The 1251 Multichannel Analyzer System 1250 Frequency Response Analyzer
16-2 AMK/1250/1
16.1 INTRODUCTION
Used with the 1250 Frequency Response Analyzer, the 1251 Multichannel Analyzer
System allows the number of analyzer channels to be incremented to a maximum of 34
parallel channels. The 1251 system is not available with 1250N.
16.2 DESCRIPTION
The 1251 system consists of:
a. Up to four individual free-standing 1251 Multichannel Analyzer Units, each Unit
accommodating a maximum of eight analyzer channels. Inputs to the channels are
via eight pairs of BNC sockets, marked HI and LO, mounted on the rear panel.
b. Up to four lengths of ribbon cable with 25-way sub-miniature D-type connectors at
each end, one cable per 1251 Unit. These cables together form the 1250-1251
Interface Bus, which connects the individual 1251 Units to each other and to the host
1250.
16.3 SYSTEM CONFIGURATION
The configuration of a complete multichannel frequency response measurement system
is illustrated schematically in Fig. 16.1. The full system comprises four 1251 Units and a
host 1250, providing a total of thirty-four input channels if required. The number of
channels additional to the two in the 1250 can be varied anywhere between one and
thirty-two, each group or part-group of eight extra analyzer channels requiring an
individual 1251 Unit.
16.3.1 1250-1251 INTERFACE BUS
The 1251 Units and the host 1250 are interconnected via the 1250-1251 Interface Bus
as shown in Fig. 16.1. This bus is used to route all control commands from the 1250 to
the 1251 Units; it can also route measured data from each 1251 Unit back to the 1250
for display or other processing or for onward transmission to the IEEE 488 Interface Bus
via the IEEE 488 port of the 1250.
16.3.2 IEEE 488 INTERFACE BUS
In addition to the 1250-1251 Interface, each 1251 Unit contains its own IEEE 488
Interface port. This allows direct connection of the 1251 Unit to the IEEE 488 Interface
Bus for the rapid transfer of measured data to a Controller. Details of data transfer
speeds are given in Section 7.4.
16.3.3 1250 SERIES 0PTIONS
Connecting the 1251 Units to a 1250 FRA does not affect the operation of any of the
Options fitted in the 1250. In particular, each analyser channel of the 1251 System
contains the demodulation facilities necessary for operation with a 1250 incorporating
the 12502A Modulator/Demodulator Option Unit.
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