Web Page Created by L. Cochrane Oct. 22, 2013
LGT4.5 Geophone Measurements 

R1 
R2 
M (gm) 

Loaded 
No Load 
D=0.707 
D=1.000 
100000 
16667 
11.3 

Damping 
Damping 
Damping 
Damping 

Factor 
Factor 
Resistance 
Resistance 
A1 
A2 
K 
V0 
T1 
G 

X Axis (East/West) 
0.657 
0.1072 
0.0070 
1251 

R1 Positive Step 
0.650 
0.638 
17897 
3119 
0.1031 
0.0070 
1268 
0.0339 
0.0390 
0.282 

R2 Positive Step 
0.712 
0.0944 
0.0039 

R1 Negative Step 
0.663 
0.650 
21386 
3152 
0.1112 
0.0069 
1235 
0.0352 
0.0394 
0.291 

R2 Negative Step 
0.723 
0.1016 
0.0038 

Y Axis (North/South) 
0.685 
0.1123 
0.0059 
1437 

R1 Positive Step 
0.680 
0.666 
33777 
3861 
0.1066 
0.0058 
1419 
0.0340 
0.0402 
0.278 

R2 Positive Step 
0.749 
0.0974 
0.0028 

R1 Negative Step 
0.690 
0.676 
45804 
4101 
0.1180 
0.0059 
1454 
0.0352 
0.0418 
0.293 

R2 Negative Step 
0.761 
0.1075 
0.0027 

Z Axis (Up/Down) 
0.590 
0.1234 
0.0124 
1449 

R1 Positive Step 
0.608 
0.593 
12762 
3306 
0.1362 
0.0123 
1502 
0.0341 
0.0584 
0.309 

R2 Positive Step 
0.681 
0.1225 
0.0066 

R1 Negative Step 
0.570 
0.556 
8853 
2759 
0.1105 
0.0125 
1395 
0.0354 
0.0449 
0.243 

R2 Negative Step 
0.638 
0.1012 
0.0075 

No Load 
No Load 
D=0.707 
D=0.707 
D=1.000 
D=1.000 
100K Ohm 
Generating 

Damping 
Transducer 
Damping 
Transducer 
Damping 
Transducer 
Resonant 
Coil DC 

Factor 
Gain 
Resistance 
Gain 
Resistance 
Gain 
Frequency 
Resistance 

Measurement Units 
V / (cm/S) 
Ohms 
V / (cm/S) 
Ohms 
V / (cm/S) 
Hertz 
Ohms 

X Axis (East/West) 
0.644 
0.287 
19517 
0.282 
3137 
0.256 
4.627 
381 

Y Axis (North/South) 
0.671 
0.287 
39186 
0.284 
3982 
0.262 
4.322 
382 

Z Axis (Up/Down) 
0.576 
0.277 
10653 
0.268 
3032 
0.246 
3.786 
383 

Note:
The two large blocks at the bottom show the final output, including the damping factors, the damping resisters and the transduction gains for the three different damping factors.
Addition Information:
R1 is a 100K 1% resistor in
series with the signal generator, while R2 represents the thevenin equivalent
generator
source resistance after switching in
a 20K 1% resistor in parallel with the geophone. Hence each geophone is
tested
with 100K and 16.667K damping
resistors to determine the various parameters. The resonant frequencies were
only
measured with the 100K damping
resistor. Both positive and negative step responses were measured and an average
computed for the final results. Every
cell with a pale yellowgreen background shows the data entered and all of the
remaining plain background cells show
the calculated results. Also note that the moving mass is in units of
grams.
Summary:
Based on the very small
sample size for the horizontal geophones (2), I'm seeing a 4% to +3% variation
in the resonant
frequency and about a +/0% variation
in the open circuit damping factor, all of which are well within the +/10%
specs.
The vertical geophone has a 19%
resonant frequency deviation (obviously a much lower frequency than the spec
range)
and a 4% damping factor deviation,
both are relative to the manufacturers nominal values. All three geophones are
well
within their +/5% coil resistance
specifications.
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