Ratio of the change of the output variable to the input signal, i.e. the gradient of the characteristic curve. In the case of non-linear characteristic curves, the area for which the transfer factor applies should be stated. A differentiation is made between:
- Average transfer factor Gradient of the average characteristic curve,
- flow rate/signal transfer factor (flow rate gradient): Only for continuously adjustable direction and flow valves: Gradient of the flow rate/signal characteristic curve (DIN 24 311) (Figure U 7).
- Pressure (signal) transfer factor (pressure gradient): Gradient of the pressure/signal characteristic curve, taking the respective inlet pressure and input signal as a basis.

Figure U 7: Transfer factor