Avoiding orifice meter emasurement errors at low differential pressures

In contrast, only a small portion of the RG regression data was taken below 10-inch H2O, and no guidelines exist for low differential pressures. Measurement accuracy is of more concern in this range, where otherwise acceptable uncertainties in differential pressure measurements could interfere with accuracy. For a differential pressure transmitter with a range of 0 to 250 inches of water column, a stated uncertainty of 0.1% of full-scale is equal to 0.25-inch H2O.