Back Connected: A condition where pipe connections are on normally exposed surfaces of hydraulic equipment. (Gasket mounted units are back connected)

Back Pressure: Usually refers to pressure existing on the discharge side of a load. It adds to the pressure required to move the load.

Baffle: A device usually a plate, installed in a reservoir to separate the pump inlet from return lines.

Bar: An international standard unit of pressure equal to 100,000 Pascals approximately 14.5 psi.

Back EMF: The voltage produced across a winding of a motor due to the winding turns being cut by a magnetic field while the motor is operating. This voltage is directly proportional to rotor velocity and is opposite in polarity to the applied voltage. Sometimes referred to as counter EMF.

Bandwidth: A measure of system response. It is the frequency range that a control system can flow.

BCD: Binary Coded Decimal is an encoding technique used to describe the numbers 0 through 9 with four digital (on or off) signal lines. Popular in machine tool equipment, BCD interfaces are now giving way to interfaces requiring fewer wires, such as RS-232C.

Binary Number System: A number system used in digit equipment that has a base of 2. The digits 0 and 1 are the only digits used in forming numbers in this system.

Bit: Abbreviation of Binary Digit, the smallest unit of memory equal to 1 or 0.

Bleed-off: To divert a specific controllable portion of pump delivery directly to reservoir.

Block Diagram: A simplified schematic representing components and signal flow through a system.

Brake Valve: A valve used in the exhaust line of a hydraulic motor to (1) prevent overspeeding when an overrunning load is applied to the motor shaft and (2) prevent excessive pressure buildup when decelerating or stopping a load.

Breather: A device which permits air to move in and out of a container or components atmospheric pressure.

Bode Plot: A graph of system gain and phase versus input frequency which graphically illustrates the steady state characteristics of the system.

Break Frequency: Frequency(ies) at which the gain changes slope on a Bode plot (break frequencies correspond to the poles and zeroes of the system).

Brushless DC Servo: A general term referring to a motor drive that generates trapezoidal shaped motor currents in a motor wound as to generate trapezoidal Back EMF.

Byte: A group of 8 bits treated as a whole, with 256 possible combinations of one and zeroes, each combination representing a unique piece of information.