When Flow-Mon decided to upgrade its range of locally indicating flow
meters with a remote readout facility, it came up with a novel idea that
involved an internal mechanical modification and the use of miniature
linear potentiometers. As fluid passes through the unit, an integral
analogue indicator needle rotates to display the flow rate. Flow-Mon
designed a special cam arrangement that translates the rotation of this
needle into a linear movement. This movement is tracked by a
Variohm-Eurosensor model 9605 miniature linear potentiometer and the
change in resistance value converted into a 4-20mA signal via the
Flow-Mon unit's integral electronics. This signal provides the remote
readout capability.
The 9605 was originally chosen for its compact size but as it meets the
requirements for 'simple apparatus' classification, it can be used in
hazardous areas when connected via a suitable barrier.