Owners Manual Release Date: Thursday, December 29, 2011

Transcription

1 S MFD/LRL Generators Page 1 Ground Current Generator GCG By Tim Williams Owners Manual Release Date: Thursday, December 29, 2011 This document is subjected to change without any notice. Please check the release date. IMPORTANT NOTICE No parts of this document may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, electric, photocopying, recording or otherwise without written permission of Tim Williams. Copyright, All rights reserved. By Tim Williams

2 Description: S MFD/LRL Generators Page 2 The GCG unit is a 2 probe system, but different than other 2 probes systems on the market today. There are two modes of operation for the GCG. One is normal and the other scaled. The GCG injects voltage into the ground and the voltage drop value is logged on the logger. The unit can also be used alone with a digital voltmeter and log the values manually. Normal Mode: This mode is used when searching for large changes in ground anomalies like caves. Scaled Mode: This is the mode that makes the GCG stand out from other 2 probe systems! Here's how it works. The GCG takes a sample of the average ground value determine by a number of probe samples in the area. Once you are sure the data values are constant, during a sample in Normal mode the mode switch is switched to scaled. The unit now knows the background value and all readings sampled will show above and below that value! This increases the resolution of the standard 2-probe system! The GCG has a micro-controller that handles all the data. The unit is designed to be used with the logger, but can be used with a meter also. There is an output that connects to the logger via the cable that comes with the logger. The unit also has the standard 4-probe 6- sample selection switch if you are used to using that method. The method for this unit with the logger is placing your probe in the ground at selected points in the grid with one probe back out from the center of the grid about 30 feet. You move the probes the same way you do when you log using a metal detector! If you want to use the unit alone you can by connecting a digital voltmeter with a cable supplied with the GCG unit. Mark each value down and the position and later place in software to view the plot! Note: Ground resistivity is a relative measurement and changes from site to site and ground conditions. I would suggest that you read up on ground resistivity and why it works to understand what you are looking at with the plots from the GCG unit. I will try to help you understand how to use the GCG unit properly. Methods of Use: The first method is the method you will be using the most, the X, Y method. The setup is as follows. Grid the area you want to log using some ropes marked every 3 feet. You will end up with the similar to the grid shown below. You will use probes 1 & 2 and place the switch in that position. It s just like using a metal detector, except you move the probe to each square and take a sample.

3 S MFD/LRL Generators Page 3 Fig 1. Logger Setup: Set the Arc-Geo grid size as shown in the Arc-Geo manual and place the Log Mode switch to Manual. The Sense should always be at 100% if you have an older model. Connect the cable from the GCG to the logger. Setup the logger for the grid size you want. You should see the L for log mode and the X, Y first position 1,1. That is the first position you would place the probe to start your grid in the upper left corner. Make sure the mode is set to manual. GCG Scaled Mode: Place the MODE switch in the manual mode. Place the remote probe out 30 feet from the grid. The probe should be 30 foot apart. Press and hold the test button and note the data on the logger. Set the +/- button on the logger so that when you adjust the threshold on the GCG down the data goes down. Take the 4 to 6 readings in different positions about 12 foot apart. You want to take a number of readings to see the average background reading of the ground in the area you are plotting. Press the button and note the reading on the logger. You want to note the value of each. What you are looking for is a little change between readings. For example: if you have the following 5 readings. 330, 335, 325, 338, 340 these values are not changing a great deal and can be used to set the GCG in Scaled mode. But if you are seeing 330, 390, 425, 500, 300, then you may be over an object. You would have to move to another area and repeat. Each time you take a reading move both probes about 4 feet and take another reading. Press and hold test and adjust the threshold so that the data is around 50 or so on the logger. To set the scaled mode press and hold the sample button, change the Mode switch to Scaled and release the test button. The GCG has sampled the ground and set the reference and is now ready to log in scaled mode.

4 S MFD/LRL Generators Page 4 NOTE: DO NOT CHANGE THE THRESHOLD OR THE MODE SWITCH DURING THE PLOT. If you change the mode switch back to Normal you have to resample and select Scaled. Once Scaled is set you can do multiple grids in that area. Set Threshold: With the remote probe out 30 feet and the sample probe in the first position on the grid, press the test button and adjust the threshold for around 50. Threshold is used to set a background value above 0. The threshold should be set before starting each grid. Probe Placement: Place a probe out 30 feet from the center of the plot you have setup to log. With the other probe place it in the first location X1, Y1 in the grid area. Y = the row in the grid and X = the column in the grid area. Now each time you place the probe in the ground you need to press the test button and watch the logger for the data to settle so that the number stops changing but maybe +-1 or 2 digits. While holding the test button, press the log button on the logger and log the value then release the test button. Move the probe to the next position and repeat. Do this for until the grid is complete. Download and view the plot.

5 S MFD/LRL Generators Page 5 Here you can see the grid setup using ropes marked every 3 feet. This is a 4 x 16-yard plot. Notice that the tank is to one side of the plot. You will see this at the end of this manual. The first position on the grid.

6 S MFD/LRL Generators Page 6 Move the probe in the direction on the grid at each mark till the grid is complete. See fig 1. Normal Mode: You can log in normal mode, but Scaled is better for smaller ground anomalies. If you are looking for a cave or large vault you can use normal mode. Both modes will show ground anomalies. Depth: For a 2-probe system the depth is about half the distance of the probes. So if you have the probes 50 feet apart you should be close to reaching 25 feet in the ground. To find the depth of an object, the object first has to be located and centered.

7 S MFD/LRL Generators Page 7 Notes: Make sure you are not touching the probe when the Test button is pressed! High voltage is on the probes 110vac! DO NOT PRESS THE TEST BUTTON WHEN SOMEONE IS HOLDING OR TOUCHING THE PROBE! Try to place the probe in line on the grid locations. The better your lines and marks, the better your plots will be. If you are logging in the scaled mode and the data sample goes way off from 134 to 800 then you are over a high resistance area. Or if you see 675 and the data changes to 200, you are over a low resistance area. Any large change should be checked out by doing an X, Y plot over that area. If the values change from high to low more than 100 then switch to Normal and grid the area. It would be faster for 2 people to work with the probes. One person to move the probe to each location and one person to log the data and telling the other person when to move the probe. The tank shown using the GCG and Arc-Geo Logger. The reds and greens are high resistivity and the blues are lower resistivity. Water has collected around the tank area. At the back of the tank (far left) is the lowest reading in purple.

8 S MFD/LRL Generators Page 8 Remember the condition of the object you are looking for will show in the plot. If you are plotting an area for old graves, some may be high resistance colors while other may be low. This is due to the amount of water that may be in the container. You have to know how to read a plot. The important thing to remember is, if the object/pattern is man made or natural? The color bar shows you the high to low colors and from the data values. Box Square Method: I will touch on this method a little. I included the 6-sample on my unit because some units have it and some are used to using that method. The X, Y method I fell will give you far better results. Here is what you are looking for in a nutshell, changes in data from one set of probes to the others. Remember low values are low resistance objects like water, metals or conductive materials. High values are high resistance objects like rocks, sand, and different levels of less moisture content in the ground. The square can be any size depending on the depth you are trying to reach. If you were looking for a target 5 feet deep, you would place the probes about 10 foot apart. If one set of probe reading is lower than the others and the cross readings, you should move the square over and center the square over the lowest reading. If the square is centered over the target the lowest reading should not be between the cross sections of the square setup. To find the depth you would increase or decrease the square and note the data changes.

9 S MFD/LRL Generators Page 9 Straight Line Method: I choose to use this method over the box method. Sense I know the location of the anomaly whether it is low or high readings, I can tell the depth by the method below. Starting over the X, Y position of the anomaly, I would place probes (1 & 2) 4 feet apart and log the data. Next move both probes out 4 feet out in a straight line and log a reading. Repeat this for the maximum depth you would expect the target to be or greater and log each value in the logger. You would setup a Depth grid in the logger for a depth plot. A depth plot is Y (the number of reading probe movements) and X as 1. So the first square when viewing the plot would be 4, next 8, 16 and so on. Remember the depth is half the distance of the probes. Diagram of depth plot. 1.5 = = = = =69 Here is the plot you would see in ArcheoSuveyor-LT. You do not use graduated shade to view the depth plot. This is a depth plot of the tank. The probes were moved 3 feet out for each reading. So the probe distance for each reading would be; 3 ft, 9ft, 15ft, 21ft and

10 S MFD/LRL Generators Page 10 27ft. You can see from the data and color change where the top of the tank is and the bottom! The top of the tank is about 1 foot from the surface. So for a depth of 1.5ft the data was 132. The body of the tank (center) is at 4.5ft and a reading of 138. In the 7.5ft reading you can see the data reading is starting to drop again at 133. Now you can see at 10.5ft the data is 76 and the signal is passing under the tank! Still deeper at 13.5 ft the data drops more to 69. So by looking at the depth plot you can see the top of the tank is close to the surface and the bottom of the tank is about 7.5 ft deep in the ground. This could be a vault. By doing a depth plot you can view the plot and see the depth to the object and the bottom of the object at one glance. Depth plots can be as many samples in depth as you want to go. You only need to remember the distance you move each probe as you increase the space keeping the object in the center of the plot. So if you 3 foot spacing, move both probes the same amount 3ft, the distance would be 9ft. Then another 3ft the distance would be 15ft, 21ft, 27ft and so on. Of course the depth would be half of each measurement distance. 3ft=1.5ft deep 9ft=4.5ft deep 15ft=7.5ft deep 21ft=10.5ft deep 27ft=13.5ft deep You can see the depth at a glance once you see the color bar of the depth plot and know the distance of each sample. Using a Jig:

11 S MFD/LRL Generators Page 11 Test Jig This is a 3-foot test jig for locating anomalies to a depth of about 1ft to 3.5ft. The sample is taken between the tow probes mounted on the PVC pipes. The logger is setup the same way for an X, Y grid and you walk with the unit sampling at each location. This is a good method for seeing foundations and old roads and even graves. The two plots below were done using this jig with the GCG and logger.

12 S MFD/LRL Generators Page 12 Scaled Mode. Normal Mode. Specifications: Small compact design, easy to carry. 6V 4.5ah Lead Acid Rechargeable Battery, charge LED. Normal Mode used for large anomalies. Scaled Mode, used for smaller anomalies, better detail. Low Battery LED indicator. 6-Posistion Sample Switch Box Method. Log directly to Arc-Geo Logger. Output for viewing and logging on DC Volt meter Manual Log. Voltage output 20ma Charging: Charge the GCG for 12 hours (overnight). Do not over charge the battery! If you over charge the battery and it harms the PCB by leaking acid, it is not covered under warranty. Testing the unit:

13 S MFD/LRL Generators Page 13 I would suggest that you find an old tank or something-large underground to test on. Test and test until you get an idea for comparing the plot to the object you tested on. You have to think if the object is an insulator or a conductor. If you have some culverts near you try to fine one made of iron lower resistance and one made of cement higher resistance. Do plots over both and also do depth plots and you will see the difference. You cannot use an instrument unless you know how and why it works. Water is a good conductor. Metal is also a conductor. But at the same time a cement vault is a high conductor! You can see it is not an easy way. This unit will show you high and low anomalies in the ground. I don t know if any equipment that will produce a treasure for you! Test until you know what you are looking at. This unit is a very important part of your treasure hunting equipment. Probes: You can make your own probes if you want. Simple probes to make are an 18 piece of copper-coated grounding rod and sharpen one end. You can connect to them using a clamp. Or you can make a rod with the top bent into a handle. Here are some pictures of the rods I am offering on my site. The pictures are as follows; 18 T-Rod, 48 T-rod with footrest, Wire Connection, Hammer spot on T-rod. These Probes are made with 401 Stainless Steel 3/8 rod and 5/8 SS handles. Check my site for current price and availability.

14 S MFD/LRL Generators Page 14 Clamp Used to connect to rod. I like to use a fork connection instead of a clamp shown above. NOTE: Make sure the probe contact is the same for each sample. The probe should be the same depth each time. The depth of the probe will be different for the ground conditions. A minimum of 12 deep is good for average ground conditions. Closing Notes: You can get added information on a site using ground resistivity. You should know that values change with ground conditions. From sand to rocks and clays all have different background values. Some instruments have lamps and fixed resistivity values for metals like gold and silver. I have to say that it does not work that way. Down here near the coast and at sea level the normal resistance is around 150 to 200 ohms! The lamp would stay on all the time. Does that mean I have metal in the ground everywhere I use it? No! Every area is different. You have to sample the background normal ground resistance for that area and look for changes from that value high or low. An iron strongbox 2x2 feet at 4 feet may only change the value ohms in a dry area. The amount of change depends on the size of the target and ground conditions in that area. The same strong box may show a change of 100 from normal because water may be collected around it. Or if you live where I do you may never see that box because it may be sitting in the water table! Resistance is relative to the area you are searching! Get information of the depth of the water table and other information of the site you intend to search. I m using example values of change. A change of 2 10 is still a change. I hope you enjoy the GCG unit. It can be a valuable tool in the field and give added information on a site. Along with the Arc-Geo logger you have the tools you need to see in the ground and determine if you want to dig or not. No matter what equipment you use, the decision to dig will be up to you. I am being straight up here. No one wants to waste time digging. The more information you have the better. I will have more on the CGC unit soon and update the manual as needed.

15 S MFD/LRL Generators Page 15 WARNING! Be careful when handling the probes. When the test button is pressed, around 20ma maximum is present on the probe. NEVER press the test button when a person is holding or touching the probe. All ground resistivity units can shock you with high voltage. Some have higher voltage than the GCG unit. Always be careful. By using this equipment you understand the dangers involved and with any ground resistivity system, that it is dangerous and you do not hold me responsible for your actions and use of this equipment. Best wishes to you and good hunting! Regards, Tim Williams