When you have a question about process automation that needs a short answer, let us know with #WishIknew and @Visaya! We’ll reply with a #WishIknew post. It’ll give a quick explanation, then some related articles, videos, or reviews if you want to know more.

I wish I knew what calibration range is!

Good that you asked this! When you need a new instrument, you have all kinds of ranges to consider – the instrument range, the measuring range, and the calibration range, or calibrated range as some call it.

These ranges are all part of the same device. The first, the instrument range, tells you the working range of the device, the maximum and minimum values that it can handle without damage.

Next we have the measuring range, defined by the upper range limit (URL) and the lower range limit (LRL). These are the minimum and maximum values your device can read.

calibration range
Courtesy of Yokogawa

Finally, we come to the calibrated or calibration range. This range of values, inside the measuring value, defines what your instrument will read according to your calibration settings.

When you set up a device for the first time, you’ll need to set an upper range value (URV) and a lower range value (LRV). The calibration range covers all the values between the URV and LRV.

Still confused? Shall we go to an example?

Suppose you want a pressure transmitter. The vendor site states that the transmitter can measure from 0 to 400 bar, which gives you your measuring range. However, in your application, you’ll only have pressures between 10 and 50 bar. So you set the LRV to 10 bar and the URV to 50, and that makes your calibrated range from 30 to 50 bar.

Before setting your calibration range, you should also check the minimum and maximum calibrated span and make sure your calibration span falls within this range. If you want to to know more about calibration span, we have a #WishIKnew about that too. Hope this helps!

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