For the #LiknkedInsights feature, we cover popular discussions around the Process Automation industry in social media platforms. In today’s article, we evaluate and discuss the difference between nominal and calibrated range that Instrument Engineers usually work with. Read on to find out more…   If you have similar conversations to share, please write to us.

Range Differences

Identifying the difference between nominal and calibrated range is essential for an Instrument Engineer. This is because both ranges illuminate a device’s capability and quality. Basically, the nominal range is an instrument’s selection range. Meanwhile, a calibrated range is the capability to adjust an instrument to the zero range and then set the desired span. An Instrument Engineer from Hi-tech Engineering, Korea wants to understand the difference between a nominal and calibrated range. So, a Senior Applications Specialist from Laurentide Controls, Canada suggests that nominal range refers to when a device performs at its best under certain conditions.
Image of Coriolis
Image courtesy of icce.rs
Essentially, “for a Coriolis flow meter, most often, the nominal range is the flow of water that generates 1 bar of pressure drop across,” he offers. However, in regards to the calibrated range, he notes that this can be different. Namely, it might be smaller or larger than the nominal range. “Calibration range is application-specific,” he highlights.   To define the difference, it is essential to understand your instrument. A Support Engineer from Jay Electronique, France elaborates on this. He notes, “Nominal range is the range of input values set by the instrument supplier. Specifically, it is the range of values where the instrument performance (such as noise, linearity, SNR, uncertainty) is well known. Calibration can establish this. So, in that case, the two ranges are similar.”

Range Similarities

Similarly, an Instrumentation Engineer from Worley Parsons, Australia, pointed out that both the ranges are similar. Together, they are a calibration range. “A process team for measuring process value will design this. This can also be termed LRV and URV. But, as a matter of fact, LRVL (lower-value limit) and URVL (upper-value limit) are the maximum transmitter capabilities,” he explained. PB Control & Measurement Services Ltd Director from Scotland believes it is critical to note these terms’ use. “We need to see these terms in context. In my opinion, a nominal range would be a device’s maximum output span. Meanwhile, in the calibrated range measures the output against a standard with a known uncertainty. Thus, this gives a known uncertainty for the device over a specified range.

Conclusions

A Senior Vice President Technical Services at Coastal Flow Gas Measurement, Texas concludes the discussion. He agrees that a nominal range refers to the maximum calibration span that you should not exceed. “Though many don’t do this as often anymore, you can calibrate a sensor (say a pressure sensor) with a nominal range of 0-100 to a different calibrated range of up to the same span in many cases. The sensor reads from 50-150.  The calibrated span is less than or equal to the nominal range.” To see the full discussion, click here. To view this, don’t forget to join the Instrument Engineers!
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