Hydraulic Proportional – Performance Terms

Hysteresis is max. position error which depends on direction history

Reversal Error is the smallest signal that moves spool in the opposite direction

Response Sensitivity is the smallest signal to move spool in the same direction, after stopping (resolution of valve)

Repeatability – Ability to achieve the same spool position (or pressure) given the same valve, under the same conditions, with the same command input
– Force controlled valves: 2% to 3%
– Stroke controlled: 0.1% to 0.5%
– Typically half the Hysteresis

Question… if you need to achieve 100 psi pressure repeatability on a system operating at 5000 psi, should you use a proportional relief valve with a repeatability of 3%?
– No… maximum repeatability is 0.03 x 5000 psi = 150 psi

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