Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
161 words
A temperature measuring apparatus for measuring temperature of a metallic body utilizing eddy current effect, comprising: a differential amplification type operational amplifier having its one input terminal connected to a detecting coil and including a dummy coil to which positive feedback connection is made; an oscillator connected to the other input terminal of said operational amplifier to supply thereto a signal having a constant amplitude and a predetermined oscillation frequency, the other input terminal of said operational amplifier being connected to provide a negative feedback circuit having an adjustable negative feedback factor; a phase shifter connected to an output terminal of said oscillator for adjusting the phase angle of the signal from said oscillator to produce a synchronous detection reference signal; and a detection circuit connected to said operational amplifier and said phase shifter for synchronously detecting the output of said operational amplifier with the reference signal applied from said phase shifter to produce a signal indicative of a measured temperature.
Claim 2
Dependent Claim
161 words
A temperature measuring apparatus for measuring temperature of a metallic body utilizing eddy current effect, comprising: a differential amplification type operational amplifier having its one input terminal connected to a detecting coil and including a dummy coil to which positive feedback connection is made; an oscillator connected to the other input terminal of said operational amplifier to supply thereto a signal having a constant amplitude and a predetermined oscillation frequency, the other input terminal of said operational amplifier being connected to provide a negative feedback circuit having an adjustable negative feedback factor; a phase shifter connected to an output terminal of said oscillator for adjusting the phase angle of the signal from said oscillator to produce a synchronous detection reference signal; and a detection circuit connected to said operational amplifier and said phase shifter for synchronously detecting the output of said operational amplifier with the reference signal applied from said phase shifter to produce a signal indicative of a measured temperature.
Claim 3
Dependent Claim
63 words
An apparatus according to claim 1, wherein the operational amplifier has the following amplification degree ##EQU2## where β N is the negative feedback factor, Z 1 is the impedance of the dummy coil, and Z (t, d) is the impedance of the detecting coil determined by the temperature of the metallic body and the distance between the detecting coil and the metallic body.
Claim 4
Dependent Claim
73 words
An apparatus according to claim 1, wherein the measured temperature signal output e out of the apparatus is given as e.sub.out = A·e.sub.in cos (φ-θ) where A is the amplification degree of the operational amplifier, e in is the input voltage from the oscillator, θ is the phase angle set by the phase shifter, and φ is the phase difference between the input voltage e in and the output voltage e out .
Claim 5
Dependent Claim
57 words
An apparatus according to claim 1, wherein the negative feedback factor of the operational amplifier and the phase angle of the phase shifter are adjustable, whereby preventing a variation in the distance between the detecting coil and the metallic body from causing variation in the measured temperature signal level and the temperature measuring sensitivity of the apparatus.
Claim 6
Dependent Claim
39 words
An apparatus according to claim 1, wherein said negative feedback circuit including the oscillator for supplying a signal of a constant amplitude and predetermined oscillation frequency is connected in parallel with the positive feedback connection including said detecting coil.