Operator`s manual

14-1
SECTION 14. INSTALLATION AND MAINTENANCE
14.1 PROTECTION FROM THE
ENVIRONMENT
The normal environmental variables of concern
are temperature and moisture. The standard
21X is designed to operate reliably from -25 to
+50
o
C (-55 to +80
o
C, optional) in
noncondensing humidity. When humidity
tolerances are exceeded, damage to IC chips,
microprocessor failure, and/or measurement
inaccuracies due to condensation on the
various PC board runners may result. Effective
humidity control is the responsibility of the user.
The 21X is not hermetically sealed. Two half
unit packets of DESI PAK desiccant are located
by the batteries. This desiccant should, in most
cases, keep the interior components dry
between battery changes. A dry package
weighs approximately 19 grams and will absorb
a maximum of six grams of water at 40%
humidity and 11 grams at 80%. Desiccant
packets can be dried out by placing the packets
in an oven at 120
o
C for 16 hours (desiccant
only, not the 21X).
Campbell Scientific offers two enclosures for
housing a 21X and peripherals. The fiberglass
enclosures are classified as NEMA 4X (water-
tight, dust-tight, corrosion-resistant, indoor and
outdoor use). A 1.25" diameter entry/exit port is
located at the bottom of the enclosure for
routing cables and wires. The enclosure door
can be fastened with the hasp for easy access,
or with the two supplied screws for more
permanent applications. The white plastic
inserts at the corners of the enclosure must be
removed to insert the screws. Both enclosures
are white for reflecting solar radiation, thus
reducing the internal enclosure temperature.
The Model ENC 10/12 fiberglass enclosure
houses the 21X and one peripheral such as a
Storage Module. Inside dimensions of the ENC
10/12 are 12"x10"x4.5", outside dimensions are
16"x11.5"x7" (with brackets); weight is 8.5 lbs.
The Model ENC 12/14 fiberglass enclosure
houses the 21X and one or more peripherals.
Inside dimensions of the ENC 12/14 are
14"x12"x5.5", outside dimensions are
18"x13.5"x8.13" (with brackets); weight is 11.16
lbs.
TABLE 14.2-1. Typical Current Drain for Common 21X Peripherals
Typical Current Drain (mA)
Peripheral Quiescent Active
RC35 Cassette 0 300
P50-VHF 5 Watt Radio 18 1350
P50-UHF 4 Watt Radio 15 1100
RF95 RF Modem 1.4 30
SM192/SM716 Storage Module 0.25 3
MD9 1.2 80
RAD Modem and SC932 Interface 2.2 10-15
DC112 Phone Modem 0.002 45
SDM-A04 10.5 --
SDM-CD16 6.0 11/LED lit
SDM-INT8 0.4 6.5
SDM-SW8A 3 6