GS_VE-1x_2x_Operation_Manual_V09.docx/14.09.2020
VE-1x/2x Series Velocity Sensor
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8 / 10
Table 5. Typical Twisted Pair Shielded Cable Specifications
Diameter mm
Square mm2
Resistance
W
/km
AWG
0.25
0.051
371
30
0.42
0.14
135
-
0.45
0.159
114
25
0.51
0.204
93
24
0.53
0.22
86
-
0.64
0.321
52
22
0.80
0.5
39
-
0.81
0.515
34
20
0.98
0.75
26
-
1.02
0.817
21
18
1.13
1.0
19
-
While selecting a cable, a maximum total resistance of 100
W
should be taken into account and the values out
of the table above must be doubled (forward and back path) to have the correct resistance value.
Cable length may be extended or a thinner cable might be used via utilizing several conductors for the VA+
and GND signal. Geophones using current loop output will draw 75 mA, maximum.
Verify that voltage drop does not lower the voltage at the geophone to less than 10 VDC.
3. Operation and Configuration
3.1. Axis Orientation Configuration
The axis orientation configuration is printed on each sensor’s label that takes place on the housing. Geophones
are sensitive to the gravity; therefore the VE velocity sensor has to be placed in accordance with the intended
(and as purchased, i.e. horizontal or vertical) orientation.
Do not exchange the geophone axis orientation(s) without contacting GeoSIG. Doing so will
void the warranty of the instrument and might as well damage it completely.
The polarity of the signal can be changed basically by exchanging the connections to the geophone.
Also this action has to be coordinated with GeoSIG and must be executed by a skilled electrician.
3.2. Scale Factor / Gain
The standard scale factor is 100 mm/s. Other ranges are available. A gain ranging option allows the user to
select one of three scale factors by connecting S_TEST and S_MODE to VA+ or GND. See the following table.
Table 6. Scale Factor / Gain / Test; 0 = Ground, 1 = VA+
S-Mode
S-Test
Gain
0
0
Mid Gain
1
0
High Gain
0
1
Mid Gain with sensor test
1
1
Low Gain
3.3. Self Test
When S_MODE is grounded and S_TEST is connected to VA+, the VE velocity sensor responds with a pulse.
The pulse is positive and decays to zero after releasing the test input condition. This test is an excellent
indication about the proper working of the sensor. Geophones might get damaged due to large shocks (e.g.
by falling down to the ground). Such a damaged geophone would have developed internal contact between
