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Mainframe Description
A mainframe is a device into which plug-in modules may be installed to create an instrument
in the modular measurement system. The HP 70001A mainframe provides the structural
environment for plug-in instrument modules along with cooling, power, and digital
communication interface buses.
It can accommodate 1/8-, 1/4-, 3/8-, and 1/2-width modules, and has a maximum capacity of
eight 1/8-width modules.
Standard rack compatibility is provided, and bench-top use is facilitated with integral bails and
retracting handles.
The Hewlett-Packard Modular System Interface Bus (MSIB) supports high-speed digital
communication among instrument modules within a mainframe and among instruments
connected to the external MSIB loop.
Every module in a mainframe has access to the standard Hewlett-Packard Interface Bus
(HP-IB). This bus provides a path of communication among controllers, other HP-IB instruments
and individual modules.
The ac power input is switchable between several ranges.
90-132 Vac, 47|66 Hz
199-264 Vac, 47|66 Hz
103-132 Vac, 356|444 Hz (with Option 400)
The mainframe power supply processes the ac line power to produces regulated 40 kHz
ac power for the modules, 5 Vdc for the MSIB, dc power for the cooling fans and a TTL
compatible line syncronization signal.
The primary power output, 24.3 Vac (average voltage, not rms) at 40 kHz, provides up to 200
Watts of power.
Two fans provide cooling for both the mainframe and up to eight installed 1/8-width modules.
The cooling fans operate at variable speeds: they are slow at temperatures below 30
increasing their speed linearly above 30
This provides adequate cooling over the permitted range of temperatures.
Mainframes with serial numbers 2704A01796 and lower may have single speed fans. A Fan
Speed modi cation kit can be ordered for these units. This modi cation will provide variable
speed fans, reducing fan noise about 3 dB at ambient temperatures below 30
1-2 General Information
C to a maximum speed for temperatures above 55
C,
C.
C.
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