GeoSIG VE-3x Series Velocity Sensor

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GeoSIG Ltd reserves the right to change the information contained in this document without notice. While the information contained herein is assumed to be accurate, GeoSIG Ltd assumes no responsibility for any errors or omissions.

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No part of this document may be reproduced without the prior written consent of GeoSIG Ltd. The software described in this document is furnished under a license and may only be used or copied in accordance with the terms of such a license.

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GeoSIG Ltd
Switzerland

Warnings and Safety

⚠️ The sensor housing provides no protection against explosive atmosphere. It must not be directly operated in area where explosive gases are present.

1. Introduction

The GeoSIG VE-3x series velocity sensors consist of the following sensor types:

• VE-31 uniaxial
• VE-32 biaxial
• VE-33 triaxial

All sensor types are implemented in the same water- and dustproof, 195 x 112 x 95 mm cast aluminium housing. The modules inside the VE velocity sensors are quality geophones. Small size and single bolt fixation allow for both saving space and installation time. Levelling is accomplished via three point levelling screws. Alternatively, the flanges that support levelling can be used for mounting if desired.

2. Electrical Connector

All the VE-3x velocity sensors are supplied as standard with a 2 m connection cable. Based on the intended use, the 12 pin metallic style connectors will be supplied in one of the following options: Binder Serie 623 or Binder Serie 423.

2.1. Binder Serie 623

Description: A 12-pin metallic circular connector.

Part Numbers: P/N #J CIR.012.002.F, P/N 99 4606 00 12

Visual Description: The connector is a circular, metallic plug with a threaded coupling mechanism. It features a knurled grip for manual tightening. The front view shows 12 pins arranged in a circular pattern. The connector body has markings indicating dimensions and pin numbering.

The cable gland nut is determined according to the cable external diameter and must be separately ordered. It must also provide the cable shield connection to connector case.

2.2. Binder Serie 423

Description: A 12-pin metallic circular connector.

Part Numbers: P/N #J CIR.012.010.M, P/N 99 5629 00 12

Visual Description: The connector is a circular, metallic plug with a threaded coupling mechanism. It features a knurled grip. The front view shows 12 pins arranged in a circular pattern, labeled A through M (with G being SHIELD). The connector body has markings indicating dimensions and pin assignments.

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 case.

2.3. Connector Pin Description

The connector pin assignment and cable colour code are provided in the table below:

The analog output voltages of VE velocity sensor are referenced to 0 VDC with a sensitivity of 27.3 Vs/m.

2.4. Cable Configuration, Specification and Length

The cable configuration, specification, length, and quality of installation significantly affect the analog signal quality, material costs, and long-term system reliability. GeoSIG engineers can review installation plans and cable specifications, considering environmental conditions, to help achieve a reliable and cost-effective installation.

Cables must be capable of transmitting power and signals while withstanding the operating environment, including chemical exposure, UV exposure, impact, cut protection, temperature extremes, and regulatory safety requirements. While specific manufacturer part numbers are not listed due to the vast permutations, GeoSIG engineers will assist in specifying appropriate cables.

For optimal protection from electromagnetic interference (EMI), the cable construction should be an overall shielded twisted pair type. A foil wrapper with a drain wire is standard. An overall braided shield is recommended for installations near high-voltage power cables.

For optimum noise shield performance and maximum cable run lengths, the VE velocity sensor signals should be paired as shown in Table 2:

Connect the cable shield to the local ground at the recorder.

Cables do not generate noise, but longer cables can increase noise from external sources. Route cables away from power distribution and control wiring. An overall braided shield is recommended if cables must be near power cables.

Cable resistance primarily determines maximum cable length, mainly due to voltage drops in the power supply. The following table lists typical conductor resistance values for twisted pair shielded cables:

When selecting a cable, a maximum total resistance of 100 Ω should be considered. The values in the table must be doubled (for forward and back path) to calculate the correct resistance.

3. Installation

The VE velocity sensors are simple to use, but careful installation is crucial for proper performance. Review all sections of this manual before installation to ensure a smooth process. Verify sensor and cable assembly functionality by testing the output signal before and after installation.

The sensor location, preferably near the associated recorder, should be level and smooth. The foundation should be concrete, rock, or similar material bonded to the ground or structure. Special installations, such as mounting vertically on a reinforced concrete wall, are possible if the sensor orientation is compatible, the location is appropriate, and the sensor is properly mounted.

3.1. Installing

The VE velocity sensor must be firmly mounted to the foundation and levelled using the single centre pivot bolt and three point levelling screws. The "T" slot on the bottom and side of the sensor housing accepts an M8 x 35 mm stainless steel bolt head. Fasten the centre pivot bolt to the foundation, leaving approximately 18–20 mm of height above the surface. Slip the sensor onto the bolt head via its "T" slot and orient it correctly. Adjust the three point levelling screws to level the sensor and fasten it securely.

⚠️ To prevent damage to the sensor housing or fixation components, do not tighten the levelling screws with excessive force.

3.2. Axis Orientation Configuration

Use a bubble level on the top sensor surface to level first along one axis, then the other, as final levelling adjustments are made.

The axis orientation configuration is printed on the sensor's label. Geophones are sensitive to gravity, so the VE velocity sensor must be placed according to its intended orientation (horizontal or vertical as purchased).

⚠️ Do not exchange the geophone axis orientation(s) without contacting GeoSIG. Doing so will void the warranty and may damage the instrument.

⚠️ The polarity of the signal can be changed by exchanging connections to the geophone. This action must be coordinated with GeoSIG and executed by a skilled electrician.