Application Notes on pH Transmitters.

pH transmitters provide electrical outputs that are proportional to potential of hydrogen (pH) inputs. The pH scale is used to express the acidity or alkalinity of a solution by measuring the concentration of hydrogen ions in the solution. An acidic solution has a higher concentration of hydrogen ions than an alkaline solution. pH transmitters include a pH sensor, which uses electrodes or wires to test the solution’s pH measurement, and a controller which processes the raw signal from the pH sensor and delivers it to the transmitter. In this way, a pH transmitter is able to convert the pH of a solution into an electrical signal. Some pH transmitters are designed to be completely submersible and can simultaneously transmit both pH and temperature readings.
There are several basic types of pH transmitters. A loop pH powered transmitter is a two-wire device typically powered by a 24 VDC powered transmitter or a 120/240 VAC powered analyzer. These pH transmitters often include a built-in preamplifier which conditions the signal coming from the pH sensor and provides a 4-20 mA output signal to the transmitter. An ion sensitive field effect transistor (ISFET) is a type of transistor that responds to changes in the hydrogen ion concentration in a solution. When the hydrogen ion concentration or pH changes, less electrical current flows through the transistor. Consequently, ISFETs are well suited for use in pH sensors and pH transmitters. ISFET silicon chips are more durable and reliable than glass pH electrodes, which may break in harsh environments. ISFET-based pH electrodes also offer more stable pH measurement, with a response rate typically ten times faster than glass electrodes. ISFET-based pH transmitters are popular in pharmaceutical applications and the food processing industry. Their durability allows them to be easily sterilized without the risk of breaking during handing.
Sebastian

G.M. Technical

Nunes Instruments

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