Auto-ranging glucose measuring system

An auto-ranging continuous measuring system for determining the concentration of glucose in a glucose containing solution, comprising:

• continuous sampling means for receiving said glucose containing solution,
• a source of diluent including a buffer solution,
• dilutor means coupled to said sampling means and to said source of diluent for combining said glucose containing solution and said diluent in a predetermined dilution ratio to produce a flow of diluted glucose containing solution,
• converter means having an inlet and an outlet, said inlet being coupled to said dilutor means for converting the glucose in said diluted glucose containing solution into hydrogen peroxide as one of the products at said outlet,
• detector means coupled to said oulet of said converter means and responsive to said hydrogen peroxide for producing an analog electric output signal indicative of the glucose concentration in said diluted glucose containing solution,
• limit means coupled to said detector means responsive to said analog electric output signal for producing a high limit signal representative of the upper limit of linearity of said analog electric signal and a low limit signal representative of the noise level in said analog electric signal, and
• control means coupled between said limit means and said dilutor means responsive to said high limit signal for increasing the dilution ratio of said glucose containing solution relative to said diluent and responsive to said low limit signal for decreasing the dilution ratio of said glucose containing solution relative to said diluent;
• whereby said dector means analog electric output signal is maintained between said high limit and said low limit and the glucose concentration in said glucose containing solution is determined jointly from said analog electric signal and said dilution ratio.

An auto-ranging glucose solution measuring system, comprising:

• a sampling means for receiving said glucose solution,
• a source of diluent including a buffer solution for maintaining a pH between 5 and 8,
• dilutor means coupled to said sampling means and to said source of diluent for producing a diluted glucose solution, including a variable speed, motor driven, peristaltic pump for changing the dilution ratio,
• a glucose oxidase enzyme converter column coupled to said dilutor means for converting said diluted glucose solution into hydrogen peroxide as one of the products on conversion,
• an amperometric detector coupled to said converter column responsive to said hydrogen peroxide for producing an analog electric output signal proportional to the concentration of said hydrogen peroxide,
• a high limit circuit coupled to said amperometric detector and responsive to said analog electric signal for producing output pulses of short duration when said analog electric signal has exceeded a predetermined high limit, each of said short pulses being separated by a duration substantially equal to the response time of said measuring system,
• a low limit circuit coupled to said amperometric detector and responsive to said analog electric signal for producing output pulses of short duration when said analog electric signal is less than a predetermined low limit, each of said short pulses being separated by a duration substantially equal to the response time of said measuring system,
• a pulse generator,
• a pulse count divider coupled to said pulse generator for dividing the pulse count per unit time from said pulse generator and having a plurality of outputs, and
• selector means coupled between said pulse count divider and said variable speed motor of said dilutor for transmission of pulses to energize said variable speed motor, and responsive to said output pulse from one of said high limit and low limit circuits for selecting one of said plurality of outputs from said pulse count divider to said variable speed motor to change the dilution ratio of said dilutor by changing the speed of such motor.

In a continuous glucose solution concentration measuring system, an improved dilutor comprising:

• a source of glucose containing solution,
• a first pump having a positive measured output and an input connected to said source of glucose containing solution to supply a measured quantity of a glucose containing solution at its output,
• a source of diluent,
• a second pump having a positive measured output and an input connected to the output from said first pump and to said source of diluent, and
• means to operate at least one of said pumps at an adjustable speed to adjust the amount of diluent provided by said dilutor at the output of said second pump.