Simpson 270-5, Инструкция по эксплуатации

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5
1. INTRODUCTION
1.1 General Description
The Simpson Volt-Ohm-Milliammeter 270 Series 5 is a rugged, accurate, com-
pact and easy-to-use instrument that will make accurate measurements of AC
and DC voltage, direct current, resistance, decibels, and output voltage. The
output voltage function is used for measuring the AC component of a mixture of
AC and DC voltage. This occurs primarily in amplifier circuits.
New Features for the 270 are:
New connectors between the Instrument and the test leads, eliminating a
shock hazard if a connector is inadvertently pulled out of the Instrument jack.
An OFF/TRANSIT position, which is added to the function switch to protect
the meter movement during transit. (This position shunts the meter move-
ment and opens the internal connections to the COMMON and + jacks.)
A test lead set with molded elbow plugs at one end for connection to the front
panel input terminals and test probes at the other end. The test probes have
a non-slip grip surface and a barrier to maintain the spacing between the
user’s fingers and the probe tip. Threaded shoulders at the probe tip accept
screw-on alligator clips (supplied).
1.2 Overload Protection
No single protective device nor even a combination of devices as found in the
270 can fully protect a multipurpose instrument under all overload conditions.
Despite all the built-in-protection provided, however, severe overloads can dam-
age the Instrument when the Instrument is misused. The fuse/varistor combina-
tion in the 270 has been designed to afford maximum instrument protection un-
der foreseeable overload conditions which might occur within the measuring
capabilities of the Instrument. However, the operator must use care to avoid
severe overloads, particularly when working in high voltage circuits.
a.
Fuses: Basic overload protection is provided by a small, inexpensive and
easily obtainable 3 AG type, 1 ampere, quick-blow fuse. This fuse is rated to
interrupt circuit voltages up to 250 volts. A supplemental high energy fuse is
provided for additional protection from severe overloads. This fuse is the
Bussman Type BBS 2A 600 V and has an interruption capacity of 10,000
amps AC. The Littlefuse Type BLS 2A 600 V with an interrupt capacity of
100,000 amps AC may also be used.
b. For maximum protection replace the 1A fuse with a Littlefuse Type 312001
only. This will allow the combination 1A and 2A fuse to give maximum protec-
tion to the unit and user under overload conditions which may occur within
the measuring capability of the VOM.
c. If the Instrument fails to indicate, the 1 Amp or the 2 Amp fuse may be burned
out. (Refer to paragraph 5.3 for fuse replacement.) A 1 Amp spare fuse is
furnished with each Instrument. Fuses are located in the battery and fuse
compartment.
NOTE: The 0-10A range is not fused. The shunt connects directly to the -10A and
+10A jacks.
d. Two diodes connected across the meter movement afford protection to the
movement by circumventing excessive current around the movement in the
event of an overload.