User Manual JCI 178 Charge Measurement Unit
Contents
1. User Manual rge Measurement Unit 4 1 Introduction 2 Practical Design Features 3 Arrangements for Measurements 4 JCI 179 Discharge Probe 5 Calibration 6 Specification Features Chilworth Technology Limited 44 O 23 8076 O722 T Beta House Southampton Science Park 44 O 23 8076 7866 F Southampton SO16 7NS Iinfo chilweorth co uk E United Kingdom www chitwortn co uk w CHILWORTH GLOBAL IS A TRADING NAME OF CHILWORTH TECHNOLOGY LIMITED REGISTERED OFFICE AS ASOVE REGISTERED IN ENGLAND AND WALES NUMBER 2000153 THE EXPERTS IN PROCESS SAFETY Chilworth WARNING Please note that this equipment is not suitable for use where hazardous flammable atmospheres are or may be present hazardous areas as defined in IEC 60079 10 1 and IEC 60079 10 2 inside or outside the equipment Furthermore even in the absence of designated hazardous areas this equipment should not be used in close proximity to flammable substances without first conducting a risk assessment which is the responsibility of the end user company Chilworth CE Conformance Declaration of CE conformance Chilworth Technology Ltd Beta House Southampton Science Park Southampton S016 7NS UK declares as designer and manufacturer of the JCI 140 Static Monitor that the design and construction of these instruments conform to the requirements of the EC Directive on Electromagnetic Compatibility EMC 89 336 EEC to Standards EN 50081 1 1992 and2. and this can be mounted directly on the input BNC connector of the JCI 178 The input for the virtual earth amplifier is buffered with a capacitor earth to avoid overloading the output drive capability of this amplifier The circuits of the JCI 178 are not specially fast so they will not resolve any fast steps in the rising edge of a charge transfer but they will show correctly the overall quantity of charge transferred Observations may usefully be recorded using a digital storage oscilloscope for instance a Picoscope 5 Calibration The sensitivity of charge measurement may be calibrated 3 by charging a calibrated quality capacitor to a calibrated voltage and discharging this to the instrument input Because the input is to a virtual earth preamplifier all the charge Q C V will be transferred and used as a basis for instrument calibration For example a 10nF 1 polystyrene capacitor charged to 1 0V is a convenient arrangement for providing 10nC of charge See also Calibration section on JCI Website since the JCI 178 used a virtual earth charge measurement circuit an alternative approach is to provide calibrated quantities of charge on the basis of switching a defined current into the output connection for a defined period of time 3 The current is defined by a stable and known reference voltage and a precision resistor The period of current flow is defined by selected number counting of cycles from a crystal controlled clock The
3. JCI 256 Charge Calibrator provides this calibration capability for quantities of charge from 1 999nC with an accuracy better than 1 Provision is included to enable the unit itself to be formally calibrated with measurements whose accuracies are traceable to National Standards References 1 J N Chubb G J Butterworth Charge transfer and current flow measurements in electrostatic discharges J Electrostatics 13 1982 p209 2 J N Chubb Measurement of charge transfer in electrostatic discharges J Electrostatics 64 2006 p321 325 JCI Website www jci co uk cache ProbeStudies pdf 3 J N Chubb Methods for the Calibration of Electrostatic Measuring Instruments http www jci co uk Calibration Calibration pdf 6 Specification Features 20nC amp 200nC FSD Noise and Zero stability Noise within 10pC Zero stable within 100pC Accuracy and linearity Within 5 FSD Display 3 2 digit liquid crystal display of charge transfer directly in nC LO BATT indication Power supply PP3 replaceable battery external isolated 12V supply for example a JCI 142 mains unit Controls ON OFF switch selecting OFF ON 20nC amp ON 200nC Screwdriver set alarm threshold Zeroing push button in rear cover Connections BNC input connector on front for charge measurement Combination Durable Dot 4mm bayonet earth bonding connector 8w min DIN output connector 2V FSD analogue signal output 5 violet Analogue ea
4. Measurement Unit for general measurement of small quantities of charge and measurement of charge transfer in static discharges 1 Introduction The JCI 178 is a compact and easy to use instrument for the sensitive measurement of charge in the range 10pC to 200nC The unit is shown in Figure 1 The unit incorporates a 31 2 digit liquid crystal display showing directly the quantity of charge transfer measured in nano coulombs nC It has an analogue output for remote display and recording of readings with opportunity for remote zeroing For measurement of charge transfer in electrostatic discharges the unit can be fitted with a JCI 179 shielded probe This ensures that observations can be interpreted with confidence 1 2 and valid judgements made on the risk of ignition presented in relation to quantities of charge transferred 2 Practical Design Features The charge measurement unit has many of the same physical design features as the JCI 140 Static Monitor instrument It is thus easy to handle to control and to read the values from observations The unit is based on a virtual earth charge measurement circuit As this ensures the input remains essentially at earth potential insulation leakage problems are minimised Circuit design features such as guarding minimise zero drift and droop of readings Two ranges of sensitivity are available These are selected by the 3 position slide Switch in the back cover of the instrument Th
5. on the front end panel of the unit This may be linked directly to the charge source or via a low noise coaxial cable Care needs to be taken that no significant quantity of charge is generated by flexure or vibration of a connecting cable The display and analogue output readings are zeroed by pressing the zeroing push button in the rear panel of the instrument or using the appropriate connections to the 8w mini DIN connector in the back panel Zeroing involves shorting the charge measurement feedback capacitor of the virtual earth charge sensing input circuit At this time the input is isolated from the preamplifier If there is some appreciable Capacitance in the charge source then it may be useful to re zero a few times to get a good low zero reading For sensitive measurements it is best to hold the circuit in a zeroed condition until a measurement is to be made The zero should be released a short time a few seconds before a measurement is made so that a good value of the zero reading and any drift is obtained from which to evaluate observations In preparing for practical studies for example with a Faraday Pail it is wise to check for drift of zero and droop of finite charge readings from the system before taking measuremenis 4 JCI 179 Discharge Probe Charge transfer measurements in spark type electrostatic discharges need to be made using a shielded probe such as the JCI 179 1 2 The JCI 179 probe is a general purpose shielded probe
6. EN 50082 1 1992 These instruments also conform to the requirements of the Electrical Equipment Safety Regulations 1994 S I 1994 3260 Dr Stephen Rowe for and on behalf of Chilworth Technology Ltd sulle RoHS and WEEE Directives JCI Chilworth electrostatic measuring instruments are not required to conform to the ROHS Directive because they come within Category 9 exemption To comply with the requirements of the EC WEEE Waste Electrical amp Electronic Equipment Directive all JCI Chilworth instruments at the end of their useful life should be returned to Chilworth Technology Ltd for disposal or recycling in an environmentally appropriate way Chilworth Technology Ltd is a member of the Producer Compliance Scheme ECONO WEEE Lid registration number WEE KB1414VU Chilworth PRODUCT WARRANTY All test instrumentation supplied by Chilworth Technology Ltd is manufactured to the highest specification and as such Chilworth Technology Ltd warrants the product against defects in materials and workmanship for a period of twelve 12 months from the date of receipt at the Customer premises on a return to base policy lt is a necessary requirement of the warranty conditions that the instructions given in the user manual are read understood and adhered to before putting the instrumentation into first use If any doubt exists please consult the manufacturer for further assistance In such cases where the product is returned to Chi
7. is provides selection as OFF ON 20nC FSD ON 200nC FSD When the instrument is operating on its most sensitive range the sensitivity can be changed to its second lower sensitivity range remotely by shorting pin 4 of the 8w mini DIN to earth yellow lead A small push button is provided in the back cover for zeroing readings before observations No zero setting adjustment is provided so it is necessary and always wise to take note of the zero reading after the zeroing button has been released and just before charge is received Note that with sensitive charge measurements it is desirable to hold the unit in the zeroing state until just before measurements are made This will reduce the chance of any zero drift The back cover also includes a combination Durable Dot 4mm bayonet pin earth bonding connector an 8w min DIN connector and a 2 1mm 12V external power Supply input connection The 8w miniature DIN connector provides for analogue output of observations input of external power supply and opportunity for zeroing with a remote push button The instrument must be bonded to earth for meaningful measurements An audio alarm is included with a user settable threshold level This may help recognition of untoward charge generation situations and identification of hazardous discharges in practical testing 3 Arrangements for Measurement Connection to the source of charge to be measured is made via the BNC connector
8. lworth Technology Ltd we will inspect the product on receipt to diagnose the fault and will issue the Customer with an inspection and condition report lf the product proves defective during the warranty period Chilworth Technology Ltd at its option will repair the product at our facilities in Southampton UK Provided the product has been used in accordance with the manufacturers guidelines and that the fault is due to a manufacturing defect or component failure and is not due to expected wear and tear caused by the operating environment in which it is used this warranty covers all parts and labour but specifically excludes any consumable parts supplied with the product and any shipping costs to Chilworth Technology Ltd Chilworth Technology Ltd shall not be obliged under this warranty a to repair damage resulting from attempts by personnel other than Chilworth Technology Ltd representatives to install repair or service the product unless directed by a Chilworth Technology Ltd representative b to repair damage malfunction or degradation of performance resulting from improper use or connection to incompatible equipment or memory c to repair damage malfunction or degradation of performance caused by the use of non Chilworth Technology Ltd supplies or consumables or the use of Chilworth Technology Ltd supplies not specified for use with the product d to repair an item that has been modified or integrated with other product
9. products and services visit process safety services visit www jci co uk www chilworth co uk email sales jci co uk email info chilworth co uk Chilworth Technology Ltd Beta House Southampton Science Park Southampton SO16 7NS UK Tel 44 0 23 8076 0722 Fax 44 0 23 8076 7866
10. rth 2 white Remote zeroing 3 red Remote sensitivity change 4 yellow External power supply inputs 8 ve brown 6 ve blue 2 1mm d c input for external isolated 12V power supply 160x66x34mm Weight 300grams Optional extra Shielded discharge probe JCI 179 for measuring charge transfer in electrostatic and spark discharges Figure 1 JCI 178 Charge Measurement Unit Figure 2 JCI 178 with JCI 179 Discharge probe attached JCI Chilworth manufactures a wide range of high quality state of the art electrostatic instrumentation We also carry out servicing and repairs for JCI instruments and where appropriate calibration traceable to national and international standards JCI Chilworth is part of Chilworth Global Chilworth Global brings together leading expert consultants in the fields of electrostatics and process safety and GLP compliant laboratories to provide a single point of contact for all electrostatic and process safety needs Our laboratories provide material properties data for electrostatic problems and hazards fire and explosion hazards including liquids vapours gases and powders chemical reaction hazards and regulatory testing Our consultant engineers are all experienced in process safety with individual expertise that includes electrostatics chemical reaction hazards and other particular aspects Contact Information For further information on JCI Chilworth For Further information on Chilworth Global
11. s when the effect of such modification or integration increases the time or difficulty of servicing the product or degrades performance or reliability e to perform user maintenance or cleaning or to repair damage malfunction or degradation of performance resulting from failure to perform user maintenance and cleaning as prescribed in published instruction user manual f to repair damage malfunction or degradation of performance resulting from use of the product in an environment not meeting the operating specifications set forth in the instruction user manual g to repair damage malfunction or degradation of performance resulting from failure to properly prepare and transport the product as prescribed in published product materials h to replace items that have been refilled are used up abused misused or tampered with in any way i to Support software not supplied by Chilworth Technology Ltd j to provide software or firmware updates or upgrades In the maintenance of the product Chilworth Technology Ltd may use new or equivalent to new parts assemblies or products for equal or improved quality All defective parts assemblies and products become the property of Chilworth Technology Ltd Any additional service identified and provided by Chilworth Technology Ltd at the Customer s request shall be invoiced to Customer at Chilworth Technology Lid s current rates for parts labour and travel User Manual JCI 178 Charge
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