TM 5-3820-256-10
Figure 2-43. Setting up Logging Equipment
NOTE
If unable to zero the galvanometer, the instrument probably has too little current flow. See
Troubleshooting the Well Logging Equipment later in this section.
(2)
Logging.
(a)
To balance out the "SP", set the electrode selector switch to 0.25-foot NORMAL; set the function
switch to LOG; zero the galvanometer needle by adjusting the self-potential potentiometer. The dial
reading on the potentiometer thus obtained is the SP in millivolts with the polarity of the probe
electrode as indicated on the reversing switch. If unable to zero the galvanometer, reverse the
polarity switch and try again.
(b)
To measure resistivity (after balancing the SP), hold the current switch ON and return the
galvanometer needle to zero by adjusting the ohmmeter; then release the current switch. The dial
reading of the ohmmeter is the resistivity in ohm-feet (each division equals 1 ohm foot) for the 0.25-
foot NORMAL electrode spacing.
2-102
