Camlab Limited

Buy Smarter – what questions should you ask when buying a pH meter?

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Courtesy of Camlab Limited

When you’re looking to buy a pH meter, whether it’s to start measuring or to replace an existing meter, the range of brands and specifications available is huge.

With so many options it can be difficult to know where to start, but taking a little time to choose carefully could save you a lot of time and money overall by making sure the meter you choose is right for you.

Try our list of questions below to make sure you choose the right pH meter

Portable or Laboratory

The first decision to make is whether you require a very small and portable stick meter (also known as a pocket pH tester), a portable handheld meter which often have more functions, or a benchtop meter for use in the lab.

Electrodes

It’s the electrode which is the sensitive measuring part of the pH meter.

Even robust electrodes will need replacing eventually, so find out more about the electrodes the meter uses so you can predict the costs and availability.

  • What type of connector does the meter use?
  • Is it a standard BNC or DIN?
  • Is it proprietary or can other manufacturers’ probes be used with it?
  • What is the replacement cost for a pH electrode?

BNC or DIN connectors are the most common types, this will allow you to use electrodes from different manfuacturers which means you can shop around for both price and specifications.

Samples containing sulphides, proteins, heavy metals or those that are thick, sticky, or solid (e.g. if you’re measuring the pH of foods, soils or other difficult samples) will need a specialised electrode.

Again, choosing a meter with a standard BNC connection will mean you have the biggest choice of specialised electrodes.

  • Is the electrode supplied suitable for my samples?
  • If not, is a suitable specialist one available?

Technical Specifications

Other specifications of the meter can make measurements more accurate, but also increase the cost of the meter, so ask yourself how accurate the measurements need to be for your task.

Temperature compensation is important for accuracy and is built in to most meters. Very low cost meters may not have this feature, which will mean the results are less accurate.

  • Does the meter have automatic temperature compensation? (ATC)
  • Is a temperature probe included?

Buffer recognition is automatic in most meters, which saves a lot of time when calibrating. Very basic meters may instead need manual calibration by turning a screw to meet the correct value – this can save money but will add time to the calibration.

  • Are buffers automatically recognised?
  • What buffer values are recognised, and how readily available are buffers?

Calibration can also then be made more accurate by calibrating against more points – for most applications a 3 point calibration is fine, lower cost meters may only offer a 2 point calibration, while highly accurate work for example in pharmaceuticals could use a 5 point calibration. Displaying the results in mV as well as pH units can allow more in depth analysis and is useful for troubleshooting.

  • How many points calibration can I perform?
  • Can the meter display in mV ?

For high accuracy work or where results need to be stored or reported, you should check the meter has additional features such as being GLP compliant, having room to save results, or being able to connect to download results.

  • What additional types of features are offered? (GLP data, PC connectivity, USB or RS 232 connectivity)

Some meters may also be able other parameters like Ion measurement by ISE, or conductivity, but this might need extra expansion packs or electrodes.

  • Can the meter expand to other methods like ISE or conductivity?
  • What is required to do this?

You may also want to identify any other unique points this meter may have over others

  • What makes the company different from other companies that manufacture similar products?

Additional items and accessories

Accessories to the meter can make your measurements easier, and often there may be “kit” options that have some of the accessories included.

The accessories might range from basics like a carrying case for field work, up to additional analysis software for your results – again the level you need will depend on how accurate your results need to be.

  • What accessories are included with the meter?
  • What other accessories are available?

Repairs and Support

Finally find out what help is available, either as troubleshooting over the phone or web chat, or for bigger repairs which require spare parts or a qualified engineer

  • What type of after sales support is offered?
  • What is the warranty period?
  • Can service and repairs be performed? On site or by sending the meter back?
  • What is the general turnaround time for repair?

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