Encoder

A method of setting up a sealed encoder module for measuring relative displacement of first and second relatively moveable parts of a machine, the sealed encoder module comprising:

• a scale;
• a readhead comprising a scale signal receiver;
• and an integral protective housing which encapsulates at least the scale and the scale signal receiver, wherein the sealed encoder module is configured to determine and output diagnostic information regarding a scale signal detected by the readhead, and wherein the sealed encoder module is configured to measure relative position of the scale and the scale signal received in a first degree of freedom, the method comprising:
• using the diagnostic information to determine whether the scale and the scale signal receiver are in a desired relative positional relationship in at least one degree of freedom other than the first degree of freedom.

A sealed encoder module for mounting onto a machine so as to measure relative displacement of first and second relatively moveable parts of the machine, the sealed encoder module comprising:

• a scale;
• a readhead comprising a scale signal receiver and a mounting block for mounting the readhead to one of the first and second moveable parts of the machine;
• and
• an integral protective housing which encapsulates at least the scale and the scale signal receiver, wherein:
• the mounting block is external to the integral protective housing;
• the sealed encoder module is configured to measure a relative position of the scale and the scale signal receiver in a first degree of freedom;
• and
• the sealed encoder module comprises at least one visual output device provided on the mounting block or on the integral protective housing and configured such that the at least one visual output device outputs diagnostic information as an optical signal.