For additional information, see
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
N1
)
option for CRBasic analog input measurement instructions
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:
l
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
Hz or 60 Hz, which originate from mains-power lines.
Filtering time is inversely proportional to the frequency being filtered.
17. Tips and troubleshooting
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