Campbell CR510, Operator'S Manual

Page: 120 / 264

SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-16
*** 131 Enhanced Vibrating Wire
Measurement ***
FUNCTION
Excites a vibrating wire sensor with a swept
frequency (from low frequency to high), then
measures the response period and calculates
1/T
2
, where T is the period in ms. Excitation is
normally provided for each repetition. As an
option, a single excitation can be made prior to
all repetitions of the measurement. An AVW1
Vibrating Wire Interface is required for these
sensors, but it may have trouble reading the low
frequencies.
T - Amount of Time to sweep between the
specified frequencies
N - Number of steps to use when sweeping
from the Starting Frequency to the
Ending Frequency
The 1/T
2
value stored in the first Input Location
specified in Parameter 11 is the result after the
# of Cycles specified in Parameter 9. The 1/T
2
value stored in the sequential Input Location is
the result after 5 times the # of Cycles specified
in Parameter 9. The value in the second Input
Location is the correct value to use unless
the
reading falls into a certain range. This
instruction is most often used with the Slope
Indicator Vibrating wire. Slope Indicator has
datalogger programming instructions they
recommend using to decide which of the 2
readings to use.
PARAM DATA
NUMBER TYPE DESCRIPTION
01: 2 Repetitions (Index (- - )
to skip repeat of
excitation)
02: 2 Single-ended channel
for first measurement
03: 2 EX CHAN
04: 4 Starting Frequency
(HZ)
05: 4 Ending Frequency (HZ)
06: 4 T (sweep, Units = 1
msec)
07: 4 N (Number of steps)
08: 4 Delay after excitation
before measurement
(Units = 1 msec)
09: 4 CYCLES to measure
10: 4 DELAY between reps
(Units = 0.01 sec)
11: 4 First Input Location
12: FP Multiplier
13: FP Offset
Input Locations Altered: 2 per repetition