Self calibrating strain gage torquemeter

Claim 2

Apparatus for providing an electrical signal representative of torque in a rotating shaft as derived from a shaft mounted torque sensor and providing compensation for signal variations resulting from other than torque changes, said apparatus comprising: means for applying external electrical energy to said shaft; means for receiving said applied energy on said shaft; means responsive to said received energy for energizing said torque sensor whereby said torque sensor provides an output torque signal representative of shaft torque; means for periodically biasing said torque signal to provide an output reference signal in place of said output torque signal, said reference signal being representative of a predetermined shaft torque; means for coupling said torque and reference signals from said shaft to points external of said shafts; means responsive to said torque and reference signals coupled from said shaft for providing said electrical signal representative of shaft torque as the ratio of said torque and reference signals.

Claim 3

The apparatus for indicating torque of claim 1 wherein said means for periodically biasing said torque signal includes means for adjusting said reference signal by a predetermined percentage of said torque signal.

Claim 4

Apparatus for providing an output indication of torque in a rotating shaft in response to variations in a shaft mounted torque sensor and providing compensation for output variations resulting from other than torque changes, said apparatus comprising: means for generating electrical excitation with distinct repeating characteristics thereto; means for coupling said excitation to said shaft; means secured to said shaft and responsive to said electrical excitation for energizing said torque sensor whereby said torque sensor provides an output torque signal representative of shaft torque; meAns responsive to distinct repeating characteristics of said excitation coupled to said shaft for alternately biasing said torque sensor to provide an output reference signal in place of said torque signal; means for coupling said torque and reference signals from said shaft; and means responsive to said torque and reference signals coupled from said shaft for providing said output indication of shaft torque compensated for said variations resulting from other than shaft torque.

Claim 5

Apparatus for providing an output indication of torque in a rotating shaft in response to variations in a shaft mounted torque sensor and providing compensation for output variations resulting from other than torque changes, said apparatus comprising: means for generating electrical excitation with distinct repeating characteristics thereto; means for coupling said excitation to said shaft; means secured to said shaft and responsive to said electrical excitation for energizing said torque sensor whereby said torque sensor provides an output torque signal representative of shaft torque; meAns responsive to distinct repeating characteristics of said excitation coupled to said shaft for alternately biasing said torque sensor to provide an output reference signal in place of said torque signal; means for coupling said torque and reference signals from said shaft; and means responsive to said torque and reference signals coupled from said shaft for providing said output indication of shaft torque compensated for said variations resulting from other than shaft torque.

Claim 6

The apparatus for indicating torque of claim 3 wherein said coupling means comprises a single rotary transformer.

Claim 7

The apparatus for indicating torque of claim 3 wherein: said torque sensor is a strain gage bridge; said biasing means is operative to shunt one of the strain gage elements of said bridge with a predetermined resistance; and said output indication providing means includes means for differencing said coupled torque and reference signals to provide a difference signal and for indicating the ratio of said torque signal coupled from said shaft to said difference signal.

Claim 8

Apparatus for indicating torque in a rotating shaft comprising a first electronic system mounted on said shaft and a second electronic system mounted external of said shaft with transformer electrical coupling means for coupling electrical signals between said first and second electronic systems, said coupling means being susceptible to variation in its coupling efficiency, said second electronic system comprising: first generating means for generating electrical oscillations at a first frequency; second generating means for generating electrical oscillations at a second, different frequency; means for alternately applying said first and second frequency oscillations to said coupling means and providing intervening intervals when neither of said oscillations is coupled thereto; said first electronic system comprising: means for alternately receiving said first and second frequencies of electrical oscillations from said coupling means; means operative to provide system operating power from said received oscillations during the intervening intervals between application of said first and second frequencies of electrical oscillations to said coupling means; a torque sensor affixed to said shaft for sensing torque; means responsive to said system operating power for energizing said torque sensor to provide a torque signal representative of shaft torque; means for applying said torque signal to said coupling means; means responsive to said alternately received first and second frequencies of electrical oscillations for alternately biasing said torque sensor to provide a reference signal representative of predetermined torque for application to said coupling means in place of said torque signal; said second electronic circuit further having means for receiving said reference signal and said torque signal during said intervening intervals and operative to provide an output indication of shaft torque compensated for variations in said torque signal resulting from other than torque changes.

Claim 9

Apparatus for indicating torque in a rotating shaft comprising a first electronic system mounted on said shaft and a second electronic system mounted external of said shaft with transformer electrical coupling means for coupling electrical signals between said first and second electronic systems, said coupling means being susceptible to variation in its coupling efficiency, said second electronic system comprising: first generating means for generating electrical oscillations at a first frequency; second generating means for generating electrical oscillations at a second, different frequency; means for alternately applying said first and second frequency oscillations to said coupling means and providing intervening intervals when neither of said oscillations is coupled thereto; said first electronic system comprising: means for alternately receiving said first and second frequencies of electrical oscillations from said coupling means; means operative to provide system operating power from said received oscillations during the intervening intervals between application of said first and second frequencies of electrical oscillations to said coupling means; a torque sensor affixed to said shaft for sensing torque; means responsive to said system operating power for energizing said torque sensor to provide a torque signal representative of shaft torque; means for applying said torque signal to said coupling means; means responsive to said alternately received first and second frequencies of electrical oscillations for alternately biasing said torque sensor to provide a reference signal representative of predetermined torque for application to said coupling means in place of said torque signal; said second electronic circuit further having means for receiving said reference signal and said torque signal during said intervening intervals and operative to provide an output indication of shaft torque compensated for variations in said torque signal resulting from other than torque changes.

Claim 10

The apparatus for indicating torque of claim 6 wherein said coupling means is a unitary rotary transformer.

Claim 11

The apparatus for indicating torque of claim 6 wherein said means operative to provide an output indication of shaft torque includes means for differencing said received torque and reference signals to provide a difference signal more directly representative of said known torque and for indicating the ratio of the received torque signal to said difference signal.

Claim 12

The apparatus for indicating torque of claim 8 wherein: said shaft torque sensor includes a four element strain gage bridge; said energizing means includes an oscillator applying electrical excitation to opposite junction points on said bridge; and said biasing means is operative to periodically change the resistance of one or more of the elements of said bridge to cause the output of said bridge to change substantially more than the output produced by a full scale torque change in said bridge.

Claim 13

The apparatus for indicating torque of claim 6 wherein: said shaft torque sensor includes a four element strain gage bridge; said energizing means includes an oscillator applying electrical excitation to opposite junction points on said bridge; and said biasing means is operative to periodically change the resistance of one or more of the elements of said bridge to cause the output of said bridge to change substantially more than the output produced by a full scale torque change in said bridge.

Claim 14

Apparatus for measuring torque in a rotating shaft and for providing an output indication of said torque at a point external of said shaft including: means for generating electrical oscillations with first and second characteristics; a rotary transformer having a primary coil external of said shaft connected to receive said electrical oscillations and a secondary coil mounted to said shaft and oriented for inductively receiving said oscillations; a filtered rectifier responsive to electrical oscillations from said secondary coil to provide operating power; an oscillator responsive to said operating power for generating alternating electrical signals; a strain gage bridge having a plurality of strain gage elements secured to said shaft to provide a variation in the resistance of said elements representative of said torque; said alternating current output of said oscillator being applied to said strain gage bridge whereby said strain gage bridge has an electrical output representative of shaft torque; means for applying the bridge output to said rotary transformer for coupling to the primary thereof; means for sensing the first and second characteristics in said oscillations; switch means having first and second states, said first state existing in response to detection of said first characteristic and said second state existing in response to detection of said second characteristic; at least one resistive element having a resistance substantially higher than the resistance of the elements of said strain gage bridge and alternately connected in parallel with an element of said bridge during one of said first or second states of said switch means; means for alternately directing said bridge output coupled to said primary coil along first and second paths respectively in synchronism with the first and second characteristics of said electrical oscillation and correspondingly the first and second states of said switch means; said first path including means for sampling said bridge output to provide a first sample signal representative of shaft torque; said second path including means for sampling said bridge output to provide a second sample signal representing said bridge output during intervals when said resistive element is connected in parallel with one of said strain gage elements; means for differencing the first and second sample signals to provide an output difference signal more directly representative of said predetermined known shaft torque; and means for indicating the ratio of said first sample signal and said output difference signal to provide said output indication of actual shaft torque compensated for variations in said first sample signal resulting from other than torque changes.

Claim 15

Apparatus for measuring torque in a rotating shaft and for providing an output indication of said torque at a point external of said shaft including: means for generating electrical oscillations with first and second characteristics; a rotary transformer having a primary coil external of said shaft connected to receive said electrical oscillations and a secondary coil mounted to said shaft and oriented for inductively receiving said oscillations; a filtered rectifier responsive to electrical oscillations from said secondary coil to provide operating power; an oscillator responsive to said operating power for generating alternating electrical signals; a strain gage bridge having a plurality of strain gage elements secured to said shaft to provide a variation in the resistance of said elements representative of said torque; said alternating current output of said oscillator being applied to said strain gage bridge whereby said strain gage bridge has an electrical output representative of shaft torque; means for applying the bridge output to said rotary transformer for coupling to the primary thereof; means for sensing the first and second characteristics in said oscillations; switch means having first and second states, said first state existing in response to detection of said first characteristic and said second state existing in response to detection of said second characteristic; at least one resistive element having a resistance substantially higher than the resistance of the elements of said strain gage bridge and alternately connected in parallel with an element of said bridge during one of said first or second states of said switch means; means for alternately directing said bridge output coupled to said primary coil along first and second paths respectively in synchronism with the first and second characteristics of said electrical oscillation and correspondingly the first and second states of said switch means; said first path including means for sampling said bridge output to provide a first sample signal representative of shaft torque; said second path including means for sampling said bridge output to provide a second sample signal representing said bridge output during intervals when said resistive element is connected in parallel with one of said strain gage elements; means for differencing the first and second sample signals to provide an output difference signal more directly representative of said predetermined known shaft torque; and means for indicating the ratio of said first sample signal and said output difference signal to provide said output indication of actual shaft torque compensated for variations in said first sample signal resulting from other than torque changes.

Claim 16

The apparatus for measuring torque of claim 11 wherein: said generating means includes first and second oscillators of first and second frequencies of oscillation alternately connected to the primary of said rotary transformer to provide said excitation with said first and second characteristics; the connection of said first and second oscillators to the primary winding being separated by intervening intervals when neither of said electrical oscillators is connected to said primary winding; and further wherein said filteRed rectifier means includes means for maintaining the operating power output thereof during said intervening intervals when no electrical excitation is received in the secondary winding of said rotary transformer.