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• Zero Adjust (4-20 mA, 0-5 VDC, and 0-10 VDC only)
The zero output (4mA, or 0 VDC) can be adjusted by holding a magnet perpendicular to the can,
approximately 1-1/2” from the top or bottom of the can.
Holding the magnet close to the top of the can increases the output (See Figure 3.1). Holding the magnet
close to the bottom of the can decreases the output (See Figure 3.2).
If the zero output values do not change right away, hold the magnet in place near the top of the can until
the values change, for up to two minutes. If there is no change, repeat the procedure near the bottom of the
can. If there is still no change, consult the factory.
Unvented PT-500A transmitters do not automatically adjust to changes in barometric pressure. We recom
-
mend that PT-500A transmitters be zeroed upon receipt, and after major weather events.
Condensation in the vent tube can damage the electronics in your sensor, resulting in unreliable readings.
APG offers two methods of preventing vent tube condensation: a venting cap, and a desiccant drying
cartridge.
The venting cap is a PVC tube with a hydrophobic patch that allows moisture to pass out of the tube without
allowing water in (See Figure 3.3). The cap is sealed by an o-ring, and is easily installed in the field.
The desiccant drying cartridge with vent tube adapter absorbs any moisture in the vent tube to keep vapor
from condensing (See Figure 3.4). The installation of the desiccant drying cartridge is quick and easy.
Common installation methods are cable tie, Velcro, and cable clamps.
•
Vent Tube Drying
NOTE
: Span calibration must be done at the factory for all analog models.
Figure 3.1
Figure 3.2
