Bronkhorst Mini CORI-FLOW - Manual (Page 15)

BRONKHORST CORI-TECH B.V.
Gas and liquid
(mini) Cori-Flows can be used for gases and liquids.
In all instruments capable of density measurement (e.g. mini CORI-FLOW series) there will be an automatic
adjustment for change in density. CORI-FLOW M50-series however, cannot measure density.
For those instruments it is advisable to calibrate them on air for gases and on water for liquids.
Multi-range instrument
Thanks to extremely high linearity of the sensor, (mini) Cori-Flow instruments can be easily re-ranged to a
different full scale range (100% point). The analog output and the digital measured flow value will be scaled to
this FS 100% point.
E.g. An M13 can be used for a full scale between 50 g/h and 2000 g/h.
Switching between these ranges can be realized using fieldbus, E-7000, Bright module or RS232 interface.
There is free tooling software (FlowPlot) available for this purpose. Mini Cori-Flow instruments will get a
calibration certificate for all possible FS ranges. The actual FS of the instrument is set to a value wanted by the
customer and can be found on the gray sticker on the instrument.
Summary
In general: a (mini) Cori-Flow instrument is independent of physical properties.
Performing an auto-zero on actual conditions (with zero flow) before use will get rid of offsets in the sensor.
When these properties, like temperature, pressure, density and dynamic viscosity do not affect the mass in the
tube or the mechanical sensor construction to much, error due to zero-stability will be small.
Environment conditions are important to the mechanical behaviour of the sensor:
• Vibrations (of sensor, rack, pipes etc.) with frequencies or harmonics close to the sensor’s natural
frequency could result in errors in the measurement. Sensor oscillation frequencies vary from 90…450 Hz,
depending on the model.
• Pulsation of supply pressure may have negative influence on accuracy. Avoiding this is the best. Filtering is
an option for improvement.
• Turbulences in flow may add extra noise to the measured value. Especially with high flow of gases straight
pipes with lengths of 20..30 cm. at least are advisable for realizing a more undisturbed flow.
For other applications (e.g. liquids) inlets of about 10x inner diameter of tube are sufficient.
Smooth reducing from wide to small tubes is advisable. See below:
Optimal angle is approx. 7°
• Gas bubbles entrapped in liquids (and/or locked-up in sensor tube) give disturbances to flow
measurement, especially in the lower flow ranges. Try to avoid this and purge with high flow to remove
them.
• Fluid drops in gas flow (and/or locked-up in sensor tube) give disturbances to flow measurement,
especially in lower flow ranges. Try to avoid this and purge with high flow to remove them.
9.17.050 page 15