4.1 Mounting ST 3000 Transmitter, Continued
ATTENTION
The mounting position of a model STA122 or STA922 Absolute
Pressure Transmitter or a model STD110 Draft Range Differential
Pressure Transmitter is critical as the transmitter spans become smaller.
A maximum zero shift of 2.5 mm Hg for an absolute transmitter or 1.5
in H
2
O for a draft range transmitter can result from a mounting position
which is rotated 90 degrees from vertical. A typical zero shift of 0.12
mm Hg or 0.20 in H
2
O can occur for a 5 degree rotation from vertical.
Precautions for
Mounting
Transmitters with
Small Absolute or
Differential Pressure
Spans
To minimize these positional effects on calibration (zero shift), take the
appropriate mounting precautions that follow for the given transmitter
model.
For a model STA122 or STA922 transmitter, you must ensure that the
transmitter is vertical when mounting it. You do this by leveling the
transmitter side-to-side and front-to-back. See Figure 6 for suggestions
on how to level the transmitter using a spirit balance.
Figure 6 Leveling a Model STA122 or 922 Absolute Pressure Transmitter.
Models STA122 and STA922
Center
Section
Process
Head
Position spirit balance on
center section of meter
body only.
Continued on next page
2/05 ST 3000 Release 300 Installation Guide
27
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