Keithley 515 Service manual

INSTRUCTION MANUAL

MODEL 515

MEGOHM BRIDGE

WARRANTY

We warrant each of our products to be free
from defects in material and workmanship. Our
obligation under this warranty is to repair or

replace any instrument or part thereof which,

within a year after shipment, proves defective

upon examination. We will pay domestic
surface freight costs.

To exercise this warranty, call your local
field representative or the Cleveland factory,

DDD 216-248-0400. You will be given assist-

ance and shipping instructions.

REPAIRS AND RECALIBRATION

Keithley Instruments maintains a complete re­pair service and standards laboratory in Cleve­land, and has an authorized field repair facility
in Los Angeles and in all countries outside the

United States having Keithley field repre­sentatives.

To insure prompt repair or recalibration serv­ice, please contact your local field representa-

tive or the plant directly before returning the

instrument.

Estimates for repairs, normal recalibrations,
and calibrations traceable to the National Bu-

reau of Standards are available upon request.

MODEL 515 MEGOHM BRIDGE

CONTENTS

TABLE OF CONTENTS

Section

INTRODUCTION . . . . . . . . . I-l

I.

SPECIFICATIONS . . . . . . .

II.

III. OPERATION. . . . . . . . . . . III-1

Outline of Procedure . . . 111-1

A.

Description of Controls

B.

and Terminals . . . . . , III-2

Operation Steps. . . . . . . III-3

C.

Standardization. . . . . . . III-4

D.

Connecting the Unknown

E.

Resistor. . . . . : III-4

F. External Bridge Voltage

Supply. . , , . . . . . , III-8

Voltage Across Unknown and

G.

Standard Resistors. , , , . III-8

Accuracy Considerations. . . III-9

H.

1. Null Detector

Sensitivity . . . . . . III-9

Null Detector Zero

2.

Drift , . . . . . . . . III-10

Resolution of the

3.

Readout . . . . . ; . . III-10

Accuracy of the Read-

4.

out and Standard

Resistors . . . . . . . III-10

5. Temperature and Voltage

Coefficients in the

Bridge Resistors. . . . 111-12

Leakage Resistance

6.
Across the Unknown. . . III-12

Errors Caused by Guard

7.
to Ground Resistance. . 111-12

Page

II-1

Section

8. Time Constants - Slow

Response . . . . . III-13

9. Transients Caused by
Push-to-Read Switch. III-14

Verification of the

10.

Accuracy . . . . . III-14

CIRCUIT DESCRIPTION . . . . .

IV.

A. power Supply. . . . .

B. Null Detector . . . . .

C. Bridge Circuitry. .

Overvoltage Protection. .

D.
MAINTENANCE . . .

V.

REPLACEABLE PARTS . . . . .

6.
6-l. Replaceable Parts List.

6-2. How to Order Parts. .

Model 515 Replaceable

Parts List . . . .

Model 515 Schematic

Diagram 14522D . . .

Green Calibration

and Repair Form . . . .

* Change Notice

*Yellow Change Notice sheet is included

only for instrument modifications affect-

ing the Instruction Manual.

Last page

Page

IV-1
IV-1

IV-1
IV-3
IV-4

V-l

6-l
6-l

6-l
6-2
6-10

6-11

0568R

i

SECTION I -

INTROlXJClTON

The Model 515 Megohm Bridge
resistors from 105 ohme to 10

1.0%.

It is complete, with an electrometer null detector, shielded

if5a Wheatstone Bridge for measuring

ohms with accuracies from 0.05% to

enclosure for the unknown, and a bridge voltage supply.

A unique system of switches is provided to allow corrections to be
made for the slow changes in resistance of the standard high megohm

resistors.

This enables all values of resistance to be read with rated

accuracy, directly from the bridge dials.
Bridge voltages in one volt steps up to 10 volts are available from

the internal supply.

With external supplies, voltages as high as

1,000 volts csn be used.

A

connector is provided so that unknown resistors can be measured

outside the instrument as well as in the built-in shielded enclosure.

SECTION II - sPFXXF1cATI0NS

RANGE:
ACCURACY: As tabulated below, if bridge is operated so that volt-

age *cross stendard resistor does not exceed 10 volts.
RangeOhms

105 to 10-f
10

;I

10
109 to 1010
1010 to loll
loll to loI2 0.25 1t0lOo0 1

12 to lo13
El3 to 1014
1014

For less than minimum voltage, accuracy decreases in proportion

to the ratio of applied voltage to minimum stated voltage.
INKTT:

insulated triexial cable.

GROUNDING:

lO5 to l&5 ohms with a six-dial in-line readout.

Accuracy

0.05%

to 108 0.05 1tolocn
to 109

to lo15

Built-in compartment or Remote Test Chamber with teflon-

One terminal of unknown is at ground potential.

0.10
o.l.5

0.2

0.30 1 to 1000

0.5

1.0 10 to 1000

Possible Bridge

Voltage
1tolooOV
1 to loo0

1toloco
1 to 1000

1to 1000

Min. Volt. for
Rated Accuracy

5v

50

3
2
1

1;

100

yy4DmmR
volt per diw in decade ranges. Reading is non-linear past l/3 of

full scale for ease in balancing.
ZERO CREYX Normally closed zero-check button shorts out null de-

tector input except when depressed.
BRIWEFQTERTI&z

selectable from the front panel. External:
or 241Power Supply, from zero to 100 volts on any resistance reading,
from 100 to 1000 volts provided the readout dial is at least in the

x10 position. Bridge interlocks, and the inherent overload protection

of the Keithley power supplies, prevent damage if readout dial is in­advertently placed in the wrong position. Since other types of power

supplies do not provide the correct overload protection, only the

Keithley Model 240 or 241 is recormnended.

POWER:
TIJBE AND TRANSIS!t.OR COMPLE!MER?

6-21il381.
ACCESSORIES AVAILABLE:

rubber feet.
60" triaxial cable and bridge connector; Model 5153 60" trisxial. cable

with bridge connector on one end.

amperes and sensitivity ranges of lvolt perdiv. to 1 mill-i-

100-130 or 200-260 volts, 50-60 cps. 10 watts.

Electrometer with a grid current of less than 5 x

Internal: From zero to 10 volts in one volt steps

With Keithley Model 2443

i-5886, 2-6418, 1-0~2; 1-2~1535,

Model 5151 End Frames with mounting hardware,

Model 5154 Cabinet; Model 5152 Remote Test Chamber with

515

II - 1

DIMENSIONB:

Model

5154 Cabinet, 21" w x 25" h x 16&f a.

Model 515 bfegolpn Bridge, 19" w x 14" h x I@" d.

NE2 WEIGR!J!z Model 515

inet, 52 lbs.

Megolm

Bridge, 24 lbs. Model. 5154

Cap-

515

II - 2

SECTION III - OPFRATION

OUTLINE OF PROCEDURE, (taken from instructions fastened to the

A.

inside of the door of the Shielded Measuring Compartment).

1. Connect power cord to 115 volts, 50/60 cps unless specified
on rear for 230 volt.

To change line voltage see Section V -

Maintenance.

Turn on power; set MILLIVOI/IS PER DIVISION switch to 1000;

2.

release HJSH 'IO READ switch. Set meter to zero with FINE ZERO.

If necessary use COARSE ZERO. Increase sensitivity and rebal-

ace. Drift which msy be apparent at maxirann sensitivity will

become negligible after a short warm-up.

STANDARM- Set FUNC'IION switch to STANDARDIZE: MULT-

3.
1PLIERdialtom;

and RESISTAEtX, OHMS dials to 10.000. Bring
to exact null with ORMS dials; at the same time increase the null
detector sensitivity to ma%-. Release HJSH 9 READ button
and set FUNCTION switch to CALIBRATE. Adjust l0 CALIBRATE

potentiometer to give a null when T II 9?3 FOND switch is oper-

ated.

Next set exponent dial t&IO and repeat step 3. Do
the same in sequence UJP thrn I.0 . This completes the bridge
standardization.

4. 0PEwJ!I0N:

Place resistor to be measured in compartment.
Locate the ground clip to suit the resistor length, and close
compartment.

Select bridge voltage.

or external voltages up to 100 volts may be used

precautions.

Above

Internal voltages from 1 to 10 volts

with no

special

I.00 volts the xl0 or xUl0 dial must not be
set at zero. With the Kelthley 240 or 241 Power Sypp3y, the
interlock circuit will prevent damage.

Set null detector sensitivity to minimum and operate PUSH M
READ button.

If miU. detector deflects to left the readout
dials (RESISTAECE, OBMS) are set below value of resistance.
Increase the indicated mISTAWCE until a null is obtained.
If null detector deflects to right reduce the indicated RE-

SISTANCE.

If no deflection is observed increase null detector
sensitivity. Final balance should be made tith enough sensltiv­ity to give required accuracy.

For external operation, attach special cable only to input con-

nector and set FUEtX!ION switch to

door

interlock

is now inoperative observe care with high bridge

EiilWNU OPEW. Since the

voltages.

ACCURACY: As tabulated below, if bridge is operated so

5.

that voltage acrose stendard resistor &es not exceed 10 volts.

515

III -1

Rang% ohms

Accuracy Possible Bridge

Voltage

Min. Volt. for
Rated Accuracy

I.05

to lo;

I.07

: $9

108

I.09 to 1010
lo~tolo~
lo~tolLG
lo12 to I.013

lo13 to lo*
lo14 to I.015

For less then mlnimm voltage, acouracy decreases in proportion
to the ratio of applied voltage to

B. DEWRIPl!IONOFCONTROU3AND~AIS:

BRIR3EVOUCS:
to the bridge In 1 volt steps up to I.0 volts and &so Is used
to

energize

position.
ON: Toggle switch is the main power switch. Preseme of power

is indicated by the i-ted meter dial.

MIUXVOIfE3 PER DIVJSIOIk Rotary switch provides decade step6

of nuU detector sensitivity.

0.36 1 to 1000 ;

0.5 ltolcoo

1.0 lotoKxxl

This rotary switch adjusts the voltage applied

the external supply circuit when it is in the EK!l!

1tolooov
lo to loo0
1to lGQ0
1 to loo0 2

1

to loo0

1tOlOOO

lE

minirmpm stated voltage.

5v

50

3
1

FINE ZERO: Ten-turn control18 used for sett%ng the null de­tector to zero.

COARBEZERO:

,&thin the range of the FINE ZERO controls. It mey be swltchee8

with a screwdriver from the fxont panel.
NUT& INDICAMR: Three-inch meter, Incorporating a non-linear

;mvement for easy bridge balancing,
'RTSH 9X) READz Push-button switch mxnNJy shorts the miJ.l de-

tector @put. It may be locked In the open position.

'FUNCTION Four position rotary stitch provides the necessary

circuit arrangements for calibration of the standards, and also

employed when the unknown resistor is outslde the instr7.mvd.

'RESIS'JANCE, OHMS: These seven di.als include five decade step
xw-itches and one rheostat which forn the variable arm

bridge.

the unknown resistance is read directly from these dials.
Below these dials is the shielded test chamber. This contains

the external input connector and 81s calibration controls in
addition to the guarded test terminal. The external input con­nector is a teflon insulated triexial receptacle

Eleven position rotary switch sets the meter zem

of

the

!W seventh dial is a nailtiplier switch. At b&lance,

(Gremw

5632~).

515

III - 2

EUSE: A fuse extractor post Is located on the rear of the in-

strmnent . For ILL5 volt operation use a 3 AG, t amp. fuse; for

230 volts use a 3 b3, l/8 mqp.
POWER CORD: The three wire cord with the NlNA approved three-

prong plug provides a ground connection for the cabinet. An
adapter to allow operation from twn prong outlets is provided.

ACCESSORY OUTLET:

vided on the rear for operation of an external power supply.
It is wired directly to the powr cord and is not controlled
by the bridge power stitch.

EXTEBNAL INHTl!z UHF receptacle on the rear of the instrument,
used to connect an external power sqpply when bridge voltages

above 10 volts are desired.
OPERATION STEPS

C.

Connect power cord to ll5 volt, g/f50 cps, unless specified

1.

on resx for 230 volts. !Co change line voltage see Section V,
Maintenance.

2.
the null detector is normeSLy shorted corresponding to sn open

galvanonder key).

Set null detector to l.CW milklvnlts per cllvislon and un-

lock PUSH 'JB READ snitch so null detector input is shorted (note

!Cum power on and allow 30 seconds for warm-up.

3.

should indicate zero.

if necessary. If the detector cannot be set to zero, use the

coarse zero control.

A three-terminal convenience outlet Is pro-

Increase mill sensitivity and re-zero

The meter

4. Standardize the bridge if necessary (See D - Stsdardiza­z, following).

Insert the component to be measured in its test fixture.

5.

Set the function switch to OPRRATE when using the self-contained

shielded measuring compartment, or set it to EWERNAL OPFJWCE
when the unknown is located in the Model 51.52 Ren&e Test Chamber
or in another external sample holder. See E. Connecting to the

Unknown Resistor, which follows for detailed instructions for

connecting the unknown.

6. Set the BRnaE MU16 to the desired value. For external

bridge supplies, see F. External. Bridge Voltage Supply following.

Operate the FWH M RENI button and b&Lance for null with

7.
the resistsnce dials.

(See H.Aa?uracy) to give the desired accuracy at final belsxxe.
The resistance of the comnent is then read. directly from the
resistence dlaJ.8.

Use x M to x O.OOldi

Increase the null detector sensitivity

515

III - 3

STAEDARDIZ4TION

D.

Wire-wound resistors have the greatest accuracy and keep their cali­brations over long periods of time. Values greater then about one­megohm, however, are too large and too expens
Carbon film resistors provide values up to

e to be widely used.

ei

10

ohms and higher with

reasonable SUCC~QS and this type resistor is used in the Model 515.
But then value of these resistors changes wlth time, sometimes one
or two percent per year.

The Keithley Model 515 Megohm Bridge has been designed so that fre-

quent compensations can be made for variations of its high-megohm

standard resistors. This process is called Standardization and is

carried out as given below. Section IV - Circuit Description dis-

cusses the circuitry involved.
The bridge should be restandardized following a chenge in tempera-

ture of greater than about lOoF, and at least once each week, to

compensate for the errors introduced in the carbon standards by tem­perature and time. For the utmost accuracy possible from the bridge,

it can be standardized. daily, hourly, or immediately before a crit-

ical measurement.
To Standardize the Bridge:

1. Set the Multi 8 lier
OfJim dials) to 10

2.

Set TXINCTION switch to STANDARDIZE
Set NCLtL DETECTOR to 1000 mv per division.

3.

4.

Operate IUSH ltl READ switch and balance the bridge as in

normal operation.

.

The reading will be close to 10.00. The

(the farthest right of the RESISTANCE,

final balance should be made with maxinnun null sensitivity.

Release BUSH To READ switch and set FUNCTION switch to

5.

CWBRATE.

6., Operate PUSH To READ switch and re-balance the bridge with
the 10 CALIBRQE potentiometer located in the Shielded Measur­ing Compartment.

Turn FUNCTION switch back to

7.

STANDARDIZE.

8. Turn multiplier to I.07 and repeat steps 4 thru 7. Do this
for each successive mult
is ot used since the 10

I.?

multiplier position.

lo

lier thru 1011. The 1Ou position

f?i

ohm standard is calibrated in the

E. COIVNKTING TREUEKWOWWR.E3IS'lrOR

1.~ Using Internal Test Chsmber

515

III -

4

Fig. 1 Shielded Measuring Compartment,

With Unknown Installed

The bottom section of the bridge contains the shielded compart­ment for holding the unknown resistor, and is accessible when
the hinged door has been opened. The compartment has been de-

signed for greatest user convenience.

Its being shielded elim-

bates troublesome pickup, and the unit construction eliminates

the necessity for having cables running from the unknown to
the bridge, with their associated flexure noise.

The measuring compartment will accept resistors up to about
eight inches long.
banana jacks.

Connections to the bridge are made through

A convenient clip to use with the banana jack

is the readily available Grayhlll Test Clip #2,1; it has a ban­sna plug on the bottom snd spring clips on the top for holdin@;
the resistor heads;

three are supplied with each bridge. These

clips are illustrated in Fig. 1, holding a typical high-megohm
resistor.

A number of ground jacks have been provided so that the ground

clip can readily be placed for conveniently holding the unknown

resistor, irrespective of its length.

In measuring high

resistances,

the many precautions necessary
in electrometer techniques must be borne in mind; most important
are the need for dryness and cleanliness so that leakage resist­ance paths from the HI terminal to ground will not affect the
accuracy of measurement, and mounting the resistor so that its

body does not touch conductors or other insulators setting up
undesired or inadvertent leakage paths.

53.5

III - 5

2. Unknown Resistance Ecternal to ths Bridge.

The Moe1 51.52 Remote Test Chamber shown in Fig. 2 Is used for
testing irmilation or making other external shielded measure­ments.: This test chamber is equipped with an integral &I-Inch
teflontinsulated trisxial cable fitted with a conuector for
attaching to the mating cqnnector in the Shielded Measuring
Compar&nentlnthebr.Mge. The chamber and connecting cable

are rated for continous operation at temperatures as Wgh as

125w.

Flg. 2.Model 5152 Remote Test Chamber

The eLectrical connections are made throngh banana jacks in

the oh&her.

are furnished to facilttwte installing unkuowns tith axisJ~lea&s.
The banana jacks of course, can be used with any other connectors
or resistor holders.

To use:the Model 5152 Remote Test Chamber, fasten its cable

connector into the mating connector located in the Measuring
Compartment in the Bridge, and connect the unknown resistor
betweeq the RI and GROUND banana jacks in the Test Chamber (us-

ing the Cks+yhil.l test clips if possibae).

The third bsnsz.% jack in the Renwbe Test Chamber Is QUARD; it

Is cdn@ected through the inner shield braid of ths triaxial

cable to the guard connection in the Bridge.
Guarding is used exbenslvely in the Bridge to reduce the e&or6

causedfby spurions Le&age cwrents. WaxIing should also be

en@.oyed in the construction of test electrodes fitted to the
RemoteITest Chamber, in order to obtain the greatest accuracy

from We bridge measurement,

The hw.yhilJ. #2-1Test Clips as shown in Fig. 2

515

III - 6

The guard conductors are driven from the galvanometer junction
of the low tiedance standard arms of the bridge; a total re-

sistance less than 10" ohms from guard to gmund till stit
the standards sufficiently to create errors great enough to
impair the rated accuracy of the bridge. Great care has been
taken in the construction of the bridge to

GROUND resistance substantial& higher than 10

should be taken by the user to maintain that high level.

Fig. 3 is a simplified schematic diagram showin@; the electrical
connections of the standard and readout resistors, the unknown,
the null detector, and the guarding. A more extensive discus-

sion of the circuit operation and guarding will be found in

Section IV Circuit Description.

kee the GUARD to

Yl

ohms, and cexe

Fig. 3 Model 515 Megohm Bridge, Simplified Schematic Diagram
In cases where measurements with the unknown external to the

bridge are necessary and the Model 5152 Remote Test Chambe?

is not suitable, the user can make his own holding fixture

and connect it to the bridge.
Teflon insulded trisxial cable should be used for the con-

nection. The central conductor is the High Impedance conductor;
the inner shield braid is the Guard, and is driven from the
low impedance arms of the bridge; and the outer braid is GND,

to provide shielding. Amphenol 21-529 is a suitable cable.

515

III - 7

The connector should also be teflon insulated. Gremar 7991

is satisfactory. Fig. 4 shows the connector and cable.

MTERWAL BRIIGEVOLTAGESUPPLY

F.
Bridge voltages higher than the 10 volts available from the internal

4 are desired when measuring resistances greater than about

;;r;

ohms, or in studying the voltage coefficient of a resistor.

A UliF connector labelled EXTERN& LLNFVT is mounted on the rear of
the bridge cabinet for ready connection of a high voltage source.
The shell of the connector is at ground potential, and this grounds
one terminal of the external bridge supp4. The central conductor

is the high - voltage lead. The bridge is insulated so that the

external bridge voltage can be as high as 1000 volts.
Either the Keithley Model 241 or the 240 Regulated High Voltage Sup-

ply makes a very satisfactory source for external bridge voltage.
The over-current protection on each is an important feature in pre-

xenting damage to the bridge resistors or to the unknown.

Whenusing externalbridge supply, setBRII?GEVOLTSto EXTafter

connecting the supply to the UHF receptacle on the rear panel. Do

not app4 more than 100 volts unless the x ICC or the x 10 dial is

in a position other than "O",
the bridge resistors. With the recommended Model 240 or 241 Regulated
Voltage Supp4 the over current protection will prevent damage in
the eventthis precaution is not observed.

for too much current will flow through

In making voltage coefficient measurements, it should be kept in
mind that the voltage applied to a Wheatstone Bridge is greater than
the voltage appearing across the unknown resistance being measured.
The relationship between the bridge voltage and the voltage across

the unknown is given in Section 0, below.

The shielded measuringcompartment in the bridge has a safety switch
which is operated when the door is closed. This switch operates
a relay whiah applies the voltage from the external bridge supply

to the bridge circuit. With the door open, the voltage is renmved,

so that the unknown can be changed without possible harm to the operator.
When the unknown is located outside the bridge, and the FUNCTION

switch set to MTERNAL

the circuit< Unless the external bridge voltage supply is turned

off or disconnected, voltages dangerous to the operator may be present

at the unknown terminals.

source is to switch the BRIDGE VOLTAGE from EXT to zero.

G. MLTAGEAC!RGSSURKD3WNARDSTANBARB

In many cases, particular4 in measuring coefficients of resistors.

it is important to know the voltege across the unknown. In measuring

OPERATE, this safety interlock is removed fmm

A convenient means of disconnecting the

515

III - 8

the leakage resistance of capacitors,

the applied voltage must be
known to avoid breakdown. Also, for rated accuracy, the voltage
across the standard resistor must not exceed ten volts.

If the bridge voltage is E, the unknown resistance X, and the stand­ard resistance S, then the voltage across the unknown is:

and the voltage across the standard is:

The bridge voltage is read from the BRImE VOLTS dial or from the
external bridge voltage supply.

The standard resistance is the value

indicated by the m&tiplier dial.

H. ACCUHACYCONSIDEHATIONB
The accuracy of measurement of an unknown resistor in a Wheatstone

Bridge depends primarily on the accuracy and stability of the other
three arms in the bridge, upon the resolution of the variable arm,
and upon the ability of the null detector to respond to the small
incremental changes in the variable arm. There are also numerous
secondary effects.

These will aU be discussed below.

1. Null Detector Sensitivity.

To be able to detect a desired fractional deviation of the un­known, corresponding to the wanted percent accuracy of the measure­ment, the required null detector sensitivity is given by the
approximate expression*:

e is the null detector signal in volts
x is the incremental pa-t of the unknown resistance
E is the Bridge Potential in volts
S is the Standard Resistance, in ohms
X is the Unknown Resistance, in ohms

For resolutions of O.l$ in the unknown,

x = 0.00l.x

If X and S are approximately equal,

and

the Bridge Potential

is 10 volts,

o.oolx = 0.0015,

OY63R

e =

0.0025

v0its

(2.5 millivolts)

*See Electrical Measurements by F. K. Harris. John Wiley & Sons, N. Y. 19.52

515

III - y

In the case when X is approximately 10 S,

e = .W8 volts

(o .8 miuvolts)

The maximum sensitivity of the null detector in the Model 515
Megohm Bridge is one millivolt per meter dial division, and

is thus sufficient for the rated accuracy of the bridge. Care
should be taken, however, to be certain that the detector sen­sitivity and the bridge potential are great enough end the re­sistance of X end S are sufficiently close to each other to

obtain the expected accuracy of measurement.
A check on the sensitivity of the system may be made by unbalanc-

ing the bridge readout dials a given percentage and observing

the null detector deflection.

Null Detector Zero Drift.

2.
Vacuum tube electrometers drift about one to two millivolts

per hour, and this rate can be expected in the Null Detector.
Obviously, a false balance is indicated if the meter points

to zero, indicating balance, when in reality thereare several

millivolts at the input.
This error is easily eliminated by adjusting the null detector

to zero,whlle the PUSH 7.0 READ button is released, then depres-

sing the button end balancing the bridge.

Resolution of the Readout.

3.

Using only the readout dials x10 through x.001, full rotation

of the x.001 dial is O.l$ of the total setting. The dial can

be easily read to one-twentieth of its full rotation, giving

a readout resolution of 0.005%. This is ten times the best
accuracy specified for any range.

When using all the dials, the readout resolution is very much

greater than the maximum accuracy.

4. Accuracy of the Readout Resistors,the Standard Resistors,
end the Standard Calibration Controls.
location of each of them in the Wheatstone Bridge Circuit).

The accuracy of the resistors on the switches controlled by
each Readout Dial (RFSISTANCE, OHMS) is:

(See Fig. 3 for the

515

III

- 10

Xl00

0.5%

O%$

x.01 X.001

0.1%

1.0%

ma~i.smm accuracy with the bridge is obtained when using the

dials xlOthroughx.001.

!l!his is because the most accurate

readout resistors are used, and also because the unknown re-

sistance and the standard resistance are sufficiently close

that the null detector has enough sensitivity with bridge Wit-

eges less than ten volts (see Section III R. 1).
!Che xl00 dial has only 0.5% resistors associated with it

because of the extremely high cost of more
value resistors, and because resistors above 10 ohms

act

te high

Y

are not very stable high accuracy measurements are not

warranted.
The resistors on the x.01 end x.001 dials are less accurate

because they are not followed by enough diels to give high

resolution, and their accuracies are great enough for rated
accuracy when using the x1.0 to x.001 dials.

With the MCLTIPLIER dial in either the 105 or 106 position

all three aTm6 in the bridge itself are wirewound resistors
accurate to .02f&, permitting the unknown to be measured to an
accuracy of .05$.

With the MUTEIPL.lRR in the lo7 position, after the Standardiza­tion process, the bridge accuracy is that of the previous re,nge

(.05$) plus the error introduced by standardizing, which is

conservatively set at .05$.

FoUowing this pattern, the accuracy of the bridge at each suc-

cessive step of the lrmltiplier dial is the accuracy of the pre-

vious step plus the .05$ standardizing error. It is in this

fashion that the accuracies in the specifications up thru 1012

ohms were derived.
FromlO~tto l.014

to warrant the 0.5% rating, and above I.0

ohms, enough secondaryl~ffects are present

ohms, the xl00 dial

is used, adding enough further error to bring the overall accuracy

rating to l.O$.
The standard resistors used are as follows:
Multiplier

q
3
30

I&
ld2

Resistor !Pype

Wire Wound

0 (1

Dezosit,ed Carbon

Sealed,?-Meg

II
I! II
II 11

Accuracy

0.0s

0.0s

1.0 %

1.0 5

2.0 $3

2.0 $

515

III - XL

The Standard Calibration Controls arm is either a wirewound
resistor accurate to 0.02$, or deposited carbon resistors in

series with trinnaing potentiometers.

5. Temperature and Voltage Coefficient of Bridge Resistors.

The wirewqind resistors employed are free from voltage coefficient.
They use one of the lowest temperature coefficient of resistance
alloys available, changing 20 parts per million per 'C, or O.OG~$,/~C.

They are measured at room temperature, 25oc, end for greatest
accuracy, the bridge should be used near this temperature.

The depositedcarbon and Hi-Meg resistors have substantially
higher temperatuqe coefficients of resistance than the wire-

wound resistors.

But if the bridge is allowed to come to its

working temperature and standardized, it will have its rated

accuracy unless the temperature changes. In this case it should

be restandardized.

Deposited carbon and Hi-Meg resistors also exhibit voltage co­efficientof resistance.

The'Hi-Meg resistors used in the bridge

are spiralled and have about one tenth the voltage coefficient

of standard Hi-Meg units.

Nevertheless, the voltage across

these resistors should not exceed 10 volts for ms.xitmsn accur-

acy . Seem Section G. Voltage Across Unknown and Standard Re­sisters .

6. Leakage Resistence Across the Unknown.
6

lOlo ohms shunting one megohm (I.0

ohms) produces a change of

0.015; and 1015 ohms shunting 1012 ohms produces a 0.1% change.

With high resistance resistors end high accuracies leakage re­sistance is an important consideration.

The termipals of the Model 515 Megohm Bridge have been carefully
made with teflon insulation, and guarding has been employed

extensiveily .

The major concern of the operator in using the

bridge is to keep the insulation clean and dry. The user, how-

ever, should be greatly concerned with the bobbin and housing
or casing of his unlrnown resistor and with any specielly built
holdllng fixture. Paper base bakelite which has been handled
and allowed to remain in a humid atmosphere has a surprisingly

low resistance.

Glass envelopes which have been handled and
have finger oil and salt paths between fused-in wire conductors,
or simple water vapor paths, also csn have a surprisingly low
resistance. E&reme care is necessary to avoid unsuspected

errors or: instabilities in measuring high resistances.

Errors Caused by Guard to Ground Resistance.

7.

Guarding, as described in Fig. 3 Section III E, is used exten-

sively in.the construction of the

Model

515 Megohm Bridge to

515

III - l2

reduce errors caused by undesired leakege currents. The Guard
conductors are driven from the low impedance side of the Null
Detector.

on the Readout Mel switches and the Standard Calibration con-

trols.

Resistance from Guerd to Ground shunts the resistors

The Readout Mal resistors of xl0 to x.OClmay be as

hlghas10me@ms

shunted with 5 x 10

In the buildl

shunting error was establish;d for the lowest Guard to Grouud
resistence, and the user should da nothing to lower it.

The Guard &onductors are mstly inside the instrument cabinet
but Gusrd is exposed in the connector on the external unknown.
Wreme care must be taken at all times, with the instrument

cover on or'off, to maintain the cleanliness and dryness of

the Guard to Ground insulators.

The Guard conductor is also exposed in the 5152 Remote Test
Chamber.

T&M&% 5 5 G

8. Time Constants - Slow Responses

If sny resistor-holding electrode is connected to
ohms to ground, for meximum accuracy.

of ~~~nt~~~$o~~<C~~f~~.

T

12

uard, it too, must have a resistance greater

Ten picofarads and ICE
the wiring capacitances in the bridge end null detector input

combined with an unknown of about 1012 ohms produces a time
constant of several seconds.

The time constant is apparent in the length of time required
for the null detector meter to reach its final position after

an ed.justmellt has been made in the bridge.

For maxin~~~ measuring accuracy, the bridge null mnst be care-

fully determined, and readings taken only after the null detector
meter pointer has stopped moving.

The bridge has been carefully designed to keep the stray capacit­ances as low as possible, so that measurements can be made as
rapidly as possible. In measuring resistors greater than lOl2
ohms, the standard resistor is never greater than 1012 ohms,
thus the time constant is never longer then several seconds.

Measuring the leakage resistance of capacitors with the Model

515 Megohm Bridge can be a very tedious process, for with good
capacitors with very little leakage, the time constants with
the bridge impedances c&n be as long as several days. It is
recommended that this sort of measurement be done by charging
the capacitor to a known voltage and measuring its voltage at
known times later with a Keithley electrometer voltmeter.

ohms have a time constent of I.0 seconds;

515

III

- 13

Transients Caused by Push-to-Read Stitch

9.

Whenever two conductors have been m&zing contact and are.separ­ated, a~ charge appears on the contictors. In the Model 515

Megobm Bridge, this charge transfer is apparent in the null

detector meter when the Push-to-Read swltch is operated, re­moving the short circuit across the detector input. It

is mxt~noticeable when using the

EP

ohm multiplier and measur-

10

ing unknowns of 10” ohm or greater.

The Push-to-Read switch has been very carefully designed and
constrnqted to minimd.ze charge transfer, but a few nKU.Llivol.ts
are often induced in the bridge circuit by its operation.
!Phis is not harmful,

but it is necessary to wait each time the
switch Is operated, for several time constants during which
the voltages come to their steady-state value, and the null-

detector meter pointer stops drifting.

10. Verification of Accuracy

In chec
105,

ng the ccuracy of prototype bridges, resistors of

F ?

10 , ani 10 ohms were coqpared between the Model 515,
and. a Leeds and Northrup Guarded Wheatstone Bridge, Catalog
4232-B. These measurements were thus traceable to the National
Bureau gf Standards, e& were verified with various resistor
manufackurers. Agreement was within O.Ol$, which is weld. tithin
Model 515 specifications.

Resisttlllce values between 107 and. I.010 ohms were s-ted

a deltzwye

Transformation;

AIEE !!kansactlons Paper

58-556

by

gives the details.

Resistance values up to 10U

ohms were also measured carefulJy
by meas~ing the discbarge times of accurately known capacitors.
Above I.+ ohms, stray capacitances Introduced too much
Both the
well within the specified accuracy of the

ohm range was checked by measuring ten 10
,,,,cogy$2hm Y

delta-wye and capacitor

series. Agreement was obtained within

to 10 5 ohs, accuracy is assured by the care-

discharge measurements were

de1 515. !Che 10”

3Y

ohm resistors and

error.

ful. meaqurement of the resistors In the xl00 and xl0 switches

in the peadout arm of the bridge.

Ten resistors connected in parallel, measured accurately, and
then cowected in series is another method of obtaining high
value resistors to great accuracies, end was used extensively

in developing the bridge in production tests. This method is
described in “ElectrlcalMeasurements” by Harris. See Section

H, part 1.

515

III - 14

In the manufacture of each Model
the bridge resistors is measured and found to be within its
rated limits before the bridge is assembled. After assembly,

each step on each decade is checked with a precision decade
box as the unknown resistor.
veloped standard resistors are used to check each step of
the multiplier switch. The internal applied bridge voltage

supply and nul.l detector sensitivity and zero drift are also

checked.

515

Megohm Bridge, each of

Following this, Keithley de-

515

III

-

15

CIRCUIT DESCRIPl'ION - SECTION IV

The circuit of the Model

components:

the Dower supply, the electrometer null-detector and

515

Megohm Bridge consists of three major
the Wheatstone Bridge.
A. FowEFl SUPPLY
The power supply consists of a transformer, rectifiers and filters,

a transistor regutitor supplying I.2 volts dc, and a transistor con­verter which supplies voltages Isolated from ground to the null-

detector. A portion of the I2 volts dc Is used to polarize the

bridge.
A detailed description of the power supply is as follows: Drawing

14522-D at the rear of the manual is the complete schematic. Tl

is the power transformer operating from the power line. The primary
may be connected for either IlO or 220 volts. One secondary is center­tapped and, with diodes r@ and DlO, supplies 18 volts at 250 ma. The
other secondary and half-wave rectifier Dll supplies 20 volts at 10
ma. The 18 volts is applied to the collector of $1 and is dropped
to I.2 volts through the action of Ql and the associated regulator

circuitry.
Q4 and

Q5

form a difference amplifier which compares a portion of
the I.2 volt output with the reference voltage derived from zener
diode Dl4.

Q3

and Q2 are used as amplifier and driver for output
transistor Ql. D13 is supplied from the 20 volt supply referred
to above.

This supply is "boot-strapped" on the I2 volt regulated
supply to furnish a regulated return point for R2l2, the load resistor
for

Q3.

The circuitry is so designed that any change in load cur-

rent, or line voltage is compensated perfectly within the operating

range.
consisting of transistors

The regulated I2 volts supplies the transistor inverter,

Q6

and Q7 and transformer T2, and also

the ten volt bridge polarizing potential.
Transformer T2 and transistors Q6 and Q7 form a dc inverter operat-

ing at approximately 200 cps. The feedback winding to the bases

of the transistors provides the oscillator drive. The primary in-

ductance of the transformer determines the frequency of oscillation.

T2 Is especially well insulated to provide the necessary insulation
of guard to ground in the bridge circuit. Since the l2 volt source

is exceedingly well regulated, all the secondary voltages are unaf­fected by line voltage variation. Therefore, the operation of the

null-detector is not affected by line voltage variations.

NULL,Dhl'FZ!tDIC)R:

B.
Fig. 4 is a simplified circuit diagram of the null detector. The

component designations are the same as used In the complete schematic.
The power supply potentials are represented by batteries for simplicity.

515

Iv -1

DRIVEN

GUARD

RI50

LO

GUARD

FIG. 4

The filaments of Pl, V2 and V3 are in series and supplied with 3.6
volts. This voltage also is used to bias the electrometer tube,
Vl. V2 is an amplifier and V3 is the output tube. The output clr­cuit is somewhat unique and operates as follows: The meter will
have zero deflection only if there is no potential difference be­tween the plus terminal of B3 and minus terminal of FE. This will
occur only if the drop across Rl@+ is equal to the potential of B3.
This zero output condition is set by adjusting the screen voltage
of Vlwith the fine zero control, ~164, and the coarse zero control,

An input signal will cause the plate current of V3 to change,

89.

and. the drop across Rlk.4 will increase or decrease, depending on the

polarity of the signal.

A current will then flow thru the meter
and one of the range resistors on SlO, the sensitivity switch. Since
the low impedance side of the input is the minus meter terminal the
potential drop across the range resistor will alter the potential
of the filament circuit in such a way that the grid-filement potential
of Vl will remain nearly constant.

The filament is the "Driven Guard"

since its instantaneous ac potential is nearly equal to the ac poten-

tial of the input signal. All the guarded points of the bridge em-

cept Sll are returned to this point.

This acts as a driven shield

and a considerable increase in response speed is realized in certain

cases.

J

51.9

IV - 2

The simplified bridge circuit is shown in Fig. 5. One ratio arm,
A. is the six read-out dials.
I.cO K ohms for each multiplier rage.
105 the standard resistor S and the ratio arm B are both 105 ohm

.O

f~ wirewound units.

2

10

ohm ,025 wire wound and B is 105 ohm .02$. With the multiplier
at 107 or higher the standard resistor is a carbon film unit of limited
accuracy and B is a 95 K fixed resistor in series with a 10 K rheo-

stat. By the standardizing procedure described below B is set to an
appropriate value to compensate for error in S and the bridge will
be direct reading.

The first step in standardizing is done with the multiplier at 106
and the FUNCTION switch at STANDARDIZE.
as shown in Fig. 6.

standard resistor for the 107 range is in its place.
bridge with the read-out
ard as compared to the 10 standard.
accurate wirewound unit the value in cated for the 107 resistor

is quite accurate. In Fig. 3 the 10
be 5% high and the read-out dials will indicate 10.500.

Leaving the read-out dials set the FUNCTION switch is next set to
CALIBRATE. As shown in the simplified schematic of Fig. 7 the

standard and unknown resistors are replaced with a network of 1O:l

ratio, *ccurate to
a sociated with the 10

6f

B

a null will be obtained when B is 1.05 X 10 ohms.

When the multiplier is set at 106,

The unknown X has been disconnected and the

gi

.Ol

Ratio arm B is now B7, the adjustable leg

q* d"r"d.

ohm stan

The other ratio arm, B, is nominally

With the multiplier set at

S Is a

The basic circuit is then

Balsa

eJ.s will give the value60f the 10

Since the 10 standard is an

"i'

ohm resistor is assumed to

Rebalanc

ng the bridge with

f

ng the

3

stand-

This completes the standarization of the 107 ohm standard resistor.
After this, when using this resistor as a standard its 5% error is

exactly corrected for by B7 being 5% high.

515

IV - 3

To standardize the 10' ohm standard the multiplier is set at 107,
the FUNCTION switch is returned to STANDARLWE, and the bridge is
again balanoed withgthe read-out dials. The indicated read-ou
the value of the 10 ohm resistor compared to the corrected 10 ohm

is

ft

standard. Next the RJETION yitch is set to CALIBRAT'g and the bridge

is rebalanced with ratio arm B .

Af$3r folio* this procedure in sequence for multiplIer positions

10 thru l0 the bridge is completely standardized and will be direct
reading on *Xi ranges.

OVEBVOLTAGE PF0TEcTION

D.
The function of V4, 8 gas regulator tube, is to prevent damage to

the readout resistors from excessive bridge voltage. It is connected
thru auxiliary contacts on the xl00 snd xl0 dials across the bridge
voltage.

Thus if both dials are at zero the circuit is complete
and, if snore than 133 volts is applied to the bridge, the tube will
conduct current.

With a Keithley Model 240 or 241 Voltage Supply
this current W-XL be enough to trip the overload relay and no damage
will be done.

If an unprotected source is used it is possible that

V4 would be ruined and then possibly the readout resistors would

overheat from excessive current.

IV - 4

SDTJIONV - MAIRTRNARCE

Very few maintenance problems will arise from ordinary use of the
bridge. The components used have adequate safety margins and, since
the total power consumption is only 10 watts, very little tempera-

ture rise will occur even with continuous operation.

If it becomes apparent that the bridge is not working properly the
first step is to check the voltage on the printed circuit boards.

Remove the six screws on each side and the two on top and remove

the cover.
null detector board as shown on Drawing 14363-c.

If the difficulty is determined to be in the null detector proper
the following procedure will be helpful in isolating the cause:

Short circuit the feedback by jumpering the feedback resistor in

use.

The sensitivity w-ill. now be about 500 microvolts per division and
it will be rather difficult to keep the meter on-scale with the ZERO

control. However, if it is possible to swing the tube voltages thru
the values indicated on 14363-c the stage is working satisfactorily.
Start with Vland workthru to V3.

located check the tube itself and then the associated components.
If it is necessary to replace the electrometer tube avoid touching
the glass near the lead wires.

These resistors are mounted on S-10, MILLIVWIS PER DIVISION.

Check the voltages on the main power supply board and

Once the defective stage is

Once the bridge is operating a good check on the accuracy may be
amde by placing the multiplier at 105 and the IUNCTION switch at
STARDARDIZR. A null balance should be obtained with the readout

dials at IO.000 f.O5$. If the reading is not within these limits

it is recommended that the unit be returned to the factory for re­pairs.

The overvoltage tube, Vk, will ordinarily not carry any current and

should last indefinitely. However, if the instrument has been used
with a supply lacking adequate overload protection it is possible
the tube may be damaged. If this has happened it is likely that
other components have been damaged also. Check the resistors in
arm A and B of the bridge (RIJJ. thro RI.23 and Rl71 thrn Rlgl).

230 volt operation:
To change the power line voltage to 230 volt remove the two jumpers

at the bottom of the main power supply board and connect a single

jumper as shown in the circuit schematic, 14522-D. Be sure the line

cord is removed from the power when doing this. Replace the 4 ampere

yrC: fuse with a l/8 ampere unit.

515

V-l

MODEL 515 MEGOHM BRIDGE

REPLACEABLE PARTS

SECTION 6. REPLACEABLE PARTS

6-1.

Model 515.

manufacturer, the manufacturer's part number and the Keithley Part Number.
address of the manufacturers listed in the "Mfg. Code" column are in Table 2.

6-2.

Part Number, the circuit designation and a description of the part.
and those parts coded for Keithley manufacture (80164) must be ordered through Keithley
Instruments, Inc. or its representative.
Parts List, completely describe the part,

ment, Keithley Instruments, Inc.

REPLACEABLE PARTS LIST. The Replaceable Parts List describes the components of the

The List gives the circuit designation, the part description, a suggested

TIE name and

HOW TO ORDER PARTS.
For parts orders,

a.

b. Order parts through your nearest Keithley representative or the Sales Service Depart-

sw

CerD
Camp

3Cb
EMC

ETB

E

:Cb
<
LOC.

ampere

Ceramic, Disc
Composition

Deposited Carbon

Electrolytic, Metal Case

Electrolytic, tubular
farad
Glass enclosed carbon
kilo (103)
Location

include the instrument's model and serial number, the Keithley

All structual parts

In ordering a part not listed in the Replaceable
its function and its location.

M

2,.

0

PMC
Poly

I-r
v volt

w watt
ww
WWVar

mega (106)
milli

Manufacturer
ohm
Paper, Metal Cased‘

Polystyrene

(10e3)

micro (10-6)

Wirewound
Wirewound Variable

1065R

TABLE 1.

Abbreviations and Symbols.

6-l

REPLACRABLE PARTS

(Refer to Schematic Diagram 14522D for circuit designations)

MODEL 515 MEGOHM BRIDGE

MODEL 515 REPLACEABLE PARTS LIST

CAPACITORS

circuit

Desig.
Cl01

Cl02
Cl03
Cl04

1,

C201 203

c202
C204 7-100 IJ.f

-C205 1000 IJ.f
C206 10 pf

-C207 500 pf
C208 .os pf
c209 500 pf
c210 -i 50 pf

Circuit

Desig.

Value Rating

22 pf
22 pf
22 pf

.047 uf

100 100 wf

IlOO vf

pf

TYPO

1000 v
600 v
600 v
1000 v

50 v
25 v
50 "
25 v

15 v

25 v
25 v
200 "
50 v
25 v

Mfg.

TYPO

CerD 56289
CerD 72982
CerD 72982
Poly 96733

EMC 56289
ETB 56289
EMC 56289
EMC 37942
EMC. 14655

ETB 14655

EMC 14655
PMC 00656
EMC 14655

ETB 56289

Number

Cbde Part No. Part No.

DIODES

Mfg.

5GAQ22

ED22

ED22

MW94 Ml0473

TVL2326~

TVA1207
TVL2326
FP335A
BO 040

BBRlO-25

AA0120

P82

AA0160

TVA1206

Mfg.

Code Part No.

Keithley

C72-22P
c22-22P
c22-22P
C67-.047M

C33-lOO/lOOM
ClO-100M
C33-lOO/lOOM

ClOO-100M

C59-LOOO/lOOOM
ClO-1OM

C58-500M
C18-.05M

C57-500M
ClO-50M

Keithley

LOC.

LOC.

Dl
D2
D3
D4
D5

D6
D7
D8
D9
D10

Dll
D12
D13
D14
D15

Silicon
Silicon
SiliCOll
Silicon
Silicon

Silicon
Silicon
Silicon
Silicon
Silicon

Silicon

SiliCOtl
Zener
Zener
ZC?lll?r

lN3253
lN3253
lN3253
lN3253
lN3253

lN3253
lN3253

lN3253 02735
lN3253
lN3253 02735

lN3253
lN3253
lN1314
lN706
1N715

02735 RF- 20
02735 RF-20
02735
02735 RF-20
02735

02735
02735

02735

02735
02735 RF-20

99942 DZ-2

12954 DZ-1
12954

RF-20
RF-20
RF-20

RF-20
RF-20
RF-20
RF-20

RF-20

DZ-22

6-2

0668R

MODEL 515 MEGOHM BRIDGE

REPLACEABLE PARTS

MISCELLANEOUS PARTS

Circuit
Desig.

DSl

DS2

Fl (117~)
Fl (234~) Fuse, .

Jl
52
53

54

Kl

Ml

Pl

Miniature Lamp, 6.3 v at 0.2 amp (Mfg. No. 51)
Miniature Lamp, 6.3 v at 0.2 a&p (Mfg. No. 51)

Fuse,

Guarded Input Terminal (Mfg. No. 6804)
Triaxial External Operate Connector (Mfg. No. 5632A)
UHF Receptacle, External Volts (Mfg. No. 6804)

3-Terminal Accessory Outlet (Mfg. No. 160-2)

Relay, DPDT

3-Wire Power Cord, 6 feet (Mfg. No. 4638-13)

Description

.25 amp (Mfg. No. 313, 250)

125 amp (Mfg. Type HDL)

Mfg. Keithley

Code
08804

08804

75915
75915

91737
91737
91737

02660

80164

80164

82879

Part No. LOC.
PL-8

PL-8

FU-17
FU-20

~~-64
CS-67
CS-64
cs-66

RL-12

ME-34

co-2

Sl

S2

s3

54

s5

~6

Rotary Switch, less components, FUNCTION, 4-position
Rotary Switch, with components, Function Switch
Knob Assembly, Function Switch

Rotary Switch, less components, RANGE, 8-position
Rotary Switch, with components, Range Switch

Rotary Switch, less components, BRIDGE VOLTS, 120-

position

Rotary Switch, with components, Bridge Volts Switch

Rotary Switch, less components, DECADE Xl00
Rotary Switch, with components, Decade Xl00 Switch

Knob Assembly, Decade Xl00 Switch

Rotary Switch, less components, DECADE X10

Rotary Switch, with components, Decade X10 Switch
Knob Assembly, Decade X10 Switch

Rotary Switch, less components, DECADE Xl

Rotary Switch, with components, Decade Xl Switch

Knob Assembly, Decade Xl Switch

80164

80164 22118~

80164

80164

80164 22116~

80164
80164 22113B

80164
80164 22120B

80164 14829A

80164
80164 22112B

80164 14829A

80164 SW-122

80164 22117B
80164 14829A

SW-87

16323A

SW-80

SW-91

SW-123

SW-123

0668R

6-3

REPLACEABLE PARTS MODEL 515 MEGOHM BRIDGE

MISCELLANEOUS PARTS Cont'd.

Circuit
Desig.

s7

58

s9

510

511
512

513

Mfg. Keithley

Description

Rotary Switch, less components, DECADE X0.1

Rotary Switch,
Knob Assembly, Decade X0.1 Switch

Rotary Switch, Less components, DECADE X.01
Rotary Switch, with components, Decade X.01 Switch
Knob Assembly, Decade X.01 Switch

Rotary Switch, less components, COARSE ZERO, 11-position 80164

Rotary Switch, with components, Coarse Zero Switch

Rotary Switch, less components, SENSITIVITY, 4-position 80164
Rotary Switch, with components, Sensitivity Switch

Zero Switch Special Push Button 80164
Toggle Switch, on-off S.P.S.T. 80164

Door safety switch

with components, Decade X0.1 Switch 80164

Code Part No. LOC.~
80164
80164 148298
80164 SW-122

80164
80164 14829A

80164

80164

80164

SW-122
221!4~

22115~

SW-88

22111B

SW-92
22119B

14377A
SW-4
SW-94

---

Tl

T2

circuit Mfg.
Desig.

RlOl

R102

R103
R104
RL05

R106
R107
RL08
R109
RflO

RLll

R112

R113
R114 94.5 kn

R115- 94.5 kR

6-4

FINE ZERO Control Knob Assembly

Power Supply Transformer
Inverter Transformer

RESISTORS

Value Rating

10 kfi .02%, l/2 w w 80164
100 k0 .02%, l/2 w w 80164
100 kn
1 M.O .02%, L/2 w W 15909 1252
LO MO

100 MO 1%. l/2 w DCb
109 a
1010 R

;;:: R

f-l

100 kc2 .02%, L/2 w

94.5 kil L%, l/2 w DCb 00327

94.5 kcl L%, l/2 w DCb 00327

(1) RlOl and R102 are a matched set, Keithley Part Number 13992A

.02%, l/2 w w

I%, L/2 w

l%,

112

w

l%, 1,'2 w

Type

DCb

GCb
GCb
GCb
GCb

W

DCb

DCb

Code

15909
00327
91637

80164 --­80164 --­80164 --­80164 ---

15909

00327
00327

80164

80164 TR-39
80164 TR-40

Mfg.

Part No. Part No. Lot .

1252
NLLA RLZ-L0M
DC-2

1252
NllA R12-94.5K
NllA R12-94.5K
NllA R12-94.5K
NlLA R12-94.5K

Keithley

R47-100K
R47-1M

R14-100M

148388

(1)
(1)

20658A
20659A
20660A
20661A

R47-LOOK

MODEL 515 l.fEGOHM BRIDGE

REPLACEABLE PARTS

RESISTORS Cont'd.

Circuit
Desig.

Rll6

R117

Rllt?
Rl19
R120

R121
R122
R123
~124
R125

R126
R127
R128

R129

R130

R131
R132
R133
R134
R135

Value

94.5 kn

94.5 kQ
10 k.Q

10 kQ

10 kR

10 kR
10 kn
10 kfi
100 a
100 sz

100 n
100 R
100 R
100 n
100 a

100 R
100 n
100 n
1 MO

3.3 Ma

Rating

l%, l/2 w
l%, l/2 w

lO%, 2 w
lo%, 2 w
lO%, 2 w

lO%, 2 w
lO%, 2 w

lO%, 2 ,w
I%, l/2 w
l%, l/2 w

1%; l/2 w
l%, l/2 w
l%,

l/2

w
l%, l/2 w
l%, l/2 w

l%, l/2 w
l%, l/2 w
I%, l/2 w
lo%, l/2 w
l%,

112

w

Mfg. Mfg. Keithley

Type Code Part No.
DCb

DCb
ww
ww
ww

ww
ww

ww

DCb
DCb

DCb
DCb
DCb
DCb
DCb

DCb
DCb
DCb

DCb’

00327 NllA
00327 NllA

12697 43-10K
12697 43-10K
12697 43-10K

12697 43-1OK
12697

43-1OK
12697 43-10K
00327 NllA
00327 NllA

00327 NllA
00327
00327

NllA

NllA
00327 NllA
00327 NllA

00327 NllA
00327 NllA
00327 NllA
01121

EB

00327 NllA

Part No. LOC.
Rl2-94.5K

R12-94.5K

RP27-10K

RP27-10K
RP27-10K

RP27-10K

RP27-10K
RP27-10K
R12-100
R12-100

R12-100
R12-100
R12-100
RL2-100
R12-100

R12-100
R12-100
R12-100

Rl-1M

R12-3.3M

R136
R137
R138
R139
R140

R141
R142
R143
R144
R145

R146
R147

R148
R149
R150

R151
R152
R153
R154
R155

R156

3.3 MXl
10 Ma

3.3 Mfi

100 kR
100 kQ

8.2 Ma
22 MQ

4.7 k0
220 kQ
10 k0

5 kQ
Not Used
Not Used

420 i2

4.3 k0

40 kR

390 k0

1.4 kn
2 kO

1 kR
4 kQ

I%,

112

w

I%,

l/2

w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w

'IO%, l/2 w

lO%, l/2 w
lO%, l/2 w
I%,

112

w
lO%, l/2 w

I%,

l/2

w

l%,

112

w

l%, l/2 w
l%, l/2 w

l%,

l/2

w

l%,

l/2

w

I%,

l/2

w

l%, l/2 w
I%,

l/2

w

DCb
DCb
Comp
Comp

Comp

camp
DCb
Comp

DCb

DCb
DCb

DCb
DCb
DCb

DCb

DCb

DCb

00327 NllA
00327 NllA
01121 EB
01121

EB

01121 EB
01121

01121

EB

EB
01121 EB
00327 NllA
01121 EB

00327 NllA

00327

NllA

00327 NllA
00327

NllA
00327 NllA
00327

NllA
00327 NllA
00327 NllA

00327

NllA

Rl2-3.3M

Rl2-~1OM

Rl-3.3M
Rl-100K
Rl-100K

Rl-8.2M
Rl-22M
Rl-4.7K
Rl2-220K
Rl-1OK

Rl2-5K

R12-420
R12-4.3K

Rl2-40K

Rl2-390K

Rl2-1.4
R12-2K

R12-1K
R12-4K

0668R

6-5

REPLACEABLE PARTS

MODEL 515 MEGOHM BRIDGE

RESISTORS (Cont'd)

Circuit Mfg.
Desig.

RL57
~158
R159
Rl60

R161

~162
~163
~164
R165

R166

~167

R168
~169

R170

R171

R172
R173

R174

R175

Value
4 kcl

2 kQ

1 k0

4 kfl

4 kS1

Not Used

10 kQ
10 kn
1 kQ

Not Used
Not Used
Not Used
Not Used

10 kfl
2 kfi

4 kQ
4 kQ
10 kfl
20 kfl

Rating Type

I%, LIZ w

l%, 112 w
l%, 112 w

l%, l/2 w
I%,

l/2

w

lO%, l/2 w

3%, 5 w
3%-l%, 3 w

O.l%, l/2 w
O.l%, l/2 w

O.l%, l/2 w
O.l%, l/2 w

.02%, l/2 w
.02%, l/2 w

DCb
DCb
DCb
DCb

DCb

Comp
WWVar
ww

ww
ww

ww
ww
ww 15909 1252
ww

Code
00327

00327
00327
00327

00327
01121

73138
12697

15909
15909

15909
15909

15909

Mfg.
Part No. Part No. LOC.

NLLA
NllA'
NllA
NllA

NllA

EB
A RP4-1OK
CM27520NP RP25-1K

1252

1252

1252

1252

1252

Keithley

RlZ-4K
R12-2K
R12-1K
RL2-4K

R12-4K
Rl-1OK

R70-10K
R70-2K

R70-4K

R70-4K
R47-1OK
R47-20K

R176
R177
R178
R179
R180

R181
R182
R183
R184
~185

Rl86
R187
R188
R189

R201

R202
R203
~204

R205
R206

R207

40 kQ
40 kQ
100 ka
200 kfi
400 k0

400 kR

1 Ma
2 MR
4 Mn

4 MO

10 Ma
20

MCl

40 MO

40 Mel

68 R

'200 a

500 cl

500 n

200 0

1.5 kQ

8.2 kn

.02%, l/2 w

.02%, l/2 w
.02%, l/2 w­.02%, l/2 w
.02%, l/2 w

.02%, l/2 w
.02%, l/2 w
.02%, l/2 w
.02%, l/2 w
.02%, l/2 w

l/2%, 2 w

l/2%, 2 w

l/2%, 2 w

l/2%, 2 w

lO%, l/2 w
l%,

l/2

w

l%, l/2 w

l%, l/2 w

lO%, 2 w
lo%, l/2 w

lO%, l/2 w

ww 15909 1252

ww

ww
ww 15909 1252
ww 15909 1252

ww

ww

ww

ww

ww

DCb
DCb
DCb
DCb

camp
DCb
DCb
DCb

ww

camp

camp

15909
15909

15909
15909
15909
15909
15909

03888
03888
03888 PT-200
03888 PT-200

01121
00327
00327
00327
71450

01121
01121

1252
1252

1252
1252
1252
1252
1252

PT-200
PT-200

EB
NllA
NllA
NllA
R252-200

EB
EB

R47-40K
R47-40K
R47-100K
R47-200K
R47-400K

R47-400K
R47-1M
R47-2M
R47-4M
R47-4M

R52-10M
R52-20M
R52-40M

R52-40M

Rl-68
Rl2-200
R12-500
R12-500
RP22-200

Rl-1.5K
Rl-8.2K

6-6

0568R

MODEL 515 MEGOHM BRIDGE

REPLACEABLE PARTS

RESISTORS (Cont'd)

Circuit Mfg.

Desig. Value Rating Type Code
R208

R209

R210
R211

R212
R213
~214

R215
R216

R217
~218
R219
R220

R221

Circuit
Desig.

1 kQ
680 R
820 n

390 cl
27 ka
10 kQ

3.3 MR

10 n
10 n

100 n
10 s2

22 ka
470 R

*

lo%, l/2 w
lO%, l/2 w
lO%, l/2 w

lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w

lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lo%, l/2 w
lO%, l/2 w

l%,

112 w

Number Code Part No.

Comp 01121
camp 01121
camp 01121

Comp 01121
camp 01121
camp 01121
camp 01121
Comp 01121

Comp 01121
camp 01121
camp 01121
camp 01121
Comp 01121

DCb 00327

TRANSISTORS

Mfg.

Mfg. Keithley

Part No. Part No. Lot.
EB Rl-1K

EB Rl-680

EB
EB Rl-390

EB Rl-27K~

EB
EB
EB

EB

EB
EB

EB
EB R1-470

NllA R12-$<

Keithley

Rl-820

Rl-1OK
Rl-3.3M
Rl-10

Rl-10
Rl-100
Rl-10
Rl-22K

LOG.

QL

42

93
Q4

Q5
Q6

Q7

Circuit

Desig.

Vl
v2
v3

v4

* Nominal value, factory set.

2Nl535 04713 TG-7
2Nl381 01295 TG-8
2~1381 01295 TG-8
2~1381
2Nl381

2Nl375

2Nl375

Number ,&de Part No.

5886 80164 EV-5886-2X

6418 or 592 80164 EV-CK6418 or EV-CK592-4
6418 or 592 80164 EV-CK6418 or EV-CK59&4

OB2

01295
01295

01295
01295

VACUUM TUBES

Mfg.

86684

TG-8

TG-8

TG-15

TG-15

Keithley

Lot.

EV-OB2

1269R

6-7

REPLACEABLE PARTS

MODEL 515 MEGOHM BRIDGE

00327 Welwyn International, Inc.

Cleveland, Ohio

00656 Aerovox Corp.

New Bedford, Mass.

01121 Allen-Bradley Corp.

Milwaukee, Wis.

41295 Texas Instruments, Inc.

Semiconductor-Components Division

Dallas, Tex.

02660 Amphenol-Borg Electronics Corp.

Broadview, Chicago, Illinois

02735 Radio Corp. of America

Commercial Receiving Tube and

Semiconductor Division
Somerville, N.J.

03888 Pyrofilm Resistor Co., Inc.

C.edar Knolls, N.J.

04713 Motorola, Inc.

Semiconductor Products Division
Phoenix, Airzona

08804 Lamp Metals .and Components

Department, G.E. Co.

Cleveland, Ohio

12697 Clarostat Mfg. Co., Inc.

Dover, N.H.

12954 Dickson Electronics Corp.

Scottsdale, Ariz.

14655 Cornell-Dubilier Electric Corp.

Newark, N.J.

15909 Dawn Division Thomas A. Edison

Industries,, McGraw Edison Co.,

Livingston, N.J.

37942 Mallory, P. R., and Co., Inc.

Indianapolis, Ind.

56289 Sprague Electric Co.

North Adams, Mass.

63060 Victoreen Instrument Co.

Cleveland, Ohio

71450 CTS Corp.

Elkhart, Ind.

72982 Erie Technological Products, Inc.

Erie, Pa.

73138 Helipot Div. of

Beckman Instruments, Inc.

Fullerton, Calif.

75915 Littelfuse, Inc.

Des Plaines, 111.

80164 Keithley Instruments, 1nc.

Cleveland, Ohio

81453 Raytheon Co.

Industrial Components Div.
Industrial Tube Operation

Newton, Mass.

82879 Royal Electric Corp.

Pawtucket, R.I.

86684 Radio Corp,of America

Electronic Components and Devices
Harrison, N.J.

91637 Dale Electronics, Inc.

Columbus, Nebr.

91737 Gremar Mfg. Co., Inc.

Wakefield, Mass.

94145 Raytheon Co. Semiconductor Div.

California Street Plant
Newton, Mass.

96733 San Fernando Electric Mfg. Co.

San Fernando, Calif.

99942 Hoffman Electronics Corp.

Semiconductor Division

El Monte, Calif.

ABLE 2. Code List of Suggested Manufacturers. (Based on Federal Supply Code for

Manufacturers, Cataloging Handbook H4-1.)

6-8

0668R

v3

v2

6418/

j’

6418~

P

i !

.REPAIR AND CALIBRATION FORM

For

repair or calibration, please fill out this form
Sales Service Department

Keithley Instruments, Inc.

2877.5 Aurora Road

Cleveland, Ohio 44139

user’s Name
company
Division

Data

1.

Reason for Return
0 Repair and Recalibration 0 Report of Calibration Certified
0 Recalibration only (No report, except Traceable to N.B.S.

as specified in item 4 on reverse)* 0 Calibration Report

*If repairs are necessary to meet speci-

fications,
the calibration.

3.

To help repair the instrument, briefly describe the problem:

1s the problem -Constant

4.
Under what conditions does the problem occur:

Control setting e) Line voltage

=)

b) Approx. Temperature OF

b) Approx.
c) Approx. Temperature variation * OF

c) Approx. Temperature
d) Approx. Humidity (high, medium, low)

d) Approx. Humidity (hrgn, n

they will be in addition to

Telephone

Address

City

Model No.

2. Calibration Report Desired

(for details, sea reverse side of this form)

and return it with your instrument to:

R­Do not write in this space.

state
Serial No.

a Certificate of Compliance
0 Node

1 Intermittant

f) Other (such as line transients,

line variations, etc.)

Ext.

Zip

Please draw a block diagram of the system using the Keithley.

5.
nent data which can help in the repair. Include charts or other data if available.

Signal Source
Source Impedance

Readout Device:

aRecorder
0 Oscilloscope

- Other
a None

Lengths & Types of Connecting Cables

What repairs or modifications have been made on this instrument which are not on file

6.
with the Keithley Repair Department?

Please enclose any other pertinent data and charI.? which you feel might help the

7.
Repair and Calibration Department

Signature Title

1267

List any other perti-

Listed and defined below are the four types of calibrations and their associated

report formats which are presently available at Keithley Instruments.

They fall into

the following categories: .

Report of Calibration Certified Traceable to the National Bureau of

1.
Standards

Calibration Report

2.

3.~ Certificate of Compliance
Recalibration

4.

ALL calibration and certification performed by Keithley Instruments is in accord

with MIL-C-45662A.
Prices shown below are in addition to repair charges for any work necessary to place

a customer’s unit into first class condition prior to the calibration.

I

U.S.A. and Canada sales offices

european services

Keithley has a manufacturing facility in Germany and a warehouse
and office in Switzerland to provide prompt delivery in the European
area. The facilities. staffed by Keithley field engineering personnel.
give on-the-spot assistance to your Keithley representative so that

he may better serve you. A list of the worldwide Keithley rspresent­atives is given on the back.

K

EITHLEY INSTRUMENTS; INC.

28775 AURORA ROAD ­TELEPHONE: (216) 248-0400

TELEX: 98.5469

CLEVELAND,;OHIO 44139

international sales offices

NETHERLANDS

PAKISTAN

REPUBLIC OF SOUTH AFRICA
Protea Physical 8. Nuclear

I”str”nls”tati0”. my. Ltd.

P.O. BOX 1793
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Telephone: [phone]

SPAIN

Atab ,ngeniera*

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Madrid 16

Telephone: [phone]

SWEDEN

cmO”iX AB

Jamtlandgatan 125

pa Valuingby
Stockholm
Telephooe: 87.03.30

SWITZERLAND

Ssyffer and Company. 1°C.

Bade”erltra9.8 265

CH-8040 Zurich
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TURKEY

Mevag

Karatmy Bankalar Caddesi 71.73

Istmb”,

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