Bronkhorst

Is the high accuracy trend right?

August 9, 2016 James Walton

Everyone wants to have greater accuracy, it is desirable and achievable. It has been the push of R&D and marketing teams for years, describing in minute detail how accurate their new instrument is, the work, new technology and time spent to achieve it. Of course, accuracy is very subjective depending on the industry and even application, I will leave you to apply your own numbers but the definition remains the same.

Accuracy: How close a measurement is to the true value
Precision: How repeatable measurements are to the true value

But, does everyone ask the question; how accurate do you need the instrument to be?

Accuracy
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This question can create options for the end user often missed because it is assumed that greatest accuracy is the desired parameter, or the supplier does not have the facility to offer alternatives.

In terms of mass flow, accuracy requirements can change the type of sensor being discussed. If you need very high accuracy you can have a Coriolis device, if you don’t need high accuracy you may need a Constant Temperature Anemometry (CTA) or other sensor type.

These choices can have a high impact on the cost of the instrument and therefore the final solution. To achieve high accuracy requires a higher degree of engineering capability, extremely capable R&D engineers to precisely model the behaviour of the instrument across its range. This creates a very robust set of standards that future instruments can be calibrated against to ensure the end user sees that promised capability. All of this has to be applied with strict quality processes to ensure it happens every time.

When the conversation widens in this way, the conversation becomes very application specific and consultative, it could be very high accuracy in a low throughput application, or it could be lower accuracy, high repeatability in high throughput applications. Every change can result in a cost impact on the instrument, often making an instrument less expensive as many companies only offer their flagship model as standard.

Working with people that have more than one sensor type available is helpful in this situation. If you only have access to one sensor type then your options are greatly reduced. The opposite of working with someone who has access to a suite of sensor types to fit different accuracy and cost requirements.

Understanding this principle can alter the way that you purchase your instrumentation, it is also a good way to check if your flow provider is paying attention!

Check out our blog about the differences between a thermal mass flow sensor using the by-pass principle and CTA (constant temperature anemometry)


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