Geokon 8020-42 User manual

Installation Instructions
Model 8020-42
Single Coil Autoresonant Adapter
No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon, Inc.
The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes no responsibility for
errors, omissions, or misinterpretation. The information herein is subject to change without notification.
Copyright © 2000-2018 by Geokon, Inc.
(Rev D, 08/21/2018)

Warranty Statement
Geokon, Inc. warrants its products to be free of defects in materials and workmanship, under
normal use and service for a period of 13 months from date of purchase. If the unit should
malfunction, it must be returned to the factory for evaluation, freight prepaid. Upon examination
by Geokon, if the unit is found to be defective, it will be repaired or replaced at no charge.
However, the WARRANTY is VOID if the unit shows evidence of having been tampered with
or shows evidence of being damaged as a result of excessive corrosion or current, heat, moisture
or vibration, improper specification, misapplication, misuse or other operating conditions outside
of Geokon's control. Components which wear or which are damaged by misuse are not
warranted. This includes fuses and batteries.
Geokon manufactures scientific instruments whose misuse is potentially dangerous. The
instruments are intended to be installed and used only by qualified personnel. There are no
warranties except as stated herein. There are no other warranties, expressed or implied, including
but not limited to the implied warranties of merchantability and of fitness for a particular
purpose. Geokon, Inc. is not responsible for any damages or losses caused to other equipment,
whether direct, indirect, incidental, special or consequential which the purchaser may experience
as a result of the installation or use of the product. The buyer's sole remedy for any breach of this
agreement by Geokon, Inc. or any breach of any warranty by Geokon, Inc. shall not exceed the
purchase price paid by the purchaser to Geokon, Inc. for the unit or units, or equipment directly
affected by such breach. Under no circumstances will Geokon reimburse the claimant for loss
incurred in removing and/or reinstalling equipment.
Every precaution for accuracy has been taken in the preparation of manuals and/or software,
however, Geokon, Inc. neither assumes responsibility for any omissions or errors that may
appear nor assumes liability for any damages or losses that result from the use of the products in
accordance with the information contained in the manual or software.

TABLE of CONTENTS
1. INTRODUCTION .................................................................................................................................................. 1
2. CONNECTIONS..................................................................................................................................................... 2
3. CONFIGURATIONS ............................................................................................................................................. 3
3.1 MICRO-10 DATALOGGER CONFIGURATION......................................................................................................... 3
3.2 GENERIC DATALOGGER CONFIGURATION........................................................................................................... 4
3.3 STAND ALONE CONFIGURATION......................................................................................................................... 5
APPENDIX A. SPECIFICATIONS.......................................................................................................................... 7
APPENDIX B. TEMPERATURE MEASUREMENT ............................................................................................ 8
FIGURES
FIGURE 1-BLOCK DIAGRAM......................................................................................................................................... 1
FIGURE 2-INTERNAL JUMPER SETTINGS FOR MICRO-10 CONFIGURATION ................................................................... 3
FIGURE 3-INTERNAL JUMPER SETTINGS FOR GENERIC DATALOGGER CONFIGURATION .............................................. 4
FIGURE 4-INTERNAL JUMPER SETTINGS FOR STAND ALONE CONFIGURATION............................................................. 5
TABLES
TABLE 1-CONNECTOR/SIGNAL DESCRIPTION............................................................................................................... 2
TABLE 2-MICRO-10 CONFIGURATION/CONNECTIONS.................................................................................................. 4
TABLE 3-GENERIC DATALOGGER CONFIGURATION/CONNECTIONS............................................................................. 5
TABLE 4-STAND ALONE CONFIGURATION/CONNECTIONS ........................................................................................... 6
TABLE 5-SPECIFICATIONS ............................................................................................................................................ 7
TABLE 6-THERMISTOR RESISTANCE VERSUS TEMPERATURE ...................................................................................... 9
EQUATIONS
EQUATION 1-RESISTANCE TO TEMPERATURE .............................................................................................................. 8

1
LPF
φ
1
φ2
VCO
Instrumentation
Amplifier
and
Schmitt Trigger
Phase Comparator
Output Buffer
VW Gage
Coil
Microprocessor
V+
1. INTRODUCTION
The Geokon 8020-42 Single Coil Autoresonant Adapter (SCA) is a device that allows single coil
vibrating wire gages to be driven in the “Autoresonant” mode, instead of the standard “Pluck and
Read” mode. The benefits of Autoresonant vs. Pluck and Read topologies are many, including
greater reading stability and wider dynamic bandwidth. In addition, since there is no
asynchronous swept frequency or pulse pluck excitation to interfere with the vibrating wire
signal, there is the ability to read the gage frequency with a general-purpose frequency counter or
low cost datalogger, instead of a complex dedicated readout device or datalogger.
Historically, autoresonant vibrating wire gages have employed two coils. The first is the
Transmit (excitation) coil that provides a phase synchronous pulse (pluck) to maintain
oscillation, while the second is the Receive (reading) coil that recovers the vibrating wire signal.
The two-coil approach, while dependable, adds considerably to the cost and imposes a
considerable mechanical limitation to the design and construction of the gage. Since the SCA is
designed to operate as a “transceiver” using only one coil, these limitations are eliminated while
providing the benefits of the autoresonant mode.
Figure 1 - Block Diagram
Frequency
Output
Enable
PLL_OUT
VCO_HOLD
T/R
Switch

2
2. CONNECTIONS
Connector
Position
Signal
Name
Signal
Description
Type
Level (typ.)
1
T
Temperature Proportional Voltage
Output
0 – 5 VDC
2
F1
Vibrating Wire Gage Frequency
Output
200mv(pp)
3
EX
Swept Frequency
Thermistor Excitation
Input
5V CMOS
0-5VDC (max)
4
+12V
+12V Power Supply
Power Input
5.5 – 15.0 VDC
(+12V nominal)
5
GND
Ground
Power Input
0V
6
T+
3kΩ@ 25°C Thermistor + input
Input
0 – 5 VDC (max)
7
T-
3kΩ@ 25°C Thermistor – input
Input
0 – 5 VDC (max)
8
C+
Vibrating wire Gage Coil +
Input / Output
1mv(pp) / 4v(pk)
9
C-
Vibrating wire Gage Coil -
Input / Output
1mv(pp) / 4v(pk)
10
ENABLE
Enable (Micro-10 configuration)
Input
5V CMOS
11
CLOCK
Clock (Micro-10 configuration)
Enable (Generic Datalogger configuration)
Input
5V CMOS
12
F2
Vibrating Wire Gage Frequency
Output
5V(pp) @ 50Ω
Table 1 - Connector/Signal Description
NOTE: Because the 8020-42 requires each vibrating wire gage to have its own pair of twisted
leads, the 8020-42 is not compatible with Geokon models 4900 (VW Load Cell) and 4350-3
(Biaxial Stressmeter).

3
3. CONFIGURATIONS
3.1 Micro-10 Datalogger Configuration
The 8020-42 can be incorporated as the vibrating wire interface in a Micro-10 Datalogger
system, taking the place of the Campbell Scientific Inc. AVW-1. In order to configure the 8020-
42 for the Micro-10 Datalogger, internal jumpers JP1, JP2 and JP3 must be set across pins one
and two. Remove the cover of the 8020-42 and set the jumpers:
JP1 JP2 JP3
Figure 2 - Internal Jumper Settings for Micro-10 Configuration
Between readings, the 8020-42 will be “asleep”, drawing approximately 20µA from the 12V
system battery.
When it is time to take a reading, the datalogger will set C1..C7 (ENABLE) high in order to
enable the respective multiplexer, and the individual channels are clocked by pulsing C8
(CLOCK) high.
When “ENABLE” and “CLOCK” are both high, the 8020-42 will wake up and wait for the
swept frequency excitation signal to appear at EX. The 8020-42 will track and apply this swept
frequency to the VW gage. Once the swept frequency is complete, the 8020-42 will lock onto the
returned VW signal and maintain excitation by applying one excitation pulse for every 16 cycles
of VW frequency. The VW frequency is provided as both a 200mv(pp) signal at F1, and as a
5v(pp) 50Ωoutput at F2
It is helpful to add a small amount of delay ( ≈0.5 Sec. ) from the time that the swept frequency
excitation ends and the time that the reading is taken. MultiLogger software, ver. 1.4.0 and above
provides this delay when selecting a gage type that has the letters sca included within it, e.g.,
4500sca, 4700sca etc.
PIN 1
PIN 2
PIN 3

4
Connector
Position
Signal
Name
Signal
Description
CR-10
Connection
1
T
Temperature Proportional Voltage
1L
2
F1
Vibrating Wire Gage Frequency
1H*
3
EX
Swept Frequency and Thermistor Excitation
E1
4
+12V
+12V Power Supply
12V
5
GND
Ground
AG
6
T+
3kΩ@ 25°C Thermistor + input
From MUX
COM_ HI_2
7
T-
3kΩ@ 25°C Thermistor – input
From MUX
COM_ LO_2
8
C+
Vibrating wire Gage Coil +
From MUX
COM_HI_1
9
C-
Vibrating wire Gage Coil -
From MUX
COM_LO_1
10
ENABLE
Enable (Micro-10 configuration)
C1..C7
11
CLOCK
Clock (Micro-10 configuration)
Enable (Generic Datalogger configuration)
C8
12
F2
Vibrating Wire Gage Frequency
1H*
Table 2 - Micro-10 Configuration/Connections
*Either F1 or F2 can be used to connect to the CR-10 1H input.
3.2 Generic Datalogger Configuration
The 8020-42 can be incorporated as the vibrating wire interface for any datalogger that is
capable of reading a frequency input and has the ability to output a single 5V CMOS level
control signal. In order to configure the 8020-42 for a generic Datalogger, internal jumpers
JP1and JP3 must be set across pins two and three, while JP2 is set across pins one and two.
Remove the cover of the 8020-42 and set the jumpers:
JP1 JP2 JP3
Figure 3 - Internal Jumper Settings for Generic Datalogger Configuration
Between readings, the 8020-42 will be “asleep”, drawing approximately 20µA from the 12V
system battery.
When it is time to take a reading, the datalogger will set its control signal, which should be
connected to CLOCK, high. When CLOCK goes high, the 8020-42 will generate a 400-4500 Hz
swept frequency pluck in order to excite the VW gage. As with the Micro-10 configuration, once
the swept frequency is complete, the 8020-42 will lock onto the returned VW signal and
PIN 1
PIN 2
PIN 3

5
maintain excitation by applying one excitation pulse for every 16 cycles of VW frequency. The
VW frequency is provided as both a 200mv(pp) signal at F1, and as a 5v(pp) 50Ωoutput at F2.
The 8020-42 will provide continuous VW frequency output until the CLOCK control line is
brought low. At this time, the 8020-42 will go back to sleep
Connector
Position Signal Name Signal Description
Generic
Datalogger
Connection
1
T
Temperature Proportional Voltage
See Appendix B
2 F1
Vibrating Wire Gage Frequency
(200mv/pp)
Frequency input
to Datalogger
3
EX
Thermistor Excitation
See Appendix B
4
+12V
+12V Power Supply
12V
5
GND
Ground
Ground
6
T+
3kΩ@ 25°C Thermistor + input
From Thermistor
7
T-
3kΩ@ 25°C Thermistor – input
From Thermistor
8
C+
Vibrating wire Gage Coil +
From VW gage
9
C-
Vibrating wire Gage Coil -
From VW gage
10
ENABLE
Enable (Micro-10 configuration)
N/A
11 CLOCK
Clock (Micro-10 configuration)
Enable (Generic Datalogger
configuration)
5V CMOS control
from datalogger
12 F2
Vibrating Wire Gage Frequency
(5v(pp) @ 50
Ω
)
Frequency input
to Datalogger
Table 3 - Generic Datalogger Configuration/Connections
3.3 Stand Alone Configuration
When configured in the Stand Alone mode, the 8020-42 will provide continuous excitation and
frequency output from a single Vibrating Wire gage. All that is needed is a 12V (nominal)
voltage source and a frequency counter to read the VW frequency. In order to configure the
8020-42 for Stand Alone mode, internal jumpers JP1, JP2 and JP3 must be set across pins two
and three. Remove the cover of the 8020-42 and set the jumpers:
JP1 JP2 JP3
Figure 4 - Internal Jumper Settings for Stand Alone Configuration
PIN 1
PIN 2
PIN 3

6
Connector
Position
Signal
Name
Signal
Description
Connection
1
T
Temperature Proportional Voltage
See Appendix B
2 F1
Vibrating Wire Gage Frequency
(200mv/pp)
To Frequency
Counter
3
EX
Thermistor Excitation
See Appendix B
4
+12V
+12V Power Supply
12V
5
GND
Ground
Ground
6
T+
3kΩ@ 25°C Thermistor + input
From Thermistor
7
T-
3kΩ@ 25°C Thermistor – input
From Thermistor
8
C+
Vibrating wire Gage Coil +
From VW gage
9
C-
Vibrating wire Gage Coil -
From VW gage
10
ENABLE
Enable (Micro-10 configuration)
N/A
11 CLOCK
Clock (Micro-10 configuration)
Enable (Generic Datalogger
configuration)
N/A
12 F2
Vibrating Wire Gage Frequency
(5v(pp) @ 50Ω)
To Frequency
Counter
Table 4 - Stand Alone Configuration/Connections

7
APPENDIX A. SPECIFICATIONS
POWER
Power Requirements:
6-15 VDC (12V nominal)
Current Consumption: Sleep: 30 µA (max.), 20µA (typ.)
Plucking: 50 mA peak
PLL locked: 30 mA (max.), 22 mA (typ.)
PLL Capture Range: 1200 – 4000 Hz
PLL Lock Range: 1150 – 4500 Hz
Internally Generated Fsweep:
Frequency (start): 400 Hz
Frequency (end): 4500 Hz
Sweep Duration: 750 mSec
Sweep Shape: Linear
Frequency Outputs:
F1: 200mV(pp) 1kΩAC coupled
F2: 5V(pp) 50ΩAC coupled
Thermistor Output: T: Temperature Proportional Voltage (0-5V)
Control Inputs:
ENABLE: 5V CMOS
CLOCK: 5V CMOS
EX: 5V CMOS: VW excitation
0-5V (max): Thermistor Excitation
ENVIRONMENTAL
Temperature range:
0 - 70 °C
Table 5 - Specifications

8
APPENDIX B. TEMPERATURE MEASUREMENT
The temperature of the gage itself can be determined by measuring the temperature proportional
voltage output at T, use that voltage to determine the resistance value of the gage thermistor, and
then input that value into the Steinhart and Hart log equation. For example, with 2.5 Volts
connected to EX, and the voltage measured at T= 1.4025 V:
1. Determine the current (Ith) flowing through the thermistor (note: Rint1(5k) and Rint2(1k) are
internal to the SCA):
I (th)=T/Rint1⇒I(th)=1.4185V/5,000Ω⇒ I(th) = 283.7 uA
2. Determine the resistance (Rth) of the gage thermistor:
R(th) = (EX-T)/I(th) – Rint2 ⇒R(th) = ((2.5 – 1.4185)/283.7E-6) - 1000⇒
R(th) = 3812.13Ω- 1000⇒R(th) = 2812.13Ω
3. Determine the temperature using the Steinhart and Hart linearization equation:
T= 1
A+B(LnR)+C(LnR)3-273.2
Equation 1 - Resistance to Temperature
Where;
T=Temperature in °C.
LnR =Natural Log of Thermistor Resistance.
A =1.4051 ×10-3
B =2.369 ×10-4
C =1.019 ×10-7
Note: Coefficients calculated over the −50 to +150°C. span.
Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3
Resistance to Temperature Equation

9
Ohms
Temp
Ohms
Temp
Ohms
Temp
Ohms
Temp
Ohms
Temp
201.1K
-50
16.60K
-10
2417
+30
525.4
+70
153.2
+110
187.3K
-49
15.72K
-9
2317
31
507.8
71
149.0
111
174.5K
-48
14.90K
-8
2221
32
490.9
72
145.0
112
162.7K
-47
14.12K
-7
2130
33
474.7
73
141.1
113
151.7K
-46
13.39K
-6
2042
34
459.0
74
137.2
114
141.6K
-45
12.70K
-5
1959
35
444.0
75
133.6
115
132.2K
-44
12.05K
-4
1880
36
429.5
76
130.0
116
123.5K
-43
11.44K
-3
1805
37
415.6
77
126.5
117
115.4K
-42
10.86K
-2
1733
38
402.2
78
123.2
118
107.9K
-41
10.31K
-1
1664
39
389.3
79
119.9
119
101.0K
-40
9796
0
1598
40
376.9
80
116.8
120
94.48K
-39
9310
+1
1535
41
364.9
81
113.8
121
88.46K
-38
8851
2
1475
42
353.4
82
110.8
122
82.87K
-37
8417
3
1418
43
342.2
83
107.9
123
77.66K
-36
8006
4
1363
44
331.5
84
105.2
124
72.81K
-35
7618
5
1310
45
321.2
85
102.5
125
68.30K
-34
7252
6
1260
46
311.3
86
99.9
126
64.09K
-33
6905
7
1212
47
301.7
87
97.3
127
60.17K
-32
6576
8
1167
48
292.4
88
94.9
128
56.51K
-31
6265
9
1123
49
283.5
89
92.5
129
53.10K
-30
5971
10
1081
50
274.9
90
90.2
130
49.91K
-29
5692
11
1040
51
266.6
91
87.9
131
46.94K
-28
5427
12
1002
52
258.6
92
85.7
132
44.16K
-27
5177
13
965.0
53
250.9
93
83.6
133
41.56K
-26
4939
14
929.6
54
243.4
94
81.6
134
39.13K
-25
4714
15
895.8
55
236.2
95
79.6
135
36.86K
-24
4500
16
863.3
56
229.3
96
77.6
136
34.73K
-23
4297
17
832.2
57
222.6
97
75.8
137
32.74K
-22
4105
18
802.3
58
216.1
98
73.9
138
30.87K
-21
3922
19
773.7
59
209.8
99
72.2
139
29.13K
-20
3748
20
746.3
60
203.8
100
70.4
140
27.49K
-19
3583
21
719.9
61
197.9
101
68.8
141
25.95K
-18
3426
22
694.7
62
192.2
102
67.1
142
24.51K
-17
3277
23
670.4
63
186.8
103
65.5
143
23.16K
-16
3135
24
647.1
64
181.5
104
64.0
144
21.89K
-15
3000
25
624.7
65
176.4
105
62.5
145
20.70K
-14
2872
26
603.3
66
171.4
106
61.1
146
19.58K
-13
2750
27
582.6
67
166.7
107
59.6
147
18.52K
-12
2633
28
562.8
68
162.0
108
58.3
148
17.53K
-11
2523
29
543.7
69
157.6
109
56.8
149
Table 6 - Thermistor Resistance Versus Temperature
55.6
150