Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 82)

Section 7. Installation
82
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 worst-
case 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. 425)
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. 269)
) often improves
rejection of noise sourced from power mains. The CRBasic standard deviation
instruction, SDEV(), can be used to evaluate measurement noise.