To understand calibration span, let’s go back to all the ranges an instrument can have. Pressure transmitters, for example, have the instrument range, which is the pressure range the device can support. This range covers the overpressure that might occur in the device.

The measuring range covers the values where the transmitter works properly, omitting the overpressure zone. The lower range limit (LRL) and upper range limit (URL) define this range.

calibration span

What is calibration span?

Inside the measuring range, you’ll find the calibration span, the range in which your device will be working, depending on your application. The calibration span covers the difference between your upper range value (URV), the maximum value your transmitter can read, and lower range value (LRV), the minimum value the device can read. So there you go!

You should also know that each instrument has a minimum and maximum calibration span it can support. If you go below or over these limits, you’ll lose accuracy in your readings.

Let’s say you want a pressure transmitter with a measurement range of -100 to 200 kilopascals (kPa). This device can measure pressures as low as -100 and as high as 200 kPa. If your application just requires pressure between -20 to 50 kPa, then this will be your calibration range. Your calibration span is the URV-LRV. By the numbers: 50 – (-20) = 70 kPa. Therefore, you get a calibration span of 70 kPa, which falls inside the span range (10 to 200 kPa).

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