Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 397)

397
Section 9. Maintenance
Temperature and humidity can affect the performance of the CR800. The internal
lithium battery must be replaced periodically.
9.1 Moisture Protection
When humidity tolerances are exceeded and condensation occurs, damage to
CR800 electronics can result. Effective humidity control is the responsibility of
the user.
Internal CR800 module moisture is controlled at the factory by sealing the module
with a packet of silica gel inside. The desiccant is replaced whenever the CR800
is repaired at Campbell Scientific. The module should not be opened by the user
except to replace the lithium coin cell providing back up power to the clock and
SRAM. Repeated disassembly of the CR800 will degrade the seal, leading to
potential moisture problems.
Adequate desiccant should be placed in the instrumentation enclosure to prevent
corrosion on the CR800 wiring panel.
9.2 Replacing the Internal Battery
Caution Fire, explosion, and severe-burn hazard! Misuse or improper
installation of the lithium battery can cause severe injury. Do not recharge,
disassemble, heat above 100°C (212°F), solder directly to the cell, incinerate, or
expose contents to water. Dispose of spent lithium batteries properly.
The CR800 contains a lithium battery that operates the clock and SRAM when the
CR800 is not powered. The CR800 does not draw power from the lithium battery
while it is powered by a 12-Vdc supply. In a CR800 stored at room temperature,
the lithium battery should last approximately 3 years (less at temperature
extremes). In installations where the CR800 remains powered, the lithium cell
should last much longer.
While powered from an external source, the CR800 measures the voltage of the
lithium battery daily. This voltage is displayed in the Status table (see the
appendix Status Table and Settings
(p. 505)
). A new battery supplies approximately
3.6 Vdc. The CR800 Status table has a Lithium Battery field. This field shows
lithium-battery voltage. Replace the battery when voltage is approximately 2.7
Vdc. If the lithium cell is removed or allowed to discharge below the safe level,
the CR800 will still operate correctly while powered. Without the lithium battery,
the clock will reset and data are lost when power is removed.
• The CR800 is partially disassembled to replace the lithium cell. See figure
Loosening Thumbscrews
(p. 398)
through figure Remove and Replace Battery
(p.
400).
When the lithium battery is removed, the user program and most settings
are maintained. Items not retained include
o Run-now and run-on power-up settings.
o Routing and communications logs (relearned without user intervention).