Tektronix 515A Instruction Manual

Model 515A

Megohm Bridge

Instruction Manual

Contains Operating and Servicing Information

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, 440-248-0400. You will be given assistance and shipping instructions.

REPAIRS AND RECALIBRATION

Keithley Instruments maintains a complete repair service and stan-

dards 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 representatives.

To insure prompt repair or recalibration service, please contact your

local field representative or the plant directly before returning the instrument.

Estimates for repairs, normal recalibrations, and calibrations traceable to the National Bureau of Standards are available upon request.

Model 515A Megohm Instruction Manual

0Keithley Instruments, Inc

Cleveland, Ohio, U.S.A.

MODEL 515A MEGOHM BRIDGE

CONTENTS

Section

1.

2.

3.

4.

5.

Page

ii

1

4

15

17

20

29

31

1072R

SPECIFICATIONS

MODEL 515A MEGOHM BRIDGE

SPECIFICATIONS

RANGE: 105 to d5 ACCURACY: (when bridge is operated es described below):

Range, ObnlS

105

co lo7 .012%

107

to 108 to 109

100 109

1o1o ;: :$ 1011 eo

1012

1012 to 1013 1013 to 1014

1014 to 1015

ohms with a 7-dial in-line readout.

Standard Deviation (lr)r* Bridge Voltage

10 " .02% .03% .06% .08%

.16%

.25%

.3%

1.5%

10 "

100 Y 500 "* 500 v*

Decade

105 to 106 107 10;

lOlO

$1

$f

INPUT: Built-in comparfmenf or optional Remote Test Chamber with Teflon-insulated tri-

axial cable. GROUNDING: One terminal of unknown is at ground potential. NULL DETECTOR: Electrometer with sen*itivity of 100 microvoles per division to 1 volt

per division in five decade steps.

Meter is non-linear past l/3 of full scale for

ease in determining null.

BRIDGE POTENTIAL:

Internal: Prom 0 to + 110 volts dc in l-volt steps. External

With Keithley Model 240A or 241 High Voltage Supply, 1000 volts maximum, positive

only.

INTERNAL CHECKS: Built-in zero check anu leatige (guard fo ground) check. Test jacks

for checking wirewound standard resistors.

Bootstrap calibration from wirewound

standards for the 10' through 1012 decades.

ENVIRONMENT:

CONNECTORS: External Operate:

Any i O.S°C span between 20 and 3OOC, 20-50% relative humidity.

Teflon-insulated triaxial panel jack, Gremar 56328.

External Bridge-Potential Input: UHF. POWER: 105-125 or 210-250 volts, SO-60 Hz, 10 "atts. DIMENSIONS, WEIGHT:

Standard 19" wide x 14" high rack mounting, 11-l/2" behind front

panel (483 x 356 x 292 m), total depth, 12-314" (324 mm); net weight, 28 pounds

(12,s kg).

13

NOTES : *External supply required above

**Based an theoretical analysis of bridge errors.

10

ohms.

See Instrucrion

Manual

for details on obtaining specified performance.

ii

1072R

GENERAL DESCRIPTION

SECTION 1.

1-l. GENERAL. The Model 515A Megohm Bridge is an instrument

for measuring resistance from lo4 ohms to

GENERAL DESCRIPTION

Source spans a range from 1 to 110 volts in l-volt

steps.

lOI5 ohms with a limit of error from .05 to 1%. Ie comprises a solid-state, guarded, electrometer null detector; an ultra-stable, highly-regulated dc voleage ~o”rce, and B Wheatstone bridge.

c.

Shielded Compartment: Connection to the bridge

is made using a guarded terminal in the shielded

compartment which minimizes noise pickup.

1-2. FEATURES

d. Standardize Mode: This mode can be selected

a. Accuracy Verification: Accuracy is traceable

to the National Bureau of Standards by use of the

Model 5155 resistance standards available as an

for quick calibration of bridge elements eo correct for slight changes in the standard high megohm

resistors.

optional accessory.

e. Guard Leakage Check: A quick self check of the

b. Selectable Bridge Volcage: An internal voltage guard to ground resistance can be made using test

jacks on the front panel (inside the measuring cow pWCme”t.

1070

1

GENERAL DESCRIPTION MODEL 515A MEGOHM BRIDGE

TABLE 1-l.

Front Panel Controls.

Control

Functional Description Paragraph

BRIDGE VOLTS

Power Switch (S311)

Controls power to bridge; Selects INT or EXT. Xl Switch (S203) Sets voltage in l-volt steps. X10 Switch (5202) sets vo1rage in IO-volt steps.

NULL DETECTOR

Sensitivity Switch (S103) FINE ZERO Control (R120)

CO*RSE ZERO Control (5102)

READ/ZERO CHECK (S201)

FUNCTION Switch (S301)

RESISTANCE

x100 (5304) X10 (5305)

Xl X.1

X.01 (5308)

x.001

(5306) (5307)

(S309)

x.0001 (S310)

Selects null detector sensitivity, .I to'lOOOmV/div. Adjusts meter zero (inner knob). Adjusts meter zero (outer knob).

Selects READ or ZERO CHECK operation.

Selects mode of operation; 4 positions.

Adjusts bridge balance in steps of 100. Adjusts bridge balance in steps of 10. Adjusts bridge balance in steps of 1. Adjusts bridge balance in steps of .I. Adjusts bridge balance in steps of .Ol. Adjusts bridge balance in steps of ,001. Adjusts bridge balance in steps of .OOfll.

Multiplier Switch (S302) Sets multiplier ratio from lo5 to 1012,

2-2,

al

2-2, a2

2-2, a3

2-2, a4

2-2, a5

2-2, a6

2-2, a, 2-2, as

2-2, a9 2-2, a10 2-2, all 2-2, al2 2-2, a13 2-2, a14 2-2, a15

2-2, a16

Controls and Connections,

TABLE 1-2.

Front Panel Measuring comparement.

Control Functional Description Paragraph

CALIBRATE Controls

106 (R319) 107 (R320) 108 (R321) 109 (R322)

1010

1011 (R324)

(R323)

Safety Switch (~3303)

Adjusts bridge elements in CALIBRATE mode‘.

Provides a safety interlock; rernow~ bridge power when the

2-2,

compartment door is open.

INPUT Terminal (5302) Provides a guarded connection to INPUT high.

EXT. INPUT Terminal (5303)

Provides a guarded connection using a triaxial cable

2-1, a 2-1, a

for external inpllts.

Low Terminals Provides a connection to INPUT low when using the guarded 2-1, a

INPUT high terminal.

Tesr Jacks X01-210 Provide various circuit test paints for checkout.

bl

b2

2

1070

MODEL 515A MEGOHM BRIDGE

GENERAL DESCRIPTION

Power Swftch

Sensitivity

“RIO”,, VOLTS Switch Zero

Control

I Y1

I

ZERO CHECK FUNCTION Switch

S”:rch

Multiplier

Switch

FIGURE 2. FronC Panel Controls

FIGURE 3. Shielded Measuring Compartment

OPERATION

MODEL 515A MEGOHM BRIDGE

SECTION 2.

2-1. MEASUREMENT CONSIDERATIONS.

a. Connections.

Shielded Test Compartment. The Test Compart-

1.

ment shown in Figure 3 permits measurement of high

resistance while minimizing noise pickup and the effects of leakage paths. Input connections can be made using a triaxial receptacle (EXTERNAL INPUT

5303) or a guarded INPUT high receptacle (5302). a.) High Megohm Resistors.

can be easily measured by connecting TV the INPUT receptacle and any one of eight INPUT low resep-

tacles. The receptacles are designed for use with

test clips such as Grayhill 82-l which have a banana plug on one end and a spring clip on the other. The INPUT low receptacles are spaced one inch

apart for resistors up to 8 inches long. A typical

resistor connection is shown in Figure 3.

b.) External Connections. A teflon-insulated, guarded, triaxial receptacle (EXTERNAL INPUT 3303) is provided for external connections. The receptacle is a Gremar Type 56328 triaxial connector

which mates with a Gremar Type 7991-1 triaxial

plug (Keithley CS-69). A? optiQna1 accessory cable is available (Keithley MaJel 5153) for external connections; a 60" triaxial cable with CS-

69 connector on one end. The Keithley Model 5152

Remote Test Chamber permits external shielded measurements (with a 60" triaxial cable and CS-69 connector).

Discrete resistors

OPERATION

External Voltage Source. An external voltage

2. source can be connected to the bridge using the rear panel UHF coaxial receptacle (5211). This connector is a Gremar Type 6804 UHF receptacle

(Keithley CS-64) which mates with a Gremar Type

5127 plug (Keithley CS-49).

Guarding. A driven guard is used extensively

b.

in the bridge circuit to minimize the effects of spurious leakage currents.

1. Theory. taken to guard the high-resistance arm so that insulation leakage currents will not affect the balance point. Guarding in the Model 51% is shown in Figure 4. The guard enclosure is indicated by the dotted-line surrounding the high megohm

resistors, the electrometer null detector, and the guarded input terminal. The inpur high terminal utilizes a "guard ring" maintained approximately at the potential of the null detector law.

2. Circuitry. The guard potential is obtained

from the null detector (electrometer) power supply common as illustrated in Figure 5. of ehe "Driven Guard" is maintained at very

the Input High potential with the result that the High to Guard leakage is extremely small at bridge balance. The guard circuit is formed by a metal enclosure and plates which surround the STANDARD

resistors, CALIBRATE resistors, the null detector,

and the Input terminal.

In megohm bridge design,care must be

STANDARD

The potential

nearly

FIGURE 5.

Null Detector

1070

OPERATION

3. "se of the Guard. a.) connections to guard.

(5302) is a guarded receptacle (Gremar, Type

The INPUT terminal

6804)

with a center High contact and an outer Guard ring. The EXTERNAL INPUT terminal (5303) is a guarded rriaxial receptacle (Gremar, Type

5632A)

with a center High cmtact, an inner Guard confact and an outer Low confact. A drawing of the connector construction is shown in Figure

b.) Applications.

The driven guard can be used

6.

for external measurements when it is necessary to minimize the effects of spurious leakage currents across the insulation. A rypical external measurement can be accomplished using Keiehley Model 5152 Remote Test Chamber and teflon-insulated

triaxial cable. The “se of the Model 5152 is complerely described in Section 4, Accessories.

c.) Guard to Ground Leakage. The design of the

guard circuit in the Model 515A maintains the Guard

fo Low (ground) resistance greater than 1011 ohms. The Guard to Ground resistance should be high with

respect to the resistance from floating low to

ground so that the shunting effects across the Readout Resistance will not be significant. Far example the worst-case condition would be a Readout Resistance of 10 megohms or lo7 ohms with a

0.02%

tolerance.

If the Guard to Ground fe.sistaxe were 1011 ohms, an additional error of 0.01 % would result.

c. Leakage. The Input terminals of the Model 515A

have been designed using teflon insulation between High and Guard and Guard and Ground. In order eo maintain the high insularion resistance, the terminals must be kept clean and dry.

Preferred cleaning materials include: Chemically pure alcohol, sterile cotton swabs (to prevent contamination of alcohol), and a drying agent such as nitrogen. Leakage paths across the terminal can create intermitrant errors or

difficult bridge balance. The user should also take

care to insure that the unknown resistor, holding fixtures and case are insulated properly. Glass envelopes (high.megohm resistors) can be contaminated

by oil and salts from improper handling. Paper base bakeliee insulation can be degraded by improper

handling and exposure to moisture. The humidity of the laboratory environment can also affect the measurement of very high resistances. See Specificarians.

d. Noise. Noise pickup from ac electric and mag-

netic fields is minimized by the unit construction

of rhe chassis and the use of a closed, shielded

measuring compartment. When using an external unknown

resistance, care should be taken to:

1. Use shielded cables such as Keithley Model

5153 triaxial cable.

2.

Fasten dawn the cables so that flexure noise

is minimized.

3. Maintain Guard to Ground insulation using

teflon insulation.

FIGURE 6. Triaxial Receptacle

4. Use an external shielded test box such as

Keithley Model 5152 Remote Test Chamber.

e. Accuraw.

1. Specification. The specified accuracy for

measurements on various ranges is valid for the

following conditions.

a.) Minimum Bridge Potential. This potential

is the minimum voltage required for resolution.

b.) Environment. The ambient temperature and relative humidity must be controlled within limits stated.

c.) Standardization. The Standardization procedure should be performed prior to very critical measurements.

d.) Proper Operating Technique. Care must be taken when connecting the unknown (See Measure-

ment Considerations, Paragraph 2-1) and balancing

the bridge (See Accuracy Considerations, Para-

graph Z-7).

2. Verification. The Model 515A accuracy can

be verified using the Model 5155 Megohm resistance

standards.

1072R

5

OPERATION

10

3.

Technique for Measuring 10

to 1015 Ohm

Resisrances.

Set Canrrols as Indicated:

BRIDGE VOLTS: 0 FUNCTION SWITCH: MULTIPLIER:

OPERATE OR EXTERNAL OPERATE

1010, 1011, or 1012 RESISTANCE DECADE DIAL X100: lo READ/ZERO SWITCH:

Insert unknwn resistor.

ZERO

Set READ/ZERO Switch m READ and note offset of null deeector with MULTIPLIER setring to be used in measurement. Allow approx-

imately 15 minutes for reading t” stabilize. The affser of the null detector is due to offset current from the null derecror and from stressing of Teflon insulation surrounding the Hi terminal of the bridge.

Use the offset reading as null for measuring the

unknown. Ser READ/ZERO Switch to ZERO.

Select the Bridge potential for the measurement based on desired accuracy as described in derail in the OPERATION secfion af the manual. Set READ/ZERO Switch m READ and balance bridge using Resistance decade dials.

?IETER NOISE: I” balancing the bridge when measuring

resistances greater than lolo ohms there is meter noise present due to l/f noise, alpha particle noise,

It may be noted fhat the meter indication has

etc. a base-line from which meter fluctuations diverge. The actual null detector reading is this base-line when balancing the bridge.

NOTE

Care should be taken m allow enaugh time for bridge to stabilize fc, a reading. This rime will vary from one measurement to another however, a minimum time of 15 minures is advisable to decermine final null reading.

2-2. CONTROLS AND SWITCHES.

a. Front Panel.

1. Power Switch (5311). This switch controls the power to the bridge including the bridge porenrial and null detector supplies. The INT position permits a setting of the bridge potential

from 1 to 110 volts using the Xl and X10 BRIDGE VOLTS switches.

The EXT position connects the external voltage input (5211) so that a bridge potential up to 1000 V can be applied “sing an external voltage supply such as Keithley Model

241.

2.

Xl Switch (S203). This switch permits a set-

ting af the bridge p@zential in l-volt increments

up to 10 volts.

3. X10 Switch (S202). This switch permits a

setting of the bridge potential in lo-volt incre-

nle*tS up to 100 volts.

4. Sensitivity Switch (S103). This switch se-

lects the null detector sensitivity from .l to 1000

milliu0lts per division.

MODEL 515A

5. FINE Control (Rl20).

This control is the inner knob af a dual-concentric canerol. The FINE Control permits adjustment of the meter zero.

6.

COARSE ZERO Switch (S102). This switch is the Outer knob af a dual-concentric control. The COARSE Switch permits adjustment of the meter zero in 10 steps.

7.

READ/ZERO CHECK Switch (S201). This switch selects READ or ZERO CHECK operation for the meter circuit. In ZERO CHECK position the null deeecmr High and Low ‘are shorted together.

8. FUNCTION Switch (5301). This switch selects

the mode of Operation in 4 position,

OPERATE,

STANDARDIZE, CALIBRATE, and EXTERNAL OPERATE. A complete discussion of these modes is given in paragraph 2-3.

9. Xl00 Resistance Switch (5304). This switch adjusts the “Readout” am of the bridge in steps of 100.

10. X10 Reeietance Switch (S305). This switch adjusts the “Readout” am of the bridge in seeps of 10.

11. Xl Resistance Switch (5306). This switch adjusts the “Readout” arm of the bridge in steps

of 1.

12. X.1 Resistance Switch (5307). This switch

adjusts the “Readout” arm of the bridge in steps of .l.

13. X.01 Resistance Switch (S308). This switch

adjusts the “Readaut” am of the bridge in steps of .Ol.

14.

X.001 Resistance Switch (S309). This switch adjusts the “Readout” am of the bridge in steps Of .OOl.

15. X.0001 Resistance Switch (S310). This switch adjusts the “Reabou:” arm of the bridge in steps Of .OOOl.

16.

Multiplier Switch (S302). This switch sets

the multiplier ratio from 105 to 1012.

b. Measuring Cmpartment.

1. CALIBRATE Confmls. These controls are used to adjust the bridge when the FUNCTION Switch is set to CALIBRATE. The use of these controls is de-

scribed in paragraph 2-4, d (Standardization pro-

cedure).

2.

Safety Switch (5303). This switch is a normally-open interlock which remwee bridge power when the compartment door is open. The safety in-

terlock is defeated when the FUNCTION switch is set to EXTERNAL OPERATE.

c. Rear Panel.

117-234V Line Switch (5312). This switch sets the Model 515A far either 117V or 234V rms line power,

50-60

Hz.

6

1072R

MODEL 515A

OPERATION

2-3. MODES OF OPERATION.

a. operate.

This mode of operation permits meas-

urements of high megohm resistances when connected to

the INPUT receptacle.

FUNCTION switch to OPERATE.

To select this mode, set the

Either the internal voltage source (bridge potential) or an external voltage source up to 1000 volts can be used. The safety

interlock switch prevents operation of the bridge

whenever the compartment door is open.

If the unknown resisCa”ce must he measured externally, “se the External Operate mode.

b. External operate.

This mode of operation permits resistance measurements the same as for the Operate mode.

To select this mode set the FUNCTION

switch to EXTERNAL OPERATE.

WARNING

When the FUNCTION Switch is set to EXTERNAL OPERATE the safety inter-

lock feature is defeated. Therefore the bridge voltage (up to 1000 volts) is present at ehe Guard circuit at receptacle 5303.

The user should be ca”tio”s when “sing very high bridge voltages. For maximum safety, the

Power Swifch (S311) should be set to

INT when not making a measurement.

c.’ Standardize/Calibrate. These modes of operation permit adjustment of the bridge elements to compensate for slight variations of the standard high

megohm resistors. To select either made set the FUNCTION Switch to STANDARDIZE or CALIBRATE as described in paragraph 2-4, d.

2-4.

PRELIMINARY PROCEDURES

1. COARSE ZERO Switch (S102) (Outer Knob). This switch has eleven positions for adjustment of meter zero.

2. FINE ZERO Control (R120).

This control provides fine (potentiometer) adjustment of the meter zero.

c. Warmup. The instrument should be allowed to

stabilize with power on (at least 30 minutes). If

the instrument has been exposed to an extreme ambient temperature change the warmup time should be extended fo

24

hours or more. Standardize Procedure. For critical measure-

d.

ments the instrument should be standardized prior to each measuremene to compensate for slight changes of the standard high megohm resistors due to temperature variations and aging with time. The Standardize procedure should be performed as described in Table 2-l. A complete discussion of the Standardization technique

is given in paragraph 2-5. 2-5. MEASUREMENT PROCEDURE

a. Connect Unknown Resistance. Determine the method of connection to the unknown as discussed in paragraph 2-l.

b. Select the Bridge Potential. The minimum Bridge Potential should be determined for rated acc”racv as

stated in the specifications. The voltage can b; applied internally (with Power Switch set to INT) or externally as described in paragraph 2-l.

c. Standardize Bridge. For measurements where the effects of variations of the bridge elements must be minimized, the Standardization procedure should be performed as described in paragraph 2-3, d.

a. Power.

1. Line Voltage. This inscrumenc can be connect-

ed to 117 volt, 50-60 Hz line power when the Line Voltage Switch (on the rear panel) is set to 117”. The fuse should be a type 3AG, 1/4A, SLO-BLO. When using

234V

power, set the Line Voltage Switch to

234V and replace fuse with a type 3AG, 1/8A, SLO-BLO.

2. Accessory Outlet. A three terminal power outlet (5301) is provided on the rear panel far operation of an accessory such as an external power

S”PPlY. and is not controlled by the Power Switch.

3.

This outlet is wired to rhe line power cord

Power Cord. A three wire power cord is supplied (6 feet long). A third prong is used far earth ground connection for the chassis. An adapter is supplied for converting to a two prong outlet, but should only be used when a solid, earth-connec-

tion is made by some other means.

b. Meter Zero. The meter circuit can be zeroed by

adjustment of COARSE ZERO and FINE ZERO Controls. The READ/METER ZERO Switch (S201) should be -et to METER ZERO.

1072R

d. Meter Zero. Adjust meter zero as necessary.

iiridge Balance.

e.

With the FUNCTION Switch set to OPERATE, proceed to balance the bridge (set the READ/ZERO Switch ea READ).

Increase the null sensi-

riviey as necessary to obtain a precise bridge balance.

f. External Operate. If the unknown resistance is connected externallv the FUNCTION Switch should be set to

EXTERNAL

2-6.

a.

OPERATE before bridge balance is attempfed.

STANDARDIZE.

Purpose of Standardization Technique. Wirewound resistors have the greatest accuracy and keep their calibrations over long periods of time. Values greater than about one megohm, however, are too large and coo expensive to be widely used. Film type resistors pravide values up to lOI ohms and higher with reasonable SUCCESS and this type resistor is used in rhe Model 515A. B”t the value of these resistors changes with time, sometimes one percenr per year.

The Keithley Model 51% Megohm Bridge has been designed so that frequent compensations can be made for variations of its high-megohm standard resistors. This process is called Standardization and is carried out as in paragraph 2-4, d.

7

OPERATION

TABLE 2-l.

Standardization.

MODEL 515A

Step

A B

c

D

E

F

G

H

I

J

K

L

M

N

8

Power On

Meter Zero

Standardize

Calibrate

Standardize

Calibrate

Standardize

Calibrate

Standardize

Calibrate

Srandardize

Calibrate

Standardize

Calibrate

Procedure Set Power Switch to INT. Set READ/ZERO Switch to ZERO and adjust FINE

control for meter zero. Set Controls as indicated. Set READ/ZERO Switch

to READ and balance bridge using RESISTANCE

decade dials. Increase sensitivity as necessary.

Set READ/ZERO Switch to ZERO and go to next step.

With bridge at balance set FUNCTION Switch to

CALIBRATE. Adjust calibrate potentiometer for

bridge rebalance with the READ/ZERO Switch set

to READ. Set READ/ZERO Switch to ZERO,

Set Controls as indicated. Set READ/ZERO Switch

to READ and balance bridge using RESISTANCE

decade dials. Increase sensitivity as necessary.

Set READ/ZERO Switch to ZERO and go to next step.

With bridge at balance set FUNCTION Switch to

CALIBRATE. Adiust calibrate potentiometer for bridge rebalance with the R&/ZERO Switch set

to READ. Set Controls as indicated. Set READ/ZERO Switch to READ and balance bridge using RESISTANCE decade dials. Increase sensitivity as necessary. Set READ/ZERO Switch to ZERO and go to next step.

With bridge at balance set FUNCTION Switch to

CALIBRATE. Adjust calibrate potentiometer for bridge rebalance with the READ/ZERO Switch set to READ. Set Controls as indicated. Set READ/ZERO Switch to READ and balance bridge using RESISTANCE decade dials. Increase sensitivity as necessary. Set READ/ZERO Switch to ZERO and go to next step. With bridge at balance set FUNCTION Switch to CALIBRATE. Adjust calibrate potentiometer for bridge rebalance with the READ/ZERO Switch set to WAD. Set READ/ZERO Switch to ZERO.

Set controls as indicated, with zero Bridge volts and Xl00 Resistance decade dial set to 10. Set

READ/ZERO Switch to READ. Note offset of null

detector after allowing time for stabilizing after switching FUNCTION Switch (10 - 15 minutes). This offset is due to offset current. Use this offset reading as null for Standardizing 10'". Set controls as indicated. Set READ/ZERO Switch to READ and balance bridge using Resistance decade dials. Increase sensitivity as necessary. Set READ/ZERO Switch to ZERO and go to next step. Use null detector zero for null in CALIBRATE. With bridge at balance set FUNCTION Switch to CALIBRATE. Adjust calibrate potentiometer far bridge rebalance

with the READ/ZERO Switch set to READ. Set READ/

ZERO Switch to ZERO.

Set conrrals as indicated, wirh zero Bridge volts and Xl00 Resistance decade dial set to 10. set READ/ZERO Switch to READ. Note offset of null detector after allowing time for stabilizing after switching FUNCTION Switch (10 - 15 minutes). This

offset is due to offset current. Use this offset

reading as null for Standardizing 1011.

Set controls as indicated. Set READ/ZERO Switch

to READ and balance bridge using Resistance decade

dials. Increase sensitivity as necessary.

READ/ZERO Switch co ZERO and go to next step. Use null detector zero for null in CALIBRATE. With bridge at balance set FUNCTION Switch to CALIBRATE. Adjust calibrate potentiometer for bridge rebalance with the READ/ZERO Switch set to READ. Set READ/

ZERO Switch to ZERO. Set FUNCTION to OPERATE.

Set READ/ZERO Switch to ZERO.

Dial Seefing FUNCTION Switch

Set

Multiplier

(S302) Setting (S301)

10’5

106

107

108

109

lOlO

1010

lOlO

loll

STANDARDIZE

CALIBRATE

STANDARDIZE

CALIBRATE

STANDARDIZE

CALIBRATE

STANDARDIZE

CALIBRATE 109

OPERATE

STANDARDIZE

CALIBRATE

OPERATE

STAND*RDIZE

CALIBRATE

Calibrate

Control

106

107

108

lOlO

loll

1072R

MODEL 51524

b. Description of circuit and technique.

I. A simplified bridge circuit with FUNCTION

switch in ST*NDARoIZE is shown in Figure 9.

2. With Resistance Multiplier Switch eef et lo6,

then the bridge null is obtained for the condition s6,S, = B6/A, where “S,j”, s’S7’1, “B6”, and “A” are defined as follows:

= Standard resistor (lo6 ohm, .02%) selected

"'6"

“ST?<

"'6" ,,*,,

by resistance multiplier switch set at 106.

= Standard resistor (lo7 ohm, 1.0%).

= 105 ohm, .02%.

= Resistance decade potentiometer adjusted

for null (106 ohms).

NOTE

This technique is used ta determine the ratio of

r?,611 to ‘37” accurately as read by resistance

decade dials.

3. A simplified bridge circuit with FUNCTION

switch in CALIBRATE is shown in Figure 10

4. In the CALIBRATE position, a resistance ratio

network of 1:lO is connected in place of “56” and

*‘S7”. The bridge null is obtained far the condition R = +/A, where “R”, “S7”, and “A” are defined as follaws:

“Ru

= Ratio network of ‘I:10 with .005% accuracy.

OPERATION

2-7.

THEORY OF OPERATION. Bridge Theory. The Megohm Bridge has been de-

a.

signed to measure very high resistances using a Wheatstone Bridge and a sensitive null detector. The Wheatstone Bridge circuit basically consists of four

arms, identified as A, 8, S, and X as shown in Figure

11. (A

thorough

discussian of bridge meaeurement is

available in Electrical Measurement, F. K. Harris, Wiley, New York, 1952). The equation for the bridge

at balance can be described by the equation:

x = s x A/B

b. Null Detector Sensitivity. The sensitivity of

the bridge can be described by the equation:

e = Sd

OL

xE

e = sensitivity in volts d = incremental unbalance (in terme of the unknown) E = bridge potential

S = standard resistance

X = unknown resistance.

C. Voltage Across the Unknown. The Voltage acr~se the unknown resistance can be determined for a given set of conditions where:

E =

bridge potential (bridge volts setting) standard resistance (multiplier setting)

s =

x =

unknown resistance (approximate value of the

“IlkFlOWn )

“87” = Calibrate potentiometer.

= Resistance decade p@zentiometer adjusted

“A”

previously in b2.

NOTE This technique is used to set the calibrate paentiometer “8,”

such that errcx in “57”

is compensated.

5. A simplified bridge circuit with FUNCTION

switch in OPERATE is shown in Figure 11.

6.

In the OPERATE position, the bridge null is obtained for the condition ST/X = 07/A. when resistance decade potentiometer “A” is properly adjusted.

7. A simplified bridge circuit with FUNCTION

Switch in OPERATE and resistance multiplier 106

is shown in Figure 8.

TEST JACKS

5201 2 3 4 5 6

oegoouooo

7 8 9 10

JUMPERS (NORMAL POSITION)

FIGURE 7.

Test Jack Identification.

“, =

voltage across x = E x

X+S

2-a. GuARo LEAKAGE CHECK. The fallowing procedure should be used to verify the

guard to ground resistance. The teet jacks are identified in Figure 7.

Procedure :

1. Connect power cord to line voltage.

2. Place

3.

iumers

3203

and j204

5205

and 5206

set 515‘4 controls

between the followine

as foliows.

test

iacks.

BRIDGE POWER - EXT

MILLI"0l.T PER DIVISION

- 1000 FUNCTION - OPERATE MULTIPLIER - 105 READ/ZERO CHECK

- ZERO CHECK Xl00 DIAL - 1 DOOR

4.

Connect Keithley Model 240A Power Supply to

- CLOSED EXTERNAL INPUT on the rear panel.

Set Model 240A to 1000 volts with

5.

6.

Set READ/ZERO CHECK switch to READ. Allow

7.

five minutes for the Made1 515A reading to

OUTPUT to +.

stabilize. Reading shall be less than 1000 mV.

NOTE.

The meter indicates the voltage drop acrcse a 108 resistox in series with the leakage path. Leakage resistance from GUARD to

GROUND

is deter-

mined as fallows.

Leakage current = (Voltage drop : lo* ohms) Leakage resistance = (1OOOV + leakage current) Typical GUARD to GROUND resistance is greater

than 1011 ohms.

9

OPERATION

MODEL 515A MEGOHM BRIDGE

Calibrate Position, lo6 Multiplier.

10

. _ _ _ .._

Operate Position, lo7 Multiplier.

MODEL 515A

OPERATION

2-9. ACCURACY

Standard Deviation.

a. the bridge eiven in the Soecifications is defined as the “standard deviation” br lo-level.

- I

CONSIDERATIONS.

The overall accuracy of

In a system where several components of error make up the total error, it is grossly unfair (when specifying the

system) to use worst-case limits in describing accuracy.

In many cases, the error so described may have a probability of less than one in a billion while human error (usually neglected in such an analysis) can easily contribute gross errors on the order of one in a thousand.

It is far more reasonable to use a limit between one in a thousand (99.9% or 3.3) and one in ten thousand (99.99% or 3.9) as a specification

of system accuracy.

If the 3rlimits of two or more

normally distributed (n) randomly occurring corn-

poqents of error are summed in quadrature (G12T

1 ) the sum is the 3Uerrar for the group. If

=2

three uniformly distributed (-) randomly occurring components of error have equal limits, the arithmetic sum of these limits will closely represent the 30 points of the near normal error distribution generated

by the interaction of these error components. These

TABLE 2-2.

3 r Error Computation.

(All numbers in % of Reading with minimum bridge potential specified and dials between 1 and 10).

31r limits may then be used to sum in quadrature with the 3s limits of other normally distributed error components. The effect of error components which are

not randomly distributed but are fixed or have a fixed

rate of change (systematic errors) must be added directly to the random errors. If one component Of error occurs more than once and does not have random change to have changed, it must be summed directly

far the number of times occurred before being added in quadrature to other errors.

b. Error Analysis. The various factors which can

be identified as sources of error include the follow-

ing .

1. Bridge Arm. The errors pertaining to the

bridge arm consist of the decade dial errors and

the fixed arm to decade ana ratio.

a.) Decade Dial. The decade dial errors include the worst case dial setting within the decade span used, the inherent resistor error,

the temperature and time stability of the resistors, and the effect of leakage resistance.

Range zero ohms

105 - 10’

107 108

108

- 109

Check Null

,006 .006 - .03 .OOl .031

,006 ,006 .02 .04 .002 ,009 ,005 .03

.006 .006 .03 .08 ,004 .012

109 - lOlo ,006 .012

1010 - 1011

1011 - 1012 ,006

1012 - 1013

1013 - 1014 .006

1014 - 1015 .06 0.6 .07 .72 .064 .04 .030 .03 0.1

.006 .012 .04 .24

.03 .05 .48 ,022

.006 .12 .07 .72 .064

.24 .07 .72 .064 .04 ,030 .03 .Ol .77 500 *

Temp. volt Coef.

Coef. Coef.

Temp.

Null

R&b

Bridge

AKIllS

.OlO .03 .OOl

.03 .16 ,006 .015 .015 .03

.OlO

.020

,024 .025 .03 ,001 .49

.04 .030 .03

.020 .03 .OOl .25

Leakage %

Ladderinn

Total Error

Minimum

Bridge

Potential

10

,001

.056 10

,085

10

.OOl .17 10

10

.OOl .74 100

1.1

500 *

* ~a obtain this accuracy specification an external voltage supply is required. Accuracy (30) for

1015

range would be + 6% at a bridge potential of 110 V.

1072R

11

OPERATION

MODEL 515A

b.) Fixed arm to decade arm ratio. The errors

associated with the ratio accuracy include the

basic Standard resistance error, the accumulative

laddering error and the temperature and voltage

coefficient of the Standard resistor.

2. Null Uncertainty. The errors pertaining to

null uncertainty include the null detector sensi-

tivify, the bridge voltage, the bridge ratio, and the l/f noise.

c. Error Computation. The computation of total

error at rhe 3D-level is sham in Table 2-2 far each

NOTE

The assumptions made to simplify the error

analysis include the following. individual resistors are within their tolerance limits and have a uniform random

distribution between these limits.

temperature coefficient and voltage coefficient an wirewound resistors are negligible in the face of other errors. to-peak null detector meter excursions observed over several fime constants represent the +3Ulimit of a normally distributed random

null certainty.

1. All

2. The

3. Peak-

d. Error Factors.

1. Worst Case Dial Setting. Far the "optimumuse range" between 1.0000 to 9.9999, the worse case dial setting would be 1.0999. Since each dial setting of 9 represents 3 resistors, the total contribution of dial settings .0999 would be:

3uerror =~(.005)2+(.0025)2+(.001)2 : +.006%.

If this error is added to the base tolerance of .OI% and divided by the higher resistor value (1.0999), the result is:

% error = * - .015%

If this error is separated into components, then the uniformly distributed error = .Ol% while the

normally distributed error = .005%.

2. Resistor Accuracy.

the various dials is given in Table 2-3.

Dial Resistance Xl00 10 1 .1 .Ol .OOl

TDleratKe

I

1

3. Temperature Coefficient. The temperature coefficients for the Standard resistors are given in Table 2-4 (assuming a +.5'C temperature).

1.0999

The resistor accuracy for

TABLE 2-3.

Dial Resistor Accuracy.

.OOOl

. 5% .Ol% .Ol% .Ol% .05% .25% 1%

I I

12

1072R

MODEL 515A MEGOHM BRIDGE

OPERATION

TABLE 2-4.

Leakage Resistance.

4. since the Readout Dials are shunted by approximately 1011 ohms. The error should be added directly since it is a relatively fixed systematic errm.

VOltage Coefficient. The valtage coefficient

5.

for each Standard resista is given in Table 2-5.

Voltage Coefficient (l-lOV)/V. in %.

IResistance lo7 1OB lo9 lOlo 1011 101’1

Coefficient -.005

I

6. Null Resolution. Null uncertainty is approxirately the ratio of the smallest voltage drop eceoss the bridge arm to the null resolution. AS the bridge ratio departs from 1:l the null uncertainty becomes

mre significant.

-.005

Leakage causes an error

TABLE 2-5.

-.Ol

-.03 -.03

7. Laddering. Laddering is the process of using the bridge Co calibrate itself. Several errars compound during this process to increase the error of the bridge at higher resistances. The process consists of two modes:

I* CALIBRATE Mode: ~6 = &

where R6 is the 106 miltiplier (20.01%) and R7 is

the 107 multiplier resistor (+O.Ol%), B6 is the “fixed” arm associated with the 106 multiplier and D is the dial setting.

In STANDARDIZE Mode: R, =

where

Ra/Rb

is the 1:lO ratio pair (20.005%) and B7

I

is the “fixed” arm associated with the lo7 multi-

plier (adjusted for proper ratio). Thus, B7 = ~6 R,

laddering. The tion and only 3 resistive error factors ere included,

~6, R6

ey at 106

(use 0.006%) muef be included. If can be shown that further nullings give

and Ra/Rb. In addition, a nulling uncertain-

x r at the end of the first

diai accuracy

and a nulling uncertainty at low impedance

STANDARDIZE and CALIBRATE.

7 D

87

K

b

0

a

drops from considera-

Teble 2-6 gives the null uncertainty for the caee where the ratio is 1O:l and the bridge voltage is

10”. (1OO:l @ 100” for lOI4 range and 1OOO:l @ SOOV for 1015 range).

Null Uncerrainey-Null Detecmr Resolution.

105 106

Range

% Error ,006 .006

N.D. Resolution

In” f<

+

I

*With a 10” bridge potential.

to to to to to 106 107

.05 .05

107 108 109

,006 .006 ,012 ,012

.05 .05 .lO .10

108

TABLE 2-6.

109

1o1o $11

thue adding one mme Ra/Rb uncerraincy, one mre

low impedance null uncertainty and an additional

null uncertainty at IO7 ohms. The voltage acmes

1010

1011 ;;12 $3

.03 .12 .24 .6

.25 1.0

1012

1013 1014 :;14 ;;15

1070

13

OPERATION

MODEL 515A MEGOHM BRIDGE

the hi-meg changes from about 10 volts in “STAND-

ARDIZE” pcxition to about 1 volt in ehe next “CAL-

ISRATE” position. Since the voltage coefficiene is always negative, these errors must be added together prior to the sunning procedure in quadrature wieh ocher random variable. The effect of voltage co-

I

Range

Range Time to Calibrate Temp. Change

W/V

,005 ,005 .Ol .Ol .03 .03

Temperature Errors During Laddering.

TABLE 2-7.

TABLE 2-8.

efficient need only be accounted for one time. Table 2-7 shows the sum of the voltage coefficienr

errors on each range during laddering. For ladder-

ing the meaaamnent time can be assumed short with respect to ineernal temperature changes. (The thermal time constant for the Model 515A is about

10 minutes). Table 2-S shows the total error for

temperature changes

v “C Error “C ErT-21

8” 8V 8” 8” av 8V

TC Total Error TC *

.04 .04 .08 .08 .24

.24

107

108

Jt

TC represents the “root square sum” or total error for each range due to temperature coefficient errors

during laddering.

1 min 1 min

1 min 2 min 5 min

10 min

Range

r

107 108 109

(a) Normal Distribution.

(b) Uniform Distribution.

(c) Ra/Rb will not change so addition of subsequent errors is direct, not in quadrature.

,:; .04 ,002 1x.006%

.08 ,004 2x.006

16

124

.48 ,022 5x.006 .72 .064 6x.006

(a;

.006 3x.006 .OlO

o,05°c

0.05%

0.05oc O.lOC

0.2QC 10 .02% ,022

0.4OC :15 .06% .064

TABLE 2-9.

Lo 2 nulls

4x.006

Hi

3x.006-.012 =.020

3x.006-2x.012 =.024 2x.01 5x.005 = .025

3x.006-2x.012-.03 =.040 2x.01 6x.005 = ,030

.04 .06 .003% .Ol .0035% ,006 .08 .008%

7. nulls

.006 =.009 2x.01 lx.005 = .005 2x.006 =.012 2x.01 2x.005 = ,010 3x.006 =.015 2x.01 3x.005 = ,015

.002%

nulls ~61~6

(a) (b)

2x.01

RaIRb

4x.005 = ,020

,002 ,004

.OlO

RI

9 (a) cc

14 1070

MODEL 515A MEGOHM BRIDGE

CIRC”rf DESCRIPTION

SECTION 3.

3-1. GENERAL. The Model 515A comprises a solid-state,

guarded, electrometer null detector; an ultra-stable, highly-regulated dc voltage source, and a Wheatstone Bridge.

3-2. N”LL DETECTOR. A simplified diagram of the null detector circuit is shown in Figure 12. The null detector utilizes a Keithley Model 302 Electrometer Amplifier and a 3 &/division meter (MlOl). Power is

supplied by 212 volt regulated supplies. graph 3-4.) The Sensitivity Switch (5103) has five

positions which provide sensitivity from 1000 mVi division to 0.1 mVldivision. The meter will indicate

a center scale (zero) if there is no potential across

the Sensitivity Switch resistors. With switch 5201

set to ZERO CHECK, any offset indicated by the meter

is due to the Model 302 offset voltage. COARSE (5102) and FINE (R120) zero canrrols the meter can be adjusted for center scale indication (thus the zero controls can be used to compensate for amplifier offset). With switch S201 set to READ, the potential difference between High and Low causes a current flow

through the meter. A voltage is developed across the

sensitivify resistor such that Ifl= e/Y+, where I, = meter current, RS = sensitivity resistor and e = unbalance potential.

the meter, and diodes 0103 and DlO4 are used to ob-

tain a non-linear meter response beyond five divisions. The voleane developed across RlO2 will forward bias

either diode so thet diode so that diode conduction

occurs.

giving a logarithmic meter sensitivity.

The current is shunted around meter thus

Resistor. R102, in series with

(See para-

By use of fhe

The null de-

CIRCUIT DESCRIPTION

tector ‘rDriven Guard” is the Cownon of the 212 volt supplies. The ac potential of the “Driven Guard”

follows the ac poeential of the input High so that

guarding of rhe input High can be used.

3-3. WHEATSTONE BRIDGE. The bridge circuit utilizes

four resistance’arms identified as Standard Resistor Arm “S”, Unknown Resistor Arm “X”, Calibrated Resistance Arm “Cl’, and Read-out Re?,isCance Arm “A”.

a. Standard Resistor Arm. The Standard resistors R304 through R311 are connected to the Multiplier Switch S302. Resistors R304 and R305 are 0.01% wirewound eypes; resistors R306 and R307 are 1% deposifed carbon types; resistors R308 through R311 are specially

selected High-Meg types. A 1O:l (.005%) ratio divider composed of R301 and R302 is used in the Stand-

ardization procedure. (See paragraph 2- 4).

b. Unknown Resistor Arm. The unknow,, resistance

“X” is connected at the Input connector (5302 or 3303).

Calibrated Resistance Arm.

C.

resistance arm consists of a 94.5 kilohm, 1% deposited carbon type in series with a 10 kilohm, wirewound

variable resistor. Resistors R313 through R318 and

potentiometers R319 through R324 are connected to the

Multiplier Switch 5302. The Calibration potentiometers

can be adjusted during the Standardization procedure and are accessible an the front panel (inside the shielded enclosure).

d. Readour Resistance Arm.

composed of Resistance Dials S304 through 5310

The calibrated

The Readout Arm is

1070

t*

0

HIGH

READ

ZERO CHECK

0

LOW

FIGURE 12. Null Detector.

.

DRIVEN

GUARD

15

POWER SUPPLY. ,The payer supply consists of a

3-4.

series regulated supply for Bridge Voltage and a floating 212 V supply for the null detector circuitry. T-201 is the power transformer operating from power

line, switch selectable for 117V-234V operation. One secondary is center-tapped and supplies a floating plus and minus voltage for the regulator amplifier. This secondary also drives the isolation transformer T101. The other secondary is full wave rectified to supply the unregulated voltage to series pass trans-

istor Q206. Q201 and Q202

form a difference amplifier which compares the regulated output voltage to a reference voltage supplied by 0203 in a resistance programable power supply with the Bridge volts Adjustment setting a ha current ehru the reference divider

string. Q203 and Q204 are used as amplifier and driver for Q206, correcting far any change in load current or line voltage.

The secondary of TlOl is center-tapped and full-wave rectified to supply unregulated plus and minus voltage to QlOl and Q102 re-

spectively which supply a constant load current. Zener diodes D103 and D104 set the null detector supply voltages to a nominal i12 volts respectively. TlOl

is especially well insulated to provide the necessary

insulation of guard to ground in the bridge circuit.

MODEL 515A MEGOHM BRIDGE

External Voltage mode only. Thus if both dials are

set to zero the diode is directly across the bridge. For an external voltage greater than 100 volts, the zener will conduct. When using a current-limited voltage supply (such as Keithley Models 240A or 241)

the diode will limit the voltage to 100 volts and prevent over-heating of the Dial resistors.

WARNING

If the voltage supply used does not have current limiting (1O~mA approximately), the zener pro-

tection diode could be overheated causing possible damage co the Dial resistors.

3-5.

OVER-VOLTAGE PROTECTION CIRCUIT.

The Model 51%

utilizes a zoner diode (D301) eo prevent damage ea the

readout resiseors (Xl and lower) from excessive bridge

voltage from an external voltage source.

The diode is connected (through auxiliary.contacts on the Xl00 and X10 dials) across the bridge voltage terminals when in

,

I

C203 -

i 101

R220

r j

’ L-

I

- K218

0201 -, ,.

___ D220

J ---*02,6 R224-

~ 0219

-

FIGURE 13. Null Detector, K-233.

*

. .

~7201

(““4 .

/D223\

c21:

R230

D2t6 - :.

f

R231 --~

0212 T----- ‘0

+

Cl21?

ivl0

c201

0205

l --

C206 -‘-

FIGURE 14. Bridge Voltage Supply, PC-244

- ‘* D213

1070

MODEL 515A MEGOHM BRIDGE

SECTION 4.

4-l. GEl33UL. The fallowing Keithley accessories can be used with the Model 515A to provide additional convenience and versatility.

Mndel 5151

Description: The Node1 5151 is a bench mounting kit. The end frames

provide convenience when carrying the instrument.

End Frames

ACCESSORIES

4-2.

OPERATING INSTRUCTZONS. A separate Insrruction Manual is supplied with each accessory giving complete operating information.

Model 5152 Remote Test Chamber

The Model 5152 is a shielded test chamber for remote

resistance measurements. A 60 inch triaxial cable is

provided. Application: The Model 5152 can be used for resistance measurements

when the self-contained test compartmenr on the Model 515A is not useable. A separate GUARD eerminal is

provided an the Test Chamber.

Model 5153 Triaxial Cable

Description:

the Model 5153 is a triaxial cable 60” long which mates with the EXT. INPUT connector on the Model 515.4.

Application:

The Model 5153 can be used for external measurements which require a shielded and guarded cable.

1070

17

ACCESSORIES

MODEL 515A MFGOHM BRIDGE

Model 241 Regulated High Voltage SUDP~V

he Node1 241 is a very stable, accurate high voltage

over supply especially useful as a laboratory refer-

rice. ,pplication: 'he Model 241 can be used as an external voltage supply

or the Model 515.4 when applications require a bridge otential from 110" to 1000". The Model 241 can be asily rack mounted with the Model 515A by use of the

.odel 5154 Cabinet.

pecifications:

Voltage: 0 to 1000 volts dc in O.Ol-volt steps. CUrrelIt: 20 milliamperes dc maximum.

Polarity: Positive 01 negative.

Floating: 50 volts maximum off chassis ground.

.CCUlUCY: ~0.05% of dial setting or +l millivolt,

whichever-is greater.

*SOLUTION: A "Trim" potentiometer permits interpola-

tion between steps with a reso1urion of better than

100 “icro”olts.

ESETABILITY: ~0.025%.

TABILITY: +0.005% per hour with constant load, line

and ambient temperature.

EMPERATURE COEFFICIENT OF REFiRENCE: 210 ppm/OC. ,INE REGULATION: +0.003% or 1 millivolt far 10% line

change. ,OAD REGULATION: +O.OOS% from no load to full load. ,IPPLE AND NOISE: Less than 1 millivolt rms above 5

HZ.

"'PUT IMPEDANCE: Less than 0.05 ohm at dc.

.ECO"ERY TIME: No load eo full load, less than 1 sec-

ond to raced accuracy.

8VERLOAD PROTECTION: Output is disconnected within

50 milliseconds if current exceeds approximately

24 milliamperes. :ONNECTORS: Output: Teflon-insulated type UHF type. 'OWER: IIMENSIONS, WEIGHT:

CCESSORIES SUPPLIED: Mating connectors.

105-125 or 210-250 volts, 50-60 Hz, 105 watts.

7" high x 19" wide x 12" deep,

net weight, 26 pounds.

Model 5154 Cabinet

Description: The Model 5154 is a rack style cabinet with dimensions

25" high x 21" wide x 16-l/2" deep.

Application:

The Model 5154 can be used to rack mount the Model

515.4 with an auxilliary power supply such as the

Keithley Model 241.

18

Parts List: Item

NO.

1 2

3

Description Cabinet 14343c Panel, Blank 14203B Cable, UHF-UHF 166398

Part No.

1070

MODEL 515.4 MEGOHM BRIDGE

ACCESSORIES

Model 5155 High Meg&m Resiseance Standards !scripeion: ie Model 5155 has been developed t0 verify rhe cali-

cation of the Keithley 515A Meg&m Bridge with trace~ility to rhe Nafionai Bureau of Scanda;ds. These lits are convenient LO use, since they plug directly I~O the 515A. The 5155 consists of six individually leased high megohm resistors with values af 108 thro:h 1013 ahms in decade steps. A certificate is inLuded showing the actual value af each resistor with I accuracy limited by the maximum accuracy certified i Naeional Bureau of Standards.

Each resistor’s mperature coefficient, voltage coefficient and hisfry of measured values is also given.

,ecifications: 3SISTOR V*LUES: Sin resistors 100, 109, lOlO, loll,

1012, 1013 ohms 215%.

:CUPJ.CY: ~0.2% af certified value except 1013 ohms

which is ~0.5% (relative to I1.B.S. certified stanCiZlL-dS).

CABILITY: Less than ~0.1% change in value per thou-

sand haurs. ILTAGE COEFFICIENT: -. <MPERAT”RE COEFFICIENT:

03% per volt, nominal.

-0.1% per OC, nominal.

JARDING: Case is a~ guard potential when the resist-

or Standard is used in a Keithlev Model 515A Mee~hm

Bridge.

OS”LATION: Teflon.

DIMENSIONS: Each resistor standard is 4” long x 2”

deep x 1” wide.

WEIGHT: Each resistor Standard is approximately 6

ounces. Six Standards in carrying case, 3-l/2 lbr

SERVICE AVAILABLE: Recertification traceable t0

National Bureau of Standards.

Resistor Installation:

REPLACEABLE PARTS

MODEL 515A MEGoHM BRZDGE

SECTION 5.

5-1. REPLACEABLE PARTS LIST: This section contains

a list of componenets used in this instrument for user reference. The Replaceable Parte List describes

the individual parts giving Circuit Designation,

Descriptian, Suggested Manufacturer (Code Number),

Abbreviations end Svmbols A Cb”ar Carbon Variable

CerD Ceramic Disc Cer Trinnner Ceramic Trimmer camp Cmnp0sifion

DCb Desig.

EAL ETB ETT

ampere

Deposited Carbon Designaeion

Electrolytic, Aluminum Electrolytic, tubular Electrolytic, tantalum

F Fig

GCb k

P

M Mfr. MS

MY

REPLACEABLE PARTS

Manufacturer’s Part Number. Also included is a Figure Reference Number

where applicable. The complete name and address of each Manufacturer is listed in the CODE-TO-NAME Listing following the parts list.

TABLE 5-1.

farad

Figure Glass enclased Carbon

kilo (10 3, micro (10-6) Meg (106)

Manufacturer Metal Film Mylar

Number

Number,

end the Keithley Parr

a

P PC

j ohm : PlCO (lo-l2)

i Printed Circuit

Paly : Polystyrene Ref.

i Refere”ce

TC” i Tinner Copperweld

v ; volt w

ww

i watt

: Wirewound

WWVar i Wirewound Variablt

5-2. ELECTRICAL SCHEMATICS AiW DIAGRAMS. Schematics and diagrams ere included to describe the electrical circuits as discussed in Sectian 3. Table 5-2

idenfifies all schematic part numbers included.

5-3. HOW To USE THE REPLACEABLE PARTS LIST. This

Parts List is arranged such that the individual types of components are listed in alphabetical order. Main Chassis pares are listed followed by printed circuit boards and ocher subassemblies.

HOW TO ORDER PARTS.

5-4.

a. Replaceable parts may be ordered through the

TABLE 5-2.

Circuit Designation

Description

t

Description

I

Megohm Bridge Megohm Bridge

Circuit Designation Schematic

PC-233, PC-244 PC-233, PC-244

* *

Sales Service Department, Keithley Instruments, Inc. or yaur nearest Keithley representative.

b. When ordering parts, include the following

infarmetion.

1. Instrument Model Number.

2. Instrument Serial Number.

3. Part Description. Schema+zif Circuit Designation.

4.

5. Keithley Part Number,

c. All parts listed are maintained in Keithley Spare Parts Stock. Any part not listed can be made available upon request. Parts identified by the Keithley Manufacturing Cade Number 80164 should be

ordered directly from Keithley Instruments, Inc.

I

Schematic

24820E 24820E

1

I I

20

1070

MODEL 515A MEGOHM BRIDGE

REPLACEABLE PARTS

NULL DETECTOR PARTS LIST

(X-233)

CAPACITORS

Keithley

Value

Rating Type

Mfr.

Code

Mfr. Part NO. Pare No.

Cl01 .02 &F 1000 " cerLl 56289 loss-s20 C64-.02M

__

Cl02 Not Used --

Cl03 100 pF 40 EAI. 73445 C437ARIGlOO C15O-1OOM Cl04 100 &F 40 SAL 73445 C437ARIGlOO C150-100M 13

Circuit Desig.

0101 D102 D103 0104 D105

D106 D107 D108

Type

Transistor, NPN, Case TO-106

Transistor, NW, Case TO-106 Silicon Silicon zener

Ze"er Si1iC.X' Silicon

-- -- --

Mfr. Mfr.

Keithley

Code Part NO. Part No.

07263 2N3565 TG-39 07263 2N3565 TG-39 01295 1N645 RF-14 01295 lN645 RF-14 12954 lN706 LIZ-1

12954 lN706 02-l

01295 lN645 RF-14

01295 lN645 RF-14 13 0109 Silicon 01295 1N645 RF-14 13 Ill10

0111

0112

Silicon 01295 lN645 RF-14 13

(TG-39*) Transistor, NPN, Case TO-106

(TG-39*)

Transistor, NPN, Case

TO-106

07263

2N3565 2N3565

24220‘4" 24220A*

Fig. Ref.

1;

Fig.

Ref.

13 13 13

13

*Selected. Order from factory.

Circuit oesig.

TlOl

Ml01

s102

s103

PlOl JlOl 5102 P102

Transformer Meter

Rotary Switch, COARSE ZERO Rotary Switch, Null Detector Connector, Connector, Female, 15 Pins Comector, Female, 15 Fins Connector, Male, 15 Pins

Type

Male,

Circuit oesig.

Value

RlOl 10 MO R102 RI03 R104 R105

12.1 kQ 333 kn

33.3 k!l

3.33 kll

MlSCELwEO"S PARTS

Sensivity ---

15 Fins

Rating Type

lO%, l/Z W CO"P l%, l/8 w MCF l%, l/2 w MCF l%, l/2 w MtF l%, l/2 w

MtF 07716

Mfr. Code Part NO.

80164 ___ m-121

80164 ___ ME-86

--- --- SW-294 27264 1625-15P CS-227

27264 1625-15R CS-228 27264 1625-15R B-228

27264 1625-15P CS-227

RESISTORS

Mfr.

Code 01121 EB-1OM

07716 07716 07716

Mfr.

Keithley Part No.

___

Mfr.

Part No.

SW-292

Keithley

Part No.

RI-10" CEA-lZ.lkn-1% R88-12.1K CEC-333kR-1%

R94-333K

CEC-33.3k+1% R94-33.3K CEC-3.33kQ-1% R94-3.33K

Fig. Ref.

14

Fig. Ref.

1072R

21

P.EPLACF.ABLE PARTS

MODEL 515A MEGOHM BRIDGE

RESISTORS (cont'd)

Circuie

Lksip.

R106

RI07

R108 R109 RllO

Rlll R112

Value

33.3

2.7

1 kfi 1 k0

1 ki2

1 kfl R113 1 k* R114 1 R115 1 kR

RI16

R117 R118 R119 R120

R121 R122

RI23

R124

R125

R126

R127

1 kD

1 kfi

1 k0

10 kR

4.7

2.7 700

4.99

700

15k n 1%. l/8 w

0 n

k#

kfl

kfi kR*

n kn k0

a l%, l/2 w

Rating Type 1%,

l/2

l%,

l/2

1%,

l/2

l%, l/2 w l%, 112 GI

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

l%,

If2

1%,

l/2

l%,

l/2

l%,

l/2

5%,2

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

l/2

l%, l/2 w

*Nominal value, selected in final test.

w w w

w w w w W

w

Mfr. Code

McF

07716

MtF 07716

DCb

MtF

91637 07716

MCF 07716 MtF

MtF

07716 07716

MtF 07716

M-LF

MfF 07716 MtF 07716 MeF 07716 MtF

wwvar

07716

12697

DCb 91637 DCb

DCb 91637 MtF

MtF DCb

MtF

91637

07716

07'716 91637

07716

TRANSISTORS

Mfr. Keithley Fig.

Part No. Part NO. Ref.

CEC-33.3kR CEC-33.3k0

R94-33.3K R94-33.3K

DCF-l/2-2.7kn RlZ-2.7K CRC-lkn R94-1K CEC-lkll R94-1K

CEC-1kQ CEC-lk0

R94-1K

R94-1K CEC-lkn R94-1K CEC-lkn

R94-1R

CRC-1kR R94-1K CEC-1kQ

CRC-lkn CEC-lk&i CRC-lkR 62JA-10kR

R94-1K

R94-1K R94-1K RP42-10K

DCF-l/2-4.7k0 RlZ-4.7K DCF-l/2-2.7kR RlZ-2.7K DCF-l/2-700~7

RlZ-700 CEC-4.99k0 R94-4.99K CEC-4.99kn

R94-4.99K DCF-l/2-700D RlZ-700

cm-15&l%

R88-15K

13

Circuit

tIesip.

QlOl

Q102

Circuit

Desip.

c201

c202 .0015 LlF 600 C203 0.1 pF 400 C204 C205

C206 C207

C208 C209 c210

c211

Type PNP, Case R-110 NFN, Case

TO-106

Value RafinR

0.5

UF

100 UF 100 b

100 p3

100 p

Not Used

20

z

100

0.047

"F

BRIDGE VOLTAGE SUPPLY PARTS LIST

(PC-244)

CAPACITORS

400

v

” CAD 72982 v MY 13050

40

v

40

” EAL 73445

40

” F.AL 73445

40

”

450

v EMC 37942

40

v

100 v

MY

EAL

EAL P&y

Mfr.

Code

07263 07263

Mfr.

Code

13050

73445

Mfr. Keithley Part NO.

S17638 2N3565

Mfr. Part: NO.

Pal-e NO.

TG-33

TG-39

Keifhley Part NO.

SMlA-0.5uF C117-.5M

ED-.0015 CZZ-.OOlSM 14

Fig.

Ref.

13 13

Fig. Ref.

14

SMlA-O.lpF C73-.lM 14 C437AR/GlOO C150-100M

14

C437ARfGlOO C150-100M 14 C437AR/GlOO c150-1OOM 14

C437ARiGlOO C150-1OOM FP144-20uF

C36-20M 14

14

C437ARfGlOO c150-1OOM 14

Mw9410473

C67-0.047M

22

1072R

MODEL 515A MEGOHM BRIDGE

REPLACEABLE PARTS

DIODES

CirC”it Desig.

Type

D201 SiliCO” D202 Silicon D203 Zt!"er 0204 zener 0205 zener

D206 zener D207 Silicon 0208 Silicon 0209 Silicon 0210 Silicon

0211 Not Used 0212 Silicon

0213 SiliCO" D214 Silicon 0215 zener

Mfr. Code

Mfr.

Part NO.

02735 IN3255 02735 lN3255 04713 lN936 12954 lN718 12954 lN706

12954 lN718 01295 lN645 01295 lN645 01295 lN645 01295 113645

-_

__

01295 IN645 01295 01295

lN645 1~645

12954 lN723 DZ-17

D216 zener 12954 lN723 D217

Silicon 02735

lN3255

D218 Silicon 02735 lN3255 D219

Silicon 02735

lN3255

D220 Silicon 02735 lN3255 0221 Silicon 01295 113645

D222 Silicon 01295

lN645 0223 Silicon 01295 lN645 0224 Silicon 01295 1~645

Keithley

Part NO.

Fig. Ref.

RF-17 m-17 D7.-5 DZ-18 m-1

DZ-18 RF-14 RF-14 w-14 RF-14

14 14 14

-_ w-14

RF-14 RF-14

14 14 14 14

m-17 14 RF-17 14 RF-17 14 RF-17 14 RF-17 14

RF-14 14 RF-14 14 w-14 14 RF-14 14

Circuit Lksig.

5211 s201 5201 5202 5203 5204 J205

3206 3207 5208 5209 5210 SL201 SL201 s203 s202 K201a K201b T201 K202

Type

Kecepcacle, UHF 'Toggle Switch, ZERO CHECK Test Jack Test Jack Test Jack Test Jack Test Jack Test Jack Test Jack Test Jack Test Jack

Text Jack Shorting Link Shorting Link

votary Switch, X1 BRIDGE VOLTS

Rotary Switch, Xl0 BRIDGE VOLTS Solenoid, ZERO CHECK Reed Relay, SPST Tl-a"SfO~~X Relay, INTERLOCK

MISCELLANEOUS PARTS

Mfr.

Code

91737

80164

71279 71279 71279

71279 71279 71279 71279 71279 71279 71279 71279 71279 80164 80164

-_95348

SO164

_--

Mfr.

*art No. 6804

-__ 4352-l-0319

4352-l-0319 4352-l-0319 4352-l-0319

4352-l-0319 4352-l-0319 4352-l-0319 4352-I-0319 4352-l-0319 4352-l-0319 3771-20310 3771-20310

El55

"R406 TR-120 KAllDY

Keithley Part No.

Fig. Ref.

CS-64 SW-236 2 TJ-9 3 TJ-9 3 TJ-9 3 TJ-9 3 TJ-9 3

TJ-9 3 TJ-9 3 TJ-9 3 TJ-9 3 TJ-9 3

TJ-10

TJ-10 3

SW-291 2 SW-291 2 SOL-2 RL-25B TR-120 14 RL-36

3

7.3

REPLACEABLE PARTS

MODEL 515A MEGOHM BRIDGE

RESISTORS

CitTUif Desig.

R201 R202 R203 R204 R205

R206 R207 R208 R209 R210

R211

R212

R213

R214 R2l5

R216 R217 R218 R2l9 R220

R221 R222 R223 R224 R225

R226 R227 R228 R229 R230

Value Rating

56 0 20 k.Q 10 kc2

40.2 k0

40.2 kfi 2

kR

1

kfl

4.02 kfl

4.02 k.0

8.06 kfl 2 kI2

10 kn

40.2 kR

40.2 kfi

1

kil

47 k0 10 kfi 47 kR 2 kn 47 kR

6

kn 500 n 6 kR 100 0 15 n

68 k!?

4.7 k0 1

k,?

1

kfl

700 ,n

lO%, l/2 w l%, l/2 w l%, l/2 w l%, 112 w 1%, l/2 w

1%. 112 w l$ I;* w l%, l/2 w

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

20%, 2 w lO%, l/2 w 1%, l/2 w l%, l/2 w lo%, 112 w

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

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

L%, l/2 w

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

l%, l/2 w

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

Type camp

MtF MtF MCF MfF

MtF MtF MtF MtF MtF

WWVW conlp MtF MeF Camp

Camp camp camp

MtF

camp DCb

DCb DCb DCb Camp

DCb DCb Deb DCb

Mfr. Mfr.

Code Part No. 01121

07716 07716 07716 07716

ES-560

CEC-20kn CRC-lOkQ CEC-40.2kn

CEC-40.2kO

07716 cm?-2kQ 07716 CEC-lkn 07716 07716 07716

CEC-4.02kn R94-4.02K CEC-4.02kO CEC-8.06kO R94-8.06K

71450 lNS-115-2kn

01121

07716 07716

RB-1OkQ RI-10 CRC-40.2kQ R94-40.2K CEC-40.2kn R94-40.2K

01121 EB-lkn 01121

01121 01121 07716 01121

91637

EB-47kn EB-1Okn EB-47kR CEG2kR

BB-47kn

DCF-l/2-6k0 91637 ~~~-112-50On 91637 DCF-l/2-6kn 91637 DCF-l/2-1000 01121

91637

EB-15n

DCF-l/2-68kR

91637 DCF-l/2-4.7kn 91637 DCF-l/2-lkn 91637 DCF-l/2-1kQ 91637 DCF-l/2-7000

Keiehley

Part No.

RI-56 R94-20K R94-10K R94-40.2K R94-2K

R94-2K

R94-1K

R94-4.02K

RP-50-2K

Rl-1K Rl-47K

Rl-1OK RI-47K R94-2K Rl-47

RlZ-6K RlZ-500 RlZ-6K R2-100 Rl-15

R12-68K

RlZ-4.7K R12-1K Rl2-1K R12-700

Fig.

Ref. 14

14 14 14 14

14 14 14 14 14

14

14 14 14

14 14

14 14 14 14

14 14

14 14 14

14 14 14 14 14

Q201 Q202 Q203 Q204 Q205

Q206 NPN, 0207 PNP, 0208 PNP, Q209 PNP, 4210 Q211

24

NPN, Case TO-18 WN, Case TO-18 PNP, case R-110 NPN, Case TO-106 NPN, Case TO-106

Case TO-5 Case R-110 case R-110 case TO-5

PNP,

Case Case

TO-5 TO-5

NW,

TRANSISTOQ

Mfr. Code

73445 73445 Al380 TC-32 07263 07263 07263

02735 07263 07263 02734

02734 02,734

Mfr.

Part NO.

A1380

Keithley Fig.

Part No. Ref. TG-32

14 14

S17638 TG-33

14 2N:,65 TG-39 14 2N1565 TG-39

40327 TG-63 S17638 TG-33 S17638 m-33 40319 TG-50 40319

TG-50

40317 TG-43

14

1072R

MODEL 515A MlxOHM BRIDGE

SWITCHING ASSEMBLIES MISCELLANEOUS PARTS

Mfr. Keithley

Pat? NO.

Part NO.

REPLACEABLE FART8

0301 Diode, zener, loo", SW 04713 OS301 F301 F301 5301

Lamp, 24v, clear Fuse, SLO-BLO, .25A, 3AC Fuse, SLO-BLO, l/8.4, 3AG

Receptacle, 3-Prong

03508 75915 71400

___

3302 Receptacle, INPUT Hieh, UHF 91737

3303 P301

Recebtacle; Triaxial; EXT. INPUT

Power Cord, b ft.

RESISTORS

CiPC”it Mfr. wsig.

It301 R302 R303 R304 R305

R306 R307 R308 R309

R310

R311 R312 R313

R314 R315

Value Rating

10 kR

1O:l Divider Network, .005% 80164

100 kR

10 kn 100 kfl 1

Mn

10

MD

100 MR 109 n 1010 1011 :

1ol2 n

100 kn

94.5 kn

94.5 kR

94.5 kn

I%, 112 w .Ol%, 1 w .Ol%, 1 w

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

Selected Selected

Selected

SekCWd

.Ol%, 1 w 1%, l/2 w l%, l/2 w l%, l/2 w

Type

Code

MEF 07716 ww 15909 ww 15909

DCb 91637 DCb 91637

-__ 80164

___

80164 80164

___ 80164

ww 15909

DCb 91637 DCb 91637 DCF-l/2-94.5k0 R12-94.W DCb 91637

lN5378-8 DZ-46 1450

PL-53

313.250 FU-17

MDL

1604 6804 5632Al5321Alh CS-67

-__

F"-20 CS-248 CS-64

CO-5

Mfr. Keithley

Part NO. Part NO.

__

2365:;s

CEC-1OkR R94-10K 1252-100kR 1252-lMQ

DCF-l/tlOMI1 DC-2-lOOMi?

___

R154-100K R154-1M

R12-10M R14-100M 241598

24160~4 241618

___

241628

1252-lOOk R154-100K

DCF-l/2-94.5kn R12-94.5K

DCF-t/2-94.5kQ RlZ-94.5K

R316 R317

R318

R319 R320

R321 R322 R323 R324 R325

R326 R327 R328 R329 R330

R331 R332 R333 R334 R335

1072R

94.5 kfi

94.5 ks-I

94.5 k0 10

kn

10 kR 10 kR

10 kR 10 k0 10 kR 20 MO

4 MO 4 M* 200 kR

100 ki,

400 k0

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

l%, l/2 w 20%, 114 w 20%, l/4 w

al%, l/4 w 20%, l/4 w 20%, l/4 w

2o%, l/4 w

.5%, 2 w

.5%, 2 W .5%,2 w .5%, 2 w .Ol%, 2 w .Ol%, 2 w

.Ol%, 2 w .Ol%, 2 w .Ol%, 1 w .Ol%, 1 w .Ol%, 1 w

DCb 91637 DCb 91637 DCb DCb DCb

91637

71450 71450

DCb 71450 DCb 71450 DCb 71450 DCb 71450 DCb 03888

DCb 03888

DCb 03888 ww 15909 ww 15909

ww 15909 ww 15909 ww 15909 ww 15909 ww 15909

DCF-l/2-94.5kn R12-94.5K DCF-l/2-94.5kQ RlZ-94.5K

DCF-l/2-94.5kR R12-94.5K 45-10kn RPEl-1OK 45-1OkR RPEl-1OK

45-1okn 45-1Okn 45-10kiI 45-10kn PT~OOO-2'JMR

PT2000-10Mn PT2000-40MR PT2000-40MQ 1179-2Mn 1179-lm

1179-4m 1179-4im 1252-200kc? 1252-100kn 1252-400kn

RPBI-1OK RPEl-1OK RP81-1OK RPEl-1OK

R52-20M R52-10M

RSZ-40M R52-40M RISS-2M R155-1M

R155-4M R155-4M

R154-200K R154-100K R154-400K

REPLACEABLE PARTS

MODEL 515A MEGOHM BRIDGE

RESISTORS (cont'd)

CirCuit Lksig.

R336 R337 R338 R339 R340

P.341 R342 R343 R344 R345

R346 R347

400 kR 20 kR 10 40 40

2 kfi 1 k0 4 kfi 4 k0 200 n

100 n

400 n R348 400 a R349 R350 R351 R352

Circ”it Desig.

S301 S302

40 n

100 MO

Rotary Switch,'FUNCTION Rotary Switch, MULTIPLIER

Knob Assembly, MULTIPLIER 5303 S304

--S305

Safety Interlock

Rotary Switch, Xl00

Knob Assembly, Xl00

Rotary Switch, X10

Knob Assembly, X10

Rotary SWifCh, xi Knob Assembly, Xl

s307

Rotary Switch, x.1 Knob Assembly, X.1

S308

Rotary Switch, X.01 Knob Assembly, X.01

5309

Ibtary Switch, X.001 Knob Assembly, X.001

5310

Rotary Switch, X.0001 Knob Assembly,X.OOOl

s311

Rotary Switch, BRIDGE VOLTS

Knob Assembly, BRIDGE VOLTS

S312

Slide Switch, 117-234V

Value Rating Type

k!? kfi k0

.Ol%. 1 w ww 15909

.Ol%, 1 W .Ol%, 1 W .Ol%. 1 w .Ol%, 1 w

.04%. l/2 w .04%, l/2 w .04%, l/2 w .04%, l/2 w .l%, l/2 w

.I%, l/2 w .l%, l/2 w

.l%, l/2 w 1%. l/2 w l%, l/2 w l%, l/2 W l%, l/2 W l%, 2

W R353

ww ww ww ww

ww ww ww ww MCF

MtF MfF

MtF

Me

MS MtF MtF

DCb

Mfr. Mfr. Keithley Code Part NO. Part NO.

15909 1252-20kn R154-20K 15909 1252-lOk0 15909 1252-40kn R154-40K 15909 1252-40kR R154-40K

01686 1142-2kR R99-2K 01686 1142-1kR R99-1K 01686 1142-4kn R99-4K

Olb86

0771b 07:lb

07716 0771b 07716 07716 07716 07716 91637

SWITCHES

Mfr.

Code 80164

80164 801b4

80164 8Olb4 80164

80164

801b4 80164 8Olb4

80164 ED164 80164 80164 80164 80164 80164 80164 80164

1252-400k0

R154-400K R154-10K

1142-4k$i CECTl-2OOn

CECTI-loon CECTI-400n CECTl-400R

R99-4K R135-200

R135-100 R135-400 R135-400

CEC-20R R94-20

CEC-1on R94-10

CEC-400 R94-40 CEC-400 R94-40

DC2-100M0 R14-100M

Keithlry

Part

___

--_

---

-._ ___

--_

--___ ___

--_ ___ ___ ___

---

-__ _-_

---

Part No.

SW-293

SW-335 SW-94

SW-295

148298

SW-295

14829A

SW-296

14829A

SW-296

148298

SW-296

14829A

SW-296

14829A SW-296 14829A SW-297

148388

SW-151

26

1072R

Signalice 1°C. 1933 Heck Ave.

Neptune, N.J. 07753

Johnson, E. F., co. 297 Tenth ‘be. S.W.

waseca, Mi”“. 56093

MODEL 515A

APPENDIX

RESISTANCE DIAL ACCURACY CHECK.

The following procedure should be wed fo verify the accuracy of the various resistors of the decade dials. The test jacks are identified in Figure 7.

APPENDIX

1. Set the Model

515A

controls as follows:

FUNCTION - OPERATE

MULTIPLIER - 105

DECADE DIALS - ALL 0

2. Connect ES1 Model 242 Besiscance Bridee between

test jack 5202 and GROUND.

3.

Measure

the resistance of the DECADE DIAL resis-

tors for dial positions 0, 1, 2, 4, and 8 as in

the table

4. Connect

ES1 ?+del 242 between test jacks

X.0001 through X10

3201

and 5203.

5. Measure the resistance Of r‘ne x100 DL4L :esisto25 for dial positions 1, 2,

4, and 8.

x.001

Xl

x 10 2 2M I 10.01%

2

4

8

1 I

2 4 4OOK 10.01%

8 8OOK 10.01%

1 1M : +o.ol% 4 4M / 20.01%

a

2

400

800

lOOK

200K iO.Ol%

8M / LO.Ol%

I 1 100

+o.l%

10.1% +o.l%

10.1%

AO.Ol%

x 100 -S';-‘I

6. Measure the resis~.nce of the remaining resis-

tors by connecting ES1 Model 242 between the test jacks specified in the table

1072

CONNECT TO 5205 AND 5201

R353 R312 R305

$4 MO2

** R301

CONNECT TO 5207 AND 5201 CONNECT 3208 AND CHASSIS CONNECT 5209 AND CHASSIS

CONNECT TO 5210 AND 5209

"*Difference must be less than 50 ppm.

1 1OOM 1 +O.Ol% 1

I 1OOK I *o oi7

1M I +o.ol% I

I I 1OOK I iO.Ol% I

1OK I 10.01% j

I

. a

29

TEFLON

IN-SW-ATED LEADS 0.h)

SECONDARY (LENGTH :w’f)

FRAME

,

SIMIL~,R TO TRANSFORMER Kl-148

PRiMARY:

4”

INSULATED LEADS.

SPPLIW

SUPPLIW PART NO. E7PECIPICA~IONS~

f F~JTI?AI

PlmqumoY: so- 60 CPS (SINE WAVE)

nyI

PRIWARY

sec. t1 SOL-. +7 -.-"-.

sec. #3 sec. #b -

mm-

.-.

TR AMS

VE

*.

2s-o-a5v. _khs

FOR MEK rn.

c!!EB

-.

sec. if5

sec. #6

KEITHLEY INSTRUMENTS, INC. REPAIR & CALIBRATION FORM

MODEL NO. DATE

SERIAL NO. SHIP INSTRUMENT & FORM TO: FROM: SALES SERVICE DEPT.

KEITHLEY INSTRUMENTS, INC.

USER'S NAME RETURN ADDRESS

28775 AURORA ROAD

CLEVELAND, OHIO 44139

CITY

STATE

ZIP

TELEPHONE

REASON FOR RETURN. Check appropriate box.

1. U Repair and Recalibration cl Recalibration only. (If repairs atie required to meet specifications, an additional

repair charge will be added to recalibration cost.)

2.

CALIBRATION REPORT. Specify report desired.

(See reverse side of form for details.) n Calibration Report (Certified Traceable to N.B.S.) n Calibration Report (Production Calibration Equipment at the factory) U Certificate of Compliance

DESCRIPTION OF PROBLEM.

3.

(Include a block diagram of instruments connected in system.

Recorder charts or other data would be helpful.)

Is problem constant or intermittent?

OPERATING CONDITIONS.

4. Control setting (range, multiplier, etc.) Line voltage used Temperature

OF

Line frequency used

Temperature variation + Humidity (high, medium, low) Other (please specify, such as line transients, etc.)

5. EQUIPMENT USED. Signal source

Readout device Cables used

ADDITIONAL INFORMATION. Please indicate any other pertinent information which may help

6.

the Keithley Repair and Calibration Department.

Source impedance

(Recorder, oscilloscope, etc.)

Length

(If repairs or modifications have been

made to instrument by other than Keithley personnel, please specify below.)

OF

REV 0172

CALIBRATIONS AVAILABLE AT KEITHLEY INSTRUMENTS.

EFFECTIVE:

FEBRUARY 1, 1972

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 follow-

ing categories:

Report of Calibration Certified Traceable to the National Bureau of

1. Standards

2. Calibration Report Certificate of Compliance

3. 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.

CN515A-2 Sheet 1 of 1

0974

KEITHLEY INSTRU$L~ENTS. INC.

INSTRUCTION MANUAL

CHANGE NOTICE

MODEL 515A MEGOHM BRIDGE

INTRODUCTION: Since Keithley Instruments is continually improving pro-

duct performance and reliability, it'is often necessary to make changes

to Instruction Manuals to reflect these improvements. Also, errors in Instruction Manuals occasionally occur that require changes. Sometimes, due to printing lead time and shipping requirements, we can't get these changes immediately into printed Manuals. The following new change information is supplied as a supplement to this Manual in order to provide the user with the latest improvements and corrections in the shortest possible time. Many users will transfer this change information directly to a Manual to minimize user error. All changes or additions are

underlined.

CHARGES:

Page 26, Replaceable Parts, Resistors, Add the following resis-

(1)

tor as follows:

8354.

Page 21, Replaceable Parts, Diodes, Change D105, D106, Dill, Dll2,

(2)

lOOn. la. 1/7W. Camp. 01121. EB-1000. R

0

zLiL!M.

D113. and D114 to read as follows:

(3) Page 22. Replaceable Parts, Resistors, Change R123, R124, R125, and

R126 to-read as follows: R123, 845a, l%, 1/2W, MtF, 07716, CEC-845R, R94-645

R124, Not Used

R125, Not Used

R126,

Page 22, Replaceable Parts, Transistors, Change QlOl and 4102 to

(4)

read as follows: QlOl, Not Used-

Q102, Not Used

28776 AVRORA ROAD

TELEX: 98.5489

. CLEVELANO. OHIO 4413s . ,2,8,24S-0400

. CASLE: KEITHLEY

.

qj

REPORT ON CHANGE IN SPECIFICATIONS

8/18/71

MODEL 5,15A

~..___--

Distribution:

All Officers Herron

Nichols

Sheridan

Streets Kifer Sutphin Butler Kronenwetter

Kaplan Allen Naylor Cech Angelfne Nowac

Bartos

Sarkisian

Peabody Engrq. File

Seifertd

The following change has been approved by an executive committee and will be implemented according to the.followinq schedule:

Chanqe: Model 515A ACCURACY specifications are,chanqed

from:

ACCURACY: (wxbridqe is operated as described below)

Range,

ohms

Standard

Deviation (lm)**

Bridge

Voltaqe

,. ~..~_. . '

Decade

105

lo7

108 1oq

lOlO

1011 ;$

1o14

to lo7

to lo8 to lOlO

9 to loll ;z $2 to 1013 ;z $:

.012% .02 % .03 % .06 %

.08 % .16 % .25 % .3 % .5 %

* External supply required above 10

14

ohms.

10 v 10 v 10 v 10 v 10 v

10 v

10 v 100 v 500 v*

105 -106 107

108 109

1010

;"o::

** Based on theoretical analysis of bridge errors, see instruction

manual for details on obtaining specified performance.

to:

-

ACCURACY:

Range, Standard

ohms Deviation (lo)**

105

107 to 100 108 109 1010 1011 10'2 1013 1014

to 107 to 109

to 1010 to 1011 to 1012 to 1013 to 1014' to 1015

.012% .02 % .03 % .06 %

08 %

:16 %

25 %

.

3 %

1:5x

Bridge

Voltaqe

10

v 105 -106

1.0

" 10.7

10

v 10 v 10

v 10

v

100

" 1012

500 " * 500 v*

Decade

108

lo-9

1010

1011 Lb;;

* l,:sl:c~r-nnl. ::uppl.y rcquircd #Jl>OVC!

1013

ohms.

** Based on theoretical analysis of bridge errors, see instruction

manual for details on obtaining specified performance.

Page 2

8/18/71

Manufacturinq:

Engineering:

Sales:

Set up manufacturing procedures as necessary to achieve the revised specification.

Give notice

of the change to applicable,personnel in tech

check-out and repair.

Note revision and change any applicable drawings

for instrument or its parts. Issue notice of change to entire world-wide saLes

organization, applications engineers, etc. Change 515A manual and any other applicable manuals

to reflect revision.

,

KEITHLEY INSTRUMENTS. INC.

PRELIMINARY INSTRUCTION MANUAL

MODEL 515A

MEGOHM BRIDGE

This Preliminary Instruction Manual is supplied to permit earliest

possible delivery of your instrument. It contains Specifications, Operation Instructions, Circuit Description,

Replaceable Parts List and Schematics.

The Final Edition will contain

Servicing and Calibration information to maintain the instrument.

Please detach, fill out and return the Warranty Card attached to the instrument so that the Final Edition Instruction Manual can be sent to

your attention.

If you have further questions, please contact your

Keithley Representative or the Sales Service Department.

Product Literature Department

m

FREEPRODUCT/UPGRADEINFORMATION

To receive future information on product upgrades and enhancements, complete this card and mail, or FAX to 440/248-6168.

MODEL

NAME

CCMPANY MAIL STOP

ADDRESS

ClTY

PHONE

EMAlL For FREE additional information, check below:

SERIAL NO.

TlTLIl

STATEmxxlNCt

FAX

Reference Publications

0 Low Level Handbook 0 Switching Handbook

0 Fes Sel,s”ls Handbook

Job Function (~hcelt One)

DATE

Product Interest(s)

%96-6EIPPHOCINVXIAKI3

09ZI6E

3NI S.LN3MllIJSNI h3?H.L13X

I. What other Keithley products do you currently use?

X03 Od

2.

What effects, devices or phenomena do you measure with this instrument?

4.

Do you hwe any design suggestions concerning this unit?

Tektronix 515A Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual