The maximum pressure (pₘₐₓ) of a sensor is determined by its lowest rated part. The lowest rated part can be either the measurement tube (pₘₐₓ indicated below), the connection block/manifold (pₘₐₓ indicated in the mechanical construction section) or the process connection (for pₘₐₓ see published standards or manufacturer information).

All uncertainty statements refer to reference conditions – mass flow of water, 18 – 24 °C, 1 – 3 bar in a standard temperature, pressure and material configuration sensor. The sensor can be used to measure gas – uncertainty values for gas equal the liquid value plus 0.3 %. Reference conditions for gas are mass flow of natural gas, 18 – 24 °C, 35 to 100 bar in a standard temperature, pressure and material configuration sensor.

The turn down capability from Qnom of the flow sensor is mainly driven by its zero point stability. At the very low end of the measuring range the uncertainty (u) is dominated by the zero point stability. The zero point stability of a standard sensor is: 0.000036 kg/min (0.000079 lbs/min). Zero stability of a Gold Line sensor is 0.000019 kg/min (0.000042 lbs/min).

For flow Q ≥ zero stability / (calibration uncertainty/100) u = calibration uncertainty
For flow Q < zero stability / (calibration uncertainty/100) u = (zero stability/Q) x 100

• If sensors are not zeroed at operating conditions, minor additional uncertainties can arise from elevated temperatures and pressures:  ±0.00308 % of maximum flow per °C and  ±0.0208 % of maximum flow per bar.
• Process temperature effect on density: additional uncertainty of ±0.000641 g/cm³ per °C difference from calibration temperature with standard density calibration and of ±0.000073 g/cm³ per °C difference from calibration temperature with enhanced density calibration. This effect can be mitigated by a simple field density adjustment at operating conditions.
• Process pressure effect on mass flow: The effect of pressure on flow measurement is 0.001 % of rate per bar. Compensation is possible by pressure sensor input (analog input or digital write) or manual value entry into the transmitter.
• Process pressure effect on density: The effect of pressure on density measurement is 0.00012 g/cc per bar. Compensation is possible by pressure sensor input (analog input or digital write) or manual value entry into the transmitter.