Service manual

RC2000 Service Manual Chapter 4 Common RC2000 Questions 26
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active - anytime a pulse is received it increments or decrements the position count based on the
direction the antenna was last commanded to move. If a position pulse is received by the controller
and the controller is not either moving or in a coast period defined by the Az/El Fast/Slow Deadbands
described above a RUNAWAY error will occur.
Any time the controller is tracking an inclined orbit satellite and a system error occurs, tracking will halt and
the '**ERROR** SYSTEM" message will be displayed. A system error is any error which generates a
flashing alarm message on the bottom row of the display.
4.3 Antenna Position Sense Errors
The RC2000 antenna controllers are designed to work with pulse type sensors - either reed or Hall Effect.
The controllers can also be used with most electro-optical based pulse sensors. 5.7 volts DC is available
at the back of the controller to power Hall Effect or electro-optical based sensors. Position sense errors
affect the positioning repeatability of the controller. Repeatable antenna positioning is the main
requirement of the antenna controller.
One way to test the positioning accuracy of the controller is to repeatedly move the antenna between 2
satellites stored in the controller's memory. If the controller is experiencing position pulse count errors the
antenna will not return to the peak power position for the satellites. As the antenna is repeatedly moved
between the pair of satellites, the pointing error will increase.
If the antenna controller is used to track inclined orbit satellites, count errors can be easily seen by plotting
the figure eight pattern of the satellite's apparent motion described by the azimuth and elevation values
contained in the controller's program track table. These track table coordinates can be obtained from the
TRAK mode Menu system via the View function. If count errors have occurred the figure 8 pattern will not
close on itself.
4.3.1 Causes of Antenna Position Count Errors
1. Noise - The cables used to connect the position sensors to the controller must be shielded.
Conductors used to carry motor drive current must not be enclosed within the same shield that is
used for the sense lines. The position sense cable drains should only be connected at the controller.
If the cable is spliced the drain wires must also be connected at the splice. The drains should not be
allowed to come in contact with earth ground at the antenna or at any breaks or splices in the cable.
More information on position sensor cabling is available in Chapter 3 of the RC2000 manual.
If the source of the noise is something other than the drive current of the motor of the axis which is
experiencing the errant count a RUNAWAY error will probably occur. RUNAWAY errors are
described in the section on Antenna Azimuth and Elevation Errors.
2. The position sensors are placed on the fundamental axis of the controller. For a description of the
errors caused by placement of the position sensors on the fundamental axis of the antenna
controller please see the Antenna RUNAWAY error, item iii, above.
3. Occasionally, position sensor modules fail. This will generally occur on new actuators. If antenna
count errors persist on a given axis after the cable shield connections have been verified and
RUNAWAY errors are not occurring, the sensor may be dropping pulses. With reed type sensors
this can occur when the reed switch element is not oriented properly in the module. For any type of
sensor loose connections can also cause count errors.
4.4 Track Mode Limit Error
When a track mode limit error occurs tracking will cease and the controller will display the following error
message (as long as TRAK mode is active) '** ERROR ** LIMIT '. This error message should not to be
confused with the track mode peak limit error message which is '** ERROR ** PEAK LIMIT'.