Answer / rizwan afzal

Suppression.If transmitter is installed in such
configuration that positive pressure is acting on the HP
side even when level in tank is zero. Such as Tx is
installed below datum point then head pressure of impulse
line is always acting on the HP side of the Tx even if tank
is empty, to componsate that head pressure a -ve biasing is
applied which is equal to the head pressure.
IN OTHER WORDS the LRV of Tx is kept at +ve pressure(equal
to head pressure causing error), so that Tx should give 4mA
at that head pressure.


Elevation.If transmitter is installed in such configuration
that positive pressure is acting on the LP side(DP is in -
ve value when level in tank is zero). Such as Tx is
installed in wet leg configuration then head pressure of
wet leg is always acting on the LP side of the Tx (even if
tank is empty), to componsate that head pressure a +ve
biasing is applied.
IN OTHER WORDS the LRV of Tx is kept at -ve pressure(equal
to head pressure causing error), so that Tx should give 4mA
at that head pressure.
Or to keep range in +ve, Tx can be installed in such manner
that LP side is connected with datum point and HP side with
Wet leg.

Answer / ayaz

this term use for only when the transmitter mounting on up level on hp side or low level of hp side 
when transmitter mount above on hp side tapping is called the transmitter is zero elevation 
when transmitter installed below on hp side tapping is called the transmitter is suppression

Answer / r_vaya

Zero suppression: when a static head transmitter is installed below the zero liquid level, the transmitter gets a +ve error in the level measurement. This error is corrected  by a zero suppression method.


Zero elevation: when a static head transmitter is installed above the zero liquid level, the transmitter gets a –ve error in the level measurement. The error is corrected by a zero elevation method.

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