Methods and apparatus for correction of cable variations

Apparatus for automatically determining a selected characteristic of a primary electrical device, comprising:

• a plurality of independent electrical devices, including said primary electrical device;
• means for connecting said plurality of electrical devices to form a plurality of pairs of said electrical devices in a succession;
• means for measuring an electrical characteristic of each of said plurality of pairs of said electrical devices in said succession and for providing measured electrical characteristics associated with each of said pairs, and
• computing means for comparing said measured electrical characteristics associated with each of said pairs to determine said selected characteristic of said primary electrical device.

Apparatus for automatically determining a characteristic associated with a primary signal transmitting device subjected to an influence affecting the transfer characteristics of said primary signal transmitting device, comprising:

• a plurality of other signal transmitting devices also subjected to said influence;
• means for automatically connecting said primary signal transmitting device and said plurality of other signal transmitting devices to form pairs of said devices;
• and
• means for automatically comparing signals transmitted through said pairs of said devices to determine a characteristic associated exclusively with said primary signal transmitting device.

Apparatus for automatically correcting for variation of a selected characteristic of a primary electrical device to improve the accuracy of measurement data acquired via said primary electrical device, comprising:

• a measurement instrument;
• a signal source;
• a plurality of independent electrical devices, including said primary electrical device, each of said electrical devices having similar electrical characteristics and being subjected to similar environmental influences;
• connecting means for successively connecting said electrical devices to provide a plurality of connected pairs of said electrical devices;
• switching means for successively connecting said connected pairs between said signal source and said measurement instrument;
• means for applying a signal from said signal source to said connected pairs to provide a measurement signal to said measurement instrument during a first period and a successive period subsequent to said first period;
• means for automatically directing said switching means during each of said first period and said successive period to successively connect each of said connected pairs between said signal source and said measurement instrument,
• said measurement instrument being responsive to said measurement signals during said first period and said successive period to provide, respectively, a first measurement signal and a second measurement signal associated with each of said connected pairs;
• and
• computing means for determining said selected characteristic for said first period and said successive period in response to said first measurement signals, said second measurement signals, and a reference signal from said signal source,
• said computing means being further operative for determining a correction factor based upon said selected characteristic for said first period and said second period.

A method for determining a characteristic associated with a primary confined path signal transmitting device subjected to an influence affecting the transfer characteristics of said primary confined path signal transmitting device, comprising the steps of:

• providing a plurality of other confined path signal transmitting devices also subjected to said influence;
• connecting said primary confined path signal transmitting device and said plurality of other confined path signal transmitting devices to form pairs of said devices;
• and
• comparing signals transmitted through said pairs of said devices to determine a characteristic associated exclusively with said primary confined path signal transmitting device.

A method for compensating for influences upon a primary electrical cable utilized for transmitting signals from a device under test (DUT), comprising the steps of:

• determining an electrical characteristic of the primary electrical cable at a first time by making calibration measurements of a plurality of similarly influenced electrical cables connected in pair-wise fashion;
• making a test measurement of the DUT at a subsequent time interval using the primary electrical cable to obtain test data associated with the DUT;
• determining the electrical characteristic of the primary electrical cable at a time subsequent to the test measurement by making calibration measurements of the plurality of similarly influenced electrical cables connected in pair-wise fashion;
• computing a correction factor associated with the primary electrical cable;
• and
• applying the correction factor to the test data associated with the DUT to obtain corrected DUT test data.

A method for determining the insertion factor of a primary cable subjected to influences affecting the transfer characteristics of the primary cable, comprising the steps of:

• connecting the primary cable to a first secondary cable to form a first cable pair;
• connecting the first cable pair between a signal source and a phase-amplitude receiver;
• applying a calibration signal from the signal source to the first cable pair to provide an output signal from the first cable pair;
• measuring the output signal from the first cable pair relative to a reference signal from the signal source;
• storing the measured output signal from the first cable pair in a memory as a stored first cable pair output signal;
• connecting the primary cable to a second secondary cable to form a second cable pair;
• connecting the second cable pair between the signal source and the phase-amplitude receiver;
• applying the calibration signal from the signal source to the second cable pair to provide an output signal from the second cable pair;
• measuring the output signal from the second cable pair relative to a reference signal from the signal source;
• storing the measured output signal from the second cable pair in the memory as a stored second cable pair output signal;
• connecting the first secondary cable to the second secondary cable to form a third cable pair;
• connecting the third cable pair between the signal source and the phase-amplitude receiver;
• applying the calibration signal from the signal source to the third cable pair to provide an output signal from the third cable pair;
• measuring the output signal from the third cable pair relative to a reference signal from the signal source;
• storing the measured output signal from the third cable pair in the memory as a stored third cable pair output signal;
• measuring the reference signal;
• storing the measured reference signal to provide a stored reference signal in the memory storage device;
• and
• operating upon a set of functions formed by a ratio of said stored first cable pair output signal to the stored reference signal, a ratio of the stored second cable pair output signal to the stored reference signal, and a ratio of the stored third cable pair output signal to the stored reference signal to determine the insertion factor for the primary cable.

A method for automatically correcting for variations of a primary cable to ensure the accuracy of measured data acquired via the primary cable, comprising the steps:

• (1) connecting the primary cable to a first secondary cable to form a first cable pair;
• (2) applying a calibration signal to the first cable pair to provide a first voltage output;
• (3) measuring the first output voltage during the first time interval;
• (4) storing the first output voltage to provide a stored first output voltage associated with a first time period;
• (5) connecting the primary cable to a second secondary cable to form a second cable pair,
• (6) applying the calibration signal to the second cable pair to provide a second voltage output;
• (7) measuring the second output voltage;
• (8) storing the second output voltage to provide a stored second output voltage associated with the first time period;
• (9) connecting the first secondary cable to the second secondary cable to form a third cable pair;
• (10) applying the calibration signal to the third cable pair to provide a third voltage output;
• (11) measuring the third output voltage;
• (12) storing the third output voltage to provide a stored third output voltage associated with the first time period;
• (13) measuring a reference signal corresponding to the calibration signal;
• (14) storing the reference signal to provide a stored reference signal associated with the first time period;
• (15) acquiring measured data via the primary cable;
• (16) repeating steps (1)-(14) during a second time period occurring subsequent to the first time period and subsequent to the acquisition of data via the primary cable to obtain a stored first output voltage, a stored second output voltage, and a stored third output voltage associated with the second time period;
• (17) operating upon functions formed by a ratio of the stored first output voltage to the stored reference signal for the first time period, a ratio of the stored second output voltage to the stored reference signal for the first time period, and a ratio of the stored third output voltage to the stored reference signal for the first time period, to determine the insertion factor for the primary cable during the first time period;
• (18) operating upon functions formed by a ratio of said stored first output voltage to the stored reference signal for the second time period, a ratio of the stored second output voltage to the stored reference signal for the second time period, and a ratio of the stored third output voltage to the stored reference signal for the second time period, to determine the insertion factor for the primary cable during the second time period;
• (19) calculating a ratio of the insertion factor during the first time period to the insertion factor during the second time period to provide a correction factor;
• and
• (20) applying the correction factor to the measured data to improve the accuracy of the measured data.