Minimizing Power-Related Artifacts - Campbell CR300 Series Product Manual

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17.11.3 Minimizing power-related artifacts

Some VAC-to-VDC power converters produce switching noise or AC ripple as an artifact of the
ac-to-dc rectification process. Excessive switching noise on the output side of a power supply can
increase measurement noise, and so increase measurement error. Noise from grid or mains
power also may be transmitted through the transformer, or induced electromagnetically from
nearby motors, heaters, or power lines.
High-quality power regulators typically reduce noise due to power regulation. Using the 50 Hz or
60 Hz first notch frequency (f
often improves rejection of noise sourced from power mains. The CRBasic standard deviation
output instruction, StdDev(), can be used to evaluate measurement noise.
The data logger includes adjustable digital filtering, which serves two purposes:
Arrive as close as possible to the true input signal
l
Filter out measurement noise at specific frequencies, the most common being noise at 50
l
Hz or 60 Hz, which originate from mains-power lines.
Filtering time is inversely proportional to the frequency being filtered.
Minimizing offset voltages
) option for CRBasic analog input measurement instructions
N1
(p. 147).
17. Tips and troubleshooting 140