RAMAC/GPR Operating manual Version 1.
Table of Contents _________________________________________________ 1 Introduction 4 1.1 Unpacking and Inspection 5 1.2 Repacking and Shipping 5 2 General 6 2.1 General description of the GPR Technique 6 2.2 Basic information in investigation depths and velocities 8 3 Radar Control Unit CUII 11 4 Unshielded antennas 14 4.1 Antenna electronics 14 4.2 Antenna elements 16 4.
10 Other accessories 34 10.1 Antenna handles 34 10.2 Skid box 35 10.3 Antenna Sled 36 11 Start up of your RAMAC/GPR CUII 38 11.1 Connecting the system components 39 11.2 Running a survey 40 12 Trouble shooting 42 13 How to assemble the RAMAC/GPR Cart 44 www.malags.
1 Introduction __________________________________________________ Thank you for purchasing the RAMAC/GPR system. We at Malå GeoScience welcome comments from you concerning the use and experience of this equipment, as well as the contents and usefulness of this manual.
1.1 Unpacking and Inspection Great care should be taken when unpacking the equipment. Be sure to verify the contents shown on the packing list and inspect the equipment for any loose parts or other damage. All packing material should be preserved in the event that any damage occurred during shipping. Any claims for shipping damage should be filed to the carrier. Any claims for missing equipment or parts should be filed with Mala GeoScience. 1.
2 General _________________________________________________ 2.1 General description of the GPR Technique In its simplest form the RAMAC/GPR system consists of an external PC, a Radar Control Unit, a transmitter antenna and a receiver antenna. The Radar Control Unit is connected to the transmitter and the receiver antenna with optical fibres and to the computer with a parallel communication cable. Figure 2.1 shows a schematic diagram of the system when connected.
Trace: At each point of measurement along the profile, a specific number of samples are collected. Together, these samples make up a trace, an envelope of the received waveform. Profile: A collection of traces along a line or transect. Direct wave: This is the part of the energy that travels the shortest distance between the transmitter and the receiver. When collecting a sample, the CUII sends a timing signal (a control signal) to the transmitter and receiver antenna respectively.
D e p t h SURFACE BOULDER SOIL LAYERS Distance Figure 2.2 An example of a continuous record of radar traces. 2.2 Basic information in investigation depths and velocities The problem of range (depth) vs. resolution is well known for the type of investigations that GPR represents. Sufficient penetration depth may be achieved but it may require a low frequency that reduces the resolution. Range is defined as the distance at which a target can be detected.
Table 2.1. Approximate depth ranges for different antenna frequencies. Antenna frequency (MHz) Lower limit of object target size (m) Approximate depth range * (m) Approximate penetration depth (m) 100 0.1 - 1 2 - 15 15 - 25 250 0.05 - 0.5 1 - 10 5 - 15 500 0.04 1 -5 3 - 10 800 0.02 0.4 - 2 1-6 * In normal geological environment absent of low resistive layers For the interpretation part the velocity of different geological environment is needed for the best possible depth interpretation.
Table 2.2. Approximate values of ? r (relative permittivity) and the corresponding velocity. er varies greatly with the water content in the medium. The larger value given for velocity applies to unsaturated media.
3 Radar Control Unit CUII _________________________________________________ The Radar Control Unit CUII is the main part of the RAMAC/GPR system. As seen in Fig. 3.1, the CUII is compatible with all current RAMAC antennas, both unshielded, shielded and borehole antennas. RAMAC/GPR Control Unit II Multi Channel Modules MC4, MC16 Shielded antennas Unshielded antennas Borehole antennas 100 MHz 25 MHz 100 MHz 250 MHz 50 MHz 500 MHz 100 MHz 800 MHz 200 MHz 250 MHz 1000 MHz Figure 3.
The unit has (see Fig. 3.2 below): ?? a parallel port for PC communication, see Chapter 7 ?? connectors for an external trigger (distance-measuring devices), see Chapter 9 ?? input power, see Chapter 7 ?? fibre optic links to the transmitter and receiver antennas respectively, See Chapter 7. The CUII requires no warm up time and is ready for immediate data acquisition.
?? Mounting the CUII to the back-pack holder: The CUII is attached to the backpack with the 4 screws that have black plastic grips. Once the battery is mounted on the control unit there is a strap on the soft backpack that should be attached below the battery and firmly tightened. The shoulder straps can be adjusted for maximum comfort for the operator. This holder is easily combined with a PC holder to give you a convenient working surrounding.
4 Unshielded antennas _________________________________________________ The unshielded antennas consist of separate transmitter and receiver electronics to which the antenna elements are attached. The antennas can then be used with antenna handles, a skid box or an antenna sledge (see Chapter 10). The complete RAMAC/GPR system is shown in Fig. 4.1, where the antenna electronics are mounted to the antenna elements together with wooden handles.
centre frequency, which is dependent on the antenna dimensions. The unit has one optical connector for the transmitter trigger, a connector for a battery pack, a power switch and a LED. See Figure 4.2. When flashing, the LED on the transmitter electronic indicates trigger pulses are being received from the Radar Control Unit. No light indicates no power is being received by the electronics. A steady light indicates that no Trigger pulses are received from the Radar Control Unit.
The receiver electronic (Fig. 4.3) digitises the received signals from the antenna to a 16-bit numerical integer value (0-32768 and +32767). These numerical values represent the amplitudes of the received radar signals. This digital collected data is transmitted to the CUII via the fibre optic cable labeled D). A second fibre optic cable labeled R is used to receive the trigger signals from the Radar Control Unit. There are also a connector for a battery pack, a power switch and two LEDs. 4.
The antenna elements are also sealed to be water-resistant, however, they are not guaranteed to be water-proof and should never be submerged in water. 25 MHz 50 MHz 100 MHz 200 MHz Figure 4.4 Unshielded antennas The 25 and 50 MHz antenna elements consist of a central element with detachable end pieces. When mounting these pieces it is important that they are properly fitted so that the double O-rings at their ends seal properly against moisture and that the electrical connection is proper.
Antenna Handles are used when profiling without the use of Skid Box or Antenna Sledge. Use of the handles is recommended mainly for the low frequency antennas where the station separation is comparably great. For more information see Chapter 10. 4.3 Operation modes The unshielded antennas can be operated in a variety of modes for different survey techniques. They are: ?? Reflection profiling: This is the most common type of operation. The antennas are mounted at a fixed separation and moved along a line.
in order to produce images of the area between the antennas. For further information about such software the user is recommended to contact MALÅ GeoScience directly. www.malags.
5 Shielded antennas _________________________________________________ Presently, Malå GeoScience manufactures 100, 250, 500, 800 MHz and 1 GHz shielded antennas. The 100, 250, 500 and 800 MHz antenna’s interface with the Shielded Electronics Unit is described below (see also Fig. 5.1 to 5.4). The 1 GHz antenna contains its own built-in transmitter and receiver electronics and is described in Chapter 6. A shielded type of antenna means that the energy is only transmitted in one direction.
Figure 5.1 From left to right: Shielded 250, 500 and 800 MHz antennas. In front: electronics unit and survey wheel. Figure 5.2 Shielded 100 MHz antennas, electronics unit and survey wheel The Shielded Electronics Unit is used to operate the RAMAC/GPR shielded antennas (see Fig. 5.3 and 5.4). The Shielded Electronics Unit contains both the transmitter and the receiver electronics. Power to the electronics is provided by a standard RAMAC/GPR battery pack.
Power Switch Fiber optic connectors LED’s Battery connector Figure 5.3 Shielded electronic unit without the optical fibre cable. Encoder connection Fiber optic and enocer connectors to Radar Control Unit Figure 5.4 Shielded electronic unit with connected cable hose. As in the unshielded electronics LED-indicators show the status of communications between the Shielded Electronics Unit and the Radar Control Unit. When flashing, the T and R trigger pulses are being received from the CUII.
As seen a steady light on a LED indicates an interruption in the optical communication. This means either a fibre optic cable has failed or, the fibre optic connectors need to be cleaned with the compressed air can provided with the system. When none of the LED’s is blinking a power failure to the electronics unit has occurred. Replace or recharge the battery. If the electronics still do not function with a fresh battery then there is an internal failure in the Shielded Electronics Unit.
6 1 GHz shielded antenna _________________________________________________ The 1 GHz shielded antenna (Fig. 6.1) for RAMAC/GPR has been designed for surveys on shallow environments such as roadbeds, concrete constructions, archaeological sites etc. With the antenna a survey depth in these materials of roughly 1 m (two way travel time of 15-25 ns) can be expected. Local conditions may however affect this value in both directions. Figure 6.1 Shielded 1 GHz antenna together with cable hose.
NOTE: Take care when bending the fibres under the metal cover that attaches to the connectors with the two screws. The fibres should form a soft bend in order to obtain good light conditions. A too hard bend may result in loss of trig pulses to either Tx or Rx or the loss of data from the Rx to the control unit. ?? If the measuring wheel is used then the connecting cable should be connected to the cable from the plastic hose.
7 Power supply, Optical fibres and Communication cables _________________________________________________ 7.1 Power supply Each electronic component in the RAMAC/GPR system is powered by specially designed battery packs. These packs are interchangeable between system components. Rechargeable Ni-Cd or Pb-acid battery packs are available. The capacity of the Ni-Cd packs is approximately 5.7 Ah. The Pb-acid battery packs have an approximate 8 Ah capacity.
operating in areas where recharging of the batteries is not possible. NOTE: Alkaline batteries will NOT operate the Shielded Electronics Unit. 7.2 Optical fibres The RAMAC/GPR Radar Control Unit communicates with the transmitter and receiver electronics through fibre optic cables.
For using the shielded antennas at longer distances from the CUII than 4 m there is also a plastic hose of 20 m length available. Alternatively the standard optical fibres with lengths up to 100 m can be used. All the fiber optic cables provided with the RAMAC/GPR are reinforced with Kevlar? and feature stainless steel and ceramic tip connectors. However, care should always be exercised when handling this type of cable.
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8 Multi-channel modules _________________________________________________ The RAMAC/GPR Multi-channel unit (MC-4 and MC-16) is an optional add-on module to the CUII (See Fig. 8.1 and 8.2). The Multi-channel comes in two versions, MC-4 with up to 4 recording channels or the MC-16 with up to 16 recording channels. The MC-16 connects 4 transmitter and 4 receiver antennas. The Multi-Channel unit has the capability to operate any of the optional receiver inputs to any transmitter (controlled through software).
The multi-channel unit is connected to the D-sub connector on the CUII (see Fig 3.2) and the fixed firmly with two skrews. The multi-channel unit is provided with three short fibre optical cables for connection between the add-on unit and the CUII. The lower T, D and R connectors on the CUII are used to connect the multi-channel unit (see Figure 8.2 and 3.2). Figure 8.2 The Multichannel MC-4 add-on mounted on the CUII. www.malags.
9 Trigger devices _________________________________________________ The most efficient method of data acquisition is to use a distance-measuring wheel or profile encoder (hip chain) to control the collection of radar data. Data is acquired at user defined distance intervals so that the position of each trace along a survey line is given by the position of a radar trace in the data file. This simplifies data acquisition procedures and locating the position of reflections.
information about both the numbers of pulses that are counted per meter and the rotation direction in which it will calculate the optical pulses correctly. The triggering of readings from the GPR will ONLY be done in the positive direction of rotation. This, so you should be able to move the wheel back-wards without any readings made. However, if the wheel needs to be rotated constantly in the opposite direction this can be accomplished by changing acquisition direction in the GPR software.
10 Other accessories _________________________________________________ 10.1 Antenna handles The wooden antenna handles (see Fig. 4.1) are used for carrying the unshielded antennas and stabilizing the antennas during measurements (when not using a skid box). The handles are mounted together using the set of 8 screws and nuts. Mounting both horizontal bars for maximum stability is strongly recommended. The bars come in 0.6, 1.0 and 2.0 meters lengths for use with the 200, 100, 50 MHz antennas respectively.
10.2 Skid box The glass fibre skid boxes come in two sizes, one for the 100 MHz and one for 200 MHz antennas. The robust design of the skid boxes make them well suited for operations in rugged terrain as well as on flat terrain where smooth operation and movement at constant speed are required. The mounting of the antennas in the Skid Box is seen in Figure 10.1. It is important that the antenna elements are firmly attached to the bottom using the rubber ties.
NOTE: If this is done, remember to turn on the Power switches on the antennas before survey start. ?? If the Hip Chain is used it can be mounted on the pulling handle. ?? If the Measuring Wheel is used it is mounted on the metal clamp on the pulling handle. ?? If the Wheel set is used it should be attached using the rubber ties fastened to the plastic clamps on each side of the Skid Box. Figure 10.1 Skid Box with unshielded 200 MHz antennas mounted 10.
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11 Start up of your RAMAC/GPR CUII _________________________________________________ In order to operate the system, the following items are required: ?? RAMAC/GPR CUII ?? Transmitter and Receiver antenna electronics, if unshielded antennas are used ?? Transmitter and Receiver antenna elements, unshielded or shielded ?? Optical fibers: One transmit (single) and one receiver (dual) fiber optic cable for unshielded configuration or Cable-hose assembly for shielded configurations ?? A rechargeable power suppl
11.1 Connecting the system components ?? Mount the antenna electronics to the antenna element according to Chapter 4 - 6. ?? Connect the CUII (labeled LPT 1) to the external PC parallel port with the parallel data cable provided with the system. ?? Connect appropriate fibre optic cables between the CUII and the antenna electronics as follows: ?? For unshielded systems: Single fibre optic cable from the fibre optic connector labeled T on the CUII to the Transmitter Electronics.
11.2 Running a survey When starting out for a survey you should always have an idea about the depth/time section you are about to survey. This not only determines your depth/time section to be recorded but also your choice of antenna frequency for the survey. One antenna can be used for a wide range of depth surveys but it might not possess the maximum depth resolution required for your survey. Starting a survey routine is a simple task with RAMAC/GPR CUII.
results to a fixed geographic location. Using time triggering is as an alternative for lake, river and wetlands surveys where the equipment may be setup in a boat or raft or, for studies where a Global Positioning System may be deployed for positioning control.
Trouble shooting _________________________________________________ As with all electronic equipment it is important to handle the CUII and the antennas with great care and to avoid harsh handling and bumps against the electronics. During transport of the equipment the CUII and antennas should be packed properly and firmly in a transport box. Care should also be taken for the optical fibres so they are protected against dust and dirt.
Only a straight line appears on screen when taking a reading: Cause Action The transmitter is not turned on Signal search has not not been performed The transmitter is not triggered by the CUII The ground is too conductive for a GPR survey Turn the transmitter on Perform signal search Check the LED located on the transmitter unit.
12 How to assemble the RAMAC/GPR Cart __________________________________________________ 1. When receiving the CART you will have to mount it before use. You’ll find four pieces in the case, one handle, one frame with the skid plate attached, 4 wheels and a plastic bag with smaller accessories inside. The first piece that you must start the assemble with is the frame with the attached skid plate. 2. The first step in the mounting process is to attach the wheels.
The left back wheel is equipped with an encoder. One of the wheels are different from the others and will only have the possibility to mount the needed o-ring. The o-ring can be found in the small plastic bag with the other accessories. This o-ring attached on the wheel must then be mounted on the frame of the cart as well. The picture will show how it will look like. 3. After the wheel has been mounted it’s time to prepare the handle piece.
4. Now it’s time to mount all the pieces together into one RAMAC/GPR Cart. Start by assembling the inner legs of the handle piece to the frame. Secure the mounting with the locks. When the inner legs are fasten, mount the outer legs at the front of the frame. Now we have a mounted cart in front of us and the only thing left to do is to fasten the safety leg, if you have a 250MHz Cart. This leg does not exist for the 500MHz cart. www.malags.
5. The final part is to mount the equipment onto the CART. Attach the antenna into the skid plate and adjust the straps accordingly, the skid plate should drag lightly on the ground. Use the velcro to attach the PC or RAMAC Monitor onto the upper plate of the CART. Place the PC or the RAMAC Monitor on the upper plate and place the X3M Unit or X3M Corder unit directly on the antenna. (See RAMAC X3M Hardware Manual for additional assembly).
