1021 User Manual - Time Electronics
Contents
1. Time Electronics 1021 Current Source With Null Measuring Facility Technical Manual _sens off I ID 7 Time Electronics 1021 DC Current Source T 2 4 source 8 null V1 4 14 12 10 Time Electronics Ltd Botany Industrial Estate Tonbridge Kent TN9 1RH Tel 44 0 1732 355993 Fax 44 0 1732 770312 Email mail TimeElectronics co uk Web Site www TimeElectronics com 2 Contents Le MittOGU e t Ocio cede tecto Cen hee Ped e ests Gils e EUH e PUR P EH E CUL PE RU DRLR CR CH UR UPUEL ER ER 3 1 3 General Descrlptlonh erunt ete eei eee ieee eas 3 1 2 Specification Siir eee etal acta datie ca e adaa ra fede eee 4 2 Controls iiie ec een e en e e Re e e P e e en ee e Pee es e Pe P E IR EI ER PRI ERR 5 3 Operations ERROR IRR UR RR RERUM AAT AENEAN RE MARE EU 7 3 1 luit nnn na ee 7 3 2 Normal Operatlonh 5 1 5 ees teaches eade E a tiaau peus 7 3 3 Measurement of Cutrreht euer tereti tenes 7 3 4 Voltage Compliance Adjustment V OJP enne 7 3 5 Overload Goridlllohs eec e eee eee tite teet 7 3 6 Battery Rechatgln ce etate niea cea bea chee 7 4 Electrical Noise Pick Up ier HERRERA RR 8 b Circuit Des crpioDbcend edens ente erbe or edite rede ries eden Ps di e e e x ea dis eed etn eb 9 5A Power Supply ioa Eae e ce eter rt doe o Le eee 9 5 2 Mains Recharger eiue nie pede rende dece cpi teeter at 9 5 32. 1021 DC Current Source 0000 8 9 10 11 BATTERIES 1021 Technical Manual 5 1 Output Terminals Output current is available on two front panel terminals which are suitable for either wire compression or 4mm wander plug insertion 2 Case Terminal This is connected to the instrument case only and is isolated from the circuitry The case provides an electrostatic screen and can be earthed for rejection of noise pick up 3 Sensitivity Control A continuously variable control for adjusting the Null indicator sensitivity The range of adjustment is from 25mA fully anti clockwise to 25uA fully clockwise 4 Polarity Switch Normal or reverse polarity is selected by a toggle switch The centre position is OFF which provides an open circuit on the output terminals 5 Voltage Limit Indicator An LED which indicates when the 1021 is unable to supply sufficient drive voltage to maintain the set output current e g the maximum drive voltage of the instrument 6 LED Null Indicator Used for reading off an unknown current when the instrument is used in the Null mode 7 Digit Switch Four decade thumbwheel switch with 0 to 9 selections on each decade 8 Source Null Switch A two position toggle switch for selecting the mode of operation In the Source position the instrument operates as a current source In the Null position the instrument is used for the measurement of current 9 Supply On Off Switch and Range Sw
3. Botany Industrial Estate Tonbridge Kent TN9 1RH Tel 44 0 1732 355993 Fax 44 0 1732 770312 Email mail TimeElectronics co uk Web Site www TimeElectronics com Disposal of your old equipment 1 When this crossed out wheeled bin symbol is attached to a product it means the product is covered by the European Directive 2002 96 EC 2 All electrical and electronic products should be disposed of separately from the municipal waste stream via designated collection facilities appointed by the government or the local authorities 3 The correct disposal of your old appliance will help prevent potential negative consequences for the environment and human health Fons 4 For more detailed information about disposal of your old appliance please contact your city office waste disposal service or return to Time Electronics 1021 Technical Manual 14
4. Circuit Module and Range Switch eese 9 6 Maintenance and Repair eene 10 LANE lhicuige Heem c 10 6 2 Hepalb aes seca sa E cc a eh ee ade 10 Tae dqRe callbkatioh uo ae cae OR e NR eR e Ne Ne NR NN Ne NOR NN 11 7 1 Calibration Procedure eeeeeeeeeeeeeeeeeeeeseeeeenne nennen nnne nnne nnnnnnnu 12 TEP TN T AIA nette ete d se LL cte 13 8 Guarantee amp S BIVICIBORS Ge OR HONOR WOR ORO TR RE ORO NOR NOR OR a OR ORT 14 All Time Electronics instruments are subject to continuous development and improvement and in consequence may incorporate minor detail changes from the information contained herein 1021 Technical Manual 2 1 Introduction 1 1 General Description e 100mA output with overload protection e 0 02 Accuracy e Wide range of applications e Safety terminals e Removable protective boot e Battery level indicator The 1021 is a precision DC Current Source suitable for calibration and test applications from 100nA up to 100mA The 100mA output with overload protection is based on the popular Time Electronics type 1007 millivolt source and incorporates many of the well proven features The instrument is overload protected and a front panel indicator shows when insufficient drive voltage is available The terminal output voltage is adjustable between 14 volts and 40 volts with a maximum output power of 2 4 watts T
5. input impedance audio amplifier as far as noise pick up is concerned Therefore for high performance work at low current levels it is important to use screened leads It is also important to consider the effects of earthing when using the 1021 to calibrate mains powered equipment The major source of electrical noise pick up is the 50 60Hz mains This noise is generally present to a greater or lesser extend in all environments where mains power is available This noise pick up is capacitively coupled and is AC In most applications although superimposed the DC output it will not affect the DC accuracy This is the case with small amount of pick up but at high levels several volts peak to peak the output circuitry of the 1021 is overloaded by the noise signal and it converts it into a DC offset with results in an error in the output It is important to realise that when measuring electrical noise at the output terminals of the 1021 the voltage noise measurements must be divided by the load resistance to give the current noise A certain amount of noise is generated internally by the 1021 and when high load resistances are used this can be seen on the output terminals as a series of voltage spikes The effect of this voltage noise on the output current is very small and does not affect the DC accuracy Two of the more common sources of noise are discussed below Mains Power Lines As has been stated previously mains power lines are probably
6. the largest source of noise often covering a wide spectrum of frequencies The most effective solution is to locate its source and provide suitable filtering such as capacitor suppression on arcing contacts This noise is usually produced in one of the following ways 1 50 60Hz signal pick up This is generally caused by the close proximity of unscreened mains cables or mains powered equipment The effects of this type of noise can usually be considerably reduced by correct screening and earthing 2 Transient signal pick up This is generally caused by heavy load switching on the mains such as electric motors electric ovens etc Its effect is to cause a transient variation in the output which can last longer than the actual duration of the noise This is because the instrument has been transiently overloaded and requires time to recover Common Noise Mode Additional noise and variation of the output current can be caused by large common mode voltages These occur when the instrument is used to calibrate any input which is above ground potential or has an AC component with respect to ground Under normal circumstances it is recommended that a 100v DC common mode is not exceeded The AC common mode rejection is determined by the capacitive unbalance to ground of the output terminals and associated connections 1021 Technical Manual 8 5 Circuit Description 5 1 Power Supply The power supply circuit board is mounted on a removabl
7. 1 0MACAL trimmer to bring the output to exactly 10mA For recalibration method a the 100 ohm precision resistor should be used 4 Select the 100mA range and set all digits to 9999 Adjust the Q100MACAL trimmer for exactly 100mA output For recalibration method a the 10 ohm precision resistor should be used 1021 Technical Manual 12 7 2 Linearity The linearity of the output is determined by specially matched resistors mounted on the rear of the digit switch The matching is done when the 1021 is manufactured Under normal operating conditions the high performance of these resistors ensures that the 1021 linearity will remain within specification for the instrument s lifetime Should the resistors be damaged or become faulty a replacement procedure should be adopted ensuring that the replacement resistor s is matched to the others on that digit bank The 1K ohm values should be matched to 0 01 the 100 ohms to 0 05 the 10 ohms to 0 5 and the 1 ohm to 5 1021 Technical Manual 13 14 8 Guarantee amp Servicing Guarantee Period This unit is guaranteed against defects in materials and workmanship for a period of one year from its delivery to the customer We maintain comprehensive after sales facilities and the unit can if necessary be returned to us for servicing During this period Time Electronics Ltd will at its discretion repair or replace the defective items For servicing under guarantee the instru
8. be measured with a high performance DVM 50 ppm accuracy on the 1 volt DC range and greater than 100 Megohms input b The output current can be measured directly on a high performance DVM 50 ppm accuracy on 1 mA 10 mA and 100 mA ranges 1021 Technical Manual 11 12 7 1 Calibration Procedure Access to the recalibration trimmers is by removing the instrument s cover which is located by four small screws There are 4 multi turn trimmers which are all located on the switch module assembly These are marked ZERO 1mACAL 10mACAL and 100mACAL Fig 1 4021 MODULE TRIMMER LOCATION Switch on the instrument and allow the circuits to stabilise for a few minutes Ensure that there are no draughts or direct heating e g direct sunlight causing temperature gradients in the circuitry Calibration should be carried out at a stable temperature between 20 24 deg C 1 Select the 100mA range set all digits to zero adjust the ZERO trimmer to give 1 micro amp output For recalibration method a the precision 1K ohm resistor should be connected to the output terminals Note the zero adjustment is unipolar i e it is not possible to adjust the output to less than zero 2 Select the 1mA range and set all digits to 9999 Adjust the 1MACAL trimmer to bring the output to exactly 1mA For recalibration method a the 1K ohm precision resistor should be used 3 Select the 10mA range and set all digits to 9999 adjust the Q
9. connects with a socket on the top panel 1021 Technical Manual 3 1 2 Specifications Output Accuracy Drive Voltage Out of Limit Warning Output Polarity Output Stability Null Sensitivity Load Regulation Power Supply Dimensions Weight Optional Extras 0 100mA in 3 ranges 1 0 99 99mA in 10uA steps 2 0 9 999mA in 1uA steps 3 0 999 9UA in 0 1uA steps 0 02 of setting 0 02 of range 0 02UA Adjustable between 14 and 40 volts Maximum output power 2 4 watts A front panel indicator provides indication of insufficient drive voltage Normal or Reverse switch selected A centre OFF position provides an open circuit Better than 60 ppm per C 10 C to 50 C Better than 25 ppm per hr at constant temperature Adjustable from 25mA to 25uA Better than 20 ppm per volt change in output 8 NiMH rechargeable batteries with external mains re charger Standard mains voltage is 220 250V 50 60Hz 100 125V 50 60Hz is available but must be specified on order 200 x 75 x 110mm 215 x 100 x 120mm including protective boot 1kg 1 4kg including protective boot Leather Carry Case 9027 Factory Calibration Certificate 9153 UKAS Calibration Certificate 9105 Additional Rechargeable Battery Packs 230V mains charger and 8 NiMH cells 9529 110V mains charger and 8 NiMH cells 9528 1021 Technical Manual 2 Controls 2 3 Time aa 6 LI m
10. e bracket which runs the length of the instrument Eight NiMH AA size cells located in two plastic holders power a switch mode regulator through a 1A fuse The batteries may either be of the NiMH rechargeable type as fitted and recommended or of the Alkaline non rechargeable type The switch mode regulator supplies a stabilised 8V a stabilised 7V and a variable stabilised 14V to 40V at 2 4W The regulator circuitry incorporates a cut out which operates should the battery voltage fall below approximately 7V Battery life depends primarily upon the output current and voltage setting At output currents of less that a few mA the life of a fully charged battery should be up to 20 hours 5 2 Mains Recharger The mains recharger is a separate unit It will fully charge the batteries in 12 to 16 hours The standard recharger requires a mains input of 200V to 240V at 50 60Hz A recharger requiring 100V to 120V at 50 60Hz is also available but should be specified when ordering The recharger is connected to the 1021 by a miniature 2 pin plug and socket shaped to ensure correct polarity 5 3 Circuit Module and Range Switch The active circuitry and range switch of the 1021 are located on a printed circuit board which is mounted on the rear of the front panel Connection to this board is by a 9 pin connector The active circuitry is encapsulated and contains the precision reference circuit and output stage A single F250mA 20x5mm fuse that is moun
11. he unique circuit design ensures that it stays well within specification for at least 12 months Variation with temperature is better than 60 ppm per C and typically better than 20 ppm per hour at constant temperature To improve the switch reliability additional back up contacts have been used even if a contact fails the 1021 will still operate correctly The accuracy and stability are such that a wide range of applications are possible In the process industries it may be used to test and calibrate current sensitive transducers and their associated indicating and recording instruments The semiconductor industry requires constant current sources for parameter measurements It may also be used to measure DC current accurately by using the null facility to back off the unknown current Resolution of 1pA is possible The 1021 is housed in a robust metal case and a removable protective boot is supplied as standard The front panel safety terminals are compatible with 4mm shrouded plugs as well as standard plugs bare wires and spade terminals Rechargeable batteries give portable operation and a mains recharger is supplied with the unit Complete recharge time is 10 12 hours although sufficient charge for a few hours operation can be obtained with only 1 2 hours charge Overnight recharge is sufficient to fully charge the batteries which give up to 10 hours of typical operation The mains recharger is supplied as standard with the 1021 and
12. instrument by applying a voltage to the output terminals In most cases this will cause the output fuse to blow but could still damage the output circuitry 3 6 Battery Recharging Under normal conditions the 1021 should be switched off during battery recharge Full recharge takes 10 16 hours The battery charging rate is such that the battery cannot be damaged by overcharging It is not recommended that the 1021 be operated during battery recharge although output currents of a few milliamps at low compliance voltage can be obtained without discharging the batteries It should be noted however that additional electrical noise will appear on the output due to the indirect mains power connection 1021 Technical Manual 7 8 4 Electrical Noise Pick Up In addition to the inherent electrical noise from internal circuitry of the instrument the output can contain fluctuations with originate from outside sources The effects of noise on current sources in or parts per million P P M in general this fraction becomes larger as the signal level is reduced The 1021 current source has a very high output resistance greater than 100M ohms As will all high impedance circuits it is prone to pick up of electrical signals via capacitance coupling Voltage sources do not suffer from this problem since they have in general very low output resistances less than 1 ohm The output terminals of the 1021 can be compared with the input of a high
13. itches Four press button switches with interlocking on the three range switches to ensure that only one range can be selected at one time 10 Battery Level Indicator Located on the top end of the 1021 this continuously monitors the battery voltage A minimum mark indicates when the batteries require recharging 11 Recharge Socket This is also located on the top end of the instrument The mains recharger is a separate unit the output of which is supplied via a flying lead fitted with a non reversible plug Recharge time is between 12 and 16 hours 12 V OP The instrument is overload protected and a front panel indicator shows when insufficient drive voltage is available see 5 above Drive output voltage is adjustable between 14 volts and 40 volts with a maximum output power of 2 4 watts CAUTION UNDER NO CIRCUMSTANCES MUST AN ADDITIONAL VOLTAGE BE CONNECTED IN SERIES WITH THE OUTPUT OF THE 1021 IN AN ATTEMPT TO INCREASE THE VOLTAGE CAPABILITY AS THIS WILL CAUSE DAMAGE TO THE OUTPUT CIRCUITRY 1021 Technical Manual 6 3 Operation 3 1 Preliminaries The 1021 is supplied complete with rechargeable batteries housed in the instrument and a mains charger Before operation the batteries should be checked on the battery level indicator It is important to recheck the battery condition when the instrument is supplying currents in excess of a few tens of mA since the additional load may reduce the battery voltage to below the mi
14. ment type and serial number must always be quoted together with details of any fault and the service required The purchaser of the instrument must prepay all shipping charges Time Electronics Ltd will pay return shipping charges This guarantee is void if servicing has been attempted by an unauthorised person or agent If during the guarantee period failure is due to misuse or abuse of the unit the repair will be put in hand without delay and charged unless other instructions are received Please note that if you require a new UKAS Certificate during the warranty period this will be charged at the current rate on our price list Service After Guarantee Period Even after the guarantee period has expired Time Electronics Ltd can still service your instrument As the manufacturer we have the specialised knowledge needed to keep your instrument in peak condition and we also maintain a comprehensive spare parts service Please enclose details of the service required and your full company details including a contact name when returning for servicing Returning Instruments When returning instruments please ensure that they have been adequately packed preferably in the original packing supplied Time Electronics Ltd will not accept responsibility for units returned damaged Please ensure that all units have details of the service required and all relevant paperwork Send the instrument shipping charges paid to Time Electronics Ltd
15. nimum level 3 2 Normal Operation Using the specification together with the front panel controls makes the operation self explanatory It is important to understand the voltage capability and the voltage limit indicator of the instrument to ensure that requirements are within limits 3 3 Measurement of Current Select NULL on the front panel function switch Select NORM output Adjust SENS fully anti clockwise minimum sensitivity Select RANGE consistent with the current to be measured Connect the unknown current such that it flows into the ve terminal Adjust the digit switch and sensitivity control for null balance on the LED indicator green centre LED 7 When balance at the required sensitivity is reached the value of the unknown current equals the digit switch setting oO0c1mA cnmc 3 4 Voltage Compliance Adjustment V O P The minimum voltage compliance of approximately 14v is obtained by turning the V O P control fully anti clockwise With full clockwise adjustment approximately 40v is obtained The voltage level is checked by measuring across the output terminals when the voltage limit LED is illuminated It is recommended that the voltage level is set to the minimum required for the work in hand 3 5 Overload Conditions The instrument can withstand either a short or open circuit on the output terminals indefinitely Overload conditions can result if an attempt is made to drive current into the
16. ted on the power supply board protects the output Four trimmers for calibration are mounted on the printed circuit board See Fig 1 page 12 1021 Technical Manual 9 10 6 Maintenance and Repair 6 1 Maintenance Dismantling the Instrument Remove rubber protection boot and then removal of four 2 0mm CSK screws enables the blue cover to be taken off which provides access to all parts of the instrument The range switch assembly can be removed by disconnecting the 9 pin connector and removing the two front panel locating screws Fuse Replacement The power supply and output fuses are mounted on the power supply printed circuit board and are easily accessible on removing the instrument cover Fuses are rated at F1A F1 and F250mA F2 and have dimensions 20mm length by 5mm diameter The fuses are available from Time Electronics Ltd or your local supplier 6 2 Repair NOTE No repair work should be undertaken by the customer while the instrument is under warranty as such work may render the warranty invalid Some of the precision components used in this instrument are not readily available and make repairs by the customer difficult if these components are damaged Overload conditions can cause a fuse failure which will be indicated by one of the following conditions a Instrument inoperative and battery level indicator at zero Possible cause F1 F1A supply fuse blown b Battery level indicator displaying but no o
17. utput at the output terminals Possible cause F2 F250mA output fuse blown Fuse Location we 4 QUE Qu cR PME A TEL i BATTERY PACK 5 aa EY P c J2 q 0 n E ee E ad BATTERY PACK hel F2 F250mA EE TRI FA VERG 1021 Technical Manual 10 T Recalibration The instrument is calibrated before it leaves the factory and should require no further adjustment for at least 12 months unless the circuit module or any of the calibration determining components have been damaged Before considering recalibration the customer should ensure that any apparent error in output current is not due to inadequate measuring equipment or noise pick up The latter can be misleading at low settings of output current The customer should also ensure that the correct equipment is available before attempting recalibration There are 2 ways the 1021 can be recalibrated a The output current can be converted to a voltage by connecting a precision resistor across the output terminals 3 values are required 100 1K and 10K ohms The resistors must be accurate to better than 0 0196 and have a good stability under load The 10 ohm will dissipate 0 1 watts at 100mA and therefore must have a temperature stability good enough to ensure that it remains within 0 01 The voltage across the load resistor can
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