Time Electronics 1010 DC Voltage Calibrator - Manual (Page 11)

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1010 Technical Manual 11
4.3. Calibration Procedure
1) Ensure zero has been set as in 3.2.1.
2) Connect power supply.
3) Select 999.99mV range, normal output polarity, and output digits to 99999.
4) Connect a suitable accuracy voltage standard with microvolt null meter to the output
terminals. The voltage standard should have 0.005% accuracy or better and ranges from
10mV to 10V f.s. The null meter should have a resolution of better than 1uV and preferably
have calibrated ranges. A high performance D.V.M. can be used for calibrating.
Note: It is possible to calibrate against another 1010 but the inaccuracies in that unit (if
known) need to be taken into account.
6) Adjust the CAL trimmer on the module for better than 50uV null balance against an output
of 999.99mV from the standard. Note that the maximum range of adjustment of this
trimmer is 0.3%.
7) Select 9.9999V range and adjust the 10V range trimmer (VR4), for less than 500uV null
balance against an output of 9.9999V from the standard. Maximum range of adjustment
of this trimmer is 0.08%.
8) Select 99.999mV range and adjust the 100mV range trimmer (VR5) for less than 5uV null
balance against an output of 99.999mV from the standard.
9) The specification allowances for these 3 ranges are as follows:
9.9999V range, +/- 2.5mV.
999.99mV range, +/- 250 uV.
99.999mV range, +/- 55uV.
4.4. 10mV and 1mV Range Calibration
The two ranges are obtained by resistive attenuation of the 10V and 1V ranges. The
attenuation factor is 1000:1. The calibration of the attenuator is via the 10mV range trimmer
(VR3). Maximum range of adjustment is 0.16%.
The Attenuator is set up when the 1010 is manufactured and normally requires no further
adjustment. If, however, any of R2-R5 have been damaged by overload they will require
replacing with equivalent types.
After replacing the resistors recalibration may be necessary beyond the range of the 10mV
trimmer. The 1010 output should be checked against a 9.9999mV output from the standard
and adjusting resistors (either R6 or R7) selected to bring the calibration within range of
adjustment of the trimmer, which can then be adjusted for the final calibration as described
above.
The calibration should be done on the 9.9999mV range and due account taken of any
thermal emf’s generated in soldering the adjustment resistor in position.
Note: It is important to ensure that the zero and calibration have been set before
commencing 3.2.1.
The specification allowances for these ranges are as follows:-
9.9999mV range: +/- 5.75uV. 999.99uV range: +/- 0.75uV.