The functionality of an AC resistance bridge is obtained simply by interconnecting reference voltage output (Sine Out) and voltage sensing inputs of lock-in amplifier with the corresponding input and outputs of the AMS220, while the tested resistance is connected to the AMS220. The excitation current provided by the AMS220 is then proportional to the reference voltage provided by the lock-in amplifier and switch-programmable voltage-to-current conversion factor of the AMS220. Connection of the AMS220 in the configuration replacing the AC resistance bridge and the principal block diagram of the signal wires and signal wire shields connected to the AMS220 are schematically shown in Fig. 1 and Fig. 2, respectively.
Fig. 1  Block diagram of connection of the AMS220 with the lock-in amplifier which replaces  the AC-resistance bridge.
Fig. 2 The principal block diagram of the signal wires and signal wire shields. Indicated numbers represent pin numbers of the D-SUB 15 connector (resistance measurement input of the AMS220).
Build your own “open architecture” AC resistance bridge
Descriptions provided in this article are subject to change without notice. 

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