Apparatus for automatically performing the least squares approximation to the standard addition method of analysis

Claim 2

Apparatus for determining the initial value of a given parameter in a process by measuring a function of the parameter in a sample of the process and approximating the function by a known relation, comprising: analyzing means responsive to the function of the parameter in the sample for generating a signal; a standard parameter dispenser means for adding to the sample a multiplicity of known increments of the given parameter one increment at a time; storage means connected to said analyzing means for storing a first signal from said analyzing means generated in response to the initial value of the parameter in the sample prior to the addition of said increments and for storing each of a multiplicity of signals from said analyzing means generated in response to each added increment; combining means connected to said storage means for adding and subtracting selected combinations of the stored signals to approximate the function by the known relation according to a mathematical method of least squares approximation, said combining means providing first and second output signals, the ratio of said output signals being the parameter initial value; and ratio indicating means connected to said combining means for determining the ratio of said first and second output signals.

Claim 3

The apparatus defined in claim 1 wherein said analyzing means is a spectrophotometer into which portions of the sample are introduced to produce a radiant energy spectrum characteristic of the mixture with the given substance and which produces an electrical signal proportional to said radiant energy spectrum.

Claim 4

The apparatus defined in claim 2 wherein said standard parameter dispenser is a calibrated syringe and said standard parameter is a standard solution of known concentration.

Claim 5

The apparatus defined in claim 3 wherein said storage means comprises: a multiplicity of integrating operational amplifiers for storing each of the multiplicity of signals; a multiplicity of relay armatures sequentially connecting each of said multiplicity of integrating operational amplifiers to said spectrophotometer to store each of said multiplicity of signals.

Claim 6

The apparatus defined in claim 4 wherein said combining means comprises at least two summing operational amplifiers one of which is connected to a selected portion of said integrating operational amplifiers, the other being connected to the remainder of said integrating operational amplifiers, said operational amplifiers combining the signals stored by each integrating amplifier in an additive manner.

Claim 7

The apparatus defined in claim 4 further comprising a programmed timer for activating said standard parameter dispenser and said analyzer means in synchronism with said multiplicity of relay armatures to sequentially generate and store said multiplicity of signals.

Claim 8

In a spectrophotometer of the type wherein the concentration of a given element in a sample is determined by the standard addition method utilizing the least squares approximation, the improvement comprising: a multiplicity of input switches; means connecting said switches to said spectrophotometer for conducting to said switches a sequence of a multiplicity of signals generated by said spectrOphotometer in response to the standard addition method of analysis; a multiplicity of operational integrating amplifiers each being connected to one of said switches, one of said integrating amplifiers being actuated to store one of said multiplicity of signals when one of said input switches is closed to connect one of said signals to said one of said integrating amplifiers; a multiplicity of output switches each of a portion thereof being connected to the output of one of said multiplicity of operational integrating amplifiers, said multiplicity of output switches being divided into first and second groups, each of said groups having at least one of the switches in addition to said portion thereof connected to said connecting means; first and second summing amplifiers each providing an output equal to the sum and difference of signals applied to the input, respectively; means for connecting said first group of output switches to said first summing amplifier and for connecting said second group of output switches to said second summing amplifier; and, ratio indicator means connected to the outputs of said first and second summing amplifiers for indicating the ratio of the output signal of said first summing amplifier to the output signal of said second summing amplifier.

Claim 9

In a spectrophotometer of the type wherein the concentration of a given element in a sample is determined by the standard addition method utilizing the least squares approximation, the improvement comprising: a multiplicity of input switches; means connecting said switches to said spectrophotometer for conducting to said switches a sequence of a multiplicity of signals generated by said spectrOphotometer in response to the standard addition method of analysis; a multiplicity of operational integrating amplifiers each being connected to one of said switches, one of said integrating amplifiers being actuated to store one of said multiplicity of signals when one of said input switches is closed to connect one of said signals to said one of said integrating amplifiers; a multiplicity of output switches each of a portion thereof being connected to the output of one of said multiplicity of operational integrating amplifiers, said multiplicity of output switches being divided into first and second groups, each of said groups having at least one of the switches in addition to said portion thereof connected to said connecting means; first and second summing amplifiers each providing an output equal to the sum and difference of signals applied to the input, respectively; means for connecting said first group of output switches to said first summing amplifier and for connecting said second group of output switches to said second summing amplifier; and, ratio indicator means connected to the outputs of said first and second summing amplifiers for indicating the ratio of the output signal of said first summing amplifier to the output signal of said second summing amplifier.

Claim 10

The spectrophotometer defined in claim 7 further comprising timing means programmed in accord with the least squares approximation to the standard addition method for actuating said input switches in time sequence corresponding to the sequence of signals generated by said spectrophotometer, and for actuating each of said integrating amplifiers to store a corresponding one of said sequence of signals, said timing means actuating said first and second groups of output switches simultaneously at the completion of said sequence of signals to connect the respective signals thereon to the first and second summing amplifiers respectively.