If you’re in Proportional time mode:
If the LevelMaster 2C has been set to the ‘Proportional time’
mode rather than ‘Proportional current’ (in a page below) the valve
cycle time can be set between 100 ms (milliseconds) and 1000 ms
(or 10 Hz to 1 Hz).
If the LevelMaster 2C has been set to the Proportional current
mode, this screen is not shown.
Imagine that the sensor has been tilted to exactly the set slope; the
valves will do nothing at that point because there is no slope error.
There is a point on either side of that sensor position where the
valves will be called into action to correct the slope error. Before that,
there is a range of slope error that will not be corrected. The angular
distance between the point at which valve 1 just stops working and
the point at which valve 2 just starts working is the valve dead band,
in percent slope.
Once a tilt error sufficient to overcome the valve dead band has
been registered, one valve or the other will start to work. As the slope
error increases, the valve drive increases - perhaps to the point where
the valve is delivering maximum power. The span of slope error
between the onset of valve operation and the point at which the valve
is fully on is determined by the valve gain setting. In this case, the
(percentage) units displayed are arbitrary, but higher numbers
suggest more vigorous valve action. With the gain set to 100%, the
slightest error will fully open the appropriate valve.
To stabilize some machine control applications, it is necessary for
the control box to know not only whether the machine is at the
desired slope or not, but how fast the slope is changing and in what
direction. This is known variously as velocity or derivative (dv/dt)
feedback. The control box can vary the amount of velocity feedback
added; choose among:
High
Medium
Low
Off.
The LevelMaster 2C sensor was designed with a rather fast
response time. As a result, when mounted on a vibrating machine,
the sensor produces data which includes both tilt information and
vibration information. This fast response also reflects machine
acceleration. Either vibrations or accelerations can cause erratic
grade control.
To reduce these false signals, it will be necessary to ‘slow down’
the sensor to some degree. Select the fastest filtering level that
produces stable machine control.
When the plow strikes an unusually hard object the shoe is
bounced in a variety of directions causing the valves to correct on an
error. The LevelMaster has the intelligence to shut the valves off for
a desired amount of time as well as selecting the amount of jump it
will take to shut the valves off.
When the AI On is selected the next 2 screens will be sensitivity
and time out. The sensitivity is what it says, with 5% being able to
handle a large hit, to 95% which shut the valves off with a light
LevelMaster 2C Instructions v0.5 (Grader) (8/7/03)
page 6 of 14
Valve dead band
0.4% grade Next
Valve gain
60% Next
Derivative gain
Medium Next
FAST ---|-- Slow
Filtering Next
Valve cycle time
250ms Next
Hydraulic AI On
Change Next
AI Sensitivity
5% Next
