When choosing a new instrument for pressure measurement, 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 are all part of the same device, and understanding them is a key aspect of calibrating a device.

Instrument range definition

Instrument range tells you the working range of your pressure measurement device. Instrument range also determines the maximum and minimum pressure values that it can handle without damage.

Measuring range definition

Measuring range is defined by the upper range limit (URL) and the lower range limit (LRL). These are the minimum and maximum pressure values your pressure device can read.

Calibration range definition

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

When you set up a pressure 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.

Calibration range for a pressure transmitter

Suppose that you want to calibrate 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. Accordingly, you should set the LRV to 10 bar and the URV to 50, making your calibrated range between 30 and 50 bar.

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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.

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