Echometer Company
Model – M Manual
Phone: (940) 767-4334
5001 Ditto Lane
Page
19
Fax: (940) 723-7507
Wichita Falls, Texas 76302, U.S.A.
E-Mail:Automatic Gain Setting (AGS) Mode Characteristics
The Echometer Model M uses a microprocessor, which is programmed to evaluate the signal level before the shot
and set the amplifier gain as necessary to optimize the quality of the recording. The AGS mode on either or both
channels is activated by selecting the AUTO position before the chart drive is turned ON. Both channels are
normally operated in the AUTO mode. Changing the gain control setting from AUTO after the chart drive is
turned ON will not affect the amplifier gain. In both channels, the AUTO mode detects the noise level in the well
and adjusts the GAIN SETTING of both amplifiers so that the noise signal is recorded at a width of
1
/
8
inch on the
collar channel and 1/16 inch on the liquid level channel. The noise level in mV peak-to -peak and the gain settings
(such as A: 7.1) is printed on the header just before the legend "GENERATE PULSE" is printed. The "A:"
signifies the system was in the AUTO gain setting mode and the "7.1" indicates the gain setting.
Manual Gain Setting (MGS) Mode Characteristics
MANUAL gain setting mode is selected by locating the gain control knob to a value greater than 1 before the chart
drive is turned ON. When the acoustic traces are displayed, adjust the gain on the collar channel until
1/
8
-
inch
response is obtained. Adjust the liquid level channel gain control until
1/
16
-
inch response is obtained. Lower gain
settings may be beneficial when the traces are over-driven. Higher settings on the liquid level channel, so that the
background noise is
1/
8
-
inch, may be beneficial if the liquid level response is weak. The gain controls should not be
adjusted after the initial pulse is generated. Both channels can be set to manual mode, or either channel can
operate in manual mode while the other channel is in AUTO mode, or both channels can be set to AUTO mode.
Collar Channel Automatic Gain Control (AGC)
The
gain
of the COLLAR channel amplifier is
automatically controlled
so that the signal level is maintained at
0.6 inch peak to peak until the amplifier gain is increased to the setting that results in the background noise being
recorded at an amplitude of 1/8-inch. This results in a record showing collars at an amplitude of 0.6 inch when
strong collar signals are received. When the collar signal level fades to the background noise level or less, the
collar trace and noise will be recorded at 1/8-inch, which indicates to the operator that collars are no longer
distinguishable on the trace.
Liquid Level Channel Gain Control
When operating in the AGS mode, that is, the liquid level gain control is in the AUTO position before the chart
drive is turned ON, the LIQUID LEVEL channel amplifier gain
is kept fixed at the setting
that is established
automatically by measurement of background noise prior to the shot. AGC is not used. For large, reflected
signals after the shot, the liquid level channel recording will show that these peaks and valleys are clipped. This
method will insure that even low amplitude reflections caused by minor changes in cross section of the annulus (or
tubing) as well as the liquid level signal from deep low-pressure wells will be detected as long as their amplitude
exceeds the noise level. Adjusting the liquid level gain control after the chart drive is turned ON will not affect the
amplifier gain in the AUTO mode.
When operating in the MGS mode, that is, the liquid level gain is set greater than 1 before the chart drive is turned
ON, the liquid level gain control should be manually set so that the noise response is
1
/
16
-inch before the shot. The
gain control knob controls the gain. AGC is not used. On deep low-pressure wells, the manual gain control can be
set so that the background noise is recorded at
1
/
8
-inch before the shot is desired. If reflections from downhole
anomalies are excessive, use a lower gain setting. In manual gain mode, the proper gain should be set before the
initial pulse is detected by the electronics, which is indicated by the zero timing mark. When the initial pulse is
detected, the electronics maintains the gain setting selected by the operator at the time of the pulse detection, and
does not permit an increase in gain by the operator, which could result in the background noise being amplified and
mistaken for the liquid level.