Pure Water/Reverse Osmosis/Power Plant
pH measurement in pure water is relatively challenging, owing to the following factors:
1. Because it is pure water, its buffering capacity is extremely weak, making it highly susceptible to contamination and prone to significant pH changes. Even the addition of just 2 ppm (parts per million, a unit of concentration) of impurities can lead to a noticeable pH shift. For example, adding 2 ppm of NaOH will raise the pH from 7 to 10, while 2 ppm of CO 2 , pH decreases from 7 to 6, 2 ppm NH 3 , the pH value increases from 7 to >7.8. In typical practical pH measurements, the main sources of error are the impact of electrolyte leakage into ultrapure water on the pH value and the influence of atmospheric CO 2 When dissolved in pure water, the resulting measurement—in either case—will not reflect the pH of pure water itself. Therefore, when measuring the pH of pure water, electrode systems that require the addition of a potassium chloride (KCl) solution should be avoided as much as possible.
2. High-purity water has very poor conductivity and is easily affected by external electromagnetic fields. Moreover, during flow, it is prone to generating static electricity, acoustic fields, and other phenomena, which can compromise the stability and accuracy of measurements. Therefore, measuring the pH of pure water must employ a low-resistance sensitive-membrane Sensor, which can effectively reduce interference from static electricity, magnetic fields, and acoustic fields while ensuring sensitive sensor response.
Since there are very few ions in ultrapure water, there is still a diffusion resistance between the reference Sensor and the measuring Sensor, and this potential E 5 The stability of the Sensor also affects the stability of pH measurement; therefore, in pure water pH measurement, the distance between the reference Sensor and the measuring Sensor should be kept as short as possible to avoid excessive impedance between the two Sensors, which can make the measurement susceptible to changes in flow rate. Composite Sensors effectively solve this problem, whereas split Sensors are unsuitable. Flow rate also has a significant impact on pure water pH measurement; if the flow rate is unstable, it will lead to junction potential E 6 and the diffusion potential E 5 This instability leads to unstable and inaccurate pH measurements. Therefore, in pure water pH measurement, the flow rate should be kept as constant as possible to prevent potential instability caused by flow rate variations, which in turn can lead to pH fluctuations. This is an unavoidable reality. At present, all pure water pH Sensors worldwide are affected by flow rate, which is determined by their theoretical characteristics!
Our company’s pure water and reverse osmosis Sensors are widely used in the fields of pure water and ultrapure water due to their stable measurement performance and extremely high cost-effectiveness.
In the pure water/RO/power plant industries, our company recommends the following Sensors:
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