ETS 518 Manuale utente

MODEL 518

CONTROLLED ENVIRONMENT CHAMBER

USER MANUAL

TABLE OF CONTENTS

1.0

Introduction 1

2.0 General Description 1

2.1 Chamber 1

2.2 Humidity 2

2.3 Temperature 3

2.4 Humidity/Temperature Control Unit 3

2.5 System Operation4

3.0 Detailed System Description 6

3.1 Chamber 6

3.2 Control Unit 6

3.3 Power Panel 10

3.4 Environmental Control Systems Access Panel 12

4.0 Installation 13

4.1 Initial Set-Up 13

4.2 Initial System Checkout 14

5.0 Operation 15

5.1 Placing Instrumentation Inside the Chamber 15

5.2 Controlling Relative Humidity 16

5.3 Controlling Temperature 16

5.4 Obtaining a Given Humidity and Temperature Condition 17

5.5 Maintaining Selected Humidity and Temperature Level 18

6.0 Calibration 20

6.1 Humidity Controller 20

6.2 Temperature Controller 25

7.0 Maintenance 27

7.1 Desiccator 27

7.2 Ultrasonic Humidifier 27

7.3 Fluorescent Lamp Replacement 29

8.0 Troubleshooting 30

8.1 Humidity Control System 30

8.2 Temperature Control System 31

9.0 Warranty 33

LIST OF FIGURES

2.5-1Automatic Humidity/Temperature Control Block Diagram 4

3.2-1Control System Front Panel 7

3.3-1Power Panel 11

4.1.1-1Cooling System Installation 13

4.1.2-1Humidifier System Installation 14

5.4-1Maximum R.H. Level Versus Controlled Temperature (Table) 17

6.1.1-1Calibration Adjustment Points For Humidity Controller Unit Printed Circuit

Board 22

6.1.2.-1R.H. Sensor Calibration Adjustment Location 24

6.2.1-1Calibration Adjustment Points for Temperature Controller Printed Circuit

Board 26

1.0 INTRODUCTION

2.0 GENERAL DESCRIPTION

2.1 Chamber

The left hand side of the Chamber consists of a 12"W x 4"H opening with a

hinged access door. Towards the rear of the Chamber is a 1.25" ID access

hole for feeding cables and tubing to instrumentation placed inside. This

hole is then sealed using a soft putty compound.

The front of the Chamber consists of a large door containing a pair of

accordion neoprene gloves. The access opening is 32"W x 14"H which

enables large objects to be placed inside. To the right of the front door is the

humidity and temperature control module. This module is easily removed for

servicing by loosening the four (4) captive mounting screws.

The right hand side of the Chamber contains the power panel, desiccator,

humidifier cooling systems access panel and a 3" fan for reducing any heat

build-up in the Control component.

The rear of the Chamber contains a removable panel to which a 15 Watt

florescent light fixture is mounted. This assembly slides into a sub-chamber

that is installed inside the main chamber.

Many applications require a controlled environment for testing, fabricating and/or

storage. The Model 518 Automatically Controlled Environmental Chamber is

specifically designed to meet this requirement.

The Model 518 is a completely integrated system that incorporates precision

automatic humidity and temperature control systems that can control the relative

humidity to within ±0.5% R.H. and the temperature to within ±1.0°F (0.5°C) of the

desired levels. The Chamber is capable of precisely controlling the relative

humidity over the range of 5 -98% at lab ambient and the temperature over the

range of 32 -122°F (0-50°C). The maximum RH level obtainable with heating or

cooling will be a function of the temperature selected because of the drying

effects of the heater and the dry CO

gas cooling system.

The Model 518 Automatically Controlled Environmental Chamber is an airtight

acrylic glove box that incorporates a built-in humidity and temperature control

system. The overall size of the Chamber is 47"W x 25.5"D x 22"H including the

controller compartment. The useable space in the controlled environment section

is approximately 13 cubic feet. The entire section measures 39"W x 22.5"D x

22"H. The Chamber is fabricated from both 0.25" and 0.375" clear and white

acrylic. It is uninsulated and designed for those applications where only a

moderate temperature (±40°F) range must be maintained around room ambient.

Inside the Chamber is a perforated aluminum panel that houses a fan, heater

and accessory AC outlet. This panel is secured by six (6) thumb screws

accessed from inside the Chamber.

The inside wall separating the controlled environment section from the control

equipment section contains the fittings for mounting the humidity and

temperature sensors, the dehumidification, humidification, and cooling input

fittings. The sensors are mounted through the wall via bulkhead fittings and

are located towards the center of the wall. A duplex AC outlet with a sealed

protective cover is also located on this wall.

The relative humidity within the controlled environment chamber is

established using a desiccant drying system for dehumidification and an

ultrasonic humidifier for humidification which are controlled by the Automatic

Humidity Controller module.

The dehumidification system utilizes Calcium Sulfate (CaSo4) desiccant to

dry the air within the chamber. A built-in pump draws air from the chamber

and pumps it through a desiccator unit plugged into the panel located on the

right hand side of the Chamber. The desiccant absorbs the moisture that is

in the air being pumped through it. This dried air is pumped back into the

chamber. The process is continued until the humidity inside the chamber is

equal to the level set by the controller. The CaSO4contains an indicator that

turns the normally blue colored desiccant pink as it absorbs moisture. When

the entire cylinder turns pink, it is time for the desiccant to be renewed or

replaced.

The humidification system is based around a commercially available

ultrasonic humidifier which is specially modified for this application. The

humidifier contains a water tank, a fan and an ultrasonic amplifier and

transducer. The ultrasonic transducer breaks up the water molecules into a

fine mist that is forced into the chamber by the fan. The fan installed in the

chamber circulates the moist air to produce an even humidity. The humidifier

is turned on and off by the Controller to maintain the desired level.

Some applications may require dry nitrogen for dehumidification and non-

ultrasonic generated moisture for humidification. ETS can supply solenoid

valves and other types of humidifiers if required. Contact ETS for details.

2.3 Temperature

The Temperature within the chamber is maintained by using a 500 Watt

electric heater for heating and CO2for cooling which are then controlled by

the Automatic Temperature Controller module.

2.2 Humidity

The heater is an element located behind the aluminum panel. A thermal

safety switch is connected in series with the heater that cuts off power if the

temperature inside the chamber exceeds 135°F. The Controller is also

limited to 130°F. The Controller turns the heater on and off to maintain the

desired temperature.

Cooling is produced by converting liquid CO2to a gas. A high pressure

solenoid valve is connected to a user supplied CO2tank (tank must be

equipped with a dip tube inside) via a 48" high pressure hose. When the

solenoid valve opens, high pressure liquid is forced through a pin hole

opening which instantly converts it to a gas. The Controller turns the solenoid

valve on and off to control the cooling.

NOTE: The CO2gas is very dry and will limit the maximum RH level

achievable when the cooling system is used.

2.4 Humidity/Temperature Control Unit

The Control Unit consists of a dedicated ETS Model 514 Automatic Humidity

Controller and an ETS Model 513A Automatic Temperature Controller. In

addition, the Control Unit has Power switches to control system power, the

15 Watt florescent light and the internal circulating fan. The Control Unit is a

self-contained system that can be removed from the Chamber for

recalibration or service by simply loosening the four (4) captive screws and

unplugging the cable harnesses from the rear panel.

The Control Unit has two (2) modules: The RELATIVE HUMIDITY control

module and the TEMPERATURE control module. For those applications

where no temperature control is required, the optional TEMPERATURE

readout only module can be specified.

The RELATIVE HUMIDITY control module provides the necessary indicators

and controls to set the desired humidity level and to measure the actual

humidity inside the chamber. A 3½ digit LCD readout indicates both the

measured humidity level and the set point desired with a resolution of 0.1%

RH. A 10-turn precision potentiometer is used to adjust the set-point.

ON/OFF rocker switches are used to select the dehumidification and

humidification functions. When both of these switches are in the OFF

position, the module operates only as a precision hygrometer.

The humidity is sensed by a capacitive type sensor which has an element

whose capacitance is proportional to humidity. This type of sensor provides

a fast response over the entire 0-100% RH range with an accuracy of 2% RH

from 0-90% and 3% above 90% at 20°C. (68°F.).

The TEMPERATURE control module operates in a similar fashion to the

RELATIVE HUMIDITY control module. The 3½ digit LCD readout displays

temperature with a resolution of 0.1°. A front panel switch enables the user

to select either °F. or °C. Separate rocker switches control the heating and

cooling functions. When both switches are in the OFF position, the module

operates only as a precision temperature indicator.

When the Model 518 Chamber is ordered without the automatic temperature

control function, a temperature indicating module is provided. This module

consists of only the 3½ digit LCD readout and the °F. and °C. selector switch.

The temperature is sensed by a solid state integrated circuit sensor. The

sensor output signal has a voltage output that is proportional to temperature.

This type of sensor provides a fast response over the range of 0 -100°C (32

-199°F) with an accuracy of ±1°C (±1.8°F).

Figure 2.5-1 is a block diagram illustrating the automatic control systems and

their control of the relative humidity and the temperature inside the chamber.

Figure 2.5-1 System Block Diagram

The relative humidity and the temperature levels inside the chamber are

sensed by the respective humidity and temperature sensors. The sensor

output signals are compared to the humidity and temperature set points

chosen by the user. If the humidity measured in the chamber exceeds the set

point by more than 0.5% R.H. the Humidity Controller turns on the pump

which then circulates the chamber air through the desiccator. The desiccator

absorbs moisture, thereby lowering the humidity level inside the chamber.

When the humidity inside the chamber drops below the set point by no more

than 0.5% RH, the Controller turns off the pump. The Controller then cycles

the pump on and off to maintain the desired humidity level.

2.5 System Operation

If the measured humidity is below the set point by more than 0.5% RH the

Controller cycles the humidifier on and off to maintain the desired humidity

level.

If the temperature measured inside the chamber exceeds the set point by

more than 0.5°C (1.0°F) the Controller opens the solenoid valve that controls

the flow of the CO2. When the temperature level drops below the set point by

no more than 0.5°C. (1.0°F), the Controller turns off the solenoid valve. The

Controller then cycles the cooling system on and off automatically to maintain

the desired temperature.

If the measured temperature is below the set point by more than 0.5°C

(1.0°F.), the Controller turns on an electric heating element. The Controller

then cycles the heater on and off automatically to maintain the desired

temperature level.

NOTE: Due to the retained heat in the heating element after it has been

turned off the temperature inside the chamber will continue to rise

approximately 1 -3°C. (1.8 -5.4°F). This overshoot should be taken into

account when selecting the set point.

The humidity and temperature systems are designed to operated in

either the dehumidify (COOL) or the humidify (HEAT) modes. When

both sets of function switches are ON, the Controllers will switch from

one mode to the other causing the dehumidify (COOL) and humidify

(HEAT) functions to constantly work against each other. The most

efficient mode of operation is to have the Controllers operate the

appropriate function relative to the ambient conditions outside the

Chamber. Thus, when a humidity level below ambient is desired then

only the DEHUMIDIFY function should be selected, and conversely,

when a humidify level above ambient is desired then only the

HUMIDIFY function should be selected. The same applies to the

temperature functions.

Power to operate all of the systems is controlled by solid state Triac circuits.

When a system is to be activated the Controller turns on the respective Triac

which supplies the necessary 115/230 VAC power to operate the system.

A 4", 110 CFM fan is built into the chamber to constantly circulate the air

inside to achieve a uniform environment.

3.0 DETAILED SYSTEM DESCRIPTION

3.1 Chamber

The environmental section of the Chamber has two (2) access doors. The 4"

x 12" side door is used to place test specimens and small objects inside the

chamber without introducing a major disturbance to the environment inside.

The door is secured by three (3), ¾-turn latches. A non-setting gasket

provides an airtight seal.

The 32" x 14" door on the front of the Chamber contains the rubber gloves.

This door provides total access to the inside of the environmental section.

Large test specimens and test instruments can be placed inside the

chamber via this opening. The door is secured by eight (8) ¾-turn latches. A

non-setting gasket provides an airtight seal. Special access ports or no

access ports at all can be supplied utilizing custom built doors. If desired,

several versions can be supplied for a single Chamber. Contact ETS for any

special requirements.

A 15 Watt florescent light is incorporated in a sub-chamber inside the

environmental controlled section. This light is controlled by a power switch

located on the front control panel.

A duplex AC outlet is mounted on the inside wall to provide power for any

instrumentation that may be placed inside the chamber. This outlet accepts

the standard North American 3-prong plug. When the System is configured

for 230 VAC operation, 230 VAC is also available at this outlet. The outlet is

fused for 8 amps at 115 VAC and 4 amps at 230 VAC.

The Control Unit, shown in Figure 3.2-1, is a completely self-contained

system that incorporates the Automatic Humidity and Automatic Temperature

control modules mounted onto the front panel, along with the system, light and

fan power switches. The entire unit mounts to the Chamber by four (4) #6-32

captive fasteners. All connections to other components within the Chamber

are made by either DIN or Molex connector interface to the rear panel. A

115/230 VAC selector switch is located on the rear panel to set the

Controller for either 115 or 230 VAC operation.

3.2 Control Unit

Figure 3.2-1 Control System Front Panel

3.2.1 Automatic Humidity Controller Module Front Panel

This module is installed above the power switches on the front panel.

The module contains all of the controls and indicators necessary for

measuring and controlling the humidity inside the chamber. The

following is a description of the function that each indicator and control

performs in the operation of the Controller.

3.2.1.1 Indicators

% R.H. -This indicator is a 3½ digit LCD readout that is used

to display both the measured humidity and the desired

humidity level set-point.

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