SECTION 14. INSTALLATION AND MAINTENANCE

System operating time for the batteries can be determined by dividing the battery capacity (amp-hours) by the average system current drain. The CR10 draws <1 mA in the quiescent state, 13 mA while processing, and 46 mA during an analog measurement; the length of operating time for each datalogger instruction is listed in the programming section. Typical current requirements for common CR10 peripherals are given in Table 14.2-1.

14.3CAMPBELL SCIENTIFIC POWER SUPPLIES

The PS12 Power Supply is available from Campbell Scientific with either alkaline or lead acid batteries, the PS12ALK and PS12LA, respectively. The PS512M is also a lead acid supply with two 9-pin null modem ports for communication modems, see Section 14.3.3. The PS12ALK has 8 D cell alkaline batteries, the PS12LA has a rechargeable lead acid battery. The alkaline batteries are discarded after use. The lead acid batteries should be float charged with either AC power or a solar panel. The lead acid battery supplies power during a power failure or in times of low charge with a solar panel.

The CH12R and CH512R contain the same circuitry as the PS12LA and PS512M, respectively. They are used to float charge an external 12 VDC Yuasa battery using AC or solar power. No internal batteries are contained in the CH12R and CH512R. Their operation, however, is identical to that of the PS12LA and PS512M. Other power supply options are connecting a 12 volt battery directly to the CR10, Section 14.5, or supplying power from a vehicle, Section 14.6.

The PS12 Power Supply provides 12 volts, regulates incoming AC or DC power, limits current from the battery, and provides circuitry to connect an external 12 volt battery. The terminals on the PS12 are exposed by unscrewing the two set screws, as shown in Figure 4.3-1.

The two 12 volt and two ground terminals are for supplying power to the datalogger, or other 12 volt devices.

The two terminals, labeled CHG, are for connecting a 20 VDC adapter or solar panel to charge lead acid batteries.

The charge input can be either AC or DC, and it does not matter which terminal is positive or negative. The voltage input must be within 16 to 26 VDC, or 16 to 26 VAC RMS.

The ON-OFF switch controls power to the 12 V ports. Charging of lead acid batteries still occurs when the switch is off. The red charge light is on when a charging source is connected to the power supply.

The connectors labeled INT and EXT are for connecting the internal (power supply) battery and an external battery, respectively. A five foot cable, with connector, is included with the power supply for connection to an external battery. This is commonly used for supplying power to the datalogger while changing power supply batteries.

A thermal fuse in the power circuit limits source current. 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, eventually allowing current to pass. When excessive current is drawn due to shorting the power leads to the Wiring Panel, allow 10 to 15 seconds for the fuse to cool before connecting power.

14.3.1 PS12ALK ALKALINE POWER SUPPLY

The PS12ALK utilizes 8 alkaline D cells mounted in place of the lead acid battery shown in Figure 14.3-1. The PS12ALK can also be used with a lead acid battery connected to the external battery port, in this case the alkaline batteries act as a backup.

Before installing the alkaline batteries, connect all necessary sensor leads, control lines, and power leads. The CR10 can be turned on and off with the switch on the PS12ALK.

To replace the batteries without losing the datalogger program and data: 1) do not turn the power switch off, 2) connect an external battery to the port labeled EXT with the supplied 6 foot cable, 3) remove the old batteries, 4) replace with new alkaline D cell batteries, and 5) remove the external battery.

A fresh set of eight alkaline D cells has 12.4 volts and a nominal rating of 7.5 amp-hours at 20°C. The amp-hour rating decreases with temperature as shown in Table 14.3-1. Datalogger Instruction 10 can be used to

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