Multiplexed transducer

A circuit for producing output signals which are indicative of a plurality of different parameters as sensed by a plurality of parameter sensing devices, said circuit comprising:

• (a) signal generating means for producing two signals each comprising a regular pulse sequence the pulse width of which is modulated in a sinusoidal manner,
• (b) control means arranged to provide a quadrature phase relationship between the modulations of said signals during a plurality of successive equal first periods, said control means being such that the said modulations are in phase during a plurality of second periods each equal to and subsequent to a respective one of said first periods,
• (c) output means for applying the signals developed by said control means to a plurality of parameter sensing devices that each combine said signals in relative proportions dependent upon the value of a respective one of the parameters so as to derive a sum signal having a phase indicative of the value of the parameter during said first periods,
• (d) sum signal selecting means arranged to select sequentially one of the sum signals developed by said plurality of parameter sensing devices,
• (e) a clock pulse generator, and
• (f) counting means responsive to said control means and to the sum signal selected by said selecting means, the counting means being arranged to count upwardly clock pulses from said generator during pulses in said selected sum signal developed during one of said first periods and being arranged to count downwardly clock pulses during pulses in said selected sum signal developed during one of said second periods whereby to develop sequentially a plurality of residual counts in said counter, each residual count being indicative of the value of one of said parameters.

In a transducer for producing an electrical signal which is a function of the value of a parameter and that includes

• signal generating means for generating first and second signals having the same frequency characteristic, control means arranged to provide first and second phase relationships between said first and second signals during first and second periods respectively, a parameter sensing device for combining said first and second signals in relative proportions dependent upon the value of said parameter so as to derive a sum signal of said first and second signals, and means responsive to the sum signal and arranged to produce a phase measurement signal which is indicative of the difference in phase of the sum signal developed during said first and second periods, whereby to derive an output signal indicative of said parameter, the improvement comprising that the parameter sensing device comprises
• (a) first and second coils to receive the first and second signals from said control means;
• (b) third and fourth coils connected together to form said sum signal;
• (c) a fixed screen having apertures therein to define magnetic flux paths between said first and third coils, and said second and fourth coils respectively, and,
• (d) a movable screen for being displaced in accordance with said parameter, the screen having apertures therein arranged such that the movable screen obturates said flux paths selectively in dependence upon the relative positions of the screens.

In a transducer for producing an electrical signal which is a function of the value of a parameter and that includes

• signal generating means for generating first and second signals having the same frequency characteristic, control means arranged to provide first and second phase relationships between said first and second signals during first and second periods respectively, a parameter sensing device for combining said first and second signals in relative proportions dependent upon the value of said parameter so as to derive a sum signal of said first and second signals, and means responsive to the sum signal and arranged to produce a phase measurement signal which is indicative of the difference in phase of the sum signal developed during said first and second periods, whereby to derive an output signal indicative of said parameter, the improvement comprising that the parameter sensing device comprises:
• (a) a sum signal output,
• (b) first and second impedance elements connected to said sum signal output, said elements being connected to receive respectively said first and second signals from the control means, and
• (c) means for varying the impedance presented by at least one of said elements in accordance with the value of one of said parameters, whereby to control the relative proportions of said signals combined at said sum signal output.