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Example 3.
Calculation of battery capacity
Let's assume we measure temperature, relative humidity and global radiation.
Measuring interval is one minute. Requested autonomy for battery is 7 days.
Now we will calculate power consumption of each component of the system.
For temperature measurement we will use PT100, where excitation current is 1mA
maximum. We need to add delay of 5 second to settle the output.
For relative humidity measurement we can use HumiAir8 sensor. It has power
consumption 6mA max. Again, delay to stabilize output is 5 seconds.
For global radiation measurement we can use a pyranometer. Power consumption is
zero.
Power consumption of LOGBOX SD during measuring period is 5mA, in sleep mode it
is 20uA.
Power consumption during measurement:
1mA + 6mA + 5mA = 12mA
Power consumption during sleep mode:
0+0+0+20uA=20uA
Mean power consumption from the battery:
(12mA x 5s + 0.020mA x 55s)/60s=1.018mA
Number of hours:
24hours x 7days = 168 hours
Required minimum battery capacity:
168hodín x 1,018mA= 1711Ah
4 AA alkaline batteries are recommended for maximal logging time.
Recommendations: The LOGBOX SD data logger is a high precision instrument. For
maximum accuracy apply standard guidelines for low noise operation. Avoid strong
electro magnetical field disturbance (do not install near HF antennas, electrical
motors or generators). Use as short as possible cables. Use shielded cables and
connect shield to ground connection. Proper grounding with maximum shielding is
necessary. With extreme HF disturbance a degraded accuracy can be expected.
Connectors Layout
49
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