초록 ▼

Methods and apparatus by which a transducer is employed to create a digital signal representing numerically the value of a changeable physical parameter. The signal from the transducer is subject to large and unpredictable amounts of offset due to either or both (i) manufacturing tolerance departure

Methods and apparatus by which a transducer is employed to create a digital signal representing numerically the value of a changeable physical parameter. The signal from the transducer is subject to large and unpredictable amounts of offset due to either or both (i) manufacturing tolerance departures from the desired target of creating a zero output signal value when the sensed parameter is zero and (ii) changes in offset due to changes in one or more physical conditions (other than the sensed parameter) to which the transducer and its associated electrical components are subjected. A bistate device is associated with the transducer and controlled so as (a) to first apply substitutionally to the transducer a known, and preferably zero, value of the parameter－with the output signal value being stored so as to represent the then-existing offset, and then (b) to apply the changeable physical parameter to the transducer. The stored value of the transducer output signal is, in effect, subtracted from the output signal obtained in the second instance, to produce an accurate final signal numerically representing the existing actual value of the sensed parameter. A programmed microcomputer is preferably employed to carry out the necessary steps in the sequence, and apparatus of that character is described.

대표청구항 ▼

In apparatus for producing a digital signal to represent the sensed value of a changeable differential pressure DP, the combination comprising (a) a peizoresistive bridge formed on a silicon diaphragm, (b) a body defining two chambers with said diaphragm as a deformable wall therebetween, said chamb

In apparatus for producing a digital signal to represent the sensed value of a changeable differential pressure DP, the combination comprising (a) a peizoresistive bridge formed on a silicon diaphragm, (b) a body defining two chambers with said diaphragm as a deformable wall therebetween, said chambers having inputs to receive two respective pressures P1 and P2 so that the diaphragm is strained as a function of the differential pressure DP, where DP=P1-P2, (c) a summing amplifier having an output E, (d) circuit means for exciting said bridge and applying the output signal V from said bridge to the input of said summing amplifier, whereby said output E would normally and except for offset in said signal V and saturation in said amplifier change according to a known function of changes in the differential pressure DP in said chambers, (e) a solenoid valve connected between said two chambers and settable, by on-off control of the associated solenoid, to first and second states in which (1) said two chambers are isolated from one another and (2) said two chambers are in direct communication, (f) means for coupling into said two chambers respective changeable pressures P1 and P2 which create said changeable differential pressure DP, (g) a programmed digital computer effectively coupled to said amplifier and to said solenoid, (h) a settable correction signal source coupled to and controlled by said computer, together with means for applying a correction signal Vc from such source to said summing amplifier so that the effective input to said amplifier becomes (V-Vc) and its output E is proportional to (V-Vc) except for saturation, (i) said digital computer and the program loaded therein collectively constituting (i1) means for first applying a control signal to said solenoid to place said valve in its second state thereby to substitutionally set the differential pressure seen by said diaphragm to a known value of zero, (i2) means operable while said valve is in its second state for setting said correction signal source so as to adjust the signal Vc to a value Vpo which makes the amplifier output E equal to substantially zero, (i3) means for next applying a control signal to said solenoid to place said valve in its first state, and (i4) means, operable while said said valve is in its first state, for creating in said computer a first digital signal N having a value Nx which is proportional to the then-existing amplifier output E and thus proportional to the difference Vx-Vpo, where Vx is the then-existing value of said bridge output and Vpo is the adjusted value of said correction signal, and (i5) means for computing and producing, from the digital signal value Nx, a second digital signal representing the then-existing value DPx of said differential pressure DP.