GDP-32
II
INSTRUCTION MANUAL
January 2003 Section 10, Page 16
10.4 A NOTE ON PHASE
The CR/HACSAMT program is an absolute phase program - that is, the program measures the
absolute phase shift between the transmitted signal and the received signal. For normal
operations at low frequencies, the real-time phase shift should be around -100 to -200
milliradians. If the phase is closer to π radians (3142 mr) then you have some wires reversed.
You can get rid of the π radians of phase shift by either reversing the transmitter wires at the
transmitter, or reversing the leads going into the receiver. For multi-channel receivers, it is
easiest to make the change at the transmitter, and then maintain the same polarity throughout the
survey.
CAUTION
The sign of the calculated phase has been changed to be consistent with all of the absolute phase
programs. The original versions of the CR program produced positive phase values for
traditional "positive IP". However, an artificial sign change was implemented to do this. Since
the CR program is now used for CSAMT, FEM and MMR, as well as CR, the sign of the phase
had to be made consistent with other programs. Positive IP responses will now have a negative
phase value, just like the RPIP program. Please contact Zonge Engineering if this causes
problems with your in-house data reduction programs.
10.5 A NOTE ON SCALING
The following convention is used for all measured and calculated parameters:
Voltage (magnitudes) displayed in volts.
Current displayed in amperes.
Phase displayed in milliradians.
Apparent resistivity displayed in ohm-meters.
Dipole spacings displayed in meters.
SP displayed in millivolts
SEM displayed in milliradians
If scaling is necessary on these values, the following labels are appended to the end of the
number string:
M - Mega units
K - Kilo units
M - milli units
u - micro units
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