BRONKHORST®
Page 14
EL-FLOW
Base
Series Mass Flow Controllers
9.17.061
2.11 System purging
If explosive gases are to be used, purge the process with inert dry gas like Nitrogen, Argon etc. for at
least 30 minutes.
In systems with corrosive or reactive fluids, purging with an inert gas is absolutely necessary, because if
the tubing has been exposed to air, introducing these fluids will tend to clog up or corrode the system
due to a chemical reaction with oxygen or moist air.
Complete purging is also required to remove such fluids from the system before exposing the system to
air. It is preferred not to expose the system to air, when working with these corrosive fluids.
2.12 Zeroing
The zero point of each instrument is factory adjusted. However, the zero point may shift slightly due to
temperature, pressure, gas type and mounting position influences. If so required, the zero point of the
instrument may be re-adjusted.
Zeroing is possible over RS232 Flowbus, RS485 ModBus or by means of using the micro switch. Zeroing
by means of using the micro switch is described in this manual.
Warm-up, pressure up the system and fill the instrument according to the process conditions.
Make sure no flow is going through the instrument by closing valves near the instrument.
The setpoint must be zero.
Press the micro switch and hold it. After a short time the red LED will go ON and OFF, then the green
LED will go ON. At that moment release the micro switch.
The zeroing procedure will start at that moment and the green LED will blink fast. The zeroing
procedure waits for a stable signal and saves the zero. If the signal is not stable zeroing will take long
and the nearest point to zero is accepted. The procedure will take approx. 10 sec.
When indication is showing 0% signal and the green indication LED is burning continuously again,
then zero has been performed well.
For information how to start the zeroing procedure over RS232 FlowBus or RS485 ModBus check
chapter 4.1.4, “Auto Zeroing”
