How do generate a negative supply for op amps ICs?
Use a DC-DC converter, a charge pump capacitive inverter or an inverting buck converter. Some type of switching supply is the easiest approach if you only have a positive rail available and actually require a negative rail.

There are easily available DC-DC converters that will accept a single DC voltage input and produce (say) +/-15V rails that are galvanically isolated from the input. 

It's easier for your meter because it has an inherently isolated supply in the form of the battery.