Time Electronics 1010 DC Voltage Calibrator - Manual (Page 9)

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1010 Technical Manual 9
4. Recalibration
This is performed with the panel and p.c.b. outside the case. Please see Fig. 1 for trimmer
layouts.
4.1. Zero
The F.E.T. chopper amplifier zero must be set before calibration can be done. The zero is
set when the instrument is manufactured and under normal operation will not require
readjustment. If a new circuit module is fitted or readjustment is found necessary, the
following procedure should be adopted.
1) Connect power supply.
2) Select 99.999mV range.
3) Set all digits to zero.
4) Set output polarity to normal.
5) Connect a null meter to output terminals. The meter sensitivity should be +/- 100uV f.s.d.
with a resolution of better than 10uV. It is possible to use the Time Electronics 1007 for
this purpose, although any micro-volt null meter or sensitive D.V.M. may be used.
6) Adjust the zero trimming pot on the module for less than +/- 10uV reading on the meter.
The zero trimmer is marked on the module label.
7) Check the zero reading for the other 4 ranges. The readings should be as follows:
999.99uV range less than +/- 0.25uV
9.9999mV ranges less than +/- 0.75uV
999.99mV ranges less than +/- 40uV
9.9999V ranges less than +/- 100uV
4.2. Full Scale
Fine adjustment of the 1010 output voltage is provided by 4 trimmers. One is located on the
module is marked ‘CAL’ and provides equal adjustment of the output voltage for ranges.
The other 3 trimmers are locates on the front panel p.c.b. and provide individual adjustment
for the 10V, 100mV and 10mV ranges. Since a common attenuator is used for the 10mV
and 1mV ranges, the 1mV range is automatically calibrated when the 10mV range is
calibrated. All the trimmers are set up when the instrument is manufactured and normally
will not need readjustment. If a new circuit module is fitted or readjustment found to be
necessary the procedure below should be adopted.
It is important to note that the maximum range of adjustment provides about +/- 0.2%
variation in the output voltage. If errors of greater than this magnitude are occurring there is
no point in attempting to recalibrate using the trimmers and a fault condition will be occurring
somewhere in the unit.