MODEL 4420 VIBRATING WIRE CRACKMETER
| TAKING READINGS |
11
5.
TAKING READINGS
5.1
MICRO-6000 DATALOGGER
GEOKON
recommends the parameters in the table below when using strain
gauges with the MICRO-6000 datalogger or any other CR1000 based
datalogger. It shows the recommended gauge type selection and gauge factor
G entry to convert to microstrain. The table also lists the starting and ending
frequency settings for the excitation sweep when writing a program for the
CR1000 using the P28 vibrating wire measurement instruction.
Alternately, if a calibration sheet is supplied with the strain gauge, the exact
values can be calculated from the start and end frequencies of the calibration.
To maximize the stability and resolution of the sensor, a relatively narrow band
of excitation frequency should be selected. Calculate these settings by taking an
initial reading and then setting the starting frequency to 200 Hz below and the
ending frequency 200 Hz above.
TABLE 2:
Embedment Strain Gauge Datalogger Parameters
5.2
EMBEDMENT STRAIN GAUGE READOUT POSITIONS
The following table indicates the readout position detail for each strain gauge
model.
TABLE 3:
Readout Positions
The following sections describe how to take readings using readout equipment
available from
GEOKON
.
5.3
GK-404 READOUT BOX
The Model GK-404 Vibrating Wire Readout is a portable, low-power, hand-held
unit that is capable of running for more than 20 hours continuously on two AA
batteries. It is designed for the readout of all
GEOKON
vibrating wire instruments,
and is capable of displaying the reading in either digits, frequency (Hz), period
(
s), or microstrain (
). The GK-404 also displays the temperature of the
transducer (embedded thermistor) with a resolution of 0.1 °C.
MICRO 6000 Gauge Type
4200
Gauge Factor G
Shown on calibration sheet
Start Frequency (P28)
4 (400 Hz)
End Frequency (P28)
12 (1200 Hz)
Model
4200/4200HT
4200
6/7
4202
4204
4210/4212/4214
Readout Position
D
D
E
A (Mode: digits)
B
Display Units
microstrain (μ
ε
)
readout units
microstrain (μ
ε
)
digits (f
2
10
-3
)
digits (f
2
10
-3
)
Frequency Range
450 1200 Hz
400-1200 Hz
1400-3500 Hz
800-1600 Hz
1400-3500 Hz
Mid Range Reading 2500 μ
ε
2000
2500 μ
ε
1700 digits
6000 digits
Minimum Reading
1000 μ
ε
1000
1000 μ
ε
650 digits
2000 digits
Maximum Reading
4000 μ
ε
3000
4000 μ
ε
2750 digits
10000 digits
