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.

(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

LPF

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. CONNECTIONS

Connector

Position

Signal

Name

Signal

Description

Type

Level (typ.)

Temperature Proportional Voltage

Output

0 – 5 VDC

Vibrating Wire Gage Frequency

Output

200mv(pp)

Swept Frequency

Thermistor Excitation

Input

5V CMOS

0-5VDC (max)

+12V

+12V Power Supply

Power Input

5.5 – 15.0 VDC

(+12V nominal)

GND

Ground

Power Input

T+

3kΩ@ 25°C Thermistor + input

Input

0 – 5 VDC (max)

T-

3kΩ@ 25°C Thermistor – input

Input

0 – 5 VDC (max)

C+

Vibrating wire Gage Coil +

Input / Output

1mv(pp) / 4v(pk)

C-

Vibrating wire Gage Coil -

Input / Output

1mv(pp) / 4v(pk)

ENABLE

Enable (Micro-10 configuration)

Input

5V CMOS

CLOCK

Clock (Micro-10 configuration)

Enable (Generic Datalogger configuration)

Input

5V CMOS

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. 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

Connector

Position

Signal

Name

Signal

Description

CR-10

Connection

Temperature Proportional Voltage

Vibrating Wire Gage Frequency

1H*

Swept Frequency and Thermistor Excitation

+12V

+12V Power Supply

12V

GND

Ground

T+

3kΩ@ 25°C Thermistor + input

From MUX

COM_ HI_2

T-

3kΩ@ 25°C Thermistor – input

From MUX

COM_ LO_2

C+

Vibrating wire Gage Coil +

From MUX

COM_HI_1

C-

Vibrating wire Gage Coil -

From MUX

COM_LO_1

ENABLE

Enable (Micro-10 configuration)

C1..C7

CLOCK

Clock (Micro-10 configuration)

Enable (Generic Datalogger configuration)

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

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

Temperature Proportional Voltage

See Appendix B

2 F1

Vibrating Wire Gage Frequency

(200mv/pp)

Frequency input

to Datalogger

Thermistor Excitation

See Appendix B

+12V

+12V Power Supply

12V

GND

Ground

T+

3kΩ@ 25°C Thermistor + input

From Thermistor

T-

3kΩ@ 25°C Thermistor – input

From Thermistor

C+

Vibrating wire Gage Coil +

From VW gage

C-

Vibrating wire Gage Coil -

From VW gage

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

Connector

Position

Signal

Name

Signal

Description

Connection

Temperature Proportional Voltage

See Appendix B

2 F1

Vibrating Wire Gage Frequency

(200mv/pp)

To Frequency

Counter

Thermistor Excitation

See Appendix B

+12V

+12V Power Supply

12V

GND

Ground

T+

3kΩ@ 25°C Thermistor + input

From Thermistor

T-

3kΩ@ 25°C Thermistor – input

From Thermistor

C+

Vibrating wire Gage Coil +

From VW gage

C-

Vibrating wire Gage Coil -

From VW gage

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

Table of contents

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