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Accuracy of Measurement

Coriolis Mass Flow Meters – Accuracy of Measurement

  1. The flow ranges are presented for water at temperature of 20…25 ºC, pressure of 0.1…0.2 MPa and density of 1,000 kg/m3 under standard conditions. For liquids of different density the volumetric flow range should be calculated by dividing the ​​flow range limits under standard conditions by actual density value.
  2. If the measured flow rate is less than low flow cutoff value, the coriolis mass flowmeter will indicate zero flow and accumulation of mass and volume will pause. Low flow cutoff value is set to 1% of the maximum flow rate. Cutoff value can be changed through the menu display or through Modbus.
  3. Coriolis flow meters can measure flow over 1% of the upper limit of the full flow range but measurement error in the range of 1% to the lower limit of the full flow range (2%) is not guaranteed to be within specification. Note, this error may be estimated by the formula 1.1. below
  4. Medium density measurement range is 200…3000 kg/m3.

Relative basic error of measurement of mass flow (mass) on pulse and digital output signals (δM) calculated as

δM = ± [δ0 + (Z / QM) *100%],

1.1) where δ0 – accuracy class, %;

Z – zero stability (according to Table 1.2), kg/h;

QM – measured mass flow rate, kg/h.

Note – For the accuracy flow range, corresponding to a given accuracy class (according to Table 1.2), the value of Z is assumed to be 0.

Absolute basic error of measurement of medium density (∆ρ) is ± 1 kg/m3.

Absolute basic error of measurement of medium temperature is ± 1 °C.

Additional error of measurement of density, caused by a change of medium temperature is ±0.03 kg/m3 for every 10 ºC of deviation from the density calibration temperature.

Additional error of measurement of density, caused by a change of pressure is ±0.015 kg/m3 for every 100 kPa of deviation from the density calibration pressure.

Relative basic error of measurement of volumetric flow (volume) on pulse and digital output signals (δV) calculated as

δV = ± [δ0 + (∆ρ / ρ) *100% + (Z / QV) *100%],

1.2) where δ0 – accuracy class, %;

∆ρ – absolute basic error of measurement of medium density, kg/m3;

ρ – measured medium density, kg/m3;

Z – zero stability (according to Table 1.2), L/h;

QV – measured volumetric flow rate, L/h.

Note – For the accuracy flow range, corresponding to a given accuracy class (according to Table 1.2), the value of Z is assumed to be 0.

Relative basic error of measurement of mass flow (mass) on current output signal (δIM) calculated as

δIM = ± [|δM| + 0.2*Imax / (4+16*QМ / QМmax)],

1.3) where δM – Relative basic error of measurement of mass flow (mass), %;

Imax = 20 mA – maximum value of current output signal;

QМ – measured mass flow rate, kg/h;

QМmax – upper limit of the full mass flow range, kg/h.

Relative basic error of measurement of volumetric flow (volume) on current output signal (δIV) calculated as

δIV = ± [|δV| + 0.2*Imax / (4+16*QV / QVmax)],

1.4) where δV – Relative basic error of measurement of volumetric flow (volume), %;

Imax = 20 mA – maximum value of current output signal;

QV – measured volumetric flow rate, L/h;

QVmax – upper limit of the full volumetric flow range, L/h.

Additional error of measurement of mass (volumetric) flow rate, caused by a change of medium temperature is ±0.05 % of the maximum flow rate for every 10 ºC of deviation from the zero calibration temperature.

Additional error of measurement of mass (volumetric) flow rate, caused by a change of pressure is ±0.02 % of the maximum flow rate for every 100 kPa of deviation from the zero calibration pressure.

The effect of changes in temperature and pressure can be adjusted by zero calibration under the actual pressure and temperature (see paragraph 2.5.4 Zero point adjustment”).

© 2021, Mag Flow Meter

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