EICO 242 Service manual
242
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Input
Impedance:
1
megohm
Accuracy:
Frequency
DC Current
Range:
AC Current
Range:
Ohmmeter:
Meter:
Power Supply:
Power
A-C
Requirements
Size:
Response:
*\Vo
25
Hz to
0
to
RMS
P-P
0. 2
to
6", 200
Transformer
NEDA No. 1604
D-size
105-132
:
7-Lf2" high,
of. full scale
2
MHz
3,
1,
-
same as d-c
-
0
to 2.8,
1000
1t"
cell
volts
30, 100,
10,
megohms
a movement
isolated,
for ohmmeter
,
8-Lf2" wide,
(with
sinusoidal
(extendable
and
current
28,
8.5,
in
seven
silicon- rectifier , zener regulated;
9-volt batteries for
50f 60
Hz,
to
300
280,
85,
use.
4
1.
VA
5" deep
250
ma, and 1 amp
ranges
input
voltage)
MHz
with EICO
850 ma, and
and
portable
use.
Probe PRF-1l)
RF
2.8
amps.
three
1.5-volt
One
Weight:
CIRCUIT DESCRIPTION
Basic Metering Circuit
Model
The
stage
of
the
is
a function of the d-c
from
242
citcuirt., ahown
driving a differential
Ql,
parameter
being measured
loading tlre inputs at the
end of tlle TVOM.
6lbs,3oz,
in
input
applied to FET
probe,
simplified form
amplifier
(a-c
formed by lilPN silicon transistors
or d-c
Ql.
as
srell
in figure 1, consists of an FET
current, or resistance), the meter reading
voltage
as the
or
high input impedance of the FET
The
switching and
attenuating
Q2
source
and
follower
Q3.
Regardless
prevents
circuits at the front
it
Figure
1. Basic Metering
Circuit
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