Campbell CR3000 Micrologger, Руководство оператора

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Section 5. Overview
77
measurement interval, as compared to pulse count measurements. The
frequency resolution of pulse count measurements can be improved by
extending the measurement interval by increasing the scan interval and by
averaging. For information on frequency resolution, see Frequency
Resolution
(p. 409).
5.2.5 Vibrating Wire Measurements — Overview
Related Topics:
• Vibrating Wire Measurements — Specifications
• Vibrating Wire Measurements — Overview
(p. 77)
• Vibrating Wire Measurements — Details
(p. 417)
Vibrating wire sensors are the sensor of choice in many environmental and
industrial applications that need sensors that will be stable over very long periods,
such as years or even decades. The CR3000 can measure these sensors either
directly or through interface modules.
A thermistor included in most sensors can be measured to compensate for
temperature errors.
Measuring the resonant frequency by means of period averaging is the classic
technique, but Campbell Scientific has developed static and dynamic spectral-
analysis techniques (VSPECT
(p. 562))
that produce superior noise rejection, higher
resolution, diagnostic data, and, in the case of dynamic VSPECT, measurements
up to 333.3 Hz.
SE terminals are configurable for time-domain vibrating wire measurement,
which is a technique now superseded in most applications by VSPECT
(p. 562)
vibrating wire analysis. See Vibrating Wire Input Modules — List
(p. 605)
for more
information
Dynamic VSPECT measurements require addition of an interface module.
5.2.6 Reading Smart Sensors — Overview
Related Topics:
• Reading Smart Sensors — Overview
(p. 77)
• Reading Smart Sensors — Details
(p. 419)
A smart sensor is equipped with independent measurement circuitry that makes
the basic measurement and sends measurement and measurement related data to
the CR3000. Smart sensors vary widely in output modes. Many have multiple
output options. Output options supported by the CR3000 include SDI-12
(p. 255),
RS-232
(p. 303),
Modbus
(p. 476),
and DNP3
(p. 475).
The following smart sensor types can be measured on the indicated terminals:
•
SDI-12 devices: C
•
Synchronous Devices for Measurement (SDM): C