GF U3000 V2 Betriebsanleitung Seite 13

User Manual
3.4.2 Menus and the menu selection keys
The GF U3000 V2 (HM) menus are arranged hierarchically with the MAIN MENU being at the top level. Menu navigation is achieved
by three keys on the right hand side of the keypad which are used to scroll UP and DOWN a menu list and SELECT a menu item.
When scrolling through a menu an arrow-shaped cursor moves up and down the left hand side of the screen to indicate the active
menu choice which can then be selected by pressing the ENTER (SELECT) key.
Some menus have more options than can be shown on the screen at the same time, in which case
the 'overflowed' choices can be brought into view by continuing to scroll DOWN past the bottom
visible item. Menus generally 'loop around' if you scroll beyond the first or last items.
If you select Exit it usually results in taking you back one level in the menu hierarchy, but in some cases it may go directly to the
'Flow Reading' screen.
Some screens require you to move the cursor left and right along the display as well as up and
down. This is achieved using keys 5 (scroll LEFT) and 6 (scroll RIGHT).
3.4.3 Dual function numerical keypad
The block of keys shown in the centre of the keypad in the figure below are dual function keys. They can be used to enter
straight-forward numerical data, select the displayed flow units or provide quick access to frequently required control menus.
3.4.4 Transducers
Two sets of ultrasonic transducers are provided as standard. When setting up the instrument it will indicate the appropriate
transducer set to use for a particular application, depending on data entered by the user. Default pipe ranges are programmed
into the instrument and most of the time there will be no need to use an alternative transducer set to the one suggested by
the instrument. However, if circumstances dictate that a different set must be used it is possible to manually programme the
instrument to accept the alternative set.
Transducer set 'A'
Supplied as standard for use on pipes 13mm to 115mm outside diameter.
Transducer set 'B'
Supplied as standard for use on pipes 50mm to 2000mm outside diameter.
3.4.5 Principle of operation
The flowmeter takes accurate flow measurements by determining the difference between the transmission times of two ultrasonic
signals
A periodic voltage pulse acts on the transducer crystals and produces an ultrasonic beam at a
certain frequency. The beam is first transmitted by the downstream transducer (blue) to the
upstream transducer (red).
The beam is then sent in the opposite direction, i.e. from the upstream transducer (red) to the
downstream transducer (blue). The time taken for the ultrasonic to pass through the liquid in this direction is slightly shortened by
the speed at which the liquid flows through the pipe.
The resulting time difference T1 – T2 is directly proportional to the speed at which the liquid flows through the pipe.
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T1
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T1-T2=m/s
T2
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Principle of
Design and function
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