Campbell Scientific CR3000 Micrologger - Manual (Page 84)

Section 7. Installation
84
7.4.3.2 Internal Batteries
Internal-power supplies have a thermal fuse that limits source current and
minimizes the need for repair. If excessive current is drawn, the fuse gets hot,
increases in resistance, and limits current. When the problem is fixed, the fuse
cools and the resistance decreases, usually allowing current to eventually pass.
When excessive current is drawn, as will occur when shorting a 12-Vdc lead to a
ground terminal, allow 10 to15 seconds for the fuse to cool before reconnecting
power.
A thermal fuse in the alkaline base will allow a current drain of 1.85 A at 20°C
(1.3 A at 50°C). In event of a short, the thermal fuse will cut power after about 40
seconds.
7.4.3.2.1 Alkaline Battery Base
Consult the appendix Power Supplies
(p. 566)
for models and part numbers of power
supplies available from Campbell Scientific. The most current information is
found at www.campbellsci.com.
The alkaline battery base includes 10 alkaline, D-cell batteries. Suggested
temperature range for use is -25° to +50°C. A fresh set of high-quality cells has
an approximate voltage of 15.5 Vdc and about 10 ampere-hours of power reserve
at 20°C. Ampere-hour rating decreases with temperature as shown in table
Alkaline Battery Service and Temperatures
(p. 85).
CRBasic instruction Battery()
is used to measure battery voltage. Replace the alkaline cells before the voltage
drops below 11 Vdc.
If external power is connected to a CR3000 with an alkaline base, power will be
drawn from the source of highest voltage. In a configuration wherein an external,
float-charged sealed-rechargeable battery is connected, the alkaline base will lose
approximately 35% of its capacity before the external supply becomes the highest
voltage source, and therefore the primary power source.
Installing New Alkaline Batteries
Install new batteries with the following procedure:
1. Position the power switch on the side of the base to OFF.
2. Loosen the two knurled thumbscrews at the lateral edges of the datalogging
module face.
3. Disconnect the green terminal strips from the wiring panel, if necessary.
4. Carefully separate the datalogging module from the base, unplugging the
white connector that connects the module to the base. The connector is located
just under the lower-left lip of the datalogging module, near the ground lug. A
small lever on the side of the connector must be depressed before pulling it out.
5. Install new alkaline batteries with orientation as shown in figure Alkaline
Battery Orientation
(p. 85).
6. Reconnect the white power connector to the datalogging module. Re-seat the
module and tighten down the knurled thumbscrews. Re-seat the terminal strips if
necessary.
7. Switch the power switch to ON.