CRVW3 3-Channel Vibrating-Wire Datalogger
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Channel 1, Channel 2, Channel 3 – Excitation Voltage
This setting controls how much electrical excitation energy is inserted into the
vibrating-wire sensor just before being measured for its natural frequency. The
excitation waveform is a frequency-rich sweep, containing frequencies from
the lowest to the highest desired frequencies required for the sensor being
measured. The amplitude of the input sweep waveform is controlled by this
setting. Amplitudes of 2 V, 5 V, and 12 V can be selected. Longer cable
lengths between a sensor and the CRVW3 may require a higher voltage setting.
Sensors measured on a 3 second or shorter interval may require the lowest
(2 V) voltage setting to avoid loss of resolution.
Channel 1, Channel 2, Channel 3 – Begin Frequency
This setting controls the lower frequency boundary that is used for the
excitation sweep waveform. It also controls the high-pass digital filtering that
is used on the measurement of the sensor. Any frequency detected on the
sensor lower than this value will be ignored during processing.
Refer to your sensor documentation for guidance on what frequencies can be
expected from your sensor during both usual and extreme environmental
conditions. Sensors measured on a 3 second or shorter interval should use as
narrow of a window as possible (i.e., minimize the range between Begin
Frequency and End Frequency) to avoid a loss of resolution.
Channel 1, Channel 2, Channel 3 – End Frequency
This setting controls the higher frequency boundary that is used for the
excitation sweep waveform. It also controls the low-pass digital filtering that is
used on the measurement of the sensor. Any frequency detected on the sensor
higher than this value will be ignored during processing.
Channel 1, Channel 2, Channel 3 – Thermistor Enabled
Set this setting to
True
if you have connected a built-in resistive temperature
device from your sensor. If the temperature sensor is a thermistor that follows
the Steinhart-Hart scaling equation, you can also specify the proper coefficients
A, B, and C (given as the three settings following the
Thermistor Enabled
setting). This will result in a temperature output in units of Degrees Celsius.
Setting the three coefficient values to zero will result in only the resistance in
Ohms being given as an output from the temperature sensor. Refer to your
sensor documentation to confirm whether the temperature sensor follows the
Steinhart-Hart equation, and also to obtain the three coefficients to be used
(A,B,C).
Channel 1, Channel 2, Channel 3 – Calculate Engineering Output
Use this setting if output in engineering units is desired. The basic
measurement outputs given by the CRVW3 are sensor frequency (including
digits) and sensor temperature (if a thermistor is used). It is possible to
calculate a reading or output that is specified in engineering units (units of
measure or dimensions) using frequency/digits and temperature as the inputs.
The CRVW3 implements a polynomial that works with most vibrating-wire
sensors. Configuration of the polynomial can be an involved process and
requires knowledge of the sensor’s measurement factors, as well as an
Summary of Contents for CRVW3
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