GB692064A - Improvements in or relating to temperature measuring apparatus - Google Patents

Abstract

692,064. Electric indicating systems. SANGAMO WESTON, Ltd. March 30, 1951 [June 22, 1950]. No. 7460/51. Class 40 (i). To determine the average temperature of liquid in a tank, a resistor network consisting of a plurality of vertically arranged temperature sensitive resistors is disposed in the tank so that the network extends from the top to the bottom of the tank, and a portion of the network extending from the tank bottom to the liquid surface is connected by a selector switch in the measuring circuit. In one embodiment a plurality of temperature sensitive resistors, 51-60, Fig. 7, of different lengths are disposed vertically within the tank with their lower ends adjacent the tank bottom and that resistor whose upper end is nearest to the liquid surface is connected in the measuring circuit by a selector 63. The resistors are preferably of equal resistance under the same conditions and made from similar bare or insulated coils by differential axial stretching Figs. 1, 2 (not shown). Each coil is sealed in a flexible tube 11 e.g. of vinylite plastic, of the appropriate axial length, Fig. 3, a number of such sealed coils of different lengths being secured together as by cords 17 within a rigid tube, or, as shown, a flexible metallic hose 15, Fig. 4, with their lower ends 14 connected as at 16. The upper and lower ends of the hose 15 are liquid tight connected to rigid elements 22-25, and 19-21, the flanges 26 serving for suspending the composite resistor from the tank cover Figs. 5, 6 (not shown). The selected resistor is connected in a known bridge measuring circuit which may be housed in a casing on the side of the tank. Alternatively, the resistors 90, 99, Fig. 9, are mounted one above the other and series connected, the appropriate 'number of resistors being connected in the bridge circuit according to the liquid level by the switch 63. The meter may be of the ratio-meter type, Fig. 8, with both coils 85, 86 connected in series across the bridge output, a resistor 89, compensating for ambient temperature changes, being connected from the bridge corner shown to the junction point of the two coils of the meter.