Bronkhorst Mini CORI-FLOW - Manual (Page 12)

BRONKHORST CORI-TECH B.V.
1.4 Software for physical properties of gases and liquids.
Bronkhorst has access to the physical properties of over 600 fluids in a database called FLUIDAT.
Application software, such as FLOW CALCULATIONS, enables the user to calculate properties, not only at
20°C / 1 atm but also at any temperature/pressure combination, both for gases and for liquids.
Apply to your distributor for more details about this software.
1.5 (mini) Cori-Flow accuracy
Zeroing of a (mini) Cori-Flow instrument is required each time process conditions have been changed.
What is zero-stability ?
Due to mechanical construction of the sensor tubes each (mini) Cori-Flow sensor will have a very small offset
signal, even when the mass flow is zero. This is called the zero-stability error and is specified for accuracy
separately for all Coriolis instruments. Main reason for this is the fact that this error can be (temporarily)
neutralized after performing a zero-action.
Immediately after zeroing, zero-stability error is 0%. However, it is allowed to move between a certain band
depending on the environment (process) and fluid conditions.
In ideal situations, where actual process conditions do not change, this error will remain the same.
See below for possible reasons of change of zero-stability. See also paragraph 3.4.1. to learn how to zero.
Zero-stability depends on the (mini) Cori-Flow model:
Model DN (mm) Zero-stability Nominal flow
M12 0.25 < 0.1 g/h 100 g/h
M13 0.5 < 0.2 g/h 1 kg/h
M14 1.3 < 6 g/h 10 kg/h
M15 3.12 < 50 g/h 100 kg/h
M53 1 < 10 g/h 5 kg/h
M54 2 < 50 g/h 50 kg/h
M55 4 < 100 g/h 500 kg/h
Nominal flow: mass flow rate of liquid at a pressure drop of approx. 1 bar and based on
reference conditions of water at approx. 20 °C
NOTE:
In practice zero-stability turns out to be better than the values in the table, but for calculation we will take worst
case values.
Accuracy
The accuracy of a (mini) Cori-Flow is either 0.2% reading for liquids or 0.5% reading for gases.
This specification is based on mass flow (e.g. g/h, kg/h, etc.). If the instrument will be used on volume flow
(e.g. l/h, ml/min, etc) this will introduce an extra inaccuracy, based on the density (measurement).
Process conditions
Each time process conditions have been changed significantly a (mini) Cori-Flow needs to be zeroed in order
to get rid of the offset error due to zero-stability. At least the very first time an instrument is used a zero
procedure will be required.
The zero-stability error will mainly change when one or more of the following items change significantly:
• Temperature (of fluid or environment)
• Pressure
• Density of fluid
• Vibrations working on instrument via environment
• Pulsation of supply pressure working on instrument
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