Method and apparatus for auto-calibration of signal conditioning electronics
First Claim
1. Apparatus for conditioning and calibrating a raw electrical signal comprising:
- a printed circuit board having an input termination for said raw electric signal, a conditioning circuit connected to the input termination for conditioning the raw electrical signal to generate a conditioned electrical signal and an output termination for outputting the conditioned electrical signal;
test means for selectively disconnecting the conditioning circuit from the input termination and for connecting test signals of known magnitude to the conditioning circuit;
processing means connected to said output termination, for calibrating the conditioning circuit by controlling said test means to connect said test signals to said conditioning circuit to generate conditioned test signals, generating a calibration factor as a function of said test signals and said conditioned test signals, operating said test means to reconnect said raw electrical signal to said conditioning circuit so that said conditioned electrical signal again appears on said output termination and applying said calibration factor to said conditioned electrical signal to generate a calibrated conditioned electrical signal; and
monitoring means including temperature sensing means for sensing the temperature of said conditioning circuit, said processing means being responsive to the temperature sensed by said sensing means to perform said calibration when said temperature changes by a preselected amount since the last calibration.
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Accused Products
Abstract
Numerous signal conditioning circuits on a plurality of printed circuit boards are calibrated remotely by a signal processing unit which sends coded signals to each board, either sequentially or in parallel, to connect either on-board or off-board test signals to one of the conditioning circuits in place of its field generated input. The processing unit utilizes the actual and expected responses of each conditioning circuit to low and high test signals to generate a gain and an offset which are applied to the conditioned field signal to provide a calibrated signal. The time constant for each conditioning circuit is also measured periodically, or upon a selected temperature change, for use in generating a minimum waiting period for obtaining valid data following transfers between the field generated signals and the test signals.
33 Citations
20 Claims
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1. Apparatus for conditioning and calibrating a raw electrical signal comprising:
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a printed circuit board having an input termination for said raw electric signal, a conditioning circuit connected to the input termination for conditioning the raw electrical signal to generate a conditioned electrical signal and an output termination for outputting the conditioned electrical signal; test means for selectively disconnecting the conditioning circuit from the input termination and for connecting test signals of known magnitude to the conditioning circuit; processing means connected to said output termination, for calibrating the conditioning circuit by controlling said test means to connect said test signals to said conditioning circuit to generate conditioned test signals, generating a calibration factor as a function of said test signals and said conditioned test signals, operating said test means to reconnect said raw electrical signal to said conditioning circuit so that said conditioned electrical signal again appears on said output termination and applying said calibration factor to said conditioned electrical signal to generate a calibrated conditioned electrical signal; and monitoring means including temperature sensing means for sensing the temperature of said conditioning circuit, said processing means being responsive to the temperature sensed by said sensing means to perform said calibration when said temperature changes by a preselected amount since the last calibration. - View Dependent Claims (2, 3, 4)
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5. A method of remotely calibrating a signal conditioning circuit on a printed circuit board which conditions a field generated electrical signal connected to the conditioning circuit to generate a conditioned output signal therefrom which is applied to a signal processing unit, where the signal conditioning circuit contains reactive components which require time for the conditioned output signal to settle down in response to an applied signal, said method comprising the steps of:
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sending an electrical signal from said processing unit to said printed circuit board to disconnect said field generated signal from said conditioning circuit; applying under the direction of said processing unit test signals of known magnitude to said conditioning circuit in place of the field generated electrical signal to generate conditioned test signals which are applied to said processing unit; waiting for a selected period of time after applying the test signal to the signal conditioning circuit for the conditioning circuit to settle; generating in the signal processing unit after said waiting period a calibration factor as a function of said test signals and said conditioned test signals; disconnecting said test signals from said conditioning circuit and reapplying said field generated electrical signal; applying said calibration factor to said conditioned output signal to generate a calibrated conditioned output signal; and periodically determining the time constant of said conditioning circuit and selecting said waiting period as a function of said time constant. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of remotely calibrating a plurality of signal conditioning circuits which are mounted in groups on printed circuit boards and which condition field generated electrical signals connected thereto to generate conditioned output signals which are applied to a signal processing unit, said method comprising the steps of:
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monitoring the temperature of said conditioning circuits; sequentially under the direction of said processing unit calibrating each of said conditioning circuits when the temperature of said conditioning boards varies by a preselected amount since the last calibration to generate a calibration factor therefore and storing the calibration factor for each conditioning circuit; and applying in said processing unit to each of the conditioned output signals the associated stored calibration factor. - View Dependent Claims (16)
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17. Apparatus for conditioning and calibrating raw electrical signals comprising:
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a plurality of printed circuit boards each having a plurality of input terminations for said raw electrical signals, conditioning circuits connected to each of the input terminations for conditioning each of the raw electrical signals to generate conditioned electrical signals, and output terminations for outputting the conditioned electrical signals; test means on each printed circuit board including a test bus, on board test signal generating means for generating an internal test signal, an off board test signal for generating an external test signal, internal/external switch means, responsive to an internal/external select signal for separately selectively applying the internal and external test signals to the test bus, and test injection means responsive to a board enable signal, and a test address signal for disconnecting a selected raw electrical signal designated by said test address signal from its conditioning circuit and connecting said test bus thereto, and responsive to the absence of a board enable signal for reconnecting said conditioning circuit to said input termination; and processing means connected to said output termination and including means for generating a board enable signal for selected boards, a test address signal for each selected board designating the conditioning circuit on that board to be tested and an internal/external select signal, waiting a selected settling interval for conditioned test signals produced by the designated conditioning circuits to stabilize, generating a calibration factor for each selected conditioning circuit as a function of the test signals and conditioned test signal, terminating the board enable signal to reconnect the raw electrical signals to the conditioning circuits, and applying the calibration factors to the conditioned electrical signals to generate calibrated conditioned electrical signals. - View Dependent Claims (18, 19, 20)
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Specification