pH measurement is a standard process in the industrial sector. It’s used for plating, environmental monitoring, wastewater treatment, and more. Using a pH data logger for recording pH level provides useful and relevant information about long-term trends and the impact of various factors, along with providing information for quality control, alarming, and reporting. However, to capture accurate measurements, you should consider three critical factors that can affect the accuracy of your measurements. This article will introduce these factors to give you some insight into what you should consider when you use a pH data logger for collecting pH data.
The Voltage range provided by a standard pH sensor has a range of +400 mV to -400 mV. It corresponds to a particular pH range of zero to 14 at room temperature. Any data logger intended for pH measurement must be capable of accepting positive and negative voltages. Also, the device must be sensitive for it to be able to measure small and subtle changes in voltage adequately. A data logger that offers a full-scale input range of one to two volts ensures that sufficient accuracy and resolution to detect changes in pH levels of 0.1 to less than a negative number.
The pH electrode wire has a very high impedance. It produces a voltage, but since this voltage develops across an ion-selective glass membrane, the amount of current that the electrode supplies the one circuit is minimal. A standard voltage data logger may have an input impedance of one Megohm, which is fine for common voltage measurements. However, when taking pH measurements, the amount of current that’s drawn by this resistance causes effects in loading, which will produce large amounts of errors in the voltage readings. That’s why it’s crucial for you to choose a pH data logger that has a high impedance input amplifier.
Finally, is the effect of temperature on the output voltage of the sensors in your data logger when measuring for pH levels. The errors in the output voltage will get worse as you move away from a pH value of 7 as the temperature deviates from 26 degrees Celsius. For example, without considering the temperature, simply measuring the voltage output of a probe immersed in a solution of pH of two at a temperature of 86 degrees Celsius can potentially lead to errors that are as high as nine pH levels. By choosing a multichannel data logger that’s capable of reading temperature and voltage, you’ll be able to measure accurate temperature levels.
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