GB1082707A - Improvements in or relating to ice detection apparatus - Google Patents

Abstract

1,082,707. Detecting ice formation electrically; detecting icing conditions. ROSEMOUNT ENGINEERING CO. July 27, 1966, No.33817/66. Headings G1N and G1X. The approach of icing conditions is detected by exposing a thermally conductive element 5, Fig. 6, to the atmosphere, generating by means of a Peltier effect heat pump a temperature gradient along the element, one end 27 thereof being maintained below the ambient temperature of the atmosphere, and detecting non-linearity of the temperature gradient due to ice formation on the sub-zero portion of the element. Thermocouples TC1, TC2 measure the temperature gradient in the colder half of the element, and thermocouples TC3, TC4, the gradient in the warmer half, any difference being measured by a differential amplifier 23 and indicated on a scale 24 calibrated in percentage ice coverage of the element. The difference signal may be used to control de-icing apparatus on an aircraft. In a non-electrical temperature measuring arrangement Fig. 16 (not shown), bores (67) in one edge of the cold half of the element communicate with a first input of a differential pressure sensitive device (71), and further bores (68) in the warmer half of the element communicate with the second input of the device (71). Icing of the colder half is detected by a measured difference in the two pressure signals. The element 5 may be arranged on the leading edge of a body 1, Figs. 1 to 5 (not shown), from which it is thermally insulated by a layer (26) one heat pump (10) being arranged to heat the lower end (28) of the element, and a second heat pump (9) being arranged to cool the upper end (27). The heat pumps (9, 10) are generally similar and are connected to the ends (27, 28) of the element 5 by heat shunts (11, 12), and to an outer casing (2, 3) exposed to the atmosphere, by heat shunts (22, 21). The element, alternatively may be U-shaped Figs. 8, 9, and Figs. 13, 14 (not shown), a single heat pump (31) being arranged to contact the ends of the U, and the thermocouples TC1-4, Figs. 8, 9 (not shown) being situated in axial bores (42) in the element. In a further embodiment Figs. 20-23 (not shown) a linear element (82) is used, and has a single heat pump (88) at one end (85), the thermal connection to the opposite end being made via an elongated heat shunt (81). The temperature gradient is measured by thermistors (91, 92) arranged in a bridge circuit R1, R2, Figs. 24, 25 (not shown) which operates a measuring device (101) or a control circuit (107), Fig. 26 (not shown).