How do you know which lab pH sensor is the right pH sensor for your application? You want a sensor that will provide very good measurement accuracy for the longest lifetime, but the number of different lab pH sensors out there can be overwhelming. Before purchasing a laboratory pH sensor, it cannot be overstated the importance of understanding the conditions your application and sensor will be exposed to during use. Based on this knowledge, you can decide which features you need. Here are some features you might want to consider:
The main material
The first step in selecting a good pH sensor for an application is identifying the host material. Some things to consider when deciding on a body material are:
•temperature
• Chemicals in solution
•deal with
temperature
As a rule of thumb, polymer body sensors (including epoxy, plastic, and Ultem®) can be used in the low to moderate temperature range. In the higher temperature range (above 100°C), glass is the better choice.
chemical compatibility
With polymer electrodes, you always want to check the compatibility between the sensor body material and the chemicals that may be present in the sample. Typically, polymer body probes are never used in solutions containing inorganics. Also, when the sample solution contains highly corrosive components, you want to use glass electrodes. This is because glass is a very inert material, meaning it is resistant to the reactions of chemicals that might degrade other substances, such as polymers.
In applications where the sensor is going to be handled with heavy hands or subject to any type of impact, a good pH sensor will have a polymer body, as a polymer body absorbs more shock than glass and resists breakage.
single or double knot
If your application involves testing samples that may contain proteins, heavy metals (Ni, Cd, Cu, Cr, Ag), sulfides, cyanides, or iodides, or any other material that will react with silver or chloride ions, the double junction electrode Will provide added protection against reference fouling. This prolongs the service life of the sensor. Single junction electrodes can be used in more general applications.
Sealed or Fillable Electrodes
Sealed pH sensors require less maintenance and are more cost-effective. However, the sealed design containing the gel reference solution will eventually become depleted or contaminated and need to be replaced. The refillable pH sensor has a resealable hole near the top of the body, allowing the user to refill when the liquid internal solution is depleted. This extends the life of the sensor and ensures accurate measurements throughout the life of the sensor.
Certain refillable laboratory pH sensors will also offer flushable fittings that are specifically designed to respond quickly and accurately to rapid temperature changes. Refillable laboratory pH sensors with flushable fittings are often referred to as research grade.
Temperature compensation
pH measurement is temperature dependent. Depending on the temperature and pH of the sample, there may be an element of error. If you are looking for highly accurate pH measurements in applications with extreme temperatures, then the right pH sensor for your application will include temperature integration. Typically, laboratory pH sensors come with an integrated temperature sensor for this purpose. When choosing a probe with automatic temperature compensation (ATC), also consider whether your pH meter will accept a temperature element, and whether the temperature element in the pH sensor will match that of the meter.
Connector
Last but not least, always make sure that the connector on the pH sensor matches the connector on the pH meter. The most common connector for pH sensors is the BNC connector, but there are many other different connectors. Also, if your pH sensor has an integrated temperature sensor, make sure the temperature element's connector is also compatible with the pH meter you will be using.
