Simpson 260-8P, Instruction Manual, Page: 6 / 32

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1. INTRODUCTION
1.1 General Description
The Simpson Volt-Ohm-Milliammeter 260 Series 8P, (hereafter referred to as the
260 or as the Instrument) is a rugged, accurate, compact, easy-to-use Instrument
equipped with mirrored dial to eliminate parallax. The Instrument can be used to
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 in the 260-8P are:
0 - 25V AC/DC Range
Continuity Test Alarm
Individual Dual Jacks for the 500V AC/DC and 1000V AC/DC Ranges
1.2 Overload Protection
All the ranges, with exception of 1V, 10A, 50 μ A, 250mV, 500/1000V AC and DC
are protected by an electronic overload protection system. The protection is from
the usual overloads that would damage the VOM. A transistorized circuit senses
the voltage drop across the indicating instrument and actuates a relay when the
voltage reaches approximately three to four times rated full scale voltage. Sens-
ing of the voltage drop is by means of a bridge network so that overload protec-
tion is provided regardless of polarity. The relay operates at a uniform percent 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 CIR-
CUIT, latch open until the reset button on the front panel is depressed. The reset
button is located to the right of the output jack.
Due to its sensitivity to overloads, the electronic overload protection relay incor-
porated in the 260-8P is susceptible to electrostatic fields from high potentials or
transients either in the circuit being measured or in nearby circuitry.
Do not assume the relay to be faulty if it trips out without apparent cause. It may be
indicating a dangerous condition such as excessive circuit-to-ground (floating)
voltage being applied to the Instrument.
Avoid loading the Instrument or its test leads until certain that excessive circuit-to-
ground voltage does not exist.
a. A switch that is opened when the relay latches, opens the relay circuit and
prevents continuous battery drain. This condition occurs when the reset but-
ton has been pressed so that the VOM is operational; the protection circuit
draws less than the shelf life drain of the battery.
b. Since the 9V battery is used for both the R X 10,000V range and the protec-
tion circuit, the VOM is designed to allow the protection circuit to function
normally as long as the R X 10,000V range can be set to zero and an Alka-
line Battery is used.
c. The 1 and 2 Amp fuses in the input circuit adds protection to the relay con-
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