AC-23 Accelerometer User Manual
Contents
1. The AC 23 sensor package is a triaxial accelerometer designed for free field and industrial applications regarding STRONG MOTION earthquake survey monitoring and research This sensor is well suited for applications where a high sensitivity is required The AC 23 sensor can be optionally installed into a rugged protective housing This optional protective housing is in stainless steel for optimal environmental resistance As option the protective housing could be executed with an IP68 grade for Free field location where the possibility exists of housing submersion The sensor could be installed on floor or wall with a modification of the axis organization With the help of the TEST LINE the complete sensor can be very easily completely tested Full scale can be field selected by the user with jumpers 3 2 Principle The accelerometer is based on a geophone mass spring system with electronic correction This type of sensors gives a very good stability in temperature and aging because of the very simple principle It uses a damped mass spring oscillator called Geophone to convert seismic movement into electrical value proportional to the velocity In a graphic with constant acceleration the geophone response will present a maximum at the frequency called Natural Frequency which is the resonant frequency of the mass spring oscillator Above and below this point the response will decay with one pole slope 20 dB decade The corrector will over2. sensor Sensor AC 23 DH E diameter 54 mm Guiding system 50 cm Ve GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 12 5 4 Inclinometer casing assembly The borehole must have a casing or the soil must insure that a free path for the inclinometer tube is warranted It is recommended to insert the inclinometer tube as soon the borehole is ready The free path for the inclinometer tube should be 10 to 15 cm 12 cm typically It could be required to insert some water in the casing to sustain the water pressure at the bottom of the borehole The inclinometer tube should be mounted with a maximum deviation of 1 3 meters and with a maximum deviation from vertical at sensor location of 3 The functional limit for the sensor is 9 The water level in the inclinometer tube should be maximum 50 meters including fast elevation due to heavy rain It is recommended to use the optional assembly kit that GeoSIG can provide optional with the inclinometer tube It will insure a perfect sealing of the tube elements and would avoid concrete mix to enter the tube The dimensions of the inclinometer tube are Inclinometric casing C Coupling section and coupling section lt lt A D B B INCLINOMETRIC CASING 3 m section COUPLING ELEMENT A Inner diameter 76 1 mm A Inner diameter 81 0 mm B Groove outer diameter 86 4 mm B Outer diameter 92 0 mm C Thickness 2 2 0 1 mm C Thickness 2 2mm D Groove
3. case GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 5 2 Mounting Figure 2 AC 2X housing Small size and single bolt attachment allow the AC 2X to be easily installed saving installation time Leveling is accomplished via three point leveling screws 165 0 I A ey 68 0 28 0 14 0 195 0 41 0 15 0 15 0 152 0 Minimum Space Allowance for the Connector and Cable Sensor with Connector 300 mm from sensor housing Sensor with Cable Inlet 200 mm from sensor housin 112 0 Figure 3 Sensor housing dimensions The accelerometers must be firmly mounted to a surface and leveled as the application requires Check to be sure that the accelerometer is aligned to produce the desired output signals Acceleration in the direction indicated on the case will produce a positive output signal The orientation definitions as shipped are X North Y West and Z UP GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 6 The accelerometer has single bolt 3 feet levelling mechanism The surface should have a scribed north south orientation line accurately surveyed from reliable markers The X axis of the sensor has to be pointed to East or to any other main direction of the structure to monitor One M8 expanding nut rock anchor must be used for the sensor fixation 3 Theory of operation 3 1 Introduction
4. damp the geophone by applying a voltage with opposite polarity over the geophone and the output response will be flat and proportional to the acceleration in this frequency band Pul uso O Test input scaling po Motion on geophone Feedback Low pass Output Differential the X axis 4 5 Hz E amplifier El filter amplifier Output to recorder Motion on geophone Feedback _ Low pass Output p Differential the Y axis 4 5 Hz E amplifier El filter amplifier n Output to recorder Motion on geophone Feedback Low pass Output Differential the Z axis filter amplifier Output to recorder 4 5 Hz 5 amplifier H S 8 V O Power 8V supply Figure 4 AC 23 Sensor block diagram Note all inputs outputs amp power supply entry are surge protected GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 7 The geophone is connected in a resistor bridge driven by a feedback amplifier which applies the amplified bridge differential signal in opposite polarity The bridge is balanced during calibration The test line shifts the voltage at one side of the bridge which produces a current flow in the geophone This current flowing in the Geophone will move the seismic mass The movement of the mass generates a voltage across the Geophone which is detected by the differential amplifier and induces an output signal Feedback loop OUTPUT GEOPHONE Figure 5 TEST INPUT configu
5. GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 1 GeoSIG dw d d AC 23 Accelerometer User Manual GeoSIG Ltd Company Ahornweg 5A 5504 Othmarsingen Switzerland Tel 41 44 810 21 50 Fax 41 44 810 23 50 E mail info geosig com Author Serge Rudaz Checked Lukas G tzi Approved Johannes Grob Distribution GeoSIG Ltd 1 Customer on request GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 201 1 AC 23 Accelerometer Manual Page 2 DOCUMENT REVISION Date Version _ Author Checked 150495 0 SR LE Created 110400 1 JG GCO Format Font changes 2 SR 05 07 01 JG Update pictures and connector description for new 12 poles version Added principle of operation 30 05 2003 ste e Changes for new housing 06 06 2003 4 Corrected axis polarity for new housing Movement in axis direction gives positive response 05 05 2006 6 Ip L Adapted to new DH housing File name and title change 13 12 2007 g8___ TIB__ TB__ Detailed sensor full scale amp offset adjusiment____ 18 03 2011 8 H TAB Board connector pinning added GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 201 1 AC 23 Accelerometer Manual Page 3 TABLE OF CONTENT 1 ELEGTRIGAL CONNECTION ooscccssicceiccciscccusvcucsincedecdGaccdusvauoddaccsucddadccusvdsdsdedvsucddacccdusveveddeddsucddadddusvedus 4 1 1 MAIN CONNECTOR PIN ASSIGNMENT ocoocccnncccnncncnncn
6. e connector pins standard assignments are as follows Pin SIGNAL Comment Color 1 OUTPUT X 0 V 5 V voltage output 47 Q output impedance White 2 OUTPUT X 0 V 5 V voltage output inverted 47 Q output impedance Brown 3 OUTPUT Y 0 V 5 V voltage output 47 Q output impedance Green 4 OUTPUT Y 0 V 5 V voltage output inverted 47 Q output impedance Yellow 5 OUTPUT Z 0 V 5 V voltage output 47 Q output impedance Grey 6 OUTPUT ZC 0 V 5 V voltage output inverted 47 Q output impedance Pink 7 TEST INPUT Test input output will result in a sensor step response Blue 8 GROUND Ground not connected to mechanical ground Red 9 12 VDC power Power input 10 to 15 VDC range 50 mA 12 VDC Black 10 GROUND Ground not connected to mechanical ground Violet 11 AUX Auxiliary input reserved 12 GROUND Ground not connected to mechanical ground Table 1 AC 2X Connector Pin Assignment In case no connector is mounted at the cable end like usually for down hole version the color code is given in the above table 1 2 Mating connector GeoSIG P N J_CIR 012 002 F CONINVERS P N RC 12 S 1 N 12L 300 Binder Serie 623 P N 99 4622 00 12 1 02 i Figure 1 Mating connector Cable gland nut has to be determined as per cable external diameter and must be separately ordered It has also to provide the cable shield connection to connector
7. ed output 2 50 0 02 V 10 10 mA 0 20 mA Current loop OPTION 2 50 0 02 V The output range is written on the sensor label GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 9 5 Mounting downhole sensor The sensor must be installed in a 3 inch inclinometer tube At least a 100 mm borehole must be drilled Depending on the soil condition it could be required to drill a higher dimension hole and to implement a 120 mm PVC casing to insure a free path when the inclinometer tube is inserted in the borehole 5 1 Borehole preparation Note Do not scale the drawing 12cm Surface level S SS J NS SS MES ca Cap N Depth of drilled borehole SN Ww N Do not allow concrete mix from casing sealing to enter the casing GeoSIG Ltd AC 23 Accelerometer Manual 5 2 Inclinometer tube installation Note Do not scale the drawing The number of section is only an example 3 meters 30 cm e Y E UN 4 VW SS S Inclinometer tube in 3 meters section Sealing concrete mix of tube Coupling elements fixed with pop rivets Must be fully sealed to avoid any concrete inside the tube Bottom cap Must be fully sealed to avoid any concrete inside the tube FT 17 AN WKS pi de y CS maximum 50 Cable The maximum water level above the sensor must be meters oncrete sealing of
8. inner diameter 82 0 mm D Groove inner diameter 87 6 mm Length 3 meters Length 300 mm Weight 1 4 Kg m Weight 0 5 kg Borehole diameter gt 120 mm GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 13 The following elements will be inserted in the borehole Figure 7 Torpedo the sensor and its cable Figure 8 Guiding system Figure 9 Inclinometer tube GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 14 5 5 Axis orientation Engraved mark Figure 10 Down hole axis orientation Before the sensor is inserted in the inclinometer tube the guiding system must be mounted bellow it The guiding system must be orientated before the insertion The engraved mark on bottom cover is showing the positive direction of X axis Z axis Vertical positive up Win View for top 6 INSTALLATION VERIFICATION Please note that temperature compensation device is mounted for each axis inside the sensor and that the temperature in the sensor has to stabilize before accurate measurement can be done Allow at least half an hour for temperature stabilization
9. nnncncnncnnnncnnnnnnonncnnnncnonnnnnnnnnnnnannnnannn narco na nc Ennn Enana nnne 4 LZ MATING CONNECTOR uc dt 4 2 MOUNTING EE 5 3 THEORY OF OPERATION i occcococcococcononcononcnnanonnancnnarconarnnnarcnnarnn aaron rca arca narco narra narra narra narra nanmanna ann 6 A AAA A A A A IN A A EU ubag bee babes i 6 B22 A NN 6 3 34 eelere age 7 4 ELECTRICAL CONFIGURATION c ccoccccococconoccononconanconanconarnnnarcnnarcnnarno narco rnn narco narran KREE rra narran rnanannanas 8 5 MOUNTING DOWNHOLE SENSOR ooccccccconocccnncncnccononanananaccnnnnnnonnnnnnnnnnnnnnnnnnnnnnn rr nn rrnnnn nana nr nr nnen 9 51 BOREHOLE PREPARATION iia iaa aaa dalla aaa 9 5 2 INGLINOMETER TUBE INSTALLATION aa 10 5 3 SENSOR INSTALLATION nro nara nn n anna n anna n rra anno n anar nana n na nn naa nn cnn nn nnaninnanas 11 54 INCLINOMETER CASING ASSEMBLY cuina ala lala lalala aia aaa 12 5 57 AXIS ORIENTATION ona aa aaa aaa AA 14 6 INSTALLATION VERIFICATlON oocconccconocconocoonocoonocnnnncnnnaronnnrnonarnnnn cnn arca na rnnnn cnn na rnn arca na rnn na rnanarnanarans 14 The sensor housing provides no protection against explosive atmosphere It must not be directly operated in area where explosive gases are present GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 4 1 Electrical Connection 1 1 Main Connector Pin Assignment All the AC 2X accelerometers use the same 12 pins male metallic style connector as the AC 43 and AC 63 Th
10. ration 3 3 Basic specifications Detailed specifications AC 23 Input range Acceleration 0 2 0 5 1 0 gor 2 0g Output range 0 10 Volt differential output OR 0 5 Volt differential output OR 2 5 2 5 Volt single ended output OR 0 20 mA Current loop OPTION Frequency range from 0 1 Hz to 50 Hz Optional from 0 2 Hz Protections All connectors pins protected by Transzorb diodes and VDR Power supply 10 15 VDC Current drain Typical 30 mA 12 VDC GeoSIG Ltd GS_AC 23 UserManual_V08 doc 18 03 2011 AC 23 Accelerometer Manual Page 8 4 Electrical configuration The fullscale can be adjusted without gain re calibration by means of jumpers with fixed 0 1 precise amplifiers Fullscale Z 1 2 0 29 3 4 0 5 y 5 6 1 0g f Si 7 8 2 0 g A A ene an me 1 2 0 2g 3 4 0 5 y 5 6 1 0g 7 8 2 0 g Figure 6 Fullscale setting After the new full scale has been selected the offset potentiometers L need to be re adjusted to remove any offset at output Connect a Digital Voltmeter DVM as shown on the above figure and adjust the offset potentiometers so that the DVM readings stay within the ranges indicated in the following table according to the sensor output range given in Section 3 3 Sensor Label Sensor Output Range DVM Reading 10 Volts 0 10 Volt differential output 0 00 0 05 V 0 5 Volt differential output 0 00 0 05 V 2 5 2 5 Volts 2 5 2 5 Volt single end
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