Automatic draft compensating circuit for digital spectrophotometer

Claim 2

Apparatus for correcting for drift in substances being measured in a digital spectrophotometer comprising: means for adjusting the spectrophotometric digital output to correct for drift in said substances; said adjusting means including means to multiply said digital output by a variable factor to thereby vary the number of pulses in said spectrophotometric digital output; and means to vary said factor so that the adjusted digital output of a standard sample that has undergone drift is equal to a preselected standard.

Claim 3

Apparatus in accordance with claim 1 including means to signal when the amount of adjustment exceeds a predetermined limit.

Claim 4

Apparatus in accordance with claim 2 wherein said means to signal when the amount of adjustment means exceeds a predetermined limit includes means to evaluate the amount of variation in said factor and signal when the amount of said variation exceeds a predetermined limit.

Claim 5

Apparatus for correcting drift in accordance with claim 1 wherein said means to vary said factor include means to make the variation in successively reduced steps to bring the adjusted digital output into equality with the preselected standard.

Claim 6

Apparatus for correcting for drift in substances being measured in a digital spectrophotometer comprising: means for adjusting the spectrophotometric digital output to correct for drift in said substances; said adjusting means including means to multiply said digital output by a variable factor to thereby vary the number of pulses in said spectrophotometric digital output; means to vary said factor to correct for a present value of drift; said means to vary said factor including means to compare said digital output to a preselected standard; and means responsive to said comparison means to effect an adjustment in said factor.

Claim 7

Apparatus for correcting for drift in substances being measured in a digital spectrophotometer comprising: means for adjusting the spectrophotometric digital output to correct for drift in said substances; said adjusting means including means to multiply said digital output by a variable factor to thereby vary the number of pulses in said spectrophotometric digital output; means to vary said factor to correct for a present value of drift; said means to vary said factor including means to compare said digital output to a preselected standard; and means responsive to said comparison means to effect an adjustment in said factor.

Claim 8

Apparatus for correcting for drift in accordance with claim 5 wherein said means to multiply said output by a variable factor comprises a digital multiplier and an up/down counter connected to said multiplier.

Claim 9

Apparatus for correcting for drift in accordance with claim 6 wherein said means responsive to said comparison means causes said up/down counter to count up whenever said preselected standard is higher than said digital output and causes said up/down counter to count down whenever said preselected standard is lower than said digital output.

Claim 10

Apparatus for correcting for drift in accordance with claim 7 further including means for causing said up/down counter to count in successively reduced steps.

Claim 11

In a digital spectrophotometric measuring system including a digital spectrophotometric measuring apparatus having a means for representing the results of each measurement in the form of at least one pulse train containing a number of pulses and wherein the number of pulses is proportional to the measured value, the improvement comprising: means for adjusting the output of said spectrophotometric apparatus to compensate for drift in the substance to be measured; said adjusting means including means to multiply said output by a variable factor; means to compare the digital output representing a standard sample of said substance that has undergone drift with a preselected standard, and means responsive to said comparison to vary said factor.

Claim 12

In a digital spectrophotometric measuring system including a digital spectrophotometric measuring apparatus having a means for representing the results of each measurement in the form of at least one pulse train containing a number of pulses and wherein the number of pulses is proportional to the measured value, the improvement comprising: means for adjusting the output of said spectrophotometric apparatus to compensate for drift in the substance to be measured; said adjusting means including means to multiply said output by a variable factor; means to compare the digital output representing a standard sample of said substance that has undergone drift with a preselected standard, and means responsive to said comparison to vary said factor.

Claim 13

Apparatus for correcting for drift in substances being measured in a spectrophotometer comprising: programmable memory means for storing a quantity representing a standard sample of the substance to be measured in said spectrophotometer before said standard sample has undergone drift; input means adapted to be connected to the output of said spectrophotometer for receiving a first signal from said spectrophotometer which first signal represents a standard sample of the substance to be measured in saId spectrophotometer which standard sample may have undergone drift; means for multiplying said first signal by a variable factor; means for varying said factor to correct said first signal to said stored quantity, said varying means comprising means for comparing the output of said multiplier means with said stored quantity, means for increasing said factor in a stepwise manner whenever said multiplier output is less than said stored quantity, means for decreasing said factor in a stepwise manner whenever said multiplier output is greater than said stored quantity and means for reducing the magnitude of the steps whenever said output and said stored quantity passed through equality during the next previous increasing or decreasing step, and means for memorizing the value of said factor needed to correct said first signal to said stored quantity whereby any subsequently received signal can be multiplied by the same said value.

Claim 14

Apparatus for correcting for drift in substances being measured in a spectrophotometer comprising: programmable memory means for storing a quantity representing a standard sample of the substance to be measured in said spectrophotometer before said standard sample has undergone drift; input means adapted to be connected to the output of said spectrophotometer for receiving a first signal from said spectrophotometer which first signal represents a standard sample of the substance to be measured in saId spectrophotometer which standard sample may have undergone drift; means for multiplying said first signal by a variable factor; means for varying said factor to correct said first signal to said stored quantity, said varying means comprising means for comparing the output of said multiplier means with said stored quantity, means for increasing said factor in a stepwise manner whenever said multiplier output is less than said stored quantity, means for decreasing said factor in a stepwise manner whenever said multiplier output is greater than said stored quantity and means for reducing the magnitude of the steps whenever said output and said stored quantity passed through equality during the next previous increasing or decreasing step, and means for memorizing the value of said factor needed to correct said first signal to said stored quantity whereby any subsequently received signal can be multiplied by the same said value.

Claim 15

Apparatus for correcting for drift as claimed in claim 10 wherein said means for multiplying said first signal by a variable factor comprises a digital multiplier and an up/down counter connected to said multiplier.

Claim 16

In a spectrophotometric measuring system, including a spectrophotometer having a means for representing the result of each measurement in logarithmic form, the improvement comprising a means for correcting for drift in substances being measured in said spectrophotometer; said drift correcting means comprising: programmable memory means for storing a quantity representing a standard sample of the substance to be measured in said spectrophotometer before said standard sample has undergone drift; means connected to the output of said spectrophotometer for receiving a first signal from said spectrophotometer which first signal represents a standard sample of the substance to be measured in said spectrophotometer which standard sample may have undergone drift; means for multiplying said first signal by a variable factor; means for varying said factor to correct said first signal to said stored quantity, said varying means comprising means for comparing the output of said multiplier means with said stored quantity, means for increasing said factor in a stepwise manner whenever said multiplier output is less than said stored quantity, means for decreasing said factor in a stepwise manner whenever said multiplier output is greater than said stored quantity and means for reducing the magnitude of the steps whenever said output and said stored quantity passed through equality during the next previous increasing or decreasing step, and means for memorizing the value of said factor needed to correct said first signal to said stored quantity whereby any subsequently received signal can be multiplied by the same said value.

Claim 17

In a spectrophotometric measuring system, including a spectrophotometer having a means for representing the result of each measurement in logarithmic form, the improvement comprising a means for correcting for drift in substances being measured in said spectrophotometer; said drift correcting means comprising: programmable memory means for storing a quantity representing a standard sample of the substance to be measured in said spectrophotometer before said standard sample has undergone drift; means connected to the output of said spectrophotometer for receiving a first signal from said spectrophotometer which first signal represents a standard sample of the substance to be measured in said spectrophotometer which standard sample may have undergone drift; means for multiplying said first signal by a variable factor; means for varying said factor to correct said first signal to said stored quantity, said varying means comprising means for comparing the output of said multiplier means with said stored quantity, means for increasing said factor in a stepwise manner whenever said multiplier output is less than said stored quantity, means for decreasing said factor in a stepwise manner whenever said multiplier output is greater than said stored quantity and means for reducing the magnitude of the steps whenever said output and said stored quantity passed through equality during the next previous increasing or decreasing step, and means for memorizing the value of said factor needed to correct said first signal to said stored quantity whereby any subsequently received signal can be multiplied by the same said value.

Claim 18

In a spectrophotometric measuring system as claimed in claim 12 wherein said means for multiplying said first signal by a variable factor comprises a digital multiplier and an up/down counter connected to said multiplier.