Humminbird 531427-1_D Marine GPS System User Manual


 
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Freeze Frame: Freeze Frame is a Humminbird® feature that pauses the sonar scrolling so that the
image on screen can be studied with greater detail. See Instant Image Update.
Frequency: Frequency is a measure of the number of sound wave cycles per second of a sound
impulse transmitted underwater. A typical frequency for fishfinders is 200 kHz, which offers a
good balance of performance under many conditions. Lower frequencies, such as 50 kHz, are
capable of penetrating to greater depths, but with less resolution. Higher frequencies, such as 455
kHz, offer greater resolution, but are limited in depth performance. Humminbird® uses a variety
of frequencies that are optimized for specific applications.
Grayscale: Grayscale is the use of varying shades of gray to represent the strength of the sonar
signal on the display , and is a very intuitive method of presenting information. Traditionally, the
strongest sonar signals are represented in black, and progressively weaker signals are represented
in progressively lighter shades of gray.
Grayscale, Inverse: Inverse Grayscale is a Humminbird® feature that reverses the correlation of
sonar signal strength and the shade of gray typically used to represent it. The strongest sonar
signals are represented by "white", and progressively weaker signals are represented in
progressively darker shades of gray. While somewhat counter-intuitive, this method makes the
sonar images crisper, and has the benefit of enhancing the apparent sensitivity because the
weaker signals appear bolder. Inverse grayscale works well in very clear water. Debris-laden water
often appears as a lot of clutter on the screen.
Instant Image Update: Instant Image Update is a Humminbird® feature that updates all the sonar
information on the display when Sensitivity and a variety of sonar settings (Bottom View, Range,
etc.) are modified. This differs from the traditional functionality that only updates the new sonar
information collected after the setting change. Instant Image Update permits more accurate fine-
tuning of the display because the user can see the results on the complete sonar graph. When
combined with the Freeze Frame feature, the user can adjust and understand the effects of many
different sonar settings quickly and easily.
Maximum Depth Menu: The Maximum Depth Menu is a Humminbird® feature that optimizes
performance based on the maximum operational depth set by the user. Many Humminbird®
units can operate across a very broad depth range (up to 2500 feet) which causes the unit to
"look" up to that full depth under some circumstances. Due to the speed of sound in water, this
can result in less responsiveness because the unit has to wait for a longer period of time to receive
the sonar signal. When the Maximum Depth menu is set to a lower value, the unit only looks up
to the setting, which increases the responsiveness of the unit. This is an important feature for
anyone operating in shallower depths!
Noise: Noise is unintentional, external sound waves that interfere with the optimal operation of
sonar. Noise appears as random "dots" on the display, and is caused by a variety of sources.
Electrical noise (from trolling motors, bilge pumps, VHF radios) typically manifests as a consistent