Sencore FE149 - Page 10

long life high current cell such ав the Eveready Alkaline Enegizer No. E95 or equiv-
alent is recommended for the ohms battery. A regular type "D' cell can be used,
however, but will not last as long, especially if many low ohms measurements are
made. Тһе 9.6 volt rechargeable battery is a Burgess CD24 or equivalent.
CHARGING THE BATTERY IN THE FE149
The 9.6 volt rechargeable battery in the FE149 is automatically recharging when
the FE149 is turnedon and the unitis plugged into a 105 to 125 50-60 Hertz AC source.
The special circuit design will not allow the battery to be overcharged, no matter
how long it is left charging. When using the FE149 on the bench, it is advisable to
always have the meter plugged into the line, so that when you should require portability
or wish to make measurements with an isolated meter, the battery will be always
fully charged and ready to go. If the FE149 is used as a portable meter on the
rechargeable battery, the battery should be recharged after a days use if at all
possible. Periods ofoperation over 100 hours withoutrecharging the battery should
not be attempted as meter accuracy will be affected and also it'shard onthe battery.
То completely recharge the battery after this period, it should be charged 150 hour,
А generalrule is to charge 1. 5 timesthe usage period. If the FE149 can be IT |
into an AC source and leftcharging overnight after a day's use, no difficulty shou
ever be encountered with а run down battery. Тһе battery check on the FE149 is
used to tell the condition of the battery and when recharging may be necessary.
NOTE: Ifthe FE149 is left in the battery check position, the battery will not charge.
In the battery check position, the battery is removed from the charger and a load
placed on it to give an accurate check of its condition. Тһе battery will charge in
any other position of the Function switch, as longas the unitis plugged inand turned
on.
CONVERTING THE FE149 FOR 230 VOLT AC OPERATION
'The conversion of the FE149 to 230 volt 50 to 60 Hertz AC operation is simple and
easy. The schematic diagram shows the hook up on the special transformer. Тһе
brown and white leads are disconnected from their present location, but the blue and
black wires remain connected го ће same point. Now simply connect the brown and
white wires together, solder, and wrap with tape to insulate. Тһе FE149 will now
work from 230 volt 50 to 60 Hertz AC or the internal battery.
OVERLOAD PROTECTION ON THE ЕЕ149
The FE149 is completely protected from accidental overloads or the application of
wrong voltages so that damage to the FE149 is prevented if a mistake is made in
measurements. Four different types of protection are incorporated in the ЕЕ149.
Transistors connected as diodes protect the field effect transistors and circuitry
from damage by excessive input voltages. Тһе meter is protected from excessive
current by a pair of diodes; The diodes conduct and shunt the excessive current
around the meter. A one amp fuse protects the current and ohms functions of the
FE149. A special spark gap is also included on the ohms function to protect the
switch from input voltages. If the excessive current or voltage is left on for ап
extended period of time, the fuse will blow and open the circuit. If an A voltage of
several hundred volts is applied to the ohms ranges, the spark gap will limit the
voltage and prevent damage to the switch after the fuse blows. This prevents accident-
al application of voltage to the ohms ranges from burning out an ohms resistor in
the FE149. When Һе fuse isblown, опу the currentand ohms functions of the FEI
will beinoperative; The voltage scales can be used to measure voltage. Two spa
fuses are included with the FE149 and can be found inthe fuse holder mounted on the
inside of the battery door. Whenreplacingthe fuses, be sure to use a iow resistance
type fuse suchas the Littlefuse 312001 one ampíast blow. Afuse witha high internal
resistance will upset the low ohms ranges and give inaccurate readings.
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