US 4,288,308 AGranted

Continuous pH meter

AssigneeHach Chemical Company

InventorClifford C. Hach

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Abstract

A glass pH measuring electrode is mounted in a piston that reciprocates in a chamber which is in fluid communication with a reference electrode. Intake and outlet lines to the chamber are controlled by valves. A drive means operates the piston and the valves to pull successive liquid samples into the chamber for measurement and then to discharge them. The drive means also controls two positive displacement pumps, one of which feeds controlled amounts of electrolyte past the reference electrode and the other feeds a bacterial sterilizing agent to the chamber. The electrolyte flow past the reference electrode and into the discharge flow from the chamber maintains open electrical communication with the chamber. A deformable body, preferably a bed of finely ground methyl methacrylate grit, in the chamber engages and cleans the glass electrode as the piston reciprocates.

Claims6

Dependent claims

A pH meter comprising, in combination, a frame, a sample chamber mounted on said frame, a reference electrode mounted in fluid communication with said chamber, a piston mounted in said chamber and including a glass electrode to cooperate with said reference electrode for measuring the pH of liquid samples in the chamber, intake and outlet lines opening to said chamber, valves on said frame for each of said lines, means for reciprocating said piston in said chamber and operating said valves so that the outlet line is open and the intake line closed as the piston fills the chamber to exhaust fluid from the chamber and the intake line is open and the outlet line closed as the piston withdraws from the chamber and draws a new liquid sample into the chamber, said reference electrode mounting including an electrolyte line opening into said outlet line, a positive displacement pump in said frame driven by said means, said pump being connected to deliver controlled amounts of electrolyte past said reference electrode so as to maintain a flow of electrolyte into said outlet line, and a body of deformable material in said chamber and positioned to engage and clean said glass electrode each time said piston is reciprocated.

Dependencies are inferred from the claim text.