Proportional Valve Deadband
The center region in which no flow is delivered even though the command signal has started to rise. In spool type valves it arises from spool overlap and typically covers between ten and thirty percent of full lever travel; the operator feels it as motion starting late after pushing the lever.
At the center position the spool covers the port openings somewhat so there is no leakage. This overlap prevents the load from drifting in neutral but it has a cost: no port opens until the spool has traveled the overlap distance. That portion of the signal is wasted.
- In positive overlap valves the deadband is wide and leakage is low; most mobile equipment is of this type.
- In zero overlap servo type valves the deadband is virtually absent, but there is a small continuous leakage in neutral.
- Deadband is measured in both directions; forward and reverse may not be equal, so compensation is generally set separately per direction.
When working with a wireless proportional remote control, deadband appears as the machine staying silent when you push the lever halfway. Do not mistake this for a fault in the remote control: motion starting late is usually the normal characteristic of the vehicle's own valve and is corrected with the compensation setting.
Where this term is used: The Importance of Hydraulic Control: Why Should It Be Commanded by an Electronic Signal?