This module is designed to measure currents with a noisefloor down to 5fA/sqrtHz(@1G V/A). It is also optimised to send very little energy to the sample. For that reason it's input resistance is not "as low as possible" but fixed at a function of the [V/A] setting (see calculation below).
On the remote control panel the following functions are available:
There is a postgain switch [x1 x100] giving a max total output of 100G V/A (using 1G V/A and x100).
The postgain can also be used to obtain a lower Rin/ higher speed at high V/A settings. Example: 1G V/A could be exchanged for 10M V/A with postgain [x100dc] (you pay with higher noise).
In the [gnd] mode pin2 is connected to (warm)ground inside the module.
Rin calculation
Rinput is set at: 2kohm + 1E-3 * [V/A] for [low-Noise]
and: 2 kohm+1E-4 * [V/A] for [low-Rin]. Example: at 100M V/A the input resistance is 102kohm @[low-Noise] or 12kohm @[low-Rin]. These values are accurate within 1% so a possible voltage drop can be subtracted in the data.