This module is designed as a source for I-V measurements with range [V/A] setting the current range (1nA..10m A/V)
The output [symm/single] switch selects two output modes:
-single: pin 4 is the output node delivering the selected current/voltage, pin 2 is connected to ground (classic current source).
-symmetric: pin 4 is the output node delivering the selected current/voltage, pin 2 is a node at exactly the opposite voltage level of pin 4 driven from a source-resistance 1/R set by [RANGE].
The output voltage is then symmetrical to ground (if the sample is not grounded). Applications of symmetric operation are: preventing a common mode voltage across the sample, preventing a common mode voltage on the voltage amplifier, doubling the maximum voltage output swing of the current/voltage source. Selecting the symmetric mode gives 4..8V maximum output voltage.
The symmetric mode has a slightly higher noise level.
The unit has 2 control inputs: x1 and x0.01, these can be used to have a dc-sweep (x1 input using a dac) with a modulation (lock-in on x0.01 via the iso-amp input).
The routing should be set in the summing module S2.
Example:When S4m placed in slot A, inputs are AV1 and AV2.
Default ONLY the x1 input is enabled in the module. The x0.01 input can be enabled/disabled by a jumper inside.
The input signals are summed inside the module.
When the internal amp voltage exceeds 4 Volt (depends on loadresistance) an overload LED indicates [clip] an error. The sample resistance is then too high for the given current or the controlling voltage is too high.
The [V/A] rangeswitch sets the output current to give 100% at 1V control input on the Iso-amp or 1V output of the controlling DAC
output: Iout=Vin(Iso-amp1 or DACn) * [RANGE] + 0.01 * Vin(Iso-amp2 or DACm )*[RANGE]
lemo [OUT] pin 4/2/3 connection:
single: 4=out / 2=ground / 3=ground
symm: 4=out / 2=-out / 3=ground