Using the Geonics EM-31 with the Polycorder
EM-31
Initial setup procedures: Do Not Drop the Various Parts!
If the reading stays the same (+/- 0.2)
the phase is correct
return the COARSE control to its original position (one turn counter clockwise)
Else a phase adjustment is required
see page 11 of the EM-31 Operating Manual.
POLYCORDER Initial Setup Procedures
Lab Rule: you can erase any data files that are on the Polycorder when you check it out.
1. Enter a file name, as requested, using the keypad. Enter letters and punctuation by using the SHF key once for each letter position the desired letter is offset from the left choice on a particular key. For example, to enter "EZ": SHF SHF 8, SHF SHF 3; ENTER when done. Use up to 7 characters; the program creates header and data (H,D) files with this name. BEWARE - if you enter a '.', '-', or '/' in or after your filename the remaining sequence becomes a password and you will not be able to download data without supplying your password. Furthermore, the windows software will probably crash the computer when you try to download.
2. Select Phase, either Quad Phase, In phase, or Both as requested with 6, 9, or 7 (no shift!)
3. Select MODE to specify Vertical, Horizontal, or Both (2, 9, 7) to specify how you will be holding the instrument at each station. Vertical dipole MODE provides twice the effective depth of exploration as the horizontal MODE (~6m and ~3m respectively); see Geonics Tech note TN-6. In general, when taking horizontal measurements or both horizontal and vertical, the measurements should be taken at ground level. (no shift!)
4. Select Orientations with one digit (1 or 2) to specify if you will or won't be collecting perpendicular data at each station. You could also collect data at two different heights.
5. Enter your initials as operator and any Comment you prefer; then ENTER.
6. Select Y or N for auto. If you select Y the Polycorder will take a reading at a specified time interval; N lets you determine when the reading will be taken. N is the best general case but for a long reconnaissance profile Auto is convenient; units are seconds: 0.5-99.9
7. The next queries allow you to specify line numbers, stations and intervals appropriate for your field experiment. For Line, enter up to eight characters that identifies this particular survey line to you. It will likely be one line of several in a data file or the first of several in a grid of data. Consider using a normal coordinate system (x increases to the right, y up) for Surfer. Enter direction, and Starting station (usually zero, but up to five characters). By convention, positive station numbers signify stations in the line direction. Enter Increment in your units (e.g. meters) and (+/-) to acquire at least two points per wavelength of variation in ground conductivity; walk next to a tape or on a pre-established grid.
8. After the above, the Polycorder says "READY - ENTER to LOG". Hit ENTER, and the Polycorder displays "ST" and the current station number. The Polycorder is now ready to start recording measurements; set up the EM-31 if you have not done so already.
COLLECTING DATA
WITH THE EM-31 and the POLYCORDER
RECHARGE THE POLYCORDER'S BATTERIES BEFORE YOU STORE THE INSTRUMENT
To Download Data From the Polycorder to the PC
Windows Software - the default method for downloading data
DAT31W is Geonic's Windows program for downloading data.
DOS Software - you
probably won't use this
This is the DOS method - which might still work. The EM software is in C:\DIR\EM - DAT31.EXE. If I haven't shown you how to do this DO NOT mess with it without help:
Select Copy Files from Polycorder 720.
SELECT your files, then COPY them.
CONVERT DL files to DAT31 Format.
Your files and now in ascii, ready for manipulation in Excel or Surfer