Method and apparatus for determining tension in a cable

Claim 3

The apparatus of claim 1, wherein said tension deriving means comprises an electrical circuit adapted to solve the equations T=(2FL) 2 M where T is the tension in the object; F is the sensed fundamental frequency of vibration; L is the span length of the object under observation; and M is the mass per unit length of the object under observation.

Claim 4

The apparatus of claim 2 wherein said tension deriving means comprises: frequency to voltage converter circuit means for receiving the compensated sensor signal as an input signal and providing an output signal analogous to the frequency of the compensated sensor signal; a first multiplier circuit means for receiving the output signal from said converter circuit means as an input signal and providing an output signal which is analogous to the product of the input signal received from said converter circuit multiplied by the span length of the object under observation; squaring circuit means for receiving the output signal from said first multiplier circuit means as an input signal and providing an output signal which is analogous to the square of the signal received from said first multiplier circuit means; and a second multiplier circuit means for receiving the output signal from said squaring means as an input signal and providing an output signal which is analogous to the product of the signal received from said squaring circuit means multiplied by the weight per unit length of the object under observation.

Claim 5

The apparatus of claim 3 wherein: said first multiplier circuit means includes an amplifier circuit means an adjustable gain to permit adjustment of the multiplier value corresponding to the length of the object under observation; and said second multiplier circuit means includes an amplifier circuit means having an adjustable gain to permit adjustment of the multiplier value corresponding to the weight per unit length of the object under observation.

Claim 6

The apparatus of claim 1, wherein: said sensor means comprises means for generating a signal which is indicative of sensed velocity of vibrations in the object under observation; and said filter means includes a low pass filter circuit having a frequency response characterized by a negative six decibel per octave slope on a logarithmic scale in the frequency bandwidth of the tension measuring apparatus.

Claim 7

The apparatus of claim 5 wherein said filter means further comprises: a high pass filter circuit having a frequency response characterized by a threshold frequency corresponding to the desired low frequency response of the apparatus.

Claim 8

The apparatus of claim 1, wherein: said sensor means comprises means for generating a signal indicative of sensed acceleration of vibrations in the object under observation; and said filter means includes a low pass filter circuit having a frequency response characterized by a negative twelve decibels per octave slope on a logarithmic scale in the frequency bandwidth of the tension measuring apparatus.

Claim 9

The apparatus of claim 7 wherein said filter means further comprises: a high pass filter circuit having a frequency response characterized by a threshold frequency corresponding to the desired low frequency response of the apparatus.

Claim 10

The apparatus of claim 1, wherein: said sensor means comprises means for generating a signal indicative of the displacement of vibrations in the object under observation; and said filter means comprises a high pass filter circuit having a frequency response characterized by a threshold frequency corresponding to the desired low frequency response of the apparatus.

Claim 11

The apparatus of claim 1 wherein said sensor means may be selected to be means for generating a signal indicative of either the displacement or velocity of vibrations in the object under observation; and wherein said filter means further comprises: a lead in high pass filter circuit having a frequency response characterized by positive six decibel per octave slope on a logarithmic scale in the frequency bandwidth of the tension measuring apparatus for initially processing signals from said displacement probe only; a high pass filter circuit having a frequency response with a threshold frequency corresponding to the desired low frequency response of the apparatus; and a low pass filter circuit having a frequency response characterized by a negative six decibel per octave slope on a logarithmic scale in the frequency bandwidth of the tension measuring apparatus.

Claim 14

The method of claim 11, wherein said step of normalizing the sensor signal comprises: providing the sensor signal to a filter circuit having a characteristic frequency response which is substantially the inverse function of the frequency response of the means used to carry out the steps of sensing vibrations and generating the sensor signal.

Claim 15

The method of claim 11, wherein said step of deriving a tension value comprises deriving a solution to the equation T=(2FL) 2 M where T is the tension in the object; F is the sensed fundamental frequency of vibration; L is the span length of the object under observation; and M is the mass per unit length of the object under observation.