p 3 as soon as the pressure difference between input 2 and output 3 exceeds a threshold any difference between p 1 and p 2 is limited to the difference between p 1 and p 3 the pressure difference p 1 p 2 between the inlet 2 and the flow channel 4 cannot exceed that value if the difference between p 1 and p 2 becomes too small the flow of fluid through the valve will depend on the pressure difference between inlet p 1 and outlet p 3 fig2 illustrates this regime as a line 25 with positive slope as soon as the pressure difference 22 reaches the onset 23 of constant flow the throughput of fluid through the valve will essentially be independent of outlet pressure p 3 by changing the position of the adjusting bolt 19 the pressure difference required to achieve constant flow will also change an adjustment of the onset 23 of constant flow and of maximum throughput offers distinct benefits where pressure independent control valves need be accurate within certain limits this is often the case in applications where a control valve renders a separate flow meter obsolete pressure independent control valves are then required to produce constant flow over a given range of pressure differences constant in this context means that the flow of fluid through the valve is determined by the position of the throttle 5 in yet another embodiment a pressure independent control valve provides a plurality of temperature sensors to determine temperature drop the temperature sensors can for instance be arranged at the inlet and or at the outlet of the valve this particular embodiment is particularly useful for metering by changing the position of an adjusting bolt 19 the onset of constant flow.