Campbell Scientific CR3000 CR3000 Micrologger - Page 82
Power Sources
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Section 7. Installation Figure 29: Enclosure 7.4 Power Sources Note Reliable power is the foundation of a reliable data-acquisition system. When designing a power supply, consideration should be made regarding worstcase power requirements and environmental extremes. For example, the power requirement of a weather station may be substantially higher during extreme cold, while at the same time, the extreme cold constricts the power available from the power supply. Be aware that some ac-to-dc power converters produce switching noise or ac ripple as an artifact of the ac-to-dc rectification process. Excessive switching noise or ac (p. 449) ripple present on the output side of a power supply can increase measurement noise, and so increase measurement error. In addition to transformers and regulators, noise from grid or mains power may be transmitted through the transformer, or induced by electro-magnetic waves originating in nearby motors, heaters, or power lines. High-quality power regulators typically reduce noise due to power regulation. Utilizing the optional 50-Hz or 60-Hz rejection arguments for CRBasic analog input measurement instructions (see Sensor Support (p. 279) ) often improves rejection of noise sourced from power mains. The CRBasic standard deviation instruction, SDEV(), can be used to evaluate measurement noise. 82
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