Hewlett Packard 3746A Level Meter
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Model:
3746A
Date:
1984
Category:
Group:
Description:
SELECTIVE LEVEL MEASURING SET
Information
DESCRIPTION
1-15 The Hewlett-Packard 3746A Selective Level Measuring Set
(SLMS) is a high quality tunable power meter dedicated for
use by operators and manufacturers of high density Frequency
Division Multiplex (FDM) systems.
1-16 The SLMS has been specifically designed for
manufacturers and operators who use either CCITT
recommendations or the North American Standards.
1-17 The SLMS is basically a tunable receiver, employing a
synthesized local Oscillator, controlled by a processor. A
keyboard provides the Interface between the operator and the
processor.
-18 The SLMS measures signal powers in the range 50Hz to
32MHz at levels between +20dBm and -115dBm, depending upon
the measurement bandwidth used,
1-19 Either balanced or unbalanced measurements may be made.
1-20 Measured levels are true RMS values.
1-21 The instrument displays power levels either in dBm or
in dB relative to a dBm reference level. Automatic
correction ensures that whichever input is selected the
display will be correct for the chosen terminating impedance.
1-22 The frequencies at which measurements are required may
be entered via the keyboard either directly in kHz, or as a
description in a chosen FDM plan.
1-23 This ability to enter FDM descriptions directly into
the instrument eliminates the need for FDM charts and line
frequency tables to determine the frequencies to which the
instrument is to be tuned.
1-24 Tuning to the measurement frequency is accomplished by
mixing the received signal with a variable frequency signal
from an internal synthesized local Oscillator to give a
fixed intermediate frequency. To achieve the high degree of
selectivity and image rejection required, the SLMS uses
multiple intermediate frequency (IF) stages.
1-25 The standard instrument is equipped with selective
filters to allow a choice of measurement bandwidth.
1-26 The measurement of narrow bandwidth tones in a wideband
measuring set requires extreme accuracy in the local
Oscillator frequencies used. This requirement is met by the
use of a frequency Synthesizer as the local Oscillator in
the SLMS. A master Oscillator with a 10MHz crystal source,
high spectral purity, and an ageing rate of less than
1.5x10s parts per month is available as an option.
1-27 A processor provides overall control within the
instrument, implementing routines which govern the
measurement functions of the instrument and calculating from
the various autoranging and
analog to digital settings the levels to be displayed. The
processor also determines the frequency and bandwidth
setting required when FDM descriptions are entered.
1-28 The SLMS has a built-in control and drive circuitry
which enables the SLMS to control up to 111 Access Switches.
1-29 The processor will accept instructions either from the
operator via the keyboard or, if remote control of the
instrument is required, through the Hewlett-Packard
Interface Bus (HP-IB) connector on the rear panel. A degree
of in-built intelligence in the processor enables it to
detect if the instrument is required to perform an invalid
measurement or if incorrect data is entered. In these
circumstances a code number will appear in the TEST-POINT
display window.
1-30 The processor performs a calibration of the measuring
circuits at periodic intervals, substituting for the
incoming signal an accurately defined signal derived from an
internal high stability source. The processor stores the
result of this measurement and uses any deviation from the
expected measurement to modify the results of measurements
made on external signals. Thus any inaccuracies resulting
from thermal drift or ageing in the measurement stages are
greatly reduced.
Manual type:
Service Manual
Pages:
411
Size:
22.40 Mbytes (23483002 Bytes)
Language:
english
Revision:
Manual ID:
03746-90002
Date:
1984 03 01
Quality:
Scanned document, all readable.
Upload date:
2017 12 31
MD5:
43a5d29d7c935aa560750775efeff7a0
Downloads:
637
Information
This manual applies directly to instruments
with serial numbers prefixed 240511