RM15 Resistivity Meter

Transcription

1 RM15 Resistivity Meter The RM15 in its case with Cable Drum on the right. The case contains, charger, download cabless, remote probes, and remote probe cables... along with the RM15 itself. Step 1: Establish Grid 1) Set out Grid over area of interest using most convenient method available at the time (tape measure, TST, other). 2) Grid squares should be 20x20 m with corners marked by clearly visible survey markers such as wooden or plastic pegs (non metallic pegs if Gradiometer survey is to follow). Ideally you will set out number of squares initially so that the survey can run without interruption. 3) Always choose your starting point with the rest of the survey in mind. Surveys should proceed in a methodical way and good planning at the layout stage make this much easier. 4) REMEMBER!: Grid squares are surveyed in a very specific way using the RM15 and the FM36: The best way to survey is to visualise your grid square as a page of text. Like reading text, survey must always begin at the upper left corner of the grid square and proceed in a left-toright direction. The particular corner that you assign as the upper left is not important as long as the direction of the first set of readings is correct

2 Setting Up the RM15 1) Identify an appropriate location for the remote probes. a. Locate probes in an area that allows for several grids to be surveyed without having to change the location of the probes. b. Choose an area where the ground is not unusually damp (ideally a piece of high ground) c. Choose an area of clear ground- not too rocky d. Try and avoid placing the probes near subsurface utilities trenches or Electrical supplies e. Connect Remote probes to the Cable Drum with colour coded wires, and insert remote probes into the ground at approximately 1m separation. 2) Uncoil remote probes cable drum so that the cable runs freely across the ground (COILED CABLE can cause errors in the electrical signal) 3) Set up instrument a. Connect RM15 to the twin probe frame b. Connect Twin Probe cable to Mobile Probes connection on RM15 c. Connect Remote Probe Cable to Remote Probes connection on RM15 4) Once machine is fully connected the display screen should display a reading in Ohms eg: 91 Ohm (If it reads Open Ctr (Open Circuit), there is a faulty connection) Make sure the cable is not coiled or bunched up

3 Proceed with the survey 1) Check settings: a. Settings in Menu (Press menu to call up list of menu items: choose 1 Map-m) i. Grid size: 20m ii. Sample interval: 0.5m iii. Traverse Interval: 1m iv. Traverse mode Zigzag To exit Menu options pres End M NEVER change menu options during a survey 2) Set out tape measures to identify traverses and sample intervals 3) Before survey begins, record in notebook the Ohm reading displayed on the screen when the probes are inserted into the ground on the first sample of the first traverse. a. This will be the Ohm reading you must match when moving the remote probes to extend the survey b. Alternatively, do this step in a convenient location (perhaps the last reading in a surveyed grid), before moving the remote probes to a new location 4) Once ready to proceed with survey press Enable Log 5) Make sure memory is cleared of anyone else s survey before starting yours by holding down the CLEAR MEM button for FOUR beeps. 6) Starting at the upper left side of grid square, prepare to survey first transect (as always moving in a clockwise direction). 7) Press START to begin survey and place probes on the ground in first 50cm. The machine will make an audible warble once the reading has been logged. 8) Lift probes and place in next 50cm interval until warble sounds. Carry on to the end of the transect (which amounts to 40 readings per line) 9) Once at end of line, move to the next transect, turn, and proceed in a zigzag path 10) After 20x20m grid has been surveyed in the above way, continue with next grid. if you need to take a break, pres Enable Log to stop the survey, but remember to pres Enable Log again before resuming with survey or no points will be logged REMEMBER! Make a map of the grids you are surveying. This map should include: Spatial arrangement of the grids, Names of the grids, traverse direction (which should stay the same for each grid)

4 Extending the area of survey Once all the grid squares that can be reached from the initial remote probe location have been surveyed, it is necessary to relocate the remote probes to a location closer to any new grid squares to be surveyed. To do this: 1) Record the Ohm reading in a location that can be reached by the initial probe setup, and by the new planned setup (this may be in a grid already surveyed for convenience. 2) Remove the remote probes (but not the mobile probes), and move them to the new location. 3) Insert them in the ground at approximately 1m apart. 4) Check the reading on the instrument 5) Move the remote probes either, further apart, or closer together in order to achieve the same Ohm reading as that taken from the previous remote probe Station 6) Once the same reading has been achieved, make sure the probes are secure in the ground, and proceed with the survey. Other Buttons Used in survey Finish line- Image line- Use for obstacles that are preventing you from finishing the line. Flick the ON/ Off switch to OFF and then press the Finish Line button. Use in cases where a line has not been done, and where you would like to fill in data for presentation purposes. This button makes a copy of the previously done line Dummy Log- Use to get over temporary obstructions. Switch off machine. Press Dummy Log for the required number of readings to get over the obstacle. Switch the machine on for the required number of readings to get to the end of the line, and then switch off immediately. If more readings were taken beyond the end of the line, use the delete key to delete any accidental readings. Log- Delete- Delete line- Enable Log- Logs individual readings every time the button is pressed. Use this in difficult terrain where vegetation or other obstacles prevent you from proceeding at pace that you normally would. Individual delete Line delete Switches between survey mode and normal standby/ menu mode. ENABLE LOG must be set in order for survey to take place, otherwise readings will not be taken. ENABLE LOG must be turned off for download of DATA!

5 Menue items Menu- (pres numerical button to enter specific Menu Item then pres menu to scroll through sub-menus) *To exit Menu options pres End M 1) Map-M a. Grid Size: 20m b. Samp. Interval: 0.5m c. Trav. Interval: 1m d. Traverse Mode: Zig Zag 2) Range a. Gain: x1 b. Current: 1mA (can be 0.1 for higher sensitivity) 3) Setup a. Auto-log Speed: Medium (depends on surveyor) b. Mains Frequency: 50Hz 4) Array a. Hardware: PA5 (the one we use) b. Interface: AD1 c. Log mode: Single d. Probe configuration: Twin 5) Coms a. Baud Rate: 9600 b. Data Separator: No Space 6) Status a. Information about machine *To exit Menu options pres End M