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1. INTRODUCTION
1.1 General Description
The Simpson Volt-Ohm-Milliammeter 260 Series 8, (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 260-8 are:
0-25V AC/DC Range
Mirrored Dial
1.2 Overload Protection
No single protective device nor even a combination of devices as found in the
260 can fully protect a multipurpose Instrument under all overload conditions.
Overloads of such severity as to damage the Instrument despite all the built-in
protection provided are possible when the Instrument is misused. The 260-8 has
been designed to afford maximum instrument protection under overload condi-
tions which might occur within the measuring capabilities of the Instrument, how-
ever, the operator must exercise care to avoid severe overloads, particularly
when working in high voltage circuits.
Basic overload protection is provided by a small inexpensive and easily obtain-
able 3 AG type, 1 Amp, quick-blow fuse. This fuse is rated to interrupt circuit
voltages up to 250 V. For maximum protection it is important to replace the 1A fuse
with the Littlefuse type 312001 only.
A supplemental high energy fuse is provided for additional protection from se-
vere overloads. This fuse is rated for an interruption capacity of 10,000 Amps up
to 600 V. (Littlefuse Type BLS or Bussman Type BBS). If the Instrument fails to
indicate a reading, 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.
Two diodes connected across the meter movement affords protection to the move-
ment by circumventing excessive current around the movement in the event of an
overload.
1.3 Internal Batteries
There are two batteries in the ohmmeter circuits, a NEDA 13F size D cell that
furnishes 1.5-volts for the R X 1 and R X 100 ranges and a NEDA 1604 battery
that furnishes 9-volts for the R X 10,000 range. The 1.5-volt D cell is held in place
with two spring clips which also serve as battery contacts. The polarity symbols
for the D cell are marked near the battery contacts. The 9-volt battery is held in
place with a spring clip, but contact is made with a separate connector that is
polarized. Always observe correct polarity when replacing the 1.5-volt D cell.
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