Simpson 260-6LPM, Instruction Manual

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1. INTRODUCTION
1.1 General Description
The Simpson Volt-Ohm-Milliammeter 260 6XLPM (hereafter referred to as the
260 or the Instrument)
The 260 is a high performance, battery-operated Volt-Ohm-Milliammeter capable
of making a wide variety of electrical measurements simply and accurately. Fea-
tures are overload protection, conventional and low-power ohms, and a wide range
coverage. The case is made of high-impact (ABS) plastic and has a contemporary
style. The features, in combination with extended range coverage (Table 1-1)
make this Instrument a general purpose, portable or laboratory Instrument. It is
well suited to servicing, production, inspection and engineering applications.
The 260 uses the Simpson taut-band movement, which is self-shielding. The taut-
band suspension provides a high degree of repeatability and is highly resistant to
shock or vibration.
1.2 Overload Protection
All of the ranges with the exception of the 5A and 500/1000V AC and V DC ranges,
are protected by an electronic overload sensing circuit. The protection is from the
usual overloads that could damage the Instrument. A transistorized circuit senses
the voltage drop across the indicating instrument and actuates a relay when the
voltage reaches approximately three times rated full scale voltage. The sensing of
the voltage drop is accomplished by use of a bridge network, so that overload
protection is provided regardless of polarity. The relay operates at a uniform per-
cent of overload since the indicating instrument circuit is common to all ranges.
When actuated by an overload, the relay contacts (which are in the COMMON
circuit) latch open and remain open until the reset button on the front panel is
pressed. The white reset button is located to the left of the -5A jack. An additional
switch is opened when the relay is actuated; this switch opens the coil circuit of the
relay and the electronic sensing circuit, and prevents continuous battery drain.
Once the reset button has been pressed to make the Instrument operational again,
the protective circuit is restored to its monitoring status, but does not draw any
current from the battery (until another overload occurs). A 9V battery is used for
both the RX10,000 ohms range and the protection circuit. The Instruments are
designed so that the protective circuit will function normally as long as the RX10,000
ohms range can still be “zeroed.”
The 9V battery must be installed and tested before the Instrument is ready for use.
Perform the overload test described in paragraph 4.6 to ensure proper overload
operation before using the Instrument.
1.3 Overload Circuit Reset
When an overload of sufficient magnitude to trigger the protective circuit is applied
to the Instrument, the reset button is tripped and will extend approximately 3/16
inch above the surface of the panel. To reset the Instrument for normal operation,
first remove the overload and press the reset button. If the overload is not discon-
nected, pressing the reset button will not reset the overload protection circuit. The
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