User Manual:
Contents
1. The surface is charged by a high voltage corona discharge 3 10kV from the tips of a small conical cluster of fine wires mounted on the underside of a light moveable plate This plate is moved between the fieldmeter sensing aperture and the material surface exposed through the instrument baseplate Corona is usually generated as a brief pulse 20ms immediately before the plate is moved away The plate moves fully away within 20ms The moving plate and instrument construction shield the fieldmeter from high voltage connections so reliable measurements can be made down to even quite low surface voltages An air dam is included on the trailing edge of the moving plate This sweeps away residual air ionisation at the end of the corona period to give a so there is little influence on surface voltage measurements no more than about 10V Fieldmeter A proprietary fast response field mill electrostatic fieldmeter 5 6 gives fast sensitive and stable measurement of surface potential The response time is below 10ms and charge decay times can be measured from below 50ms to many days Fieldmeter seen through test aperture Instrument software provides for automatic zero setting of the fieldmeter just before each test In very long charge decay studies arrangements are made to check the fieldmeter zero from time to time It is not easy to measure decay times with signals where noise is significant in comparison to the signals or the signal di2. 3 fast response field mill fieldmeter measures surface voltage with response time less than 10ms surface voltage display automatically adjusts between V and kV of surface potential automatic zero setting by software with plate advanced at start of each test Zero stable within 5V over long duration runs Noise on displayed and stored values within 1V about 2 seconds to set for charging 20ms opening Slow opening operation about 2s for measurements on light powders internal feedback stabilised high voltage supply providing positive and negative potentials to 10kV 10 Megohm personnel safety resistor is used in the link to the corona discharge points direct measurement by software of corona voltage and current from about 50V to about 3kV depending on rate of charge dissipation charge decay times from below 50ms to over 100 000 seconds direct operation by integral NiMH rechargeable batteries providing about 4 hour continuous operation Automatic software progressive shut down with advice on LO BATT condition Batteries recharged via universal mains power supply 115V 240V 6VA 60 50Hz the NiMH batteries 600mAh are Smart recharged whenever the JCI 155 is connected to the mains supply 115V or 240V Charging time is about 2 hour Red LED indication of fast recharge operation mains input via fused SOOmA IEC connector Green LED indication of mains power supply active 8w mini DIN se
3. 5 Light paper 40g open repeat Serial 01091949 run 00000081 Date 27 09 2001 at 09 23 24 Corona Voltage 7000 Corona Time 0 02 Surface Temp C 20 4 Surface R H 51 08 Peak at 456 24 volts 1 e reached after 0 029297 sec 10 reached after 0 20898 sec Received charge 19 8749 nC Capacitance loading 18 7063 The business of JCI is the design development manufacture and marketing of high quality instruments for electrostatic measurements JCI also carries out electrostatic testing of materials consultancy and calibration of JCI instruments to BS 7506 Part 2 1996 ut 7 L msec 3 C JCIx 01091949 2001 09 27 00000082 jc5 Light paper 40g open new Serial 01091949 run 00000082 Date 27 09 2001 at 09 56 10 Corona Voltage 7000 Corona Time 0 02 Surface Temp C 20 81 Surface R H 50 31 Peak at 454 99 volts 1 e reached after 0 023438 sec 10 reached after 0 13672 sec Received charge 19 6917 nC Capacitance loading 18 5846 4 C ICIx 01091949 2001 09 27 00000084 jc5 Light paper 40g open repeat Serial 01091949 run 00000083 Date 27 09 2001 at 09 56 29 Corona Voltage 7000 Corona Time 0 02 Surface Temp C 20 81 Surface R H 50 31 Peak at 468 32 volts 1 e reached after 0 025391 sec 10 reached after 0 15234 sec Received charge 21 3544 nC Capacitance loading 19 5804 For further information contact Dr John Chubb at Unit 30 Lansdown Industrial Es
4. JCI 155v5 Charge Decay Test Unit The JCI 155 is a compact instrument for easy and direct measurement of the ability of materials to dissipate static electricity and to assess whether significant voltages will arise from practical amounts of charge transferred to the surface INTRODUCTION Many of the useful opportunities presented by static electricity and many of the risks and problems it can cause relate to the influence of retained electrostatic charge This is manifest as the surface voltage created by the charge retained The suitability of a material may be judged in terms of the maximum surface voltage created and or by the time for which this is maintained JCI 155v5 Charge Decay Test Unit In the JCI 155 Charge Decay Test Unit a high voltage corona discharge is used to deposit a patch of charge on the surface of the material to be tested A fast response electrostatic fieldmeter measures the voltage generated by this charge It also measures how quickly this voltage falls as the charge migrates away 1 Corona charging has been shown 2 to be a simple way to simulate practical charging events It allows control of initial surface voltage and charge polarity and is applicable for all types of surfaces whether uniform or with localised conducting features It provides consistent reproducible results that are not affected by corona exposure Operation of a JCI 155 in conjunction with measurement of the quantity of corona charge t
5. alibrator Unit provides a convenient basis for such formal calibration REFERENCES 1 J N Chubb Instrumentation and standards for testing static control materials IEEE Trans Ind Appl 26 6 Nov Dec 1990 p 1182 2 J N Chubb The assessment of materials by tribo and corona charging and charge decay measurements Proc Inst Phys Confr Electrostatics 1999 Univ Cambridge Mar 1999 Inst Phys Confr Series 163 p329 3 J N Chubb Measurement of tribo and corona charging features of materials for assessment of risks from static electricity Trans IEEE Ind Appl 36 6 Nov Dec 2000 p1515 4 J N Chubb New approaches for electrostatic testing of materials J Electrostatics 54 3 4 March 2002 p233 ESA 2000 meeting Brock University Niagara Falls June 2000 5 J N Chubb Two new designs of field mill type fieldmeters not requiring earthing of rotating chopper TEEE Trans Ind Appl 26 6 Nov Dec 1990 p 1178 6 J N Chubb Experience with electrostatic fieldmeter instruments with no earthing of the rotating chopper Proc Inst Phys Confr Electrostatics 1999 Univ Cambridge Mar 1999 Inst Phys Confr Series 163 p443 7 British Standard Methods for measurements in electrostatics BS 7506 Part 2 1996 8 Test method to determine the limitation of surface potential created by electrostatic charge retained on materials J N Chubb draft on JCI Website at www jci co uk Measurements Retain
6. edCharge pdf This facility is included in instruments built after April 2002 and can be retrofitted to earlier instruments at JCI SPECIFICATION FEATURES Controls Displays Test area Sample Fieldmeter Operating times HV supply Surface voltage Timing range Operation Battery charging Connections Software Power ON key at lower right hand corner of top panel 8 keys around liquid crystal display LED illumination to show those available for active use Key functions cover initiation of charge decay test runs inspecting data from the most recent as well as earlier runs selecting and editing test conditions and aborting operations corona voltage polarity change over rotary switch liquid crystal display with two rows of 24 character 150x25mm LED indication of connection to mains power supply LED indication that corona charging is active LED indication that batteries are in fast charge mode 45x54mm aperture in instrument baseplate the unit may be placed directly on a surface or area of sample the JCI 166 Sample Support Unit provides a simple support for open and earthed backing tests the JCI 176 Charge Measuring Sample Support provides open and earthed backing support for film and layer samples up to 5mm thick with measurement of the corona charge received by the sample powders and liquids may be studied by placing in an earthed cup e g JCI 170 or JCI 17
7. ements using the JCI 176 can be with both open and earthed backing JCI 155v5 on JCI 176 Charge Measuring Sample Support Powder samples may be presented using the JCI 170 Powder Sample Support with the JCI 155v5 supported by a JCI 172 Support Plate so the JCI 170 can be easily put in place an removed and so that the baseplate of the JCI 155v5 1s stood off a few mm to reduce risk of powder dispersal into the air by action of the air dam Powder and liquid samples can alternatively be presented for testing using a JCI 173 Powder Sample Support Plate mounted between the plates of a JCI 176 sample support Test conditions Charge decay characteristics are usually susceptible to absorption of surface moisture from the atmosphere so measurements are very likely to depend on humidity It is hence desirable to carry out testing under defined or at least known conditions of temperature and humidity This can be achieved by carrying out measurements in a controlled environment as 1s provided for example in the JCI 191 Controlled Humidity Test Chamber with adequate time allowed for acclimatisation The JCI 155v5 includes facilities to measure both temperature and humidity within the test region of the instrument These measurements are stored along with all the other information on test conditions JCl Graph All test conditions and observations are stored to a memory card slotted into the JCI 155v5 This data can be transferred to a PC using propr
8. fferences to be measured This may apply for materials that dissipate charge either so quickly that the initial peak voltage is very low only 10 50V or with materials that dissipate charge very slowly so that small differences in signal levels need to be measured to get results within modest periods of observation A special feature of the JCI 155v5 is that it uses a new stutter timing approach for decay timing This provides an excellent way to identify average values of a noisy signal without slowing down time response Sample support Measurements are normally made both with the material freely supported with an open backing and also resting against an earthed backing surface These two arrangements represent the extremes of constraints of practical application The longer of the two decay times is used for assessment of the suitability of the material The JCI 166 Sample Support provides a simple arrangement for such measurements Simultaneous measurement of the quantity of charge received by the sample surface and the initial peak surface voltage achieved enables calculation of the capacitance loading experienced by charge on the sample surface 3 4 8 The JCI 176 Charge Measuring Sample support provides the ability to measure the corona charge received by the sample This unit can be directly connected to the JCI 155v5 by an 8w 8w DIN cable so that charge measurements are stored alongside the relevant charge decay observations Measur
9. ietary Windows software JCI Graph This provides opportunity to display up to 4 graphs at a time of observations and to transfer these together with associated numerical test and result information into wordprocessed documents A summary table of test and result information is also created Test criterion A simple acceptance test criterion is that the decay time initial peak voltage to 1 e 37 of this should be less than half a second Experience is that the form of charge decay curves is usually not an exponential The form of the curve however does not usually depend on the level of the initial peak voltage or hence on the level of charging Thus a decay time measured as a set percentage of the initial peak voltage is an appropriate basis by which to rate materials A point immediately after the initial peak voltage is used as a starting point for timing as timing from this point includes as much information as possible about possibly fast initial voltage drops The point is chosen to be immediately after completion of competition between opening of the moving plate and the decay of surface potential It is also useful to record how the rate of charge decay varies during decay to see whether significant levels of charge may be retained for long times It is observed that charge decay curves may plateau out after an initial perhaps fairly rapid fall of surface voltage In this situation it may be argued that a better acceptance test c
10. ransferred to the test surface for example using a JCI 176 Charge Measuring Sample Support allows calculation of the capacitance loading experienced by charge on the surface This capacitance loading gives guidance to the maximum surface voltage likely to be created by certain quantities of charge on a surface 4 A high capacitance loading means that only low surface voltage arise per unit of charge The JCI 155v5 Charge Decay Test Unit is a development of previous version JCI 155 instruments The special feature of this new version instrument is that it includes an integral microprocessor so that all basic analysis display and storage of observations is carried out by software within the instrument Basic operation of the instrument is achieved using only very few key buttons Full versatility in setting instrument operation and measurement arrangements is provided by the instrument software and display John Chubb Instrumentation INSTRUMENT OPERATIONAL FEATURES Test Area The JCI 155 has a 45x54mm test aperture in the instrument baseplate This can rest directly on the test surface Contact with the surface around the test aperture provides a return route for outwardly migrating charge and high local capacitance to trap such charge With short duration corona charging e g 20ms the presence and position of the outer earth boundary is not important Measurements can be made on surfaces smaller than the test aperture area Charging
11. rial data communications link connector 8w mini DIN connector for linking to JCI 176 for sample charge measurements 6w mini DIN Remote control connector for linking to external operational control and indication combined Durable Dot and 4mm bayonet earth bonding point proprietary software in ROM for operation of integral TDS2020 microcomputer for control of instrument operation for setting operational parameters and for recording and analysis of charge decay curve data Data stored to PCMCIA memory card JCI Graph Windows 95 98 2000 compatible software for transfer of data and display and analysis of instrument observations Type I PCMCIA ATA removable memory card or CompactFlash memory Data storage card in PCMCIA adaptor 16M CompactFlash card in adaptor supplied Dimensions Packaging 173x216x67 mm in carrying case with IEC mains cable 8w mini DIN 9w D serial communications cable 8w 8w mini DIN cable for linking to JCI 176 JC 155 Charge Decay Test Ur Ey itt 1 C lJCIx 01091949 2001 09 27 00000080 jc5 Light paper 40g open repeat Serial 01091949 run 00000080 Date 27 09 2001 at 09 23 03 Corona Voltage 7000 Corona Time 0 02 Surface Temp C 20 4 Surface R H 51 08 Peak at 455 83 volts 1 e reached after 0 027344 sec 10 reached after 0 20703 sec Received charge 19 1395 nC Capacitance loading 18 0303 2 C JCIx 01091949 2001 09 27 00000081 jc
12. riterion would be the time to 10 of the initial peak voltage as this would better ensure that residual surface voltages were low Measurements to both 1 e and to 10 are recommended when practicable Measurement of the quantity of charge transferred to the sample and the initial peak voltage enables materials to also be assessed in terms of capacitance loading Decay timing Decay times are measured using a proprietary technique called stutter timing This approach very effectively overcomes problems with signal noise at low signal levels It is helpful a with very slow charge decay rates and b with very low initial peak voltages for example 10 50V Stutter timing works by running and stopping the timing clock according to whether the instantaneous fieldmeter signal is above or below the voltage level of interest This approach is used both in the algorithm for finding an initial peak surface voltage from which timing will start and for determining the end of timing It is also used in calculation of local charge decay time constants during the progress of charge decay Operation The JCI 155v5 operates from its own internal rechargeable batteries NiMH nominal 600mAh capacity When the instrument is connected to a mains power supply 115V 230V the batteries are Smart recharged according to need The presence of a mains power supply and application of fast battery recharging are indicated by LEDs in the top cover For measurement
13. s under defined environmental conditions it is best to use the instrument on batteries without the mains connected to minimise heat dissipation within the instrument To save battery power the instrument is automatically shut down a short time about 2 minutes after set operations have been completed if none of the key buttons are operated and if a run is not in progress Activity is restored by pressing the Power On key The instrument operation is set up and controlled using the top panel keys Operation may alternatively be controlled from an associated microcomputer connected via the serial communications RS232 port or by connections to the Remote control port Integral microprocessor An integral microprocessor TDS 2020 controls all aspects of instrument operation and enables charge decay curves to be stored analysed and displayed in real time by the instrument itself Observations are stored in a removable PCMCIA memory card inserted into the instrument Observations by the instrument can be passed to a microcomputer using a PCMCIA or CompactFlash memory card or directly via a serial data link using Windows software JCI Graph Results displayed by JCI Graph can be easily transferred into word processing and Spreadsheet operations Calibration Instrument performance can be formally calibrated to British Standard BS 7506 Part 2 1996 7 using measurements whose accuracy is traceable to National Standards The JCI 255 C
14. tate Gloucester Road Cheltenham GL51 8PL UK Tel 44 0 1242 573347 Fax 44 0 1242 251388 email jchubb jci co uk Website http www jci co uk Example of charge decay graphs HELP LINE JCI offers a consultancy Service through which we advise and assist customers who need to assess and overcome problems with Static electricity We also test customer materials for static charge dissipation and capacitance loading performance John Chubb Instrumentatian
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