effective length that is required of it the end segment of each arm is provided at its free end with a fast closure clip for attaching the vertical tube that supports the corresponding sensor with another similar clip provided in the centre web for the sensor occupying said position however it is obvious that clips can also be provided at the free end of each segment of the telescoping arms when a greater number of sensors is used it turn each sensor will have an element for attachment to the corresponding tube and the height of the sensor can be adjusted as a function of the position of the vertical tube with respect to the upper clip to which it is attached in this manner a support structure is obtained in which the various sensors can adopt any relative position deemed suitable which position can be changed in an extremely quick and simple operation with full operational reliability and with full stability of said sensors as a complement of the description being made and in order to aid a better understanding of the characteristics of the invention according to an example of a preferred embodiment a set of drawings is provided as an integral part of the.