Flow control system for liquid chromatographs
First Claim
Patent Images
1. In a liquid chromatograph system having a motor driven pump for supplying a carrier containing isocratic or gradient controlled elution solvents and for delivering the carrier to an LC column under pressure, a method of flow control of the pump output comprising the steps of measuring pump output pressure over at least one cycle of pump operation at constant pump motor speed to develop a pressure reference level for a given carrier;
- subsequently varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
measuring the pattern of pump motor speed during a cycle of operation;
storing said pattern in a memory to provide a pump motor speed reference, measuring the actual pump motor speed during operation of the system;
comparing the pump motor speed reference and actual pump motor speed to obtain a difference signal in speed caused by changes in system variables;
continually changing the pressure reference level applied to the pump in response to the difference signal.
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Abstract
A flow control system including a pump for delivering a carrier containing isocratic or gradient controlled elution solvents under pressure to a liquid chromatographic column at a substantially constant selected controlled flow rate.
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Citations
6 Claims
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1. In a liquid chromatograph system having a motor driven pump for supplying a carrier containing isocratic or gradient controlled elution solvents and for delivering the carrier to an LC column under pressure, a method of flow control of the pump output comprising the steps of measuring pump output pressure over at least one cycle of pump operation at constant pump motor speed to develop a pressure reference level for a given carrier;
- subsequently varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
measuring the pattern of pump motor speed during a cycle of operation;
storing said pattern in a memory to provide a pump motor speed reference, measuring the actual pump motor speed during operation of the system;
comparing the pump motor speed reference and actual pump motor speed to obtain a difference signal in speed caused by changes in system variables;
continually changing the pressure reference level applied to the pump in response to the difference signal. - View Dependent Claims (2)
- subsequently varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
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3. In a liquid chromatograph system having an LC column for receiving a sample to be analyzed in a liquid carrier delivered under pressure to the column, a motor driven pump for supplying said carrier containing isocratic or gradient controlled elution solvents, means for controlling the flow of the pump output comprising means for measuring pump output pressure over at least one cycle of pump operation at constant pump motor speed to develop a pressure reference level for a given carrier;
- means for varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
means for measuring the pattern of pump motor speed during a cycle of operation and for storing said pattern in a memory to provide a pump motor speed reference, means for measuring the actual pump motor speed during operation of the system;
means for comparing the pump motor speed reference and actual pump motor speed to obtain a difference signal in speed caused by changes in system variables;
means responsive to said difference signal for continually changing the pressure reference level applied to the pump in response thereto to maintain flow constant. - View Dependent Claims (4)
- means for varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
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5. In a liquid chromatograph system means forming an LC column, reservoir means for supplying carrier components at low pressure, a single pump system for taking said carrier components at said low pressure and for delivering the same to said LC column at a high pressure, operative means at said low pressure for selecting isocratic or gradient elution proportions of said carrier components and for supplying the same to said single pump system, means for controlling the flow of the pump output comprising means for measuring pump output pressure over at least one cycle of pump operation at constant pump motor speed to develop a pressure reference level for a given carrier;
- means for varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
means for measuring the pattern of pump motor speed during a cycle of operation and for storing said pattern in a memory to provide a pump motor speed reference, means for measuring the actual pump motor speed during operation of the system;
means for comparing the pump motor speed reference and actual pump motor speed to obtain a difference signal in speed caused by changes in system variables;
means responsive to said difference signal for continually changing the pressure reference level applied to the pump in response thereto to maintain flow constant. - View Dependent Claims (6)
- means for varying the speed drive of the pump motor to maintain the output pressure equal to the pressure reference level;
Specification