GB762824A - Automatic temperature compensating apparatus and method therefor - Google Patents

Abstract

762,824. Electric viscosimeters. BENDIX AVIATION CORPORATION. Oct. 18, 1954 [Nov. 9, 1953], No. 29923/54. Class 40 (1). [Also in Group XXXIX] An apparatus for temperature compensating the electrical output of a viscosimeter comprises means fed with the output and including a temperature-sensitive device exposed to the fluid the viscosity of which is being measured and arranged to give a second electrical output which is proportional to the product of the first output and the deviation of the output of the device at the fluid temperature from its output at a reference temperature, together with means for combining the first and second outputs to give an output representing the viscosity at the reference temperature. The output of a viscosity probe of known type disposed in the fluid flow is fed to a computer which gives an output voltage proportional to ##. This is applied to an amplifier 23 part of the output of which is applied through constant impedance attenuator 24 to diagonal 26-27 of resistance bridge 25, the other diagonal 28, 29 of which is connected in series with the viscosity computer output voltage across an output meter. The bridge comprises resistance thermometer 15, variable resistor 32 and equal fixed resistors 33, 34. In operation the fluid is brought to the reference temperature and the bridge balanced by adjustment of 32 until the readings of meter 32 and the output meter correspond. It is shown in the description that voltage applied to the latter is represented by the equation e<SP>2</SP> where k=-, e being the output of the viscosity # computer. T and To are the actual and reference temperatures respectively and m is a design factor which can be varied by adjustment of attenuator 24. The equation representing to a first order of approximation viscosity variations with temperature is of the form where n is a constant characteristic of the fluid so that if the fluid temperature is altered and the attenuator then adjusted to give an output meter reading corresponding to the reading of meter 22 at the reference temperature the voltage e 0 will be independent of temperature over a range in which the approximations made in deducing the formulae are valid. A bridge with balanced resistance thermometers in opposite arms and coupled variable resistors in the other arms may be used to improve the sensitivity. Amplifier 23 may be a magnetic amplifier (Fig. 3, not shown), (see Group XXXIX). Specification 736,204 is referred to.