I am planning to apply NI USB4431 and read the voltage signal from a Mounted Silicon Photodiode (SM1PD1A) with Cathode Grounded. The photodiode is connected with a bias voltage and a capacitor as shown in the following link, https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1285
1. Do I need an additional T-joint with a 50Ohm to connect the photodiode to the NI USB-4431?
2. I am interested to find a voltage difference of 2.25V wrt the shield of the NI USB-4431 input terminal. Is it normal to find a voltage drop at the input terminal of NI USB-4431?