Series 903 Inverted Magnetron Transducer Cold Cathode Ionization
Contents
1. 10 Cold Cathode lonization Vacuum Sensor Relay Inductive Loads and Arc Suppression If the set point relay is used to switch inductive loads e g solenoids relays transformers etc the arcing of the relay contacts might interfere with controller operation or reduce relay contact life Therefore an arc suppression network shown schematically below is recommended The values of the capacitance C and the resistance R can be calculated by the equations C 2 I 1x 10 and R E J where C is in farads Ris in ohms I is DC or AC eak R load current in amperes Relay E is DC or AC ok Load Cc Contact source voltage in volts a 1 50 E Note that Relay arc suppression network R 0 5 Wand C 1 0 x 10 F Cold Cathode lonization Vacuum Sensor 11 Operating the Series 903 IMT Starting the IMT The IMT starts quickly in low vacuum In the UHV pressure range starting may be delayed by several minutes The SensaVac IgniTorr Cold Cathode Starting Device may be used to reduce starting time see Accessories p 22 Reading Pressure To measure nitrogen gas pressure with the IMT turn the power on and start the high voltage Refer to the graph below showing pressure as a function of output voltage for nitrogen To independently convert voltage to pressure use the equation in the next section gt When using the graph remember that the pressure scale is logarithmic and the voltage scale is li2. cable or magnet 80 maximum for temperatures less than 31 C decreasing linearly to 50 maximum at 40 C 2000 m 6561 ft maximum Pollution Degree 2 1 relay set point SPDT 1 A 30 VDC resistive 150mV 50 msec 0 to 99 for DP from 5 0 x 10 Torr to 3 0 x 10 Torr 14 to 30 VDC 150 mA maximum 1 5 to 8 7 VDC linear output 30 w maximum output impedance 100 kw nominal 10 kw minimum 150 mV is equivalent to a change in pressure of 1 41 or 1095 times the set point e g if the relay is set to activate at 2 0 x 10 Torr 5 301 V it will deactivate at 2 82 x 10 Torr 5 451 V Cold Cathode lonization Vacuum Sensor 3 Internal Operating Voltage Installation Orientation Internal Volume Materials Exposed to Vacuum Display Electronic Casing Casing Dimensions WxDxH Typical Weight with CF Flange Vacuum Connection CE Certification 4 kV maximum current limited to 133 mA Any 0 9 in 15 0 cm maximum SS 304 SS 302 aluminum glass Inconel X 750 alumina ceramic LED indicators for set point red high voltage yellow and power green ABS plastic UL 94 5V flame rating with conductive coating 5 x 3 x 4 2 127 mm x 76 mm x 108 mm 2 3 Ib 1 04 kg KF 25 KF 40 234 CF rotatable 1 tubing EMC Directive General Product Safety Directive Design and or specifications subject to change without notice 4 Cold Cathode lonization Vacuum Sensor
3. If it is not immediately installed cover the flange with clean vacuum grade aluminum foil and cap it with a flange protector 20 Cold Cathode lonization Vacuum Sensor lon Current o Feedthrough Pin Vnus Glass Insulators D LER Locating Collar p Leaf Spring j o High Voltage gt Feedthrough Pin Anode Sensor Body 8 CZ Groove Ground Shield Q Se RA Ceramic Spacer Small C Sry Cathode Grid Washer Ceramic Spacer Large o Compression Spring Cold Cathode lonization Vacuum Sensor 21 Accessories Part Replacement Part IgniTorr Cold Cathode Starting Device for use with CF flange only 120V 100006850 220V 100007090 Internal Rebuild Kit 100002353 Cathode Grid Washer Ground Shield 1 Small and 1 Large Ceramic Spacer Spring Rebuild Sensor KF 40 104230101 234 CF 104230102 1 Tube 104230103 KF 25 104230104 HPS Series 903 Inverted Magnetron 109030025 Transducer IMT Cold Cathode lonization Vacuum Sensor User s Manual Please call HPS Products Customer Service Department at 1 303 449 9861 or 1 800 345 1967 to order any of these parts or to receive catalogs for other HPS Products 22 Cold Cathode lonization Vacuum Sensor Product Warranty Extent of the Warranty MKS Instruments
4. Inc Cold Cathode lonization Vacuum Sensor Table of Contents Table of Contents Package Contents c oat aac act t iniu Red t pete see eas Uri d 1 Symbols Used in this Manual nnen 1 Safety Precautions c s tienen nodu gena deban esi nup uen dae eb aedes QUAERE 2 Specification S as D 3 Feature and Control Locations nnen 5 Typical Applications for the Series 903 IMT 6 About the HPS Products Series 903 IMT 7 Installing the Series 903 IMT nnee eenen 8 LOGO ss digas EU E 8 OnentatiOni smetten dentist ai wa dr DL diga ree ieden ne dad equ aie 8 ContaMINalion zou ice Lone rn e EL n dene enti ear a n ener 8 Vacuum Connection eren b i Lan ae ci te ec eben ids 9 Electrical Connection nanne nanne eerenenennneereennennenneereneneenennnenn 9 Input Output Wining sistent e eA Leti 9 Relay Inductive Loads and Arc Suppression eeen 11 Operating the Series 903 IMT annen 12 Starting the IM dote ee te eH ee ete ep din 12 Reading Pressure pero rete et i eaput iet Et te dg 12 Equation for Converting Voltage to Pressure unne ennen nennen 13 Using the Set Polnt scat circi re t Pr aen Pr isa d P da 13 Venting to Atmosphere nennen eeen u EEEn REE EEN ennen ENER EEN ENE 14 Analog to Digital A D Converter nnn nennen nneneerenenneerennnervenneeenn 14 Preparing for BakeoUt sesering ea tenere de rette test 14 Leak Dete
5. remove particulates Clean aluminum and ceramic parts chemically in a wash such as a 5 to 2096 sodium hydroxide solution not for semiconductor processing at room temperature 20 C for one minute Follow with a preliminary rinse of deionized water Remove smut the black residue left on aluminum parts due to this process in a 50 to 70 nitric acid dip for about 5 minutes c amp Chemical cleaning should not be used to clean the anode mild abrasives or ultrasonic cleaning are acceptable Cold Cathode lonization Vacuum Sensor 19 STOP Do not damage the leaf spring while cleaning the Sensor Each of the above cleaning methods should be followed with multiple rinses of deionized water Dry all internal components and the sensor body Q in a clean oven The two ceramic spacers Qare slightly porous and will require longer drying time to drive off the absorbed water Assembly Wear gloves and assemble with clean tools Check the anode It should be straight and centered with the sensor body for proper operation Roll the sensor body on a flat surface and look for any radial run out motion 1 Install the ground shield 9 using tweezers Make sure that at the groove of its larger diameter the ground shield interlocks with the locating collar 2 Slide the small ceramic spacer over the small end of the ground shield Q Check that the leaf spring will contact the base of the cathode Q as shown to the right If not r
6. Feature and Control Locations 3 0 5 5 O ue 3 E E 4 2 with CF flange Front View Side View LED Power On Off Indicator Green LED High Voltage Indicator Yellow LED Set Point Indicator Red Phillips Head Screws Access to Sensor Tube Set Point Adjustment Potentiometer Tip Jack for Set Point Monitor Tip Jack for Common Male 9 pin D sub Connector Sensor Tube Vacuum Port cceoococe Cold Cathode lonization Vacuum Sensor 5 Typical Applications for the Series 903 IMT Measurement of high vacuum chamber pressures Controlof high vacuum systems and process sequencing using the relay set point Sensing abnormal pressure and taking appropriate security measures using the relay set point Controlling system pressure using the analog output as input to an automatic pressure controller Starting or stopping system processes with the relay set point Measuring pressures of backfilled gases Leaktesting your vacuum system 6 Cold Cathode lonization Vacuum Sensor About the HPS Products Series 903 IMT The Series 903 Inverted Magnetron Transducer IMT is a compact cold cathode vacuum sensor with an integrated electronic control circuit The IMT s simple modular design high reliability and low cost make it
7. D sub connector 1 2 3 4 5 6 7 8 9 The power supply input may range from 14 to 30 VDC The positive side of the power supply is connected to pin 3 and the negative side to pin 4 of the male D sub connector Damage may occur to the circuitry if excessive voltage is applied or if a wrong connection is made The analog output voltages are pins 5 and 8 Connect them to a differential input voltmeter or an analog to digital A D converter with a differential input in a system controller EE Do not connect the negative side of the analog output pin 8 to the negative side of the power supply input pin 4 or to any other ground Half of the power current would flow through this wire Measurement errors in the output voltage may be seen due to the voltage drop from this current The longer the cable the worse the error will be To enable the high voltage with an external switch connect pin 9 to the power supply input pin 4 An open connection turns off the high voltage The high voltage should be turned off at pressures above 10 Torr to prevent effects of contamination at higher pressures An output of greater than 9 5 V indicates the high voltage is off and an output of less than 0 5 V indicates no power to the transducer or that discharge has not yet started Connect pin 7 to the power supply input pin 4 to disable the set point relay ter Do not connect the set point relay terminals to the analog output
8. Inc HPS Products Inc warrants the HPS Products Series 903 Inverted Magnetron Transducer IMT Vacuum Sensor and its accessories to be free from defects in materials and workmanship for one 1 year from the date of shipment by HPS M or authorized representative to the original purchaser PURCHASER Any product or parts of the product repaired or replaced by HPS under this warranty are warranted only for the remaining unexpired part of its one 1 year original warranty period After expiration of the applicable warranty period the PURCHASER shall be charged HPS current prices for parts and labor plus any transportation for any repairs or replacement ALL EXPRESS AND IMPLIED WARRANTIES INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE LIMITED TO THE WARRANTY PERIOD NO WARRANTIES EXPRESS OR IMPLIED WILL APPLY AFTER THIS PERIOD Warranty Service The obligations of HPS under this warranty shall be at its option 1 to repair replace or adjust the product so that it meets applicable product specifications published by HPS or 2 to refund the purchase price What Is Not Covered The product is subject to above terms only if located in the country of the seller from whom the product was purchased The above warranties do not apply to l Damages or malfunctions due to failure to provide reasonable and necessary maintenance in accordance with HPS operating instructions Il Da
9. adings appear to be erratic the sensor tube may be contaminated Inspect it visually If contamination is visible you should replace the internal components with an Internal Rebuild Kit or a Rebuild Sensor see Accessories p 22 Depending on the degree of contamination and application of the IMT the internal parts may be cleaned either ultrasonically with mild abrasives or chemically For the remaining sections please refer to the figure shown on page 21 Disassembly Tools required Phillips head screwdriver clean tweezers clean smooth jaw needle nose pliers 1 Remove the two Phillips head screws holding the electronics assembly to the sensor body Remove the electronics assembly 2 Using the smooth jaw needle nose pliers firmly grab the compression spring at the tip closest to the flange 3 Pull on the compression spring while rotating it to free it from the formed groove of the sensor body Continue to pull until the compression spring is completely free 4 Carefully remove the remaining components from the sensor body Do not bend the anode Q or the leaf spring on the ion current STOP feed through pir when assembling or disassembling the sensor Cleaning If cleaning ultrasonically use high quality detergents compatible with aluminum such as ALCONOX Scrubbing with mild abrasives can remove most contamination Scotch Brite or a fine emery cloth may be effective Rinse with alcohol to
10. age pressure relationship for a gas which is not shown on the graph on the previous page you need to calibrate the IMT This requires a gas independent sensor such as a capacitance manometer or spinning rotor gauge to act as the calibration standard A curve can then be generated The Series 903 IMT cannot be calibrated for direct pressure readings of gases other than air or nitrogen The calibration is intended only to match the air nitrogen curve of the sensor Gas type dependence can either be an advantage or a disadvantage On the one hand it s possible to use a cold cathode sensor as a leak detector On the other hand the pressure indication of a gas may vary by a factor of five or more Also calibration factors or relative sensitivity factors for cold cathode ionization sensors are not the same as those for hot cathode sensors Cold Cathode lonization Vacuum Sensor 17 Maintaining the Series 903 IMT Troubleshooting and Service The Series 903 IMT is designed to be maintenance free under normal operation If a problem should occur the following chart lists symptoms possible causes and their remedies With this guide you should be able to diagnose some problems and correct them Those which fall outside the scope of this chart or problems related to the electronics assembly are generally not serviceable by the user and the IMT should be returned to HPS Products for repair Symptom Pressure readings a
11. cr MKS HPS Products HPS Products Series 903 Inverted Magnetron Transducer IMT Cold Cathode lonization Vacuum Sensor OPERATION AND MAINTENANCE MANUAL Please Note MKS Instruments provides these documents as the latest version for the revision indicated The material is subject to change without notice and should be verified if used in a critical application CI ive HPS Products HPS Products Series 903 Inverted Magnetron Transducer IMT Cold Cathode lonization Vacuum Sensor JUNE 1999 PART 1090300 REV A Cold Cathode lonization Vacuum Sensor Part 1090300XX Serial Please fill in these numbers and have them readily available when calling for service or additional information The part number can be found on your packing slip and both the part number and serial number are located on the bottom side of the housing For more information or literature contact MKS Instruments Inc HPS Products Inc 5330 Sterling Drive Boulder CO 80301 USA Phone 303 449 9861 800 345 1967 FAX 303 442 6880 1999 MKS Instruments Inc HPS Products Inc All rights reserved ALCONOX is aregistered trademark of Alconox Inc IgniTorris atrademark of MKS Instruments Inc HPS Products Inc Inconelis aregistered trademark of Inco Alloys International Inc Scotch Brite is a trademark of 3M Is aregistered trademark of MKS Instruments Inc HPS Products
12. ction cie eda cce eb rect pe n ce RAE aid CD ue RE and lend 14 Using the Series 903 IMT with Other Gases 16 Calibrating for Other Gases sssssssssssseeeeeeenen nne 17 Maintaining the Series 903 IMT eenen 18 Troubleshooting and Service nnn nen eneneerenenneerenener vennen 18 Contamination of the IMT Sensor nnen nennen vennneerennenneneeenn 19 Disassembly AEE 19 Cleaning RR 19 ASSO MDI ae ren eneen eee a E dee D AE due 20 Cold Cathode lonization Vacuum Sensor Product Warranty oa doeet n fohe Menit Ha Le sien 23 NOLS Se 24 Appendix A How the Series 903 IMT Works A 1 Theory of a Cold Cathode lonization Sensor nnn an annneenn enen A 1 NOTES eU I D DD A 3 Cold Cathode lonization Vacuum Sensor Package Contents Before unpacking your Series 903 Inverted Magnetron Transducer IMT Vacuum Sensor check all surfaces of the packing material for shipping damage Please be sure that your Series 903 IMT package contains these items 1 IMT unit integrated sensor tube and electronics 1 female 9 pin subminiature D D sub connector 1 Series 903 Inverted Magnetron Transducer IMT Cold Cathode lonization Vacuum Sensor User s Manual If any items are missing from the package call HPS Products Customer Service at 1 303 449 9861 or 1 800 345 1967 Inspect the IMT for visible evidence of damage If it has been damaged in shipping noti
13. dard IMT vacuum interfaces are shown above Use an all metal clamp to mount a KF 25 or KF 40 flanged sensor body Electrical Connection Mount the IMT to a grounded vacuum system Use a cable with a mating 9 pin D sub connector with strain reliefs to ensure proper electrical connection and to reduce stress on the connectors Connect the cable to the IMT and to your power supply or measuring device before operating the IMT Ensure a low impedance electrical connection between the IMT and the grounded vacuum system to shield the sensor from external electromagnetic sources Input Output Wiring The chart and accompanying figure on the next page identify the pins of the IMT connector and their functions Make a cable using this information To be in compliance with EN 50082 1 immunity requirements use a braided shielded cable Connect the braid to the metal hoods at both ends of the cable with the end for power supply connected to earth ground The connector kit shipped with the IMT includes a metal shell which provides an easy and effective means of connecting the braid to it Cold Cathode lonization Vacuum Sensor 9 LINT RN Set point relay normally open contact Set point relay normally closed contact Power supply input Power supply input Analog output voltage 4 Set point relay common 1 5 Set point relay disable Analog output voltage High voltage enable e 6 9 Male 9 pin
14. difficult to position an IMT with a CF flange If the bolts cannot be fed through Key the flange toward the electronics assembly it will first be necessary to remove the electronics assembly from the sensor to install the IMT WARNING Remove the two Phillips head screws on top of the IMT and remove the electronics assembly Note the alignment A of the feed through pins with the orientation of the romen O on electronics assembly as shown to the right e Q Before assembling the IMT inspect the pins to make sure they have not been bent Straighten them if necessary The sensor is keyed to the electronics assembly Rotate the electronics assembly onto the sensor until it is fully seated Install the two Phillips head screws MADE IN USA Contamination Alignment of sensor with electronics assembly Locate and orient the IMT where contamination is least likely If it is installed directly above a diffusion pump for example oil vapor could contaminate the cathode anode or other vacuum exposed components causing the calibration to shift Installing it with the vacuum port facing down is preferable as this helps prevent contaminants falling into it Operation at pressures above 10 Torr for extended periods can promote the negative effects of contamination in the sensor 8 Cold Cathode lonization Vacuum Sensor 0 76 19 mm 0 91 23 mm 0 91 23 mm KF 40 KF 25 Vacuum Connection Stan
15. emove the small ceramic spacer and the ground shield and gently bend the leaf spring towards the anode and then replace the ground shield and ceramic spacer fv fa Nh Leaf spring in contact with cathode 3 Slide the cathode Q the grid washer and the large ceramic spacer into place The grid washer has a concave shape Refer to the figure to see its installation orientation 4 Insert the small end of the compression spring into the sensor body Using your thumbs push the larger end of the spring into the sensor body until it is contained within the tube Using the smooth jaw needle nose pliers work the compression spring down into the sensor body until it is fully seated in the formed groove 3 5 Inspect the ground shield Q and the grid washer to verify they are centered with respect to the anode If adjustment is needed gently reposition the grid washer cathode assembly taking care not to scratch the grid washer HPS suggests you measure the resistance between the ion CET current feed through pin and the grid washer to verify that the leaf spring is in contact with the cathode The measurement should indicate a short circuit between them There should be an open circuit between the ion current feed through pin and both the high voltage feed through pi and sensor body Q The IMT is ready for installation
16. especially attractive to OEM equipment manufacturers Its sensor tube is available with one of four standard vacuum interfaces The IMT is designed for applications which require pressure measurement in the range from 5 x 10 down to 3 x 10 Torr Its rapid response and wide measurement range provide the equipment designer with maximum flexibility Because it can operate autonomously or as part of a control system it is adaptable to several roles including that of a monitor or an alarm The IMT is normally off and requires shorting its High Voltage Enable pin to ground to turn it on This allows the IMT to be controlled by a higher pressure sensor such as the HPS Products SensaVac Series 907 Analog Convection Transducer ACT For process control the IMT has one adjustable relay set point An LED indicates the status of the set point The IMT can be located out of sight pressure is then read from a standard digital voltmeter or analog to digital converter and computer Cold Cathode lonization Vacuum Sensor 7 Installing the Series 903 IMT Location Locate the IMT where it can measure process chamber or manifold pressure Install it away from pumps other vibration sources and gas sources to give the most representative values Orientation The IMT can be installed with the body set in any direction Operating position does not affect accuracy Where space is limited it may be
17. fy the carrier immediately Keep all shipping materials and packaging for claim verification Do not return the product to HPS Symbols Used in this Manual The first two symbols below that may be located on your Series 903 IMT identify critical safety concerns They are used throughout this manual to further define the safety concerns associated with the product The last two symbols identify other information in this manual that is essential or useful in achieving optimal performance from the IMT CAUTION Risk of electrical shock CAUTION Referto manual Failure to heed message could result in personal injury or serious damage to the equipment or both Failure to heed message could result in damage to the equipment 18 DD Calls attention to important procedures practices or conditions Cold Cathode lonization Vacuum Sensor 1 Safety Precautions f Install the IMT only on a grounded vacuum system When using an IMT with a flange and an elastomer seal use an all metal clamp to ensure electrical continuity between the IMT and the grounded vacuum system When using an IMT with a 1 inch tube use a ground strap to connect the sensor to the grounded vacuum system Do not connect power to the IMT unless its flange is attached to the vacuum system and the electronics assembly is fastened to the sensor housing Do not exceed voltage requirements as this may damage the electronics assembly Refer to t
18. g range of the cold cathode to 10 Torr Because of the difficulty in maintaining the discharge at low pressures sensors of the loop anode design do not work well below 10 Torr To reduce this problem a cylindrical anode cathode plates at each end and a cylindrical magnet are used During the 1950s the inverted magnetron sensor was developed which uses auxiliary cathodes and is able to measure pressures below 10 Torr Many electrode arrangements have been used in cold cathode sensors Single feedthrough cold cathode sensors often suffer from spurious currents due to insulator leakage and field emission which mask the small pressure dependent ionization currents The IMT uses an inverted magnetron to reduce these problems by using separate feedthroughs for the anode high voltage and the cathode current This geometry uses a cylindrical cathode a central wire anode and external cylindrical magnet which provides an axial field The cathode is insulated from the grounded metal housing The inverted magnetron geometry has a characteristic electrical conductance vs pressure curve which is more reproducible than other arrangements and also works well to low pressures without risk of the discharge going out This gives the IMT a measuring range from 5 x 10 to 3 x 10 Torr A 2 Cold Cathode lonization Vacuum Sensor Notes Cold Cathode lonization Vacuum Sensor A 3 Cold Cathode lonization Vacuum Sensor
19. he LED is off the measured pressure is above the set point value the normally open relay contact is open and the normally closed contact is closed If a power failure occurs the set point and its LED will turn off Set Point AI Potentiometer In Tip Jacks M commen f Set Point LED Cold Cathode lonization Vacuum Sensor 13 The set point can be turned off by connecting pin 7 set point disable to pin 4 power supply input STOP If the high voltage is started in high vacuum and the sensor discharge has not yet begun the IMT will indicate too low of a reading possibly tripping the set point In this case you should deactivate the set point monitor the reading until the sensor starts and activate the set point thereafter Venting to Atmosphere While the IMT can withstand rapid venting to atmosphere without damage prolonged operation at pressures above 10 Torr increases the negative effects of contamination in the sensor Contamination can result in measurement errors and in severe cases instabilities requiring more frequent cleaning of the IMT Analog to Digital A D Converter To take full advantage of the IMT s capabilities an A D converter with an input voltage span of 0 to 10 V may be used A resolution of 12 bits is needed corresponding to 2 44 mV per bit The A D converter should have a differential inputto ensure accurate measureme
20. he information on page 9 for proper connection instructions The IMT may be connected only to devices conforming to the requirements of a secondary extra low voltage in accordance with EN61010 1 Zi Allow only qualified technicians to service the IMT Users should not remove covers casings or plug in components Injury may result Turn off power to the IMT before proceeding with maintenance Only a qualified technician should replace or adjust electronic components As much as 4 kV may be present in the IMT during operation The current is limited to 100 mA The Series 903 IMT must be used as instructed by MKS Instruments Inc HPS Products Inc for safe operation Using or modifying the equipment inconsistent with specifications may render the product s inherent protection useless 2 Cold Cathode lonization Vacuum Sensor Measuring Range Set Point Range Repeatability Calibration Gas Operating Temperature Range Bakeout Temperature Relative Humidity Altitude Insulation Controls Relay Contact Rating Relay Hysteresis Relay Response Power Requirement Output Voltage Output Load Specifications 3 0 x 107 to 5 0 x 10 Torr 3 9 x 10 to 6 5 x 10 mbar 3 9 x 10 to 6 5 x 10 Pa 1 0 x 10 to 1 0 x 10 Torr 1 3 x 10 to 1 3 x 10 mbar 1 3 x 107to 1 3 x 10 Pa Approximately 5 Air nitrogen 0 to 50 C 32 to 122 F 400 C 752 F maximum for CF flanged unit without electronics
21. ive reactive harmful or radioactive materials gases or chemicals when the PURCHASER requests a return authorization Notwithstanding such inquiries it is the responsibility of the PURCHASER to ensure that no products are returned to HPS which have been contaminated in the aforementioned manner Other Rights and Remedies These remedies are exclusive HPS SHALL NOT BE LIABLE FOR CONSEQUENTIAL DAMAGES FOR ANTICIPATED OR LOST PROFITS INCIDENTAL DAMAGES OR LOSS OF TIME OR OTHER LOSSES INCURRED BY THE PURCHASER OR BY ANY THIRD PARTY IN CONNECTION WITH THE PRODUCT COVERED BY THIS WARRANTY OR OTHERWISE Some states do not allow exclusion or limitation of incidental or consequential damage or do not allow the limitation on how long an implied warranty lasts If such laws apply the limitations or exclusions expressed herein may not apply to PURCHASER Il Unless otherwise explicitly agreed in writing it is understood that these are the only written warranties given by HPS Any statements made by any persons including representatives of HPS which are inconsistent or in conflict with the terms of the warranty shall not be binding on HPS unless reduced to writing and approved by an authorized officer of HPS lll This warranty gives PURCHASER specific legal rights and PURCHASER may also have other rights which vary from state to state IV For HPS products sold outside of the U S contact your MKS representative for warranty info
22. mages or malfunctions due to chemical or electrolytic influences or use of the product in working environments outside the specification IIl Fuses and all expendable items which by their nature or limited lifetime may not function for a year If such items fail to give reasonable service for a reasonable period of time within the warranty period of the product they will at the option of HPS be repaired or replaced IV Defects or damages caused by modifications and repairs effected by the original PURCHASER or third parties not authorized in the manual Condition of Returned Products HPS will not accept for repair replacement or credit any product which is asserted to be defective by the PURCHASER or any product for which paid or unpaid service is desired if the product is contaminated with potentially corrosive reactive harmful or radioactive materials gases or chemicals When products are used with toxic chemicals or in an atmosphere that is dangerous to the health of humans or is environmentally unsafe it is the responsibility of the PURCHASER to have the product cleaned by an independent agency skilled and approved in the handling and cleaning of contaminated materials before the product will be accepted by HPS for repair and or replacement In the course of implementing this policy HPS V Customer Service Personnel may inquire of the PURCHASER whether the product has been contaminated with or exposed to potentially corros
23. near Equal increments of distance along the pressure scale do not correspond to equal pressure changes 10 10 10 105 10 107 Pressure Torr 10 10 1019 1 2 3 4 5 6 7 8 9 Output Voltage VDC 12 Cold Cathode lonization Vacuum Sensor Cold cathode ionization systems are gas dependent and the Series 903 IMT s output is defined for air nitrogen Refer to page 16 Using the Series 903 IMT with Other Gases to determine the true pressure of another gas Equation for Converting Voltage to Pressure The following equation converts the IMT voltage reading Vto a pressure reading P when using air or nitrogen The voltage must be within the domain of the equation or an incorrect pressure reading will result P 10 0 Where P is in Torr mbar microns or Pascal depending on K V is in volts for 1 5 lt V lt 8 7 K 11 000 for Torr 10 875 for mbar 8 000 for microns 8 875 for Pascal Using the Set Point Attach a digital voltmeter to the Common tip jack and the Set Point tip jack on the IMT as shown below Adjust the potentiometer with a small screwdriver until the voltage reading coincides with the desired set point pressure This pressure is shown on the graph on the previous page or is calculated from the equation above When the set point LED is on the measured pressure is below the set point value the normally open relay contact is closed and the normally closed contact is open When t
24. ng spiral trajectories increasing the chance of collisions with gas molecules thereby providing a significant increase in ionization efficiency relative to a hot cathode sensor In operation a near constant circulating electron current is trapped by the crossed fields Collisions of electrons with residual gas molecules produce ions which are collected by the cathode The sensor current as a function of pressure P obeys the relationship i kP where kis a constant Pis in Torr nis a constant usually in the range of 1 00 to 1 15 Cold Cathode lonization Vacuum Sensor A 1 This equation is valid for the pressure range from 10 Torr down to 10 Torr depending upon the series resistor used Sensitivities of 1 to 10 amperes Torr are not unusual Starting a cold cathode sensor depends upon some chance event such as field emission or a cosmic ray producing the first electron This produces additional electron ion pairs during its transit between the electrodes and the discharge soon builds up to a stable value Start of the discharge normally requires a very short time at 10 Torr or above a few minutes at 10 Torr and longer times at lower pressures If the series resistor is small e g 1 MW the current at high pressures increases and sputtering of the cathode can become a problem A larger series resistor reduces sputtering and the voltage across the tube is pressure dependent between 10 and 10 Torr This extends the measurin
25. nts Preparing for Bakeout Shut off power to the IMT and remove its cable Remove the two Phillips head screws holding the electronics assembly to the sensor body The remainder of the Sensor is ready to be baked out to 400 C if using a CF flange or to 150 C if using a KF flange Leak Detection Its inherent sensitivity to gas type makes the Series 903 IMT useful for detecting leaks in vacuum systems It is a good complement to a mass spectrometer leak detector which locates smaller leaks Probe the suspected leak areas with a gas that has an ionization potential different than that of the system gas Helium or argon gas is suitable for probing a system pumping air or nitrogen 14 Cold Cathode lonization Vacuum Sensor 1 Pump your vacuum system to a base pressure 2 Slowly and methodically probe with a small amount of gas ce Flooding the leak or moving quickly past the leak can confuse the search since time lags may be significant 3 Note the pressure reading The pressure will either rise or fall depending upon the ionization potential of the probe gas relative to the system gas The largest change in value indicates the probe gas is nearest the leak location 4 Repeat the test to confirm Cold Cathode lonization Vacuum Sensor 15 True Pressure Torr Using the Series 903 IMT with Other Gases Ee Before using the IMT to measure pressure of gases other than air or nitrogen you should read and unders
26. re too erratic 1 Troubleshooting Chart Possible Cause Contaminated sensor 1 Remedy Inspect and clean if necessary Refer to page 19 No analog output voltage D sub is disconnected Power supply turned off Defective PC board Connect D sub Turn power on Return to HPS for repair Analog output voltage higher than 9 5 V High voltage is turned off Connect pin 9 to pin 4 Refer to page 9 Input Output Wiring Analog output voltage less than 1 5 V Discharge has not started Pressure is less than 3 x 107 Torr Wait for discharge to start or increase pressure to speed up starting time Consider purchasing an IgniTorr Beyond range Increase pressure if desired Analog output voltage less than 0 5 V and LED off No supply voltage Power supply turned off Check cable connection Turn power on Analog output voltage less than 0 5 V and LED on Supply voltage too low Increase supply voltage to provide 14 to 30 V at the IMT Set point relay will not operate 18 Set point voltage incorrectly set Pin 7 of D sub connected to ground at power supply Defective PC Board Cold Cathode lonization Vacuum Sensor Check set point Check any external switches which may be controlling this line Return to HPS for repair Contamination of the IMT Sensor If pressure re
27. rmation and service Warranty Performance To obtain warranty satisfaction contact the following MKS Instruments Inc HPS Products Inc 5330 Sterling Drive Boulder CO 80301 USA at phone number 303 449 9861 You may be required to present proof of original purchase Cold Cathode lonization Vacuum Sensor 23 Notes 24 Cold Cathode lonization Vacuum Sensor Appendix A How the Series 903 IMT Works Theory of a Cold Cathode lonization Sensor A cold cathode ionization sensor has a number of inherent advantages over a hot cathode sensor These include No filament to burn out which makes it immune to inrushes of air and it is relatively insensitive to vibration damage No x ray limit for lower pressure measurement No adjustment for emission current or filament voltage is needed Since heating or degassing is not needed there is little effect on the system Properly designed sensor tubes can be cleaned and reused almost indefinitely 9 9 With only one current loop the control circuit is simple and quite reliable as opposed to a hot cathode sensor which has three The cold cathode magnetic discharge sensor consists of a cathode and anode with a potential difference of several kilovolts The electrodes are surrounded by a magnetic field arranged so that the magnetic field is essentially perpendicular to the electric field The crossed electric and magnetic fields cause the electrons to follow lo
28. tand this section To answer further questions contact Applications Engineering at HPS Products at 1 303 449 9861 or 1 800 345 1967 In a cold cathode ionization sensor the degree of ionization hence the indicated pressure is gas type dependent see page A 1 Theory of a Cold Cathode lonization Sensor The Series 903 IMT is calibrated to give a voltage output for air or nitrogen according to the graph on page 12 or the equation on page 13 If used with another gas the IMT will give an output which corresponds to the ionization from the sensor for nitrogen This is the nitrogen equivalent pressure or indicated pressure of the gas which may be higher or lower than its true pressure True versus indicated pressure curves for some common gases are shown below 10 10 1070 107 10 108 107 10 10 10 10 10 Indicated Pressure Torr 16 Cold Cathode lonization Vacuum Sensor Below is a table which shows the correction factors needed to obtain curves for selected gases other than air nitrogen You can make your own graph from this information or use the graph on the previous page which shows the same information Table of Correction Factors PaP x2 5 Indicated Pe P x8 Indicated P P x 0 8 below 10 Ar Indicated P P x 0 5 at 10 Ar Indicated P P x 0 2 at 10 Ar Indicated Calibrating for Other Gases Air calibration is indistinguishable from nitrogen To determine the volt
Download Pdf Manuals
Related Search