This module contains the voltage source most used for sample excitation when performing a V-I measurement. To prevent ground-loops the output is galvanically isolated (>10Gohm,1pF). It has two inputs: x1 (sweep) and x0.01 (modulation). Default only the x1 input is enabled.
The x0.01 input can be enabled/disabled by jumpers inside.
The input signals are summed inside the module. The Range switch (V/V) on the source-control-panel sets the output divider to the selected level.
The function x1/x0.1 switch divides the inputs (both sweep and modulation) by 1 or 10.
The last option has two advantages:
-the switching is not done on the sample-connected part so it could be performed DURING a measurement to enlarge dynamic range.
-an extra decade can be selected beyond the lowest V/V Range setting without degrading noise/drift performance because the iso-amp-in noise/drift is dominating.
The Output mute switch short-circuits the output, this gives a possibility to do a zero-check. To lower the effect of possible contact-resistance of this switch degrading the exact zero level it is advisable to also switch x0.1 on. (the remaining output offset will then be < 1uV )
Source control panel:
gain: 1m/10m/100m V/V (knobpos 1/2/3, =G1/G2/G3 )
switch: x1/x0.1(F1)
switch: Output on/mute (F2)
About the output circuit:
The internal circuitry actually consists of an 100uA/V current source which is in parallel to a resistor to create a voltage source.
The resulting voltage source has an output resistance that is: 1kohm@range-100mV 100ohm@10mV 10ohm@1mV 1ohm@100uV.
For use of the x0.01 input setting in the IVVI-rack:
If enabled: x1-input as always defined by the used source-slot: Iso-Amp in1> slot1, Iso-Amp in2> slot2
(the x0.01 input is then controlled by the other iso-amp-input).
Enabling x0.01 means that only ONE source can be used in the rack.
Front-output: Vout= Vin(Iso-amp 1or2) * gain + 0.01 * Vin(Iso-amp 2or1)*gain
(Iso-Amp channel set by chosen meas-slot)
(0.01 function is default DISabled)