The linear measuring system includes one part of a (usually steel) rod, beam or strip that is profiled with a trapezium like (subset of a) De Bruijn sequence. Each element of the alphabet is represented by a discrete height of the profile. The profile can be coated with a material with low magnetic susceptibility to enable the application on a piston rod of a pressure medium cylinder. The second part of the measuring system reads the subsequences of the main sequence by using the signals of arrays of linear Hall effect sensors, placed in a magnetic field as input for a signal processing algorithm. With a look-up table, the position of this second part of the measuring system with respect to the profile is determined. An interpolation algorithm can be used to improve the resolution to well below the sequence pitch.

The present invention provides a flow apparatus (10) having a flow control valve (12) having a housing (14), an aperture (16), an aperture obturator (18) and an actuator (20) for moving said obturator (16) between a first closed position and multiple open positions (B-L), characterised by a valve position monitor (21) for monitoring the position of the valve (12) and comprising a plurality of discrete sensors (28a to 28e) associated with a plurality of open positions (B-L) of said valve for monitoring the presence or absence of one or more members (26) movable with said valve (12). The arrangement may be used to monitor the valve position and such monitoring may be of use in the prediction of the amount of fluid remaining within a cylinder (32) to which it has been attached.

The present invention provides a flow apparatus (10) having a flow control valve (12) having a housing (14), an aperture (16), an aperture obturator (18) and an actuator (20) for moving said obturator (16) between a first closed position and multiple open positions (B-L), characterised by a valve position monitor (21) for monitoring the position of the valve (12) and comprising a plurality of discrete sensors (28a to 28e) associated with a plurality of open positions (B-L) of said valve for monitoring the presence or absence of one or more members (26) movable with said valve (12). The arrangement may be used to monitor the valve position and such monitoring may be of use in the prediction of the amount of fluid remaining within a cylinder (32) to which it has been attached.

A high-resolution encoder device to measure and retrievably encode the relative position of a first part P with a second part S comprises sensible elements on part P, said sensible elements providing a variable property for sensing, such that said variable property varies over a length of said part P, a number n of sensors for sensing said variable property, said sensors being separate from each other and disposed on part S, said sensors configured to output signals in accordance with said sensing, and a processing unit connected to receive said signals from each of said n sensors and configured for succeeding ones of said relative positions to form a vector having entries from each sensor respectively, the vector defining said relative positions respectively.

An encoder and a method for determining a rotational position of a first component relative to a second component that can be rotated relative thereto is provided. The encoder includes a first reading head, which is arranged on the second component, and a drive unit with a drive element that is driven in rotation relative to the first component, to which at least a first magnetic disc is fastened and which is designed to be arranged on the first component. The first magnetic disc has, on an end face facing the first reading head, at least one circumferential first track with a plurality of magnetic regions formed one behind the other in the circumferential direction of the first magnetic disc and having alternating magnetisation directions. The first reading head detects at least a first periodic pulse sequence.