Bronkhorst®
Instruction Manual mini CORI-FLOW™ M1x
9.17.050O
18
3.6
Valve Safe State
When a controlling instrument is not powered or cannot communicate with the fieldbus network (if applicable), all electrical
valves operated by the instrument (whether integrated or external) automatically return to their default state. The default
state is closed for 'normally closed' valves (n/c) and fully open for 'normally open' valves (n/o). Taking into account the
typical process conditions under which the instrument is used (such as the processed media and ambient conditions; see
also
), the default state is generally considered safe.
Check the serial number label or the technical specifications to see which valve type is used on your instrument (if
applicable).
3.7
Temperature considerations
Although the mini CORI-FLOW has excellent temperature stability, the best accuracy is achieved when temperature
gradients within and across the instrument are avoided. Take the following guidelines into account:
·
To avoid simultaneous heating and cooling of different parts of the instrument, make sure the ambient temperature is
as stable and evenly distributed across the environment as possible.
·
Avoid temperature shocks; heating or cooling should amount to no more than 1 °C per second.
·
Make sure that the media temperature matches the ambient temperature as closely as possible.
·
The mini CORI-FLOW will show an amount of self heating, due to power dissipation of the electronics. This effect can be
as large as approximately 15 °C (depending on media and ambient temperature). In practice, there will be a balance
between media temperature, self heating and ambient temperature.
·
Operation in a cool environment can compensate somewhat for the effect of high media temperatures.
·
Heating and cooling effects will also depend on the cooling/heat conducting capacities of the installation itself on which
the instrument is mounted.
·
To prevent damage to the electronics, make sure the temperature in the housing never exceeds 70°C. To monitor this,
the internal temperature reading can be used (parameter
).
·
The storage temperature should lie between -30 and 80 °C. Make sure the measuring tube is purged and dry before
storing the instrument.
Temperature build-up
The temperature in the instrument housing is largely determined by the media temperature (T fluid) and the ambient
temperature (T ambient). Although these temperatures cannot simply be added up to calculate the internal temperature,
they do amplify each other. Taking the self heating effect of the electronics into account, some rules of thumb can be
defined for the maximum temperatures and their sum to observe. The graph below illustrates these; the area below each
line represents the safe temperatures for the according instruments or circumstances.
