Time Electronics 1007 DC Millivolt Potentiometer & Source - Manual (Page 9)

9
1006/1007 Technical Manual 9
1007 Millivolt Source and Potentiometer
The 1007 incorporates a 1006 with the addition of a microvolt null detector. With the front
panel function switch in the ‘SOURCE’ position, the unit operates as a 1006 and the ZERO
and CALIBRATION setting procedures are identical to those for the 1006.
The potentiometer position of the function switch connects a high performance null balance
system in series with the output. The null zero and sensitivity are adjustable by front panel
controls. Maximum sens. = ± 25uV. Min. sens. = ± 250mV and zero adjust range is
approximately ± 100uV.
The null amplifier circuitry is located on a small p.c.b. which is fixed to the underside of the
output terminals. The circuitry incorporates two preset trimmers for adjustment of the null
amplifier input voltage and current offsets.
Important Note: It is important to check that the 1007 is operating correctly as a
millivolt source and that the source zero setting is within specification before
considering readjustment of the null amplifier trimmers.
Null Amplifier trimmer adjustment procedure
Voltage Offset (10K trimmer):
1) Select ’ZERO’ position on the function switch.
2) Set all digits to zero. Select 9.999mV range.
3) Adjust trimmer for equal swing (about zero) of the front panel zero control.
Current Offset (500K trimmer):
1) Select ’ZERO’ function, all digits zero, 9.999mV range.
2) Select potentiometer operation.
3) Connect a 47K ohm Resistor across output terminals.
4) Adjust trimmer for zero reading on the null display - the null sensitivity can be increased
gradually to maximum during adjustment.
Note: A low offset current is important when measurements are to be made in high
resistance circuits, but will not affect accuracy of measurements in low resistance circuits.