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Instrument

pH Meter

Physical Sciences

A pH meter is an electric device that measures the acidity or alkalinity of a solution, consisting of a voltmeter attached to a pH-responsive glass electrode and a reference electrode. Arnold O. Beckman built the first practical pH meter in 1934 at Caltech, at the request of a citrus-industry chemist who needed a reliable way to measure the acidity of lemon juice, and went on to found the company that became Beckman Instruments to manufacture it.

Facts
Invented YearSourced to the subject's own account
1934 2
Measures
The concentration (activity) of hydrogen ions in a solution, expressed on the pH scale. 3
Operating Principle
A glass electrode sensitive to hydrogen-ion activity develops a voltage relative to a stable reference electrode; the meter converts that voltage to a pH value using the Nernst equation, in which one pH unit corresponds to about a 59 millivolt change at 25 degrees Celsius. 3
Operating Range
The standard pH scale runs from 0 to 14, with 7 as neutral. 3
Open Questions
Resolution
Not stated in the cited source. 3
Commodity portable meters are commonly built to 0.01 pH units, but that figure was not confirmed in this specific source, so it is not written here as attested.
Classification
Instrument Class
Analytical Instrument 1
Connections

Invented By

Arnold Beckman, Scientists

Patented the pH meter, originally called an acidimeter, in October 1934, then founded the company that became Beckman Instruments to sell it.

Source Arnold Beckman (Wikipedia)

Used In

Chemistry, Disciplines
Source pH Meter (Britannica)
Sources
1. pH Meter (Britannica)
Encyclopaedia Britannica
  • Lede, instrument class
    A pH meter is an electric device that measures the acidity or alkalinity of a solution, consisting of a voltmeter attached to a pH-responsive glass electrode and a reference electrode.
  • Used In: Chemistry
View the Source
2. Arnold Beckman (Wikipedia)
Wikipedia
  • Career section
    By October 1934, he had registered patent application US Patent No. 2,058,761 for his 'acidimeter', later renamed the pH meter.
  • Invented By: Arnold Beckman
View the Source
3. Theory and Practice of pH Measurement (Emerson)
Emerson Automation Solutions
Quote
0 to 14
View the Source

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