Xylem Ai1 Product Manual page 35

through a color indicating desiccant pack
which is measured several hours after the Ai1 is sealed. When planning maintenance visits if the humidity is above
50% the pack must be replaced.
The internal desiccant pack can be easily recharged by placing in an oven set to 118°C (245°F)
for approximately 5 hours. Do not go over this temperature or the packaging of the desiccant
may be damaged. Do not use a microwave. Higher heats will damage the housing and the
desiccant itself. Shorter times may be applicable if you can confirm the desiccant is recharged,
via one of two methods.
•
Method 1: Remove the pack
from the oven and hold against
a glass or mirror. After 10s look
for condensation on the surface
and if present, continue to oven
dry.
•
Method 2: Weigh the pack
periodically. While the weight
decreases, continue to oven
dry. Most of the drying will
occur during the first hour,
however the pack should
continue to be dried for the full
duration to ensure maximum
effectiveness. The dry weight of
the pack is approximately 19g but can increase to 22 to 23g when at full capacity.
Current Sensor
The current sensor provides an indication to the current draw to or from the battery which is viewed from the
Current_mA public variable. Charging current (i.e., when the solar panels are in sunlight) will be negative while
discharging current (i.e., sensors or communications active in high current) will be positive. The current sensor
should only be used as an indicator for large currents as it is only accurate to approximately 20 to 40mA depending
on temperature. As the Ai1 takes the current sensor measurement while it is active (i.e., not in low power sleep) the
current is typically 20 to 25mA higher than during the datalogger sleep phase. The current sensor is particularly
useful to see when the battery is fully charged as the charging current will drop to near zero. The time of day that
this normally occurs can be used to judge solar panel effectiveness over long periods of time.
If the current sensor indicates approximately -3000mA then the Ai1 is likely off and the current sensor is running
from USB power (when excitation ports provide 2.5V instead of 5V). If the current sensor indicates approximately -
6000mA then the current sensor is not powered (i.e., excitation port is 0V) which indicates a software problem such
as another device turning off the excitation port.
GPS
The internal GPS is used to update location information (not for time setting which is recommended through
Eagle.io).
11
Original Ai1's used blue(good)/pink(bad) indicating desiccant
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11
. It is recommended to replace the desiccant if humidity is above 40%
(cobalt chloride) but now use non-toxic orange(good)/green(bad), suitable for use in the EU.