As with the square-root receiver gauge, the meter movement’s response to the transmitter signal is linear. Note the linear scale (drawn in black text labeled “LINEAR”) on the bottom and the corresponding square-root scale (in green text labeled “FLOW”) on the top. This makes it possible for a human operator to read the scale in terms of (characterized) flow units. Instead of using complicated mechanisms or circuitry to characterize the transmitter’s signal, a non-linear scale “performs the math” necessary to interpret flow