Simpson 260 Series - Page 13

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Introduction
certain that excessive circuit-to-ground voltage does
not exist.
. A switch that is opened when the relay latches, opens the relay
circuit and prevents continuous battery drain. This condition
occurs when the reset button has been released. When the
reset button has been pressed so that the VOM is operational,
the protection circuit draws less than the shelf life drain of
the battery.
. Since the 9 volt battery is used for both the R X 10,000 ohms
range and the protection circuit, the VOM is designed to allow
the protection circuit to function normally as long as the
R X 10,000 ohms range can be set to zero and an Alkaline
Battery is used.
. The 1 and 2 ampere fuses in the input circuit adds protection
to the relay contacts. Some overload conditions may cause the
fuses to burn out as well as open the relay contacts.
When an overload of sufficient magnitude,to trigger the protec-
tion circuit,is applied to the VOM, the reset button will extend
approximately 3/16 inch above the surface of the panel. To
reset the VOM for normal operation, first remove the overload
and depress the button.
If the overload remains connected to the Instrument, resetting
the overload protection reset button will not connect the VOM
input circuit.
1.2.2 Movement Overload Protection:
a. In addition to the overload protection circuit, a varistor pro-
tects the indicating instrument circuit. The varistor limits the
current through the moving coil in case of overload.
b. The relay, fuse and varistor will prevent serious damage to
the Instrument in most cases of accidental overload. However,
no overload protection system is completely fool-proof and
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