decrease - this is because the air can hold more water Dehum Heater Dehum Environmental Chambers

12 Equipment used Thermal shock and stress chambers /2404 programmable controllers - solid state relays - Recorders Temperature and humidity chambers /2404 programmable controllers - X26 chamber controller and 2704 advanced 3- loops - T800, solid state relays - Recorders Environmental Chambers

13 Environmental Chambers Cooling by-pass X26 Control block diagram Humidity Function Block Hu m PID %RH Humidity probe input Wet bulb temp Humidify op Dehum op OP Boost Heat SP Boost heat OP Boost Cool SP Boost cool OP Temp (dry bulb) Tem p PID Heating op Cooling op Compressor On Min-On Timer Event 1 Event 2 Setpoint Programme r Temperature SP Humidity SP reset Event outputs run Clock OR hold OP >0 > Drain valve AND 1  C/33  F >0 Environmental Chambers

14 Who uses them? Primarily: Avionic companies for testing Satellite and aircraft equipment Cars manufacturers The defence industries - for guns, tanks, telecomms Semiconductor manufacturers Horticultural research establishments Biological test laboratories Environmental Chambers

15 Eurotherm Advantages Tailored product in the X26 - use out of the box Wide range of solutions programmers, 2604, 2704, Solid State Relays Paper & Paperless Recorders 2500 offers front end to PLC - reducing system wiring and improving control. Humidity function block, Recorders and 26/2704 Fast digital communications- Modbus, Devicenet Large installed base Environmental Chambers