Abstract: An electric circuit includes three matched resistance thermometer sensors and is responsive to changes in rate of heat loss from at least one of them. The sensors are connected in a series-parallel arrangement to form one arm of a bridge circuit. An amplifier detects imbalance in the bridge and controls current flowing in the bridge to restore balance. Twice as much current flows in one sensor than in the other two, so that the one is maintained hotter. Environmental changes effecting a change in the rate of heat loss from the one sensor are detected as a change in current flowing in the bridge.

Abstract: Apparatus for determination of the freezing point of a liquid or solution has a probe extending into the liquid with means for vibrating the probe. Fixed elements which are cooled, e.g. Peltier plates, are arranged adjacent probe so that a mantle of solid forms on these elements and grows to touch the probe, thereby changing the resonant frequency. This change in resonant frequency is sensed and used to control the cooling so that the probe remains just in contact with a surface where solid is forming, i.e. in liquid at the freezing point. The probe temperature is sensed electrically, e.g. with a resistance thermometer.

Abstract: An analogue computer has two or more multiplication modules. Each module provides an output signal representing the product of the magnitude of an analogue input signal to the module and the factor represented by a common multiplier signal controlling the module. Output signals of two or more modules are combined to provide a composite signal. A comparator compares the composite signal with a reference level and adjusts the common multiplier signal so as to maintain the composite signal substantially equal to the reference level. Modules are connected in chains with the output of one module connected to the input of the next module in the chain. Output signals from the various modules represent terms in the polynominal expressions of equations which the computer can solve. Potentiometers allow these output signals to be scaled in accordance with the constant coefficients of the terms.