DC voltage offset to measure -ve voltages

[AliEmad2002]

After trying couple of op-amp circuits, the best solution - in my opinion - is to use an Inverting differential amplifier, for three reasons:

• Output is in the range [0:3.3V] at first stage, no need for inverting an inverted output.
• GND noise is subtracted from the input signal. (Thus, not amplified with signal in case of large Av).
• Input is not directly controlling op-amp input voltages, which prevents IC damage when inputting voltage higher than the maximum.

Vout = -R2 / R1 * (Vin - 5) (Image was edited. Reference: https://www.electronics-tutorials.ws/opamp/opamp_5.html)

[AliEmad2002]

Using R1 = 100k, R2 = 33k gives a gain of 0.33, which allows a max vpp = 10V, with an input resistance of ~ 100kOhm