Patent ID: 8542349

Claim:
An arrangement for controlling a measurement head ( 101 , 201 ) of an optical measurement instrument, the optical measurement instrument comprising first mechanical support elements ( 102 - 105 ) arranged to support a sample well plate ( 106 , 206 ) to be received, and second mechanical support elements ( 107 - 110 ) arranged to support the measurement head and to allow a distance (D) from the measurement head to the sample well plate to be changed, the arrangement comprising: a controller ( 111 , 211 ) arranged to make, in a situation in which the sample well plate is placed on the first mechanical support elements, the second mechanical support elements to move the measurement head towards the sample well plate and, as a response to a situation in which the measurement head touches the sample well plate, to move the measurement head backwards away from the sample well plate with a pre-determined length of movement so as to provide a pre-determined distance between the measurement head and the sample well plate, and a sensor device ( 112 , 113 , 217 ) arranged to detect, in the situation in which the sample well plate is placed on the first mechanical support elements, the situation in which the measurement head touches the sample well plate, wherein the sensor device is attached to the first mechanical support elements and arranged to detect, in the situation in which the sample well plate is placed on the first mechanical support elements, a mechanical effect occurring in the first mechanical support elements due to force directed by the measurement head to the sample well plate.