Arad Octave ultrasonic water meters of versions 4.02 and up have Modbus output capabilites, enabled by the Octave Modbus Module.
According to the memory map, all read operations are executed on input registers (modbus code 04).
32-bit values (signed or unsigned) are stored in 2 16-bit registers, with a AB CD byte order, whereas 64-bit values (double precision) are stored in 4 registers, with a HG FE DC BA order.