³⁷For those readers with an electronics background, the concept of “characteristic curves” for a control valve is exactly the same as that of characteristic curves for transistors. Instead of plotting the amount of current a bipolar transistor will pass through its collector terminal (I_C) given varying amounts of collector-emitter voltage drop (V _CE), we are plotting the rate of water flow through the valve (Q) given varying amounts of supply pressure (ΔP).