Eico 950B - Page 21

resistive, capacitive, or inductive, is always connected to the right-hand bind-
ing post. In the case of electrolytic capacitors, the positive lead must go to
the plus binding post and the negative lead to the minus binding post. In com-
parison measurement, the standard component is connected to the left-hand
binding posts, and, as usual, the unknown component is connected to the right-
hand binding posts. If the component tobe measured is connected in a circuit,
it will be necessary to disconnect at least one side from the circuit so that the
measurement will not be affected by other circuit components. To measure an
extremely small capacitor, it will be necessary to remove it from the circuit
entirely and connect it directly across the binding posts.
READING COMPONENT VALUES: In all component value measurements,
whether made on the direct reading resistive and capacitive ranges or on the
comparator range, the reading is made by setting the RANGE switch to the
range including the expected value (comparator has only one range) and ro-
tating the pointer knob to the pointon the dial at which the bridge is balanced.
Balance is indicated as follows: When the bridge is far from balance, the en-
tire target area of the electron-ray tube glows green with evena narrow, extra-~
bright sector resulting from "overlapping". As the pointer knob approaches the
balance point, first the “overlapping disappears and is replaced by a dark
shadow sector. The closer the pointer. knob approaches the balance point, the
wider theshadow sector grows.. If the balance point is passed the shadow sector
will narrow down again. The position of the pointerknob at which the shadow
angle is maximum is the balance point.
On the two highest capacitance ranges the power factor potentiometer is switch-
ed into the standard capacitor arm of the bridge to permit balancing of the in-
ternal series resistance frequently present in electrolytic capacitors. The "POWER
FACTOR" knob must therefore be manipulated together with the pointer knob
in order to achieve perfect bridge balance. The power factor control should
be set at "0" while the pointer is rotated to obtain a capacitive balance.
If the internal series resistance of the capacitor being measured is appreciable,
the shadow angle at capacitive balance will be less than normal. When this
occurs, the power factor control is rotated clockwise until the shadow angle
reaches its normal maximum. The % power factor of the capacitor may be
read on the power factor dial.
NOTE: Power factor is a measure of power dissipation in a capacitor due to
its effective internal series resistance. In filter applications, power factor
reduces the measured capacity as follows: At 20% p.f., C effective is 98%
of C measured; at 30% p.f., C effective is 95% of C measured; at 50% p.f.,
C effective is 87% of C measured.
If the unknown capacitance or resistance is smaller than the minimum of the