Upon a change in the temperature of thermal bulb 1, filled with a liquid and immersed in the medium whose temperature is to be measured, the pressure changes in capillary tube 2, which connects the bulb to tubular spring 3, and in the spring itself. This spring, winding up or unwinding, turns hand 6 through tie-rod 4 about fixed axis A. To compensate for the effect of the ambient temperature on the reading, provision is made for a special device consisting of compensating capillary tube 7, of the same lengt as the main tube, and auxiliary spiral tubular spring 8, having the same properties as main spring 3. Spring 8 actuates hand 6 through tie-rod 5 in the direction opposite to the action of spring 3. This eliminates the influence of the ambient temperature on the reading of the instrument.
$4065$EHP,M$