Displacement detection device

An arithmetic processing method of a displacement detection device, wherein the displacement detection device includes:

• a scale on which magnetic response units and non-magnetic response units are alternately arranged at a predetermined detection pitch in a displacement detection direction;
• a sensor head having at least four magnetic detection elements that output signals expressed by a sine function, a cosine function, a minus sine function, and a minus cosine function, respectively;
• and a processing device that receives input of an output signal of the at least four magnetic detection elements and calculates and outputs displacement information that is at least one of a relative displacement of the scale with respect to the sensor head and a change rate of the relative displacement,
• the processing device including:
• an Analog circuit having a first AD conversion unit and a second AD conversion unit, and converts a first differential signal based on a difference between the cosine function and the minus cosine function and a second differential signal based on a difference between the sine function and the minus sine function into digital signals;
• and a switching circuit that periodically switches between a first connection mode in which the first differential signal is AD-converted by the first AD conversion unit and the second differential signal is AD-converted by the second AD conversion unit, and a second connection mode in which the first differential signal is AD-converted by the second AD conversion unit and the second differential signal is AD-converted by the first AD conversion unit, and the processing device outputting the displacement information of the scale based on an addition average value of the first differential signals output from the first AD conversion unit and the second AD conversion unit and an addition average value of the second differential signals output from the first AD conversion unit and the second AD conversion unit.