Research Concepts RC2500 - Manual (Page 18)

RC2500 Antenna Controller Chapter 3 Installation/Setup 11
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas • 66218-9680 • USA www.researchconcepts.com
3.3.1 Azimuth Elevation and Polarization Resolvers
The low-voltage resolvers used for position sensing with the RC2500 are meant to directly sense the
angle of each of the principal antenna axes. Resolvers act as rotary transformers that have a primary coil
driven by a sinusoidal AC voltage and 2 secondaries, one oriented to produce a voltage proportional to
the Cosine of the angular position and the second oriented to produce a voltage proportional to the Sine
of the angular position. A converter inside the RC2500 calculates the position from these two voltages.
3.3.1.1 Resolver Resolution and Accuracy
The 360° angular region measured by the resolvers and on-board resolver-to-digital converters is divided
into 2 16 (or 65,536) discrete positions. Therefore one ‘count’ is equivalent to 360 / 65,536 = 0.005493°.
This number represents the resolution of the angular mesurement system of the RC2500. The RC2500
can position an antenna to no better than within 0.005493° of the target position. The actual positioning
performance will depend strongly on the mechanical and electrical drive components of the system. The
accuracy of the system depends almost solely upon the accuracy of the resolvers used. The standard
resolvers shipped with the RC2500 have + 7 arc-minute accuracy or + 0.11667°.
3.3.1.2 Physical Mounting of Resolvers
The recommended resolvers, RCI P/N Z-RESOLVER are size 11, that is they are 1 inch in diameter and
1and ¾ inches long. They are shipped with 12 inch flying lead connections that extend from the side of
the resolver body opposite the shaft end. A drawing of the resolver is shown in Figure 3.2. Special
bracketry may be required to mount the resolvers to the principle axes of the antenna. This will most
certainly be the case if this is a retrofit installation and larger 120VAC synchros were originally used. A
bellows type strain relief is recommended for the interconnection of the resolver shaft to the principal axis
shaft.
Care should be taken to ensure that the resolvers are protected from the weather. In most instances, a
rubber “boot” is constructed which covers most of the resolver body and has a single liquid tight fitting for
the resolver cable. The resolver cable is meant to run directly to the RC2500.
The resolvers shaft must be positioned such that the sensed position does not wrap around (from 0.00 to
360.00 or 360.00 to 0.00) within the antenna’s normal range of movement for a given installation.