Flow computer built-in
Many KROHNE flowmeters have a built-in flow computer that compensates for the effects of pressure and temperature on the flow measurement or to convert to standard volume. This saves both cost and installation efforts for an external flow computer and provides for additional benefits.
Why should I have a pressure and temperature compensated volume measurement?
As changes in pressure and temperature have physical effects on fluid volumes, they also affect the volume flow measurement. To be able to compare fluid volumes under different pressure and temperature conditions, the flow values measured under operating conditions are converted to “standard” or “normal” conditions; for example standard conditions for SI units are 15°C and 101.3250 kPa (abs) where normal conditions are 0°C and 101.3250 kPa (abs) .
This of course requires measuring both the temperature and pressure conditions under which the flow measurement is performed, and to feed these values into a flow computer that calculates from operating to standard flow conditions and standard volume.
Benefits of a built-in flow computer
The flow computer used for this calculation can either be an external device or be integrated (built-in) into the electronics of the flowmeter. For example, the ultrasonic flowmeters OPTISONIC 7300/8300 can be equipped with two current inputs to connect external pressure and temperature sensors.
The vortex flowmeter OPTISWIRL 4200 has an integrated temperature sensor as standard. Therefore, the temperature information of the medium is anytime available. Via the additional 4...20 mA input, an external temperature or pressure sensor can be connected to allow pressure compensation or net heat quantity measurement. For an easy installation, there is also a version available which has both sensors integrated. This saves approx. 45% of installation costs, and the high level of integration also provides a better overall system accuracy:
with the classic installation of a vortex flowmeter and separate pressure sensor, temperature sensor and flow computer, all errors occurring in the measuring chain must be taken into account when determining system accuracy.
This can result in a measuring error between ±3...5 %. Using the OPTISWIRL 4200 with integrated pressure and temperature compensation not only allows you to lower installation cost, but also increase the measuring accuracy of the measuring point to ±1.5 % of the measured value.