Instruction manual

SECTION 2. STATION INSTALLATION
2-7
Be sure the 21X has a good earth ground, to
protect against primary and secondary lightning
strikes. The purpose of an earth ground is to
minimize damage to the system by providing a
low resistance path around the system to a
point of low potential. Campbell Scientific
recommends that all dataloggers in the field be
earth grounded. All components of the system
(datalogger, sensors, external power supplies,
mounts, housing, etc.) should be referenced to
one common earth ground.
TABLE 2.7-1. External Battery Connections
for Example Program
Terminal Sensor
Color
Pos (+) CA27 (power) Red
KH20 (power) Red
21X (+12, see note) User
Supplied
Neg (-) CA27 (power) Black
KH20 (power) Black
21X (ground) User
Supplied
2.8 ROUTINE MAINTENANCE
Check the 127 on a daily basis. If the 127 is
broken, replace it.
Inspect the 127 for spider webs. Carefully blow
away any spider webs with a can of
compressed air. Do not put the thermocouple
junction directly in the air stream from the can
because the junction may break. Direct the air
stream to the side of the junction.
If the system is running “windows clean”, clean
the windows with a moistened swab. Set flag 1
high to disable averaging. Use only distilled
water to moisten the swab. With a fresh swab,
dry the windows after cleaning. Set flag 1 low to
resume averaging.
CAUTION: Never look directly into the
KH20 source tube (the larger of the two
tubes).
Check the net radiometer domes for dirt and
debris. A camel’s hair brush, with bellows for
blowing off dust particles such as those used in
cleaning photographic negatives, can be used
without fear of scratching the domes.