Tektronix Type 130, Instruction Manual

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General
The Tektronix Type 130 L-C Meter indicates inductance
and capacitance directly on a calibrated meter, and in-
cludes a guard-voltage circuit for separating the stray
capacitance of nearby conducting materials. The meter is
designed for rapid measurements of small inductances an d
capacitances where possible errors of the order of 5 per
cent are permissible.
This meter directly reads accurate inductance and par-
allel capacitance. To insure accurate measurements of series
capacitance and shunt inductance, a graph is included for
interpolating the correct figures from the known meter read-
ing. The accuracy of the graph is decreased somewhat for
shunt inductance.
Uses
The Type 130 is particularly useful in circuit develop-
ment for such uses as measuring components already in
place in the circuit, for sorting components , for measuring
vacuum-tube direct interelectrode capacitances and so forth.
Method of Operation
The instrument operates by measuring the change in fre-
quency the unknown reactance causes when it is added to
an oscillator tank circuit. The amount of change in fre-
quency is measured by a direct-indicating electronic counter
that counts the frequency difference between a fixed oscil-
lator and the oscillator affected by the reactance. With
zero reactance added, the two oscillators zero beat and
the counter reads zero.
Indicator
The electronic counter produces a deflection on a direct-
current meter calibrated in capacitance and inductance. A
rotary switch makes the meter more sensitive for lower
counts and less sensitive for higher counts to provide five
ranges of capacitance and five of inductance.
Guard Voltage
Any oscillator current flowing into a capacitance affects
the oscillator frequency. But current flowing into a capaci-
tance from the guard-voltage does not, because this circuit
is isolated from the frequency-determining part of the
oscillator. The guard-voltage circuit can keep stray
capacitance from drawing oscillator current by driving the
strays at exactly the same instantaneous voltage as the
capacitance being measured. Since no oscillator current will
then flow from the capacitance being measured into the
stray capacitance, the meter reds only the desired capaci-
tance.
Probe
The probe at the end of a two-foot insulated shielded
cable provides a means for measuring reactances wher -
ever they are in a circuit. The zero adjustments can set the
meter to read zero with or without the 30-
μμ
f probe-cable
capacitance so the meter reads directly.
Electrical Characteristics
Indicating Meter
—D’Arsonval, 200-microamp movement.
Meter Ranges
—All five scales begin at zero. Full-scale
readings are 3, 10, 30, 100 and 300 microhenries or micro-
microfarads. Minimum scale division, 0.1 microhenry or
micromicrofarad.
Accuracy
—within 3 per cent of full scale. The reset-ability
is excellent. By calibrating with the type S-30 Delta Stand-
ard, the accuracy at full scale will be about 1 per cent.
Voltage Across Unknown
—The instrument places an ac
voltage across the unknown, 1 volt maximum across a
capacitance, ¼-volt maximum across an inductance with fre-
quency between 124 and 140 kc.
Maximum Permissible Load Resistance
—The following
loads will not appreciably alter the indication:
Capacitance, 0.1 megohm shunt.
Inductance, 20 kilohms shunt, 10 ohms series.
A table included in this instruction manual (in Operating
Instruction Section) provides corrections for increased loads.
Guard-Voltage Output Impedance
—A cathode follower
with internal impedance of 250 ohms can safely drive 200
μμ
f.
Power Requirements
—105 to 125 and 210 to 250 volts, 50
to 60 cycles ac. A voltage regulator keeps the instrument
accurate over this voltage range. Power consumption 40
watts at 117 or 234 volts.
Physical Characteristics
—Size, 6¾” wide by 9½” high
by 9
3
/
8
” deep. Weight, 9 lbs. Construction, welded alumi-
nium alloy with blue-wrinkle baked enamel cabinet and
photo-etched anodized aluminium panel.