Answer / sam

Hi there,

This is called a normal wet leg installation. There is no
need to change the HP and LP around when you use a SMART TX.
All SMART Tx can measure in the negative with the same
amount as in the positive. exp: -1600 to +1600mmH2O

Open your manifold vents to atmosphere and do a zero trim,
next close the equalizing valve on the manifold and open HP
line to atmosphere. Fill the LP line until both catch pots
are full and the Glycerin is running out of the top catch
pot into the line going to the top tapping point of the
vessel. At this point let the liquid in the vessel fill the
HP line. Remember to do some draining to make sure there are
no air bubbles. What you need is to have the LP completely
filled with Glycerin and the HP line filled with Vessel
liquid up to the point where the tubing connects to the
vessel(not more). Whatever the transmitter reads now(neg
value)is called an atmospheric zero value(ATM).DO NOT DO A
ZERO TRIM!!
Use this formula to calculate the LRV and the URV

LRV = ATM value + (distance from bottom tapping on the
vessel to 0% point on vessel x the sg of the vessel liquid)
URV = ATM value + (distance from bottom tapping on the
vessel to 100% point on vessel x the sg of the vessel liquid)

LRV and URV UOM must first be in mmH2O if you took these Z/S
measurements in mm. After you install them with the HART you
can change it to whatever UOM you require.

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