Solid state digital strain indicators

Claim 2

Electrical indicating apparatus accommodating signal inputs from input transducers having different sensitivities, comprising a dual-slope integrator wherein input signals are periodically up-integrated for a predetermined time and then down-integrated until the integrator output is restored to a predetermined signal level, a sensitivity-adjustment variable resistance and a fixed resistance, means providing visual displays responsive to downintegration times of said integrator, first means for applying a first reference signal as input to said integrator through said fixed resistance during up-integration times thereof and a second signal to said integrator through said variable resistance as a reference during alternate down-integration times thereof, and second means for applying signals from a transducer as input to said integrator through said variable resistance during upintegration times thereof and one of said first and second signals to said integrator through said fixed resistance as a reference during alternate down-integration times therof, whereby adjustment of said variable resistance to cause said visual display means to display the known value of sensitivity of the transducer during operation of said first means results in display of measurements compensated to account for sensitivity of the transducer during operation of said second means.

Claim 3

Electrical indicating apparatus as set forth in claim 1 wherein said first and second means comprise means for electrically switching said integrator selectively either into a circuit relationship wherein said first reference signal is applied as input through said fixed resistance during said up-integration times and a second signal is applied as a reference through said variable resistance during said down-integration times, or wherein said transducer signals are applied as input through said variable resistance during said up-integration times and one of said first and second signals is applied as a reference through said fixed resistance during said down-integration times.

Claim 4

Electrical digital indicating apparatus accommodating signal inputs from strain-gage sensors having different gage factors, comprising a dual-slope integrator wherein input voltages are periodically up-integrated for a predetermined time and then down-integrated until the integrator output is restored to a predetermined voltage level, a variable gage-factor-adjustment resistance and a fixed resistance, digital indicator means providing visual digital displays responsive to down-integration times of said integrator, gage-factor-adjustment means for applying a first reference voltage as input to said integrator through said fixed resistance during up-integration times thereof and an opposite-polarity reference voltage to said integrator through said variable resistance as a reference during alternate down-integration times thereof, and measurement means for applying voltages responsive to signal inputs from a strain-gage sensor as input to said integrator through said variable resistance during up-integration times thereof and an opposite-polarity one of said reference voltages to said integrator through said fixed resistance as a reference during alternate down-integration times thereof, whereby adjustment of said variable resistance to cause said digital indicator means to display digitally the known numerical value of the gage factor of the strain-gage sensor during operation of said gage-factor-adjustment means results in digital display of measurements responsive to signal inputs from the strain-gAge sensor which are compensated for gage factor during operation of said measurement means.

Claim 5

Electrical digital indicating apparatus accommodating signal inputs from strain-gage sensors having different gage factors, comprising a dual-slope integrator wherein input voltages are periodically up-integrated for a predetermined time and then down-integrated until the integrator output is restored to a predetermined voltage level, a variable gage-factor-adjustment resistance and a fixed resistance, digital indicator means providing visual digital displays responsive to down-integration times of said integrator, gage-factor-adjustment means for applying a first reference voltage as input to said integrator through said fixed resistance during up-integration times thereof and an opposite-polarity reference voltage to said integrator through said variable resistance as a reference during alternate down-integration times thereof, and measurement means for applying voltages responsive to signal inputs from a strain-gage sensor as input to said integrator through said variable resistance during up-integration times thereof and an opposite-polarity one of said reference voltages to said integrator through said fixed resistance as a reference during alternate down-integration times thereof, whereby adjustment of said variable resistance to cause said digital indicator means to display digitally the known numerical value of the gage factor of the strain-gage sensor during operation of said gage-factor-adjustment means results in digital display of measurements responsive to signal inputs from the strain-gAge sensor which are compensated for gage factor during operation of said measurement means.

Claim 6

Electrical digital indicating apparatus as set forth in claim 3 wherein said gage-factor-adjustment means and said measurement means comprise means for electrically switching said integrator selectively either into a gage-factor-adjustment relationship wherein said first reference voltage is applied as input through said fixed resistance during said up-integration times and an opposite-polarity reference voltage is applied as a reference through said variable resistance during down-integration times, or into a measurement relationship wherein voltages responsive to said sensor are applied as input through said variable resistance during said up-integration times and an opposite-polarity one of said reference voltages is applied as a reference through said fixed resistance during said down-integration times.

Claim 7

Electrical digital indicating apparatus as set forth in claim 4 wherein said switching means includes manually-acutated electrical switches, and wherein said variable gage-factor-adjustment resistance includes a manually-adjustable multi-position tapped resistance, for setting gage factor coarsely, in series with a manually-adjustable continuously-variable resistance for fine tuning of the gage factor.

Claim 8

Electrical digital indicating apparatus as set forth in claim 5 further including a tap-position indicator associated with said tapped resistance and calibrated to indicate coarse gage factor.

Claim 9

Electrical digital indicating apparatus as set forth in claim 4 further including means for applying electrical signals related to said first reference voltage as excitation for the strain-gage sensor, and inverting amplifier means producing said opposite-polarity reference voltage responsive to said first reference voltage.

Claim 12

The method as set forth in claim 8 wherein the transducer comprises a strain-gage sensor and wherein said variable resistance is adjusted until the digital display by the digital indicator means corresponds to the numerical value of the gage factor for the strain-gage sensor.