Time Electronics 1024 DC Current Calibrator - Manual (Page 11)

11
1024 Technical Manual 11
4. Recalibration
4.1. Repairs
Access to the circuitry is by removing the front panel which is located by 4 screws. Two
preset trimmers are provided. One provides adjustment of the zero and the other full scale.
If readjustment is necessary the output should be set up against suitable standards.
Due to the precision nature of many of the components used in the 1024, they are not
readily available to enable the customer to undertake repairs.
Repairs to the power unit (Section 2.4) and the front panel components can be undertaken
by the customer provided suitable tools are available. Spare parts can be obtained from
Time Electronics or their authorised dealer.
Important Note
It is important that no repair work is undertaken by the customer while the 1024 is
under warranty. Such work may invalidate the warranty.
Overload conditions can cause the fuses to blow and the following conditions will be
observed:-
(1) The instrument is inoperative, the battery level indicator does not operate when the
1024 is switched on. Possible causes are:
a) Main fuse blown (on PU2 power unit).
b) PU2 output fuse blown.
c) Front panel P.C.B. supply fuse blown.
(2) The battery level indicator displays but no output appears at the output terminals.
Possible cause is:
a) Front panel P.C.B. output fuse F1 blown.
4.2. Recalibration
The 1024 is calibrated when it leaves the factory and should not require further adjustment
for at least 12 months unless the circuit module or any of the calibration determining
components have been changed.
It is important before considering recalibration to ensure that an apparent error in output
current is not due to inadequate measuring equipment or noise pick-up. (See Section 2.3).
The latter is a common cause of trouble at low settings of output current particularly when
mains power is being used.
It is also important to ensure that the correct equipment is available before attempting
recalibration. There are two ways in which the 1024’s output can be checked accurately –
these are:
a) By a current balancing method using an external Standard D.C. Current Source of known
accuracy and a nanometer with ranges from +/- 1nA to +/- 100uA. It is then possible to
display the difference between the 1024 output and the standard current source.