Simpson 270 Series - Page 13

Introduction
Instrument. Fuses are located in the battery and fuse com-
partment.
NOTE: The 0-10A range is not fused. The shunt con-
nects directly to the —10A and +10A jacks.
d. Varistor Protection: A varistor connected across the meter
movement affords protection to the movement by circum-
venting excessive current around the movement in the event of
an overload.
1.3 INTERNAL BATTERIES
1.3.1 There are two batteries in the ohmmeter circuits. One is
a NEDA ДЗЕ size D cell that furnishes 1.5-volts for the Rx 1
and R x 100 ranges. A NEDA 1604 battery furnishes 9-volts
for the R x 10,000 range.
1.4 PRINTED CIRCUIT
1.4.1 Most of the component parts are mounted on a printed
circuit board which simplifies assembly and maintenance, thus,
extending the useful life of the Instrument.
1.5 PHENOLIC CASE:
e The phenolic case is designed with heavy reinforced walls for
maximum durability and provides excellent protection for
the circuit components.
e The case has an externally accessible battery and fuse compart-
ment. Access to the batteries and fuses is obtained by unscrew-
1-3