ESI 250-DA User manual

mam
JANUARY
T524 S.W. MACADAM AVE. •PORTLAN DO. OREGON
REPLACES OCTOBER 1959

INSTRUCTION MANUAL,
for
MODEL 250-DA IMPEDANCE BRIDGE
CONSISTING OF:
Catalog Sheet C>16 including:
Introduction
Specifications
Model 250-DA Impedance Bridge Instruction Manaual
Lid Instructions From Model 250-DA Bridge
leisin 250 -DA H/59

INSTRUCTION MANUAL
for
MODEL 250-DA UNIVERSAL IMPEDANCE BRIDGE
TABLE OF CONTENTS
I* Controls
1.1 Circuit Selector
1.2 Multiplier Switch
1.3 Main Dial Assembly
1.4 D-Q Dial
1.5 Unknown Terminals
1.6 External Generator Terminals
1.7 External D-Q Terminals
1.8 External Detector Terminals
1.9 Detector Switch
1.10 Generator Switch
1.11 Galvanometer
1.12 Power Switch and AC Amplifier Gain
1.13 AC -DC Switch and AC Generator Gain
1.14 DC Generator Voltage Switch
1.15 AC Generator Tuning Network
1.16 AC Detector Tuning Network
1.17 AC Null Indicator
1.18 AC Amplifier Output Terminals
1.19 Fuse
1.20 Power Indicator Lamp
2. Operating Instructions
2. 1What the Bridge Measures
2. 2Resistors
2.2.1 Measuring Resistors
2.2.2 Things to Watch Out For
2.2.3 Measuring AC Resistance
(Him 250-DA 10/59

TABLE OF CONTENTS (cont. i)
Z,3 Inductors
2.3.1 Measuring Inductors
2.3.2 Series and Parallel Inductance
2.3.3 Things to Watch Out For
2.3.4 Inductance Measurements with DC
2.3.5 AC Voltage Measurement
2.3.6 AC Current Measurement
2.3.7 Sliding Balance
2.3.8 Using an External QRheostat
2.4
Capacitors
2.4.1 Measuring Capacitors
2,4,2. Series and Parallel Capacitance
2.4.3 Things to Watch Out For
2.4.4 Capacitance Measurements with DC
2.4.5 AC Voltage Measurement
2.4.6 Extended Leads
2.4.7 Sliding Balance
2.4.8 Using an External D-Q Rheostat
2. 5Using Bridge Elements
2.5.1 Standard Resistors
2.5.2 DEKASTAT® Variable Resistor
2.5.3 Standard Capacitors
3, Circuit Diagrams
3.1 Series Inductance Bridge
3.2 Parallel Inductance Bridge
3.3 Resistance Bridge
3.4 Series Capacitance Bridge
3, 5Basic Circuits
3.6 Bridge Circuit Diagram
3.7 Generator-Detector Circuit Diagram
3.8 Bridge Wiring Diagram
3.9 Bridge Parts Placement
3.10 Generator-Detector Parts Placement
|e|s| iI250-DA 8/59

TABLE OF CONTENTS (cont. ii)
4. Bridge Element Voltage and Current Limits
5. Convenient Audio Frequency Units
6. Servicing and Repair
6.
1
Preliminary Checking
6o 2Checking Procedure
6. 2.1 Test Equipment and Tools
6,2*2 Trouble Shooting Chart
6.2.3 Checking the DC Generator
6.2.4 Checking the Galvanometer
6.2.5 Checking the AC Generator
6.2.6 Checking the AC Detector
6.2.7 Checking the Range Resistors
6.2.8 Checking the Standard Resistors
6.2.9 Checking the MAIN DIAL DEKASTAT®
6.2.10 Checking the D~Q Rheostats
6.2.11 Checking the Standard Capacitor
6.3 Removing the Chassis from the Case
6.3.1 Removing the Chassis
6.3.2 Replacing the Chassis
6.4 Repairing the Bridge
lelsli I250-DA 8/59

POWER SWITCH
AND AC AMPLIFIER GAIN
POWER indicator LAMP
EXTERNAL D-Q TERMINALS AC NULL INDICATOR ^
GND IAC DETOUT
DETECTOR TUNING
NETWORK
EXTERNAL DETECTOR
TERMINALS
ZERO SET
TERMINALS
LOCK
GALVANOMETER
D-Q DIAL
DETECTOR-
SWITCH
GENERATOR
SWITCH
1KC
IMPfOANCE BKI DGE/„oo
“EXTERNAL GENERATOR TERMINALS
—-ac-dc switch
AND AC GENERATOR GAIN
/FUSE
00|||| DC GENERATOR
——VOLTAGE SWITCH
KC- ^^11 —generator TUNING
—lilgM NETWORK
-UNKNOWN
TERMINALS
-CIRCUIT SELECTOR
SWITCH
-MULTIPLIER
SWITCH
-MAIN DIAL
MODEL 250-DA PANEL CONTROLS

1.CONTROLS
1.1 Circuit Selector: The metal lever in the upper right-hand control
group selects the bridge circuit. Panel markings indicate the circuit
chosen. Two inductance measurement circuits are provided;
inductors can be measured in terms of their equivalent series or
equivalent parallel circuit. Two resistance multipliers are available;
the XI 0multiplier is included to extend the resistance range. For
capacitance, two D-multipliers are provided.
1ZMultiplier Switch: The upper right-hand black knob selects any of seven
multipliers. The pointer indicates the value of the multiplier and the
type of units used.
1.3 Main Dial Assembly: The lower right-hand DEKASTAT® decade resistor
dial is used for reading the value of resistance, inductance or capaci-
tance being measured. The measured value is given by the product of
the DEKASTAT reading and the multiplier reading. For resistance, this
product must also be multiplied by the circuit selector reading.
14D-Q Dial: The reading of the large left-hand dial times the Dor Q
multiplier reading gives the value of Dor Qat one kilocycle. At other
frequencies, the Dreading for Cor Qreading for Lseries must be
multiplied by the frequency in kilocycles, and the Qreading for L
parallel must be divided by the frequency in kilocycles.
15Unknown Terminals: An unknown capacitor is connected to the two
right-hand terminals. An unknown resistor or inductor is connected to
the third and fourth terminals from the right.
1.6
1.7
External Generator Terminals: The center pair of terminals are for
connecting an external generator to the bridge.
External D-Q Terminals: The third and fourth terminals from the left
are for attaching an external circuit element to the D-Q arm of the
bridge for special measurements. The left-hand external D-Q terminal
is connected to the bridge chassis.
1.8
1.9
External Detector Terminals: The upper left-hand terminals are
for connecting an external detector to the bridge. The internal ac
detector is connected to the bridge through these terminals by means
of ashielded double banana plug
.
>etector Switch: The switch in the lower left-hand corner of the bridge
5for choosing the detector. In the ac or external detector posiUon,
he detector corners of the bridge are connected to the externel detector
erminals. In the shunted meter position, the detector corners of the
.ridge are connected to the galvanometer through ashunting network,
nthe direct meter position, the bridge is connected directly to the meter.
lejsl i}250 -DA 6/59

1. CONTROLS (cont.)
1.10 Generator Switch: The switch at the bottom center of the panel chooses
the generator to be connected, to the bridge* In the internal ac position
the output of the internal generator is connected to the bridge generator
corners. In the external generator position the bridge corners are
connected to the external generator terminals. In the internal dc
position the internal dc generator is connected to the bridge generator
corners
.
1.11 Galvanometer: The meter in the center of the panel is asensitive
gaiygLnometer which is used for indicating abridge balance. The two
mounting screws are connected to the galvanometer terminals so that
it may be easily connected to other external circuits. The large knob
on the galvanometer can be rotated for mechanically positioning the
galvanometer pointer. When the lock button is pushed in the direction
of the arrow, the galvanometer suspension is rigidly supported for
protection during transportation.
1.12 Power Switch and AC Amplifier Gain: The left-hand control knob on
the small upper panel controls the AC detector sensitivity. The power
switch for the unit is connected to the same knob. The adjacent pilot
light indicates when power is supplied to the bridge.
1.13 AC -DC Switch and AC Generator Gain; The right-hand control knob
on the small upper panel controls the ac generator output. In the
extreme counter-clockwise position, it switches the ac generator off
and the dc generator on.
1.14 DC Generator Voltage Switch: The switch on the right-hand side of
the small panel provides for high and low values of dc voltage^ for
resistance measurements. The low value gives greater sensitivity
for unknown resistors below about 100 ohms, and the high position
gives greater sensitivity above about 100 ohms* This switch has
no effect on the ac generator.
1.15 AC Generator Tuning Network: The upper right-hand plug-in unit
controls the frequency of the oscillator.
1.16 AC Detector Tuning Network: The upper left-hand plug-in unit
determines the frequency response of the detector. With this network,
the detector has anarrow acceptance band centered at the generator
frequency. With this network removed, the detector has aflat response.
1.17 AC Null Indicator: The electron- ray-tube visual null indicator provides
high sensitivity and rapid response. Anull is indicated by the maximum
opening of the eye
.
1.18 AC Amplifier Output Terminals: The two terminals at the top of the
small panel are for connecting an oscilloscope or other indicator to the
output of the detector amplifier. They are in parallel with the visual
null indicator. The black terminal on the left is connected to the bridge
chassis. The red terminal on the right is connected through acapacitoi
to the detector output.
lelsin 250-DA 7/59

1.CONTROLS (cont.)
1.19 Fuse: The fuse receptacle is located in the upper right-hand corner
recess. Al/Z amp -3AG fuse protects the bridge. The recess is
also used to store the power cord.
1.20 Power Indicator Lamp: The red lamp on the left-hand side of the small
upper panel lights when power is supplied to the bridge.
lelsl iI250-DA 6/59

OPERATING
INSTRUCTIONS
<M lelsl i1250 -DA 6/5 9
’{^Resistance
measurements
can
be
made
using
ac,
but
they
may
require
external
reactance
compensation.

2.2 RESISTORS
2. 2, 1MEASURING RESISTORS dSD
UNKNOWN RESISTOR
V
DC GENERATOR
VOLTAGE SWITCH
LOCK
GALVANOMETER
UNKNOWN RESISTOR
CONNECT UNKNOWN RESISTOR Make good contact with the terminals.
TO L-R TERMINALS
SET DC GENERATOR VOLTAGE
SWITCH TO LOW This applies approximately 10 volts
to the bridge.
UNLOCK GALVANOMETER Adjust the zero with the zero set
knob if necessary.
turn amp control CLOCKWISE This turns on the power supply. The
red light to the left of the AMP switch
should light.
TURN THE OSC CONTROL COUNTER
CLOCKWISE FOR DC This should turn off the green
fluorescent screen of the visual null
indicator.
SET CIRCUIT SELECTOR SWITCH
TO RX1OR RX10 For resistors between 1.2 and 12
megohms, use RX10 position.
SET MAIN DIAL TO 3.000 This makes it easier to find the
correct range.
lailTI 250-DA 6/59

2, 2.1 MEASURING RESISTORS (cont.)
SET DETECTOR SWITCH TO SHUNTED
METER This makes it easier to find arough
null.
SET GENERATOR SWITCH TO
INTERNAL DC This connects the generator to the
bridge
.
ADJUST MULTIPLIER SWITCH FOR
MINIMUM GALVANOMETER
DEFLECTION
This sets the range so that the value
can be found with maximum reso-
lution on the main dial.
ADJUST MAIN DIAL FOR NULL The detector sensitivity can be
increased as null is approached by
moving the detector switch to direct
meter.
IF THE MAIN DIAL READING IS LESS This takes advantage of the increased
THAN 1.200, USE THE NEXT LOWER resolution near full scale of the dial.
RANGE AND* READJUST THE MAIN
DIAL FOR NULL
FOR RESISTANCES GREATER THAN (WARNING: This may put 300 volts
lOK SET THE DC GENERATOR VOLT- on the unknown terminals.)
AGE SWITCH TO HIGH
THE MEASURED RESISTANCE IS THE
PRODUCT OF THE READING OF THE
CIRCUIT SELECTOR SWITCH, THE
MULTIPLIER SWITCH, AND THE
MAIN DIAL
BEFORE DISCONNECTING THE
MEASURED RESISTOR SET THE
GENERATOR SWITCH TO EXT DET,
THE DETECTOR SWITCH TO SHUNTED
METER, AND THE DC GENERATOR
VOLTAGE SWITCH TO LOW
before LEAVING THE BRIDGE, This turns off the power supply and
LOCK THE GALVANOMETER AND protects the galvanometer,
SET THE AMP SWITCH TO OFF
This disconnects the generator,
protects the meter and removes the
high voltage from the bridge.
lelsl n250-DA 6/59

2.2.2 THINGS TO WATCH OUT FOR
2.
2. 2. 1HIGH RESISTANCE MEASUREMENTS
Care must be taken to avoid leakage resistance across the unit being measured.
If an external electronic null detector is being used it may be affected by ac
hum and by the hum output of the internal dc generator. In this case abattery
supplying the EXT GEN terminals may be necessary. If abattery supply is used
connect aprotective resistor in series with it. Use a resistor of greater than
(I/4)(battery voltage)^ ohms,
2. 2. 2. 2LOW RESISTANCE MEASUREMENTS
On the low resistance ranges the lead resistance in the unknown arm becomes
significant. Acorrection for this resistance can be made as follows;
1. Short the test leads together at the point where they are to be connected
to the unknown resistor and measure this "ZERO RESISTANCE".
2. Connect the test leads to the unknown resistor and measure the "RESIST-
ANCE READING".
3. The "RESISTANCE VALUE" of the unknown resistor is then the "RESIST-
ANCE READING" minus the "ZERO RESISTANCE",
4. If the unknown resistance is to be connected directly to the terminals,
the "ZERO RESISTANCE" reading can be taken by connecting apiece
of heavy copper wire between the unknown resistance terminals. (#14
AWG copper wire has aresistance of about 0.00025 ohm/inch.)
lelsin 250-DA 6/59

2.2.3 MEASURING AC RESISTANCE
For greatest accuracy resistors should always be measured with dc. The
accuracy of ac measurement will be 0,3% for one kilocycle and below over
the range from one ohm to one megohm, for resistors with low reactance.
The indicated connections for the phase correction capacitor compensate
for series inductance or parallel capacitance. It is impossible to separate
the correction for the unknown from that for the rest of the bridge circuit.
UNKNOWN RESISTOR OO 60 0
DETECTOR-
SWITCH
MVy
EEBa IMPfDAMCE SlflDCE
UNKNOWN
——tJ- resistor
terminals
NOTE: If the phase cor-
rection is small it may
be convenient to connect
afixed capacitor to one
terminal and avariable
one to the other.
UNKNOWN RESISTOR
PAtAUEl /ml {SERIES
C] rSTANDARDI
RESISTOR
MAIN OlAi DEKASTAf
CONNECT UNKNOWN RESISTOR
TO L-R TERMINALS Make good contact with the
terminals
,
SET THE AMP CONTROL WITH THE
DOT UP This turns on the unit and pro-
vides medium detector sensitivity.
The red light to the right of the
AMP switch should light.
SET THE OSC CONTROL WITH THE
DOT UP This turns on the ac supply and
provides amedium signal to the
bridge. The green fluorescent
screen of the visual null indicator
should light.
fel^ 250-DA 6/59

2. E. 3MEASURING AC RESISTANCE (cont.
)
SET CIRCUIT SELECTOR SWITCH
TO RX1OR RX10 For resistors between 1.2 and 12
megohms, use Rx10 position.
SET MAIN DIAL TO 3. 000 This makes it easier to find the cor-
rect range.
SET DETECTOR SWITCH TO AC OR
EXT DET This will connect from the bridge to
the ac detector.
SET THE GENERATOR SWITCH TO
INTERNAL AC This will connect the ac supply to the
bridge
.
TRY TO BALANCE THE BRIDGE AS
WITH DC Usually the eye will not completely
open indicating uncompensated phase
shift.
CONNECT AVARIABLE CAPACITOR
FROM THE EXT D-Q TERMINAL
MARKED GTO THE HIGH CTERMIN-
AL AND TRY TO OBTAIN ANULL
WITH IT AND THE MAIN DIALS
Connecting the capacitor from ground
to either of the generator terminals
permits compensation for some of the
possible equivalent circuits of the
unknown.
IF ANULL CANNOT BE REACHED,
CONNECT THE VARIABLE CAPACI-
TOR BETWEEN THE EXTERNAL
D-Q TERMINAL MARKED GAND THE
HIGH L-R UNKNOWN TERMINAL. A
NULL SHOULD BE OBTAINABLE WITH
ONE CONNECTION OR THE OTHER
This permits balance over the remain-
ing possible circuit combinations. If
anon-linear element is being measured
by ac ,anull balance may not be pos-
sible because the bridge will not be in
balance at all parts of the cycle.
THE MEASURED RESISTANCE WILL
BE CORRECT FOR EQUIVALENT
CIRCUITS CONSISTING OF A
RESISTOR AND CAPACITOR IN PARA-
LLEL OR ARESISTOR AND INDUCTOR
IN SERIES
This is true even for fairly large values
of phase shift. Resistance accuracy
will be 0.3% or better for resistors
between 1ohm and 1megohm at a
frequency of 1kilocycle or less.
BEFORE DISCONNECTING THE This disconnects the generator
RESISTOR SET THE GENERATOR while the resistor is being removed.
SWITCH TO EXT GEN
BEFORE LEAVING THE BRIDGE This turns off the power supply.
SET THE AMP SWITCH TO OFF
lelsl iI250-DA 6/59

2.3 INDUCTORS
2. 3. 1MEASURING INDUCTORS SSD 4518^
UNKNOWN INDUCTOR
UNKNOWN JNOUCTOR
CONNECT THE UNKNOWN Make good contact with the terminals.
INDUCTOR TO THE L-R
TERMINALS
TURN THE AMP CONTROL
CLOCKWISE FOR POWER AND
SET IT WITH THE DOT UP
This turns on the power supply. The red
pilot light to the left of the AMP switch
should light.
TURN THE OSC CONTROL
CLOCKWISE FOR AC AND SET IT
WITH THE DOT UP
SET THE CIRCUIT SELECTOR
SWITCH TO THE APPROPRIATE
LCIRCUIT
for Q<IOxfkt
Lporallel Q>10/fi,t
SET THE MAIN DIAL TO READ
3.000
SET THE D-Q DIAL AT MAXIMUM
This supplies ac to the bridge. The green
fluorescent screen of the ac null indicator
should light.
1000 100
lOKC
DISSIPATION FACTOR (0)
10 1.0 0.1 0.0 10.001 O.OOOl
aoiKc
0.001 0.01 0-1 1.0 10 100 1000 10,000
STORAGE FACTOR <Q)
These settings make it easier to find the
correct range.
[elim 250-DA 6/59

Z.3.1 MEASURING INDUCTORS (cont.)
SET THE DETECTOR SWITCH TO
AC OR EXT DET This connects the detector to the
bridge •
SET THE GENERATOR SWITCH
TO INTERNAL AC This connects the generator to the
bridge
.
ADJUST THE MULTIPLIER SWITCH
FOR MINIMUM DETECTOR SIGNAL This sets the range so that the value
can be found with maximum reso-
lution on the main dial .The ANIP
and OSC controls can be changed to
give optimum sensitivity.
ADJUST THE MAIN DIAL AND THE
D-Q DIAL ALTERNATELY FOR
THE WIDEST AND SHARPEST
POSSIBLE SHADOW ON THE NULL
INDICATOR
If more or less sensitivity is needed,
adjust the AMP control and/or the
OSC control. Changing the OSC
control may change the inductance of
iron core inductors.
IF THE MAIN DIAL READING AT
balance is LESS THAN 1.200,
USE THE NEXT LOWER SETTING
OF THE MULTIPLIER SWITCH
AND READJUST THE MAIN DIAL
FOR ANULL
This takes advantage of the increased
resolution near full scale of the dial.
THE MEASURED LIS THE PRODUCT
OF THE READINGS OF THE MULTI-
PLIER SWITCH AND THE MAIN
DIAL
AT 1KC THE MEASURED QIS THE
PRODUCT OF THE READINGS OF
THE CIRCUIT SELECTOR SWITCH
AND THE D-Q DIAL.
USE BLACK SCALE FOR L-S FRIES
USE RED SCALE FOR L-PARALLEL
FOR OTHER FREQUENCIES:
MULTIPLY Ogeries
in kc; or
DIVIDE Qarallel frequency in
before DISCONNECTING THE
INDUCTOR SET THE GENERATOR
SWITCH TO EXT GEN
This disconnects the generator.
before leaving the bridge
SET THE AMP SWITCH TO OFF This turns off the power supply.
lelsTTl 250-DA 6/59

2, 3. 2SERIES AND PARALLEL INDUCTANCE
The bridge measures asimple equivalent circuit for the impedance
connected to its terminals. This equivalent circuit consists of
either an inductance and resistance connected in series or adif-
ferent inductance auid resistance connected in parallel. The phase
and magnitude of the resulting impedance are identical for both
circuits. For values of Qless than 100 the series and parallel
inductances differ measurably (by more than 0.01%),
WHEN THE BRIDGE MEASURES
SERIES INDUCTANCE, L^:
Ls
VQJ
L=(range switch setting) x(main
®dial reading
)
Q=(D-Q multiplier setting) x(D-Q
dial reading) x(fj^^)
D
RI
Z
1
Q
•pz X2it fL
Qs
2irfL^(i +j)
Qand Din per unit
Rin kilohms
s
fin kc
L^ in henrys
Zin kilohms
To calculate the equivalent parallel
circuit:
The Qof the equivalent parallel circuit
always equals the Qof the equivalent
series circuit. The same is true of
D.
%=
R=QX2ir fL
PP
WHEN THE BRIDGE MEASURES
IDl
Lp
PARALLEL INDUCTANCE, L:
P
Q-
(range switch setting) x(main
dial reading)
(D-Q multiplier setting) x(D-Q
dial reading) *r (fj^^)
D=~
R=QX2irfL
PP
2irfL Q(l+jQ)
TE_^
1+Q
Dand Qin per unit
Rin kilohms
P
fin kc
Lin henrys
j=
Zin kilohms
To calculate the equivalent series
circuit:
The Qof the equivalent series circuit
always equals the Qof the equivalent
parallel circuit. The same is true of
D.
L=—XL
*1+q2 p
ZirfLc
R=—r
—
lelsl i \ 250 -DA 6/5 9

2.3.3 THINGS TO WATCH OUT FOR
2. 3. 3. 1LOW INDUCTANCE MEASUREMENTS
The bridge measures the total impedance connected to its terminals. Both
the unknown inductor and its leads contribute to this impedance. The leads
have some resistance and inductance, which affect the value read from the
bridge
.
Z-Impedance of unknown inductor
ZLImpedance of leads
For greatest accuracy, minimize the lead impedance. Short heavy leads
will reduce the resistance. Closely spaced twisted leads will reduce the
inductance and the pickup of stray fields.
2. 3. 3. 2HIGH INDUCTANCE MEASUREMENTS
In making high inductance measurements, there are two things to watch
out for:
1. Be careful to avoid hum pickup.
2, Keep the stray capacitance to aminimum.
To minimize both effects keep your hands as far as possible from the
inductor measured.
Keep the leads as short and direct as possible. If extended leads are
necessary, the lead from the LO terminal should be shielded. See
section 2.4.6 "Extended Leads".
Care should be taken to avoid coupling stray magnetic fields into the in-
ductor being measured.
The Dand Qreadings on the highest Lrange will be in error as indicated in
the specifications because of the residual capacitance of the range resistor.
If accurate Dor Qreadings are needed the next lowest Lrange can be used.
The Lreadings on the high range are accurate.
lelsl i1250-DA 6/59

2.3.4 INDUCTANCE MEASUREMENTS WITH DC
2. 3. 4. 1W4IEN TO USE DC
Iron core inductors are sensitive to both ac and dc current variations.
Quantitative measurements of these effects can be made with the bridge.
2. 3.4. 2THINGS TO WATCH OUT FOR
A. GENERAL PRECAUTIONS
Stray ac pickup may change sensitive components being measured or may give
erroneous null detector readings.
The ac impedance of the dc external circuit must be greater than 2000 ohms
for maximum sensitivity. If cin isolating inductor is used to raise the ac
impedance it may pick up stray signals or may-have mutual coupling with
the unknown inductor being measured. Either one may cause reading errors.
Such an inductor should be well shielded magnetically and be placed to mini-
mize its chance of interfering. For low currents isolation may be accom-
plished with aresistor instead of the inductor.
The parallel inductance circuit is recommended because it simplifies dc
current measuring and bridge protection problems. With the series circuit
the dc current divides between the bridge arms so that it is difficult to meter.
The series circuit would also require amore careful analysis to avoid exces-
sive current in any of the bridge arms.
If equivalent series inductance is required it can be easily calculated from
the parallel inductance and D(See Sec. 2,3.2).
If Qis too low to be read directly, connect an external rheostat such as the
ESI Model DB-655 DEKASTAT® to the EXT D-Q terminals. This extends
the Qrange for the Lparallel circuit. Qcan be calculated from the equation:
n-1.59
^
Where;
Rk£2
kc
Storage factor of unknown
External rheostat resistance in kilohms
Operating frequency in kilocycles
B. WITH DC SUPPLIED THROUGH THE GENERATOR TERMINALS
DC power can be supplied through the generator terminals by using an
auxiliary ac generator instead of the bridge generator. This generator must
be isolated from the dc power supply by acapacitor of at least
[mi] 250-DA 7/59