Time Electronics 1007 DC Millivolt Potentiometer & Source - Manual (Page 7)

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1006/1007 Technical Manual 7
3.4. Internal Preset Controls
IMPORTANT NOTE:
These controls are set in the factory before shipment and normally will not require
readjustment.
If readjustment is considered necessary, it is important to check that the amount of
adjustment required is within the range of the trimmer concerned. If it is greater than the
trimmer range, there is no point in attempting to readjust and a fault condition will exist in the
unit. The range of adjustment of the trimmers is given below.
Access to the 1006 or 1007 is by removing the blue cover which is located by 8 screws.
1006 Millivolt Source
The 1006 contains 3 (4 on instruments with serial number greater than 1320) internal preset
trimmers. They are located on the module p.c.b. which also contains the range switches.
Zero
The ‘ZERO’ trimmer adjusts the circuit zero and is set to bring the output voltage (with all
digits set to zero) within the specified limits.
Calibration
The 1V and 100mV ‘CAL’ trimmers adjust the full scale calibration (i.e. 9999) on the 1V and
100mV ranges respectively to within the specified limits. Instruments later than No. 1320
have an additional trimmer for the 10mV range.
It is important to set the ZERO before attempting CALIBRATION.
Test Equipment Required
1) A microvoltmeter with a resolution of better than 5 microvolts. The null amplifier section of
Time Electronics 1007 can be used although any suitable microvoltmeter or sensitive
D.V.M. may be used.
2) An accurate dc voltage source with a range 0-1V and accuracy better than 0.02%. A
Time Electronics 1010 is suitable. Alternatively a high performance D.V.M. can be used.
Zero Setting Procedure
1) Switch unit on and check battery condition is good.
2) Select 99.99 mV range and set all digits to zero.
3) Select ‘NORMAL’ output polarity.
4) Connect microvoltmeter to output and adjust ZERO trimmer for less than - 10uV reading.
The maximum amount of adjustment available on this trimmer is approximately ± 100uV.
5) Check the zero reading for other ranges. The readings should be as follows:
9.999mV range less than ± 2uV
99.99mV range less than ± 10uV
999.9mV range less than ± 100uV