This circuit is design for a differential input voltage that is required for measurement. This circuit is built using CA3140 op amp IC. Using only one operational amplifier, you can build an adapter to give your input for floating-ground reference voltage. This circuit is a simplest form. Here’s the figure of the differential input adapter circuit.
Use 1% tolerance metal film resistor for R1 and R2. Adjust VR1 to give zero output voltage when the input is shorted probe. You can use the supply voltage + UB-UB and between 3 to 20V, this is a symmetrical supply.
