Time Electronics 1021 Current Source With Null Measuring Facility Technical Manual 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.
C ontents 1. Introduc tion ........................................................................................................ 3 1.1. General Description............................................................................................ 3 1.2. Specifications ..................................................................................................... 4 2. C ontrols ..............................................................................................................
1. Introduc tion 1.1. General Description • 100mA output with overload protection • 0.02% Accuracy • Wide range of applications • Safety terminals • Removable protective boot • 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.
1.2. Specifications Output: 0-100mA in 3 ranges: (1) (2) (3) 0-99.99mA in 10uA steps 0-9.999mA in 1uA steps 0-999.9uA in 0.1uA steps Accuracy: +/- 0.02% of setting +/- 0.02% of range +/- 0.02uA Drive Voltage: Adjustable between 14 and 40 volts. Maximum output power 2.4 watts. Out of Limit Warning: A front panel indicator provides indication of insufficient drive voltage. Output Polarity: Normal or Reverse, switch selected. A centre OFF position provides an open circuit.
2.
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.
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 minimum level. 3.2.
4. E lec tric al Nois e P ic k-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).
5. C irc uit Des c ription 5.1. Power Supply The power supply circuit board is mounted on a removable 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.
6. Maintenanc e and R epair 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.
7. R ec alibration 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.
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 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.
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.
8. G uarantee & S ervic ing 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.
