Continuous calibration system and method for analytical instruments

Claim 2

In an analytical instrument for measuring constituents of a fluid comprising at least one sensor means, first circuitry for producing a signal representative of the constituent sensed by said sensor and including an analog-to-digital converter to allow display of said signal in digital form, the improvement for providing continuous calibration of the instrument by means of a second circuitry comprising a comparator circuit for continuously comparing the output signal of said analog-to-digital converter to a reference signal when calibrating the instrument and for producing an output signal representative of the difference as a result of said comparing, and a sample-and-hold circuit for receiving the output signal of said comparator circuit and for producing in turn a compensatory voltage coupled to said first circuitry.

Claim 3

The analytical instrument of claim 1 in which said reference signal is continuously produced by a memory means in response to previously stored reference information therein.

Claim 4

The analytical instrument of claim 1 further characterized in having an error display means activated by said comparator circuit when said difference between said instrument output and said reference signal exceeds the maximum allowed correction range of said sample-and-hold circuit as determined by its R-C time constant.

Claim 5

The analytical instrument of claim 3 also having a delay means interconnected between said comparator circuit and said error display means.

Claim 6

In an analytical instrument for measuring constituents of a fluid comprising at least one sensor means, circuitry for producing a signal representative of the constituent sensed by said sensor and including an analog-to-digital converter to allow display of said signal in digital form, the improvement for providing continuous calibration of the instrument by means of a second circuitry comprising a memory means for receiving and storing reference information and for producing at its output a reference signal representative of said information, a comparator circuit having one input for receiving said reference signal and a second input for receiving the output of said analog-to-digital converter when calibrating said instrument and for producing at its output a signal representative of the difference therebetween, a sample-and-hold circuit having an input and an output, with its said input coupled to said comparator circuit output and for producing in response thereto a compensatory voltage at its said output which in turn is coupled to said first circuitry to correct for errors in said signal representative of said constituent.

Claim 7

In an analytical instrument for measuring constituents of a fluid comprising at least one sensor means, circuitry for producing a signal representative of the constituent sensed by said sensor and including an analog-to-digital converter to allow display of said signal in digital form, the improvement for providing continuous calibration of the instrument by means of a second circuitry comprising a memory means for receiving and storing reference information and for producing at its output a reference signal representative of said information, a comparator circuit having one input for receiving said reference signal and a second input for receiving the output of said analog-to-digital converter when calibrating said instrument and for producing at its output a signal representative of the difference therebetween, a sample-and-hold circuit having an input and an output, with its said input coupled to said comparator circuit output and for producing in response thereto a compensatory voltage at its said output which in turn is coupled to said first circuitry to correct for errors in said signal representative of said constituent.

Claim 8

The analytical instrument of claim 5 further characterized in having an error display means coupled via a delay means to the output of said comparator circuit for displaying an error when said difference between the instrument output and said reference signal exceeds the R-C time constant of said sample-and-hold circuit for a period in excess of a pre-determined time.

Claim 11

The method of claim 7 further characterized by constantly measuring calibration standards except when a sample is presented to the instrument for measurement.

Claim 12

The method of claim 7 further characterized in that when said difference between instrument output and said reference signal is such as to be beyond the capability of said sample-and-hold circuit to correct, producing an error signal for warning the operator.

Claim 13

The method of claim 9 in which said error signal is produced following the elapse of a pre-determined time period.

Claim 16

The method of claim 11 in which said error signal is produced following the elapse of a pre-determined time period.

Claim 17

The method of claim 11 in which said reference signal has been stored in a memory means of said instrument.