8500C/8500C+ System Maintenance Manual
A-1
Appendix A. 8520C-36 Signal Selector
A.1 Introduction
The 8520C-36 signal selector is similar to the 8520C signal selector, but it has inputs for 36
Velocimeter channels, rather than 12 channels. The 8520C-36 also has a bandpass filter to conform to
Allison T-56 broadband requirements. The following sections highlight the differences between the
8520C-36 and 8520C in the areas of physical description, theory of operation, and testing.
Disassembly/reassembly instructions and a parts list are also included.
A.2 Physical Description (Figure A-10)
The 8520C-36 has 8 Velocimeter connections: 4 multichannel connectors that take 8 Velocimeter
signals each and 4 discrete single-channel connectors. This provides a total of 36 Velocimeter
channels. Like the 8520C, the 8520C-36 has 4 magnetic pickup/photocell connectors, a 28 VDC input
power connector, and a connector for receiving commands from and transmitting selected signals to
the 8500C/C+.
A.3 Theory of Operation
A.3.1
A1 Connector Boards
Instead of using a connector harness as the 8520C does, the 8520C-36 uses four A1 connector boards
to route signals to the multiplexer board A4.
A.3.2
A4 Multiplexer Board (Figure A-1)
The multiplexer board routes any of 36 Velocimeter inputs to the 8500C/C+. All of the math features
and conditioning are the same as that of the 8520C signal selector with quad peak detector board.
Aside from the number of input channels, the only other difference between the 2 models is that any
8520C-36 channel can be passed through a broadband filter and measured on this board.
A.3.3
A3 Controller Board (Figure A-1)
The 8520C-36 controller board A3 is very much like the 8520C controller board, except all mux
functions have been moved to the 8520C-36 multiplexer board A4. The 8520C-36 controller board has
the following features, which function the same as their counterparts on the 8520C controller board:
•
Analog-to-Digital Converter
•
4:1 Multiplexers
