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Chapter 4 — Theory of Operation

Chapter 4 — Theory of Operation

Overview

The Humilab Relative Humidity Generator uses a divided flow
method to accurately generate a selected relative humidity in a
large test chamber. The selected humidity is controlled using a GE
General Eastern Chilled Mirror Hygrometer System. This chapter
describes divided flow and the chilled mirror controller.

Divided flow

The Humilab’s chamber RH is controlled by time proportioning a
fraction of an air stream through a saturator and a desiccant. The
saturated air mixes with the dry air to produce the desired RH
value in the chamber. Figure 10 shows the basic block diagram of
the Humilab’s operation.

The operator selects the desired relative humidity on the front
panel, using the increment/decrement switch to scroll to the value.
The selected RH determines the duty cycle of a solenoid operated
wet air/dry air valve.

Desiccant

Cartridge

Solenoid

valve

Pump

-40

°

C DP

Air supply

(optional)

Test

chamber

Wet

gas

in

Dry
gas

in

Dry gas

temperature coil

(surrounding chamber)

Sparger

(bubbles air

through water)

Water jacket

Figure 10 — Basic Block Diagram

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Содержание HumiLab

Страница 1: ...HumiLab Relative Humidity Generator Operator s Manual 500 Research Drive Wilmington MA 01887 4498 Tel 800 33HUMID 800 334 8643 Fax 978 203 1919 www generaleastern com ...

Страница 2: ...ERT Earth ground connection removal could result in electrical shock minor injury or product malfunction The information in this manual is believed to be reliable However GE General Eastern makes no warranty expressed or implied as to its accuracy and assumes no liability arising out of its use by others We reserve the right to change this manual without prior notice Document No A40241708 Revision...

Страница 3: ...lled mirror setup 12 Initialize the dew point sensor 12 Clean and balance the dew point sensor 13 Shipping the Humilab 15 CHAPTER 2 OPERATION 16 Introduction 16 Front panel displays and switches 17 Performing routine calibrations 20 Chamber response time 21 CHAPTER 3 USING THE PROSTEP SOFTWARE 22 Introduction 22 Installing the Prostep software 23 Running Prostep 24 CHAPTER 4 THEORY OF OPERATION 30...

Страница 4: ...isplays 47 Switches 48 Option selections using the display switch 49 A simplified explanation of the option selection system 49 A more rigorous explanation of the option selection system 50 RS 232c re programming mode 52 The Main Menu 53 Scale outputs 53 Set balance type 54 Set RS 232 units 55 Display option 56 Set averaging 57 Service and troubleshooting procedures 58 Helpful hints 61 Time respon...

Страница 5: ...tern s philosophy of providing the best solutions to humidity measurement problems we offer the following products and services high quality state of the art instrumentation to assure excellent performance a broad range of humidity instruments capable of covering virtually any humidity measurement application full applications assistance to help you choose the sensor that is best for your needs wo...

Страница 6: ... the requirements of ANSI Z540 l 1994 MIL STD 45662A 10CFR 50 and ISO 9001 may be performed The included Prostep software allows you to use your PC to upload a control profile via the RS 232 port enabling an entire calibration cycle to be run About this Owner s Manual This manual provides the information you will need to set up use and maintain the Humilab Relative Humidity Generator Please read a...

Страница 7: ... must not be ignored The ground symbol indicates points that must be connected to earth ground Failure to connect or removal could result in elec trical shock minor injury or product malfunction The pointing hand icon is used to indicate information that is related or simply additional to the surrounding text This informa tion is not required for proper operation nor will any harm arise from not a...

Страница 8: ... the ambient temperature is reasonably constant This is usually the case in a calibration laboratory Ideally the room should be stable within 1 C between 20 C and 30 C Ensure that the table or lab bench is level The water jacket surrounding the test chamber and the 1 2 thick Lexan cover above it effectively isolate the chamber from short term temperature fluctuations However longer term changes in...

Страница 9: ...ng analog output connector transportation case CD ROM containing this manual HCON Humidity Conver sion software and Prostep software Optional equipment temperature bath circulator for maintaining a stable cham ber temperature from 20 C to 30 C If an item is missing contact GE General Eastern Our phone number and address are found on page 1 System diagram Interconnection of the HumiLab s components...

Страница 10: ...ide the user with less frequent desic cant replacement The HumiLab does not require an external dry gas source to operate The unit is equipped with a desiccant cartridge that provides the Humilab with a 40 C dew point dry gas The unit is designed to operate for approximately 24 hours of continuous usage at an ambient humidity less than 50 before having to replace the desiccant Gas requirements If ...

Страница 11: ...oil free gas regulated at 1 to 2 psig at 5 lpm minimum Connect the dry air or dry nitrogen source using the 1 4 instant on DRY AIR IN connector on the rear of the unit See Figure 2 Humilab Rear View Figure 2 Humilab rear view gas A C and signal connections ...

Страница 12: ...tor via the DB 15 connector located on the rear I O panel A cable suitable for connecting to a terminal block is included The connector pinout is listed below DB 15 Pin No Function 1 RH 4 20 mA 2 RH 0 5 V 3 Temp 4 20 mA 4 N C 5 Temp 0 5V 6 Status 7 N C 8 N C 9 Service 10 Gnd Rtn 11 N C 12 N C 13 N C 14 N C 15 N C ANALOG OUTPUTS REFERENCE RS 232 CONTROLLER RS 232 LINE A B C D Figure 3 Humilab elect...

Страница 13: ...wer receptacle The input voltage is noted on the label to the right The input voltage is configured at the factory and must be determined prior to shipment E Cooling fan not visible The fan is used for cooling the elec tronics The fan must stay clean and clear of any obstruction to prevent damage to the internal electronics Rear input output fitting connections Mechanical connections to the Humila...

Страница 14: ...cket and press the other end into the drain fitting until it stops Water will immediately begin to drain into the bucket To remove the tube from the fitting depress the black outer ring and pull out the tubing A built in check valve prevents water from running out of the drain port when the tubing is not in place Coolant connections The HumiLab is equipped with 1 4 instant on coolant fittings that...

Страница 15: ... able 40 C DP dry air or nitrogen 15 16 psig 4 5 l m flow If running from a desiccant cartridge make sure the cartridge is fully seated and the desiccant color is a minimum of 75 blue throughout the length of the tube Replace the cartridge or desiccant if necessary 6 Install the unit s cover 7 Install the power cord and turn the unit on Set the controller to 80 90 RH 8 Check the water fill level i...

Страница 16: ...hough it was initialized at the factory the dew point sensor bridge should be initialized again to compensate for any change during shipment This is accomplished by cleaning and balancing the sensor as described below Figure 7 shows the location of the switches and LEDs on the front panel Chapter 2 contains a complete description of the operating procedures 1 Plug the A C power cord into a wall so...

Страница 17: ...n 2 Open the test chamber cover and remove the white dust cover 3 Locate the sensor cleaning solution in the GE General East ern Maintenance Kit Wet a cotton swab with the blue clean ing solution and rub it lightly over the mirror Lightly buff the mirror dry with a clean dry swab Note If you don t have the supplied cleaning solution a solution of two parts rub bing alcohol to one part distilled wa...

Страница 18: ...nd the left hand displays will read the actual percent R H and temperature in the test chamber 8 Use the SETPOINT switch to select 30 RH by pressing on the upper or lower side of the switch as required The display will scroll one decade at a time to the desired reading Release the switch when that point is reached 9 Run the chamber for at least one hour until the water sur rounding the chamber ass...

Страница 19: ...he left with the drain tube still attached 4 The temperature bath circulator lines need to be drained prior to shipment Insert the drain tube provided into the COOLANT OUT port connector Insert a short 1 4 tube into the COOLANT IN port connector This will allow the coolant to be removed from the temperature coil This will prevent the tem perature coil from freezing during transport and possibly ca...

Страница 20: ...es are set as desired and then left in position Front panel switch settings are described in this chapter More detail is available in Appendix B For quick reference the following settings are typical for most applications Power Switch ON mounted on rear of unit Sensor Switch OPERate Display Switch OPERate Loop Switch Closed Loop Set to the filled in circle for oper ation Open Loop open circle for ...

Страница 21: ... digital display shows the desired chamber set point With the exception of the setpoint selector switch the other front panel switches are seldom used in day to day operation However they are included in case you wish to make changes to normal default operation and for system testing Appendix B contains information on changing factory set defaults A HUMIDITY Display This display is shipped from th...

Страница 22: ...dow See Balancing the sensor optics on page 37 for details This window will show various indications while reprogramming the display units or analog outputs See Appendix B D DISPLAY Switch The DISPLAY Switch is normally used in the center OPERate position This rocker switch is used to reprogram measurement units and to check the scale factor of analog outputs In the standard configuration the anal...

Страница 23: ...emperature display when programming Units or Outputs See Appendix B I SETPOINT Display This display window shows the relative humidity setpoint that has been programmed in the chamber J SET SETPOINT Switch This switch allows you to select a humidity setpoint in the display window Scroll to the desired value by incrementing or decrementing one decade at a time until the desired value is reached K L...

Страница 24: ...gital set point display will scroll toward the desired set point First the least significant decade will change and then successively more significant decades will change Release the switch when the desired humidity is reached It may be easier to stop a few counts before the desired reading and allow the least significant unit display to move in 0 1 R H steps to the set point 3 Allow 40 to 60 minu...

Страница 25: ...arge cavity size typical response time will be approxi mately 30 40 minutes At the end of that period the RH in the test chamber will be within 1 RH of the set point After that time the two will track each other within the accuracy specification of the instrument ...

Страница 26: ...ic calibration of the devices in the Humilab cavity See Figure 8 for a sample humidity profile In addition to creating humidity profiles for use in the Humilab the PROSTEP software can be configured to generate temperature control commands profiles to the recirculating water bath chiller remotely operate the Humilab customize the Humilab calibration sequence and collect humidity and temperature da...

Страница 27: ...ontrol panel system device manager ports communications port port settings Bits per second 1200 Data Bits 8 Parity None Stop Bits 1 Flow Control None Connecting the host computer Controlling Humilab For communication to the Humilab controller uploading downloading humidity profiles connect the host computer COM port connector to the 9 pin RS 232 CONTROLLER connector on the rear of the Humilab Data...

Страница 28: ...ion settings in PROSTEP Under Options Communications Setup verify the following Baud rate 1200 Flow Control Off Stop Bits 1 Data Bits 8 Com Port 1 4 matched to host computer Parity none The profile screen The main profile screen is used for entering and modifying the Humilab s humidity profile A profile must be uploaded to the Humilab before it can be used and can be downloaded back into the PC fo...

Страница 29: ...ccesses standard Windows functions for creating a new profile loading a existing profile 30 C 20 C 40 RH 80 RH SETPOINT 3 Temp R H E A C F D B time A setpoint sequence number B bath temperature C an optional delay before the humidity change is initiated to allow for temperature stabilization D initial humidity E final humidity F duration of the humidity ramp Figure 9 A typical setpoint and its val...

Страница 30: ...Runs the profile most recently downloaded to the Humilab Collect data Collect RH temperature and or DP data for Humi Lab operation See options Setup Datalogging Parameters Halt Test Stops running the current profile The Options menu The Options menu accesses all of the setup and configuration items Scale Graph Sets the parameters for the main screen profile display units and maximum minimum values...

Страница 31: ...he comm port parameters baud rate 1200 flow control None stop bits 1 data bits 8 parity not checked comm port number 1 Set up Data Logging Parameters Sets units and formats for logged data Before using this screen make the following settings set Predefined Groups to M4 set BBox Port to 1 ...

Страница 32: ...ne To add a new line enter the data and click on Add When finished click on Done Unit Number If more than one unit is connected each can be selected for configuration Enabled check box must be checked to allow datalogging the Comm Port that the Humilab or BlackBox is connected to Channel base Address default 48 Unused Channel Number the number of the first Black Box channel that is not in use Log ...

Страница 33: ...nu allows moving a profile between the computer and the Humilab Upload Profile Send the current profile from the PC to the Humilab Download Profile Transfer a profile from the Humilab to the PC The Help menu The Help menu supplies on line instructions for using the Prostep software ...

Страница 34: ... a fraction of an air stream through a saturator and a desiccant The saturated air mixes with the dry air to produce the desired RH value in the chamber Figure 10 shows the basic block diagram of the Humilab s operation The operator selects the desired relative humidity on the front panel using the increment decrement switch to scroll to the value The selected RH determines the duty cycle of a sol...

Страница 35: ...nters the chamber after having first been completely temperature stabilized so that it is virtually the same temperature as the water in the jacket surrounding the chamber This stabilization ensures that there is very little temperature gradient between the incoming air and the chamber itself The Humilab chilled mirror controller A GE General Eastern chilled mirror dew point hygrometer is built in...

Страница 36: ...a correction factor determined by the actual dew point and temperature measurement has been stored in non volatile memory Thus the test chamber has acquired the accuracy and N I S T traceability of the fundamental chilled mirror hygrometer If desired this automatic calibration of the test chamber against the chilled mirror hygrometer may be repeated at any time in the field What is optical condens...

Страница 37: ...oint The conden sate detection mirror is illuminated with a high intensity solid state light emitting diode LED A photodetector monitors the LED light reflected from the mirror A separate LED and photodetector combination are used to compensate for any thermally induced changes in the optical components For detailed information on the chilled mirror hygrometer refer to Appendix B The photodetector...

Страница 38: ...int of the gas being measured and it follows the dew point if it changes A precision thermometer element embedded within the mirror directly monitors this dew point temperature and provides a continuous readout to the user Figure 12 Chilled Mirror Sensor Block Diagram ...

Страница 39: ...r and be careful not to accidentally spill water in the test chamber If you do spill any water wipe it up completely The water level may pulse up and down while the Humilab system is operating Verifying desiccant condition Prior to each use of the HumiLab verify that the desiccant cartridge contains active desiccant mate rial The desiccant contains an indicating material which turns from blue to p...

Страница 40: ...il the system tells you that the mirror needs cleaning by lighting the letter S for Service in the Status window In normal operation the green CONTROL STATUS indicator on the left hand side of the front panel will be lit The Control Status light tells you that everything is normal with regard to the control loop that determines the mirror dew layer If the Service indicator adjacent to it does ligh...

Страница 41: ...ght wipes If the sensor has been exposed to significant contamination clean the other optical surfaces in the sensor and the sensor cavity itself 5 Replace the sensor cover Leave it in the Open position with the large holes allowing maximum air into the sensor cavity for fastest response time 6 Return switches to normal initiate a Pacer cycle and continue operation Balancing the sensor optics If t...

Страница 42: ... is lit For the adjustment screw see Figure 6 on page 14 Be sure to cover the mirror cavity while adjusting the balance screw since ambient light can cause an offset 3 The sensor is balanced when one bar is lit Replace the sensor cover if necessary and make sure one bar is still lit If not repeat Step 2 since you were allowing some light to enter the cavity Place the Sensor switch back to OPERATE ...

Страница 43: ...Chapter 5 Maintenance and Troubleshooting Page 39 Figure 13 Mirror Check and Mirror Sensor Balancing Procedure ...

Страница 44: ...tains the replacement mir ror and a container of white thermal compound for proper heat transfer Complete instructions are also included in the kit 4 Use a toothpick or similar tool to place a small amount of thermal compound in the hole into which the mirror is tight ened Do not apply the compound to the mirror stem Do not use an amount large enough to leak out when the mirror is tightened Do not...

Страница 45: ...chamber to The Humidity display upper left shows the actual R H in the chamber as read by the chilled mirror hygrom eter Do they agree within the instrument specifications Set Point RH and Actual RH do not Agree within Specifications Actuate the setpoint select switch You will instantaneously get a reading in the Setpoint display window that is the actual value needed to generate the previously di...

Страница 46: ...s in the chamber that generate heat If you are try to locate the heat producer adjacent to the temper ature sensor in the center of the chamber This way the system will correct for it automatically Is the green Control Status indicator off If so the chilled mirror is not tracking the chamber See the sec tion on page 59 in Appendix B on chilled mirror hygrometer system troubleshooting ...

Страница 47: ...C 0 3 F 0 15 C dry bulb at 77 F 25 C Analog outputs Two humidity and temperature each user scalable 4 20mA 0 5VDC Power 115 or 230 VAC 10 50 60Hz single phase Digital interface Two RS 232 ports for reference and generator interface Prostep software Windows 95 98 or above required Supplied on CD ROM with Operator s Manual PDF and HCON Humidity Conver sion Software Approvals CE approved Certificatio...

Страница 48: ...drain for gravity draining and dry air inlet compressed dry air to be regulated to 5 PSI Weight 66 lbs 30 kg dry weight Electrical I O Power IEC receptacle Analog outputs DB 15 RS 232 DB 9 Water capacity indicator Liquid sight glass color keyed indicator Desiccant Indicating type bright blue when dry pink when satu rated Chamber runs 24 hours at 50 RH and 77 F 25 C on a new charge of desiccant Dry...

Страница 49: ...ritical nature of the chilled mirror components this information is intended for trained electronics technicians If you are not comfortable performing procedures in this appendix contact GE General Eastern for assistance Chapter organization This is a large appendix consisting of the following sections A list of the Humilab Chilled Mirror System Components Front Panel Operation Using the DISPLAY S...

Страница 50: ...units B C CONTROL STATUS display The CONTROL STATUS display includes a green control light and a seven segment display The control lights comes on when the system detects both a stable dew or frost layer and a stable dew point temperature The seven segment display indicates as follows P Programmable Automatic Contaminant Error Reduction PACER mode or Automatic Balance AUTO mode is in operation S S...

Страница 51: ...s in opera tion S Service The system optics require service cleaning or adjust ment U In Units Select mode when using the DISPLAY switch O In Output Select mode when using the DISPLAY switch Horizontal bars indicate the approximate amount of condensation on the sensor mirror when the SENSOR switch is in HEAT or COOL It is an indication of dew layer thickness on the mirror See the information start...

Страница 52: ...en changing displayed units at the front panel See RS 232c re programming mode on page 52 of this appendix Balance switch The BALANCE switch is a three way switch that selects INIT A momentary position that initiates a balance cycle either PACER or AUTO MAN No balance cycle unless manually initiated using INIT AUTO The PACER AUTO cycle occurs automatically at a pre selected interval See Set balanc...

Страница 53: ...S on the bottom display OUTPUTS on the top display OUTPUTS on the bottom display Menu navigation It s easier than it might first appear to move about and select options Follow the three step process below 1 Press NEXT until you see one of the above main menus that you want When you get to the one you wish to see press Select This action puts you IN that main menu and you can proceed to scroll thro...

Страница 54: ...tions available in Program mode along with the state of the three green LED s at each step N will display the next function or scroll through alphanu meric values Depress NEXT for 1 2 seconds S will access a function or accept a new value Depress NEXT for 1 2 seconds A more rigorous explanation of the option selection system The following description describes the DEFAULT programming sequence for ...

Страница 55: ...t high value for the humidity output is shown Press N to view the low value Press N again You will then be able to view the high and low values for the Temperature out put When you are done press N to move on Changing output s You can modify the behavior of the DISPLAY switch so that the output units and scaling ON OFF limits are hidden from view or are viewable and changeable See the RS 232C Comm...

Страница 56: ...ct one The second digit from the right will blink Continue as before Finally the sign for the value will blink The choices here are 1 1 or blank Note that the 1 is a half digit and that is not shown Once the sign is set press S to continue through the output changing sequence You will now be given the opportunity to view and or change the low humidity output value Note that you cannot change the o...

Страница 57: ... INPUT 2 PARM A MOLECULAR WEIGHT E EXIT Scale outputs From the main menu press 1 to assign and scale the analog outputs The current state of the output s is echoed followed by a sub menu OUTPUT1 DP C HIGH 60 LOW 40 OUTPUT2 TMPC HIGH 60 LOW 40 1 OUTPUT1 2 OUTPUT2 E EXIT Press 1 to access Output1 the Humidity output One of the following menus will appear OUTPUT1 0 DPC 1 DPF 2 RH E EXIT Make a parame...

Страница 58: ... EXIT Press 1 to set the type of balance to PACER the default or 2 to set the type of balance to AUTO Press 3 to set the balance interval The following will appear DAY Type a value for the number of complete days between balance cycles and press RETURN The following will appear HOUR Type a value in 24 hour format e g 2 p m 14 for the number of fractional days between balance cycles and press RETUR...

Страница 59: ...following sub menus will appear 1 DPC 2 DPF 3 RH 4 TMPC 5 TMPF 6 NONE E EXIT Press numbers individually to add the associated parameter to the RS 232C data output Press 3 or 6 or 8 depending on Model for no data output or to clear before adding parameters Press E when you are done At the Data sub menu press 2 to output data at the prompt of the user The following will appear STATUS DISABLED ALLOW ...

Страница 60: ...S 3 ALARM E EXIT Press 1 to determine the behavior of the DISPLAY switch with regard to parameters The following sub menu will appear SELECTED UNITS 1 SELECT 2 FIX ALTERNATE DISPLAY E EXIT Press 1 to select the parameters shown by the DISPLAY switch One of the following sub menus will appear 1 DPC 2 DPF 3 RH 4 TMPC 5 TMPF 6 NONE E EXIT Press numbers individually to add the associated parameter to ...

Страница 61: ... Switch sub menu to determine the behavior of the DISPLAY switch with regard to alarm units and scaling The following sub menu will appear STATUS VIEW ONLY ENABLE DISABLE SWITCH FUNCTIONS 1 VIEW ONLY 2 VIEW CHANGE 3 HIDE E EXIT Make a selection in the same manner described above When you are done press E to exit Press E twice to exit to the main menu Set averaging From the Main menu press 5 to set...

Страница 62: ... analog outputs The Electronics Module has been completely tested and calibrated at the factory and is ready to plug in and operate As received it meets all of our published specifications When ordered as a complete hygrometer system with a chilled mirror sensor and cable the system is checked at a number of points against a dew point system that has been certified by the U S National Institute of...

Страница 63: ...irror is contaminated and should be cleaned Clean the sensor mirror as described in Chapter 5 Run the instrument through a Pacer cycle If at the end of the cycle the S comes on again balance the sensor optics as described in Chapter 5 Invalid dew point display This can be caused by one of three problems Clean the mirror as described in Chapter 5 Balance the sensor optics as described in Chapter 5 ...

Страница 64: ...fter a short time The sensor optical bridge may be out of balance Perform the optical balance procedure as described in Chapter 5 No analog output but the digital display operates Check the analog output scaling See the scaling procedure in Scale outputs on page 53 No digital output from the RS 232C port The instrument may not have been scaled properly via the RS 232C port Repeat the procedure in ...

Страница 65: ...se a trade off between response time control system stability and sensitivity to contamination Install the sensor cover in the open position for proper response time That is the large holes in the cover allows maximum air sample into the sensor cavity Mirror cleanliness Proper operation of a condensation hygrometer depends on the condition of the mirror surface In general accuracy is reduced when ...

Страница 66: ...te the indicated dew point 2 Clean the mirror 3 Balance the detector by initiating a Pacer cycle see below 4 Measure the dew point again If the new reading is lower than the first reading there was prob ably soluble material in sufficient quantity to cause a measurement error Consider decreasing the interval between Pacer cycles see Set balance type on page 54 since the Pacer is completely effec t...

Страница 67: ...feature operates only when the BALANCE switch is in the AUTO position When the Pacer is in operation and contaminants accumulate to a point where they can no longer be automatically reduced the S Service light will indicate that the mirror needs cleaning Figure 15 shows the effect on contaminants of using the Pacer cycle Figure 14 PACER Cycle Before Pacer After Pacer Figure 15 contaminant Reductio...

Страница 68: ...tion from dry to moist conditions particularly when accompanied by a transition from cold to warm temperatures the mirror may accumulate an over load of moisture It may then take several minutes for the sensor to dry out The process can be speeded by switching to HEAT to temporarily heat the mirror ...

Страница 69: ... RS 232 communications is to use the Microsoft Windows Terminal program Follow the steps below 1 Click your mouse on the Terminal icon 2 Select the Settings Menu 3 Select Communications A window is displayed for you to enter various communica tions parameters 4 Select the following Baud rate 1200 baud Data bits 8 Start bits 1 Parity none Hardware control none COM Port COM1or COM2 as required 5 Cli...

Страница 70: ...parameter See the Re programming mode in Appendix B for details In addition to the output data the Electronics Module will also output various status flags as shown below Some subset of these prompts will appear after the output data They will be displayed with every system update as long as they are active Each prompt is followed by a carriage return Status Flag Description ALARM The alarm relay ...

Страница 71: ...ard installed in your computer If your computer has one serial card it is addressed as COM1 If there is a second serial card it is addressed as COM2 You must also have a cable with the following connectors A 9 pin male D sub connector for the Reference Port A 9 pin female D sub connector for the computer some com puters use a 25 pin connector requiring an adaptor ...

Страница 72: ...ols used e Vapor Pressure millibars ei Vapor Pressure with respect to ice millibars ew Vapor Pressure with respect to water millibars eis Saturation vapor pressure ice millibars ews Saturation vapor pressure water millibars P Total Pressure millibars T Temperature ºC Ta Ambient temperature ºC Td Dew point temperature ºC Tf Frost point temperature ºC Vapor pressure Saturation vapor pressure with re...

Страница 73: ... were it to occupy the same total volume according to Dalton s Law The first term in parentheses in Equations 1 and 2 is the enhancement factor and corrects for the slight difference between the ideal behavior of pure water vapor and the behavior of water vapor as a constituent of air Humidity Relative Humidity is defined as the ratio of the water vapor pres sure e to the saturation vapor pressure...

Страница 74: ...wing Expressing water vapor content as parts per million by weight or mixing ratio requires multiplication of the above by the ratio of the molecular weight of water to that of air as given by the following See Figure 16 for a graphical conversion chart and Figure 17 for a Psychrometric chart PPMV 10 6 e Td P e Td PPMW 0 622 10 6 e P e ...

Страница 75: ...Appendix D Humidity Equations and Conversion Charts Page 71 Figure 16 Graphical Conversion Chart ...

Страница 76: ...Page 72 Appendix D Humidity Equations and Conversion Figure 17 Psychrometric Chart ...

Страница 77: ...s or missing items Obtaining return authorization number from Seller to return defective items to plant as directed Return of equipment freight charges prepaid or as otherwise agreed Defects caused by negligence misuse improper installation acci dent or unauthorized repair or alteration by buyer or user or any modification such as changing range resistors may void this warranty This warranty does ...

Страница 78: ...trument return procedure All GE General Eastern instruments are fully tested and calibrated prior to shipment Should a problem with the operation of the equipment arise follow the procedure below 1 Contact the factory to discuss the problem In countries other than the U S the local agent can also be contacted Some times a problem can be resolved by a change in operating pro cedure or an adjustment...

Страница 79: ...orization number the equip ment must be returned freight PREPAID 5 GE General Eastern reserves the right to apply a minimum service charge in cases where an instrument is returned for repairs or recalibration but does not require service Returning equipment without a Return Authorization number and Purchase Order significantly delays turnaround time and incurs additional costs To expedite repairs ...

Страница 80: ...Page 76 Appendix E Warranty information and return ...

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