Method and apparatus for automatic flow-through digital refractometer

A method for determining the concentration of dissolved solids in a liquid sample, comprising the steps of:

• directing a collimated beam of monochromatic light through a hollow, empty prismatic container which is enclosed in an opaque housing,
• detecting the refraction of said beam on its path of emergence from said prismatic container,
• introducing a liquid sample to be tested into said prismatic container thereby changing the degree of refraction of said beam,
• disabling measurement of said refraction and further proceeding with the method until after an amount of said liquid sample sufficient for accurate testing has been placed in the prismatic container,
• deferring and disabling the measuring step even after the predetermined amount is in the container for a period to free the liquid in the container from air bubbles,
• and only then, as soon as a predetermined amount of said liquid sample sufficient for accurate testing has been placed in the prismatic container and after said predetermined amount of said liqued sample has had time to be freed from air bubbles, measuring the refraction of the beam through the sample-filled prism, and
• displaying of the measured refraction as a function of the concentration of dissolved solids in the sample.

A method of using a refractometer for determining the amount of dissolved solids in a series of sample solutions which comprises:

• directing a collimated monochromatic light beam through an empty hollow prismatic container and refracting it onto first light sensing means,
• indicating when the refractometer is ready to receive a sample,
• introducing a sample solution into the prismatic container, thereby causing refraction of the collimated light beam passing therethrough to a second light-sensing means, instead of to the first light-sensing means,
• commencing the testing sequence only after all of the light beam has been refracted away from the first light-sensing means, and simultaneously indicating that testing is in progress,
• determining the amount of refraction of the light beam caused by passing through the sample solution,
• converting the amount of refraction of the light beam into an analog electrical signal,
• converting the analog signal to a digital signal,
• displaying digitally an amount corresponding to the digital signal, stated as a function of the concentration of dissolved solids in the sample solution,
• automatically draining the prismatic container, and simultaneously causing the light beam to be refracted to the first light-sensing means, and
• automatically recommencing the sequence by indicating that the refractometer is ready to receive another sample.

A refractometer for determining the concentration of dissolved solids in a sample solution, including in combination:

• an enclosing opaque housing,
• light source means in said housing for producing a beam of substantially collimated monochromatic light,
• a hollow triangular prismatic container in said housing having two transparent optical walls disposed in the path of said light beam and meeting at an angle between about 40.degree. and about 55.degree., and a third wall, an inlet opening located near the top of the prism, an overflow opening in said third wall located a desired distance below said inlet opening, and a drain opening located at the lower end of said prism,
• said prismatic container also having a bottom sloping downwardly from said third vertical wall toward the intersection of said two transparent optical vertical walls, and wherein said drain opening is located at substantially the lowermost point of said bottom,
• light-sensing means disposed in the refracted path of said light beam after the said beam has passed through said prismatic container when filled with a liquid sample and responsive to the exact refraction of said light beam,
• display means actuated by said light-sensing means for displaying the refraction as a function of the concentration of dissolved solids in the liquid sample,
• control means to open said drain means and to cause said prismatic container to be emptied after testing has been completed, and
• indicator means to indicate that the refractometer is ready for the introduction of a new sample.

A refractometer for determining the concentration of dissolved solids in a sample solution, including in combination:

• an enclosing opaque housing,
• light source means in said housing for producing a beam of collimated monochromatic light,
• a hollow prismatic container in said housing having two transparent optical vertical walls disposed in the path of said light beam,
• first and second light-sensing means, said first light-sensing means being disposed in the path of said light beams after the said beam has passed through said prismatic container when empty, and said second light-sensing means being disposed in the refracted path of said light beam after the said beam has passed through said prismatic container when filled with a liquid sample, said second light-sensing means including means responsive to the exact refraction of said light beam,
• control means to actuate testing as soon as said first light-sensing means ceases being illuminated by said light beam, and
• differentiating means and display means for comparing the exact refraction of said light beam through a sample to the exact refraction of said light beam through a reference sample and displaying that difference as a function of the concentration of dissolved solids in the test sample.

A refractometer for determining the concentration of dissolved solids in a sample solution, including in combination:

• an enclosing opaque housing,
• light source means in said housing for producing a beam of substantially collimated monochromatic light,
• a hollow prismatic container in said housing, said prismatic container being triangular, having two transparent optical vertical walls disposed in the path of said light beam, a third vertical wall, an inlet opening located near the top of said prism, and overflow opening disposed in said third vertical wall at a desired distance from the top of said prism, a bottom sloping downwardly from said third vertical wall toward the intersection of said two transparent optical vertical walls, and a drain opening located at substantially the lowermost point of said bottom,
• a phototransistor which emits a signal upon being illuminated, said phototransistor being disposed in the path of said light beam after the said beam has passed through said prismatic container while empty,
• an amplifier connected to said phototransistor, a Schmitt trigger connected to said amplifier, and a first timer connected to said Schmitt trigger via a first switch, the signal of said phototransistor being amplified by said amplifier and received by said Schmitt trigger so that when said phototransistor ceases being illuminated, said Schmitt trigger is operated making a sharp cutoff in the electronic circuit actuating said timer through said first switch,
• a photopotentiometer, said photopotentiometer being disposed in the refracted path of said light beam after the said beam has passed through said prismatic container while filled with a liquid sample, said photopotentiometer emitting an output voltage which corresponds to the exact refraction of said beam as caused by passing through a liquid sample,
• a differential amplifier, said differential amplifier being connected to the output voltage of said photopotentiometer to amplify an analog signal which corresponds to the difference between said output voltage and the output voltage of a liquid sample having a fixed known concentration of dissolved solids,
• an analog-to-digital converter connected to said differential amplifier, to receive said amplified analog signal and converting it to a digital signal of pulses at a frequency which corresponds to the said amplified analog signal,
• a second timer connected to the output of said first timer to be actuated at the end of its period, a gate connected to said second timer, and a decade counter connected to the output of said gate, said gate being connected to and receiving the digital signal of pulses from said analog-to-digital converter, said gate being connected to said second timer to receive its output during its period, the digital signal of pulses passing through said gate to be counted by said decade counter only when the output of said timer is also received by the gate, the number of pulses counted by said decade counter corresponding to the concentration of dissolved solids in a test sample,
• display means for displaying a digital figure which corresponds to the concentration of dissolved solids in a test sample, said display means being connected to the output of said decade counter through a decoder driver,
• a drain tube connected to the drain opening in said prismatic container, a solenoid drain valve having inlet and outlet sides, the inlet side connected to said drain tube, and a waste tube connected to the outlet side of said solenoid drain valve, leading to waste-disposing means,
• a third timer, said third timer being connected to said second timer to be actuated upon the completion of testing, said third timer to emit a signal upon being actuated, switch means connected to receive the signal from said third timer, transistor means connected to said switch means to receive the signal from said third timer means, an amplifier connected to said transistor means to receive and amplify its signal, said amplified signal actuating the opening of said solenoid drain valve for the period of said third timer,
• and warning means to indicate that the refractometer is ready for the introduction of a new sample.