Tokyo Keiki UFL-30, Installation & Operation Manual

Page: 159 / 166

III- 50
4.4 Can sensors be buried in the ground?
When pipes are laid underground, sensor mounting position is susceptible to shifting due to soil
pressure. In addition, if a problem occurs sensors must be dug out which poses maintenance
problems. As such standard specification transducers cannot be buried.
However there are optional sensors which employ special specification fixtures which allow use in
buried applications. There are restrictions to their use however, so please consult Tokyo Keiki.
4.5 How far apart can the flowmeter unit and transducers be placed?
Coaxial cable is used to connect the main flowmeter electronic unit to the transducers. Coaxial
cable length is limited to 300m. However installation should also take into consideration external
noise interference.
4.6 Why is a special trough needed for laying of coaxial cable?
Receiving signals of the sensors are very weak electrical signals and they are as such susceptible
to interference from other equipment. In addition to signal interference from power supply lines
and output signal lines, interference via coaxial cables is a principal cause of problems. Main
causes of signal interference include the following.
(1) High current lines which emit noise pulsations. Examples are power transmission lines which
open and close valves which run parallel to the coaxial cables.
(2) Broadcasting signals are normally not a problem, but if the cables are located directly below
such stations, for example, noise interference may result.
(3) AC equipment (motors), etc. are normally not a problem, but as described above, there may be
interference caused during the opening and closing of circuits
(4) Rectifier equipment, etc., may also cause problems. (The flowmeter itself should not be
located nearby to a rectifier.)
4.7 Can the coaxial cables be suspended in the air?
Compared to buried cable, suspended cable is more susceptible to exogenous noise. As such
installation also exposes the cable to lightning and thunder, coaxial cables should not be
suspended aerially.
4.8 What are the recommended installation locations for the main flowmeter electronics unit?
The main flowmeter unit should be located where humidity is minimum and where it is not exposed
to corrosive gases such as chloride or to direct sunlight. An air conditioned room is ideal but
please select a site which falls within a basic air temperature range of -10 to +60°C.
If the flowmeter is be located on site, it should be placed in a chamber, pit or enclosure.
Environmental conditions should be taken into consideration with measures such as interior
enclosure insulation and installation of a ventilation fan as necessary.
Equipment is NOT EXPLOSION PROOF, so the flowmeter must not be located in an explosive
environment.