Using the Geoscan RM4 Resistivity Meter

Using the Geoscan RM4 Resistivity Meter with DL10 Data Logger

This instrument belongs to Archaeology. The logging and download procedure are similar to that for the Geoscan Fluxgate Magnetometer.

Establish remote electrodes and instrument setup

1. Design grid
2. Select location for remote electrodes. These must be at least 15m from the nearest point to be measured and the two electrodes should be 1m apart. The cable from the remote electrodes to the mobile array is approximately 50 m long, so careful positioning should allow a single remote site to be used for two adjacent grids.
3. Secure remote electrode line to frame with cable ties to take strain off instrument.
4. Switch instrument to rural.
5. Set range (2000 typical).

Taking measurements

6. Always walk grid in same order
7. Walk with string to right.
8. Use logger controls to supply individual dummy points/lines as required.
9. instrument autologs - so don't have prolonged contact with vegetation as probes pushed to ground.
10. A dot in front of the readout indicates poor contact - but can be ignored!
11. Flatter bleep indicates end of line and 20 good readings. 12. Two bleeps given at end of grid square. 13. Typically work with 1m between readings.

Downloading

14. Connect logger to PC
15. Switch on PC, run Geoplot
16. select Input, from Logger.
17. Place floppy with template in drive and follow instructions (make certain numlock is off!!)

Moving the remote electrodes

18. In order to keep the measurements from adjacent grids standardised (and reduce the need for subsequent normalisation) take a measurement before moving the remote electrodes (either by leaving the electrodes in at the last point on the grid - or by moving them on to the new first point).
19. Move the remote electrodes to their new position - placing them 1m apart.
20. Move one of the remote elctrodes towards or way from the other until the reading obtained is equal to that obtained from the earlier remote elctrode postion.
21. Set up is now ready to continue with new grid.

Last updated by Tim Young (Tim.Young@GeoArch.demon.co.uk) 1st October 1998.