Keithley 225 Service manual

Instruction Manual

Model 225

Current Source

Publication Date: August 1976

Keithley Instruments, Inc.

Cleveland, Ohio, U.S.A.

Document Nufnber: 29039

WARRANTY

Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from date of shipment.

Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batteries, diskettes. and documentation.

During the Wmanty period, we will, at

To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio, You will be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service facility. Repairs will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance of the original warranty period, or at least 90 days.

OUT

option, either repair or replace any product that proves to be defective.

LIMITATION OF WARRANTY

This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse of any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from battery leakage, or problems arising from normal wear or failure to follow instructions.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PROVIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.

NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.

CONTENTS

MODEL 225

CONTENTS

SP*CIFICATIONS---------------------------------------------------------------------

1. GENERAL DESCRIPTION------------------------------------------------------------

2. OPERATION----------------------------------------------------------------------

3. CIRCUIT DESCRIPTION------------------------------------------------------------

4. ACCESSORIES--------------------------------------------------------------------

5. SER”ICING----------------------------------------------------------------------

lj. CALIBRATION--------------------------------------------------------------------

7. REPLACEABLE PARTS--------------------------------------------------------------

SCH~rIC------------------------------------------------------------------------

1

2

4

8

10

11

12

19

31

ii

3

ILLUSTRATIONS

Figure NO.

1

Title Prone Panel.

2 Front Panel Controls

3

Rear Panel Controls. 4 Connections. 5 6

Resistive Load

Currenf Sink 7 Capacitive Load. 8 9

10

11

Inductive Load

Floating Supply.

Volt Limit Characteristic.

Modulation

12 Block.Diagram.

13 14 15 16

17 18 19

Component Layout, PC-227 (Switch Board).

Component Layauc, PC-228 (Mother Board).

Component Layout,

Chassis - Top View

Accuracy Check ...........................

Regulation Check Modulation Check

20 Inductive Load

21 22 23

current Mode "S Voltage Made Waveforms Top Cover Assembly Bortom Cover Assembly.

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Switch 5101.

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Check

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Page

I

1 3 3 4 6 6 6 6 6

7

7 8

13 13

14 14 18 18

18

18 21 21

0676

I

iii

4

CAUTION

MODEL 225

CAUTION

IF THE DECADE CURRENT DIALS ARE

SET

TO O-O-O and if the Output Selector switch is not at STANDBY, a COMPLIANCE VOLTAGE up to 100 volts may be present at the oucpuc terminals. For r&x"rn operator safety the Model 225 Current Source should always be set to STA!IDBY mode when no current output is needed. dial seteings and/or Voltage Compliance.

The Output Selector switch (S105) should also be set to

This will ensure that no transient currente will be

STANDBY

prior to changing current

generated.

WARNING

This insrrument is no? approved for use in "hazardous locations" as defined in the National Electrical Code, Classes I, II, and III.

Class I: Those locations in which flameble gases or vapors are or may be present in the air in

quantifies sufficient to produce explosive or ignitable mixcures.

Class II: Those locations that are hazardous because of the presence of combustible dust. Class III: Those locations that are hazardous because of the presence of easily ignitable fibers

or flyings.

5

0676

MODEL 225

OUTPUT:

RESOLUTION: Three significant figuresfrom lo-’

ACCURACY: z 0.5% of reading. 2 0.05% of full

STABILITY: -0.02% of reading, _cO.O05% of

NOISE: Less than 0.01% rms of full rangeabove

SPECIFICATIONS

D.C. Current: lo-’ ampere full range to lo-’ ampere in seven decade ranges, 3.digit in. line readout. Voltage: 100 voltsmaximum. Compliancelimit continuously variable from 10 to 100 volts.

Polarity: Positive or negative. Floating: c 500 volts maximum off chassis ground, less than 5 ppm of full range change in output current per volt.

to 10-l ampere. “Trim” potentiometer permits

0.02% of full range or better resolution.

ra”ge.

full range on the 10-l to 1O-6 ampere range,

(e-0.1% of reading 20.02% of range on the 10-T ampere range) the first hour or in sub.

sequent E-hour periods after a l.hour warm-

up and at reasonably constant ambient tern.

perature.

5 HZ.

SPECIFICATIONS

1

LOADREGULATION: t0.005% offullrangefrom

no load to full load on the lo-’ to 10-6 am. pere range, 50.05% on the lo-’ ampere range (with FILTER “OFF”).

LINE REGULATION: k 0.005% Of full range for

10% change in line voltage.

OVERLOAD PROTECTION: Voltage limited tocorn.

pliance voltage setting of polarity selected. Automatic recovery from overload.

MODULATION: Transformer input permitsmodw

lation of current from 50 Hz to 500 Hr.

Input 2 approximately 500 ohms.

FILTER: For operation with inductive loads up to

100 millihenries having greater than 10.6L/R ratio. Limits shunt output impedance to 1

microfarad shunted bygreaterthan 1010ohms.

ENVIRONMENT: 50% relative humidity limit at

25’C.

CONNECTORS: Output (front and rear panels):

BNC

POWER: 105.125, 210.250 volts (switch se.

lected), 50.60 Hz; 25 watts.

DIMENSIONS, WEIGHT: 5%” high x 8%” wide x

10” deep; net weight, 8 pounds.

0571

225 CURRENT SOURCE

.IWE

1

6

GENERAL DESCRIPTION

MODEL 225

SECTION 1.

1-I. GENERAL. full scale ranges frarn 10-7 to 10-l

1-2. FEATURES.

The Model 225 is a current source with

ampere.

GENERAL DESCRIPTION

c. Accuracy. The three decade dials adjust the out-

put current to +.05% of full range and +.5% of reading.

d. Polarity. The OUTPUT SELECTOR Switch provides

polarity selection without changing connections c" the

a. Resolution.

The thpe decade dials plus a "Trim"

load.

potentiometer provides a resolution of .02% of full range.

e. Floating Capability. The instrument LOW can be

floated up t" 2500 volts above chassis.

b. Compliance Voltage. A front panel Compliance Cantral provides a" adjustable maximum compliance voltsee from 10 to 100 volts.

f. Modulation. The ""tput current can be modulated

over a frequency range from 50 t" 500 Hz.

TABLE l-l.

Front Panel Controls

CQ"trOl Punctianal Description

Power Switch (S202) Controls line power to instrument. Decimal point serves

as a pilot lamp. OUTPUT SELECTOR Switch (SlO5) VOLTAGE COMPLIANCE Control

Selects positive or negative polarity or standby pasitio".

Sets the maximum compliance voltage which can be developed

(R117> at the OUT terminal.

Paragraph

2-4, a

2-4, b 2-4, c

LIMIT Indicator (DSlOl)

When lighted, the instrument is in Voltage mode. Range Switch (SlOl) Selects the full scale range. The decimal point is auto-

matically positioned by the Range switch. Selectar Switches (S102,

Selects the magnitude af current in 3 decade positions.

s103, SlO4) FINE Control (R13S) Adjusts current. FILTER Switch (5106)

When set to "ON", the switch connects a 1 p capacitor at the OUT terminal.

TABLE 1-2.

Rear Panel Controls end Termirals

Control or Terminal

Power Cord (P201) LINE

VOLTAGE

Switch (S201) FUSE (F201) OUT Receptacle (3104) LOW Terminal (5201) GROOND Terminal (520)

Pravides line power to instrument. Sets instrument for 117 or 234 V line operatia". Type 3AG. slow slow. Output high cannectio". Output law connection. Ground (chassis) connection.

Functional Description Paragraph

117 v: 1,4A; 234 Y: l/S‘4

2-2, e 2-4, d

2-4, e

2-4, f 2-4, s

2-1, a 2-1, a 2-1, a

2.1, a

!4ODUlATE Receptacle (5101) Connection to modulation transformer.

Shorting Link

7

Provides cbnnection between LOW and GROUND.

7

2-1, b

0571

MODEL 225

GENERAL DESCRIPTION

0571

3

8

OPERATION

MODEL 225

SECTION 2.

2-l.

CONNECTIONS.

8. OUtPUt conneerors. Front Panel.

1. panel are BNC type receptacles (Keithley cs-15).

The OVP receptacle (5103) provides conr,ection to the Model 225 Output High. (The center terminal is Output High while the outer shield is connected to chassis ground.) Connections to the output load can be made using the OUT receptacle

when the Model 225 is not floating. (For a more complete discussion of floating operation, refer to

paragraph 2-2 f.) The LOW receptacle (JlO5) provides

a connection to the Model 225 Output Low.

center terminal is Output Low while the outer shield is connected to chassis ground.)

2.

asac Panel.

panel is also a BNC type. Connections can be made

to either the front panel receptacle s the rear panel receptacle with satisfactory results. The rear panel LOW terminal (3104) is a binding post (Keithley part no. BP-1lG) which is connected to the

center terminal of 5105 (on the front panel). The

rear panel GROUND terminal (3201) is a binding past (Keithley part’no. BP-118) which is connected to

chassis ground. LOW to chassis ground connections.

b. Modulate Connector. The NOD”UTE receptacle

0101) is a BNC type connector (Keithley part no. CS-

15). This connector can be used for modulating the output current using an ac modulation signal. The center terminal is connected to a transformer-coupled modulation circuit while the outer shield is connected

to chassis ground.

c. Cables. Connections should be made using coaxial cables which are low-noise types with graphite coating between dielectric and shield braid. For custom length cables, Keithley Part No. SC-9 Low Noise Coaxial Cable should be used. A mating BNC connector

is available by ordering Keithley part no. CS-44.

The connectors on the front

part

no.

(The

The OUT receptacle on the rear

The shorting link (supplied) permits

OPERATION

2-2.

MEASUREMENT CONSIDERATIONS.

a. Accuracy. The accuracy is specified in terms of the front panel dial setting or reading as well as the full range selected. (The FINE current control

must be set accuracies.) Since the total accuracy of the Model

225

is the s of the readina accuracy and the full

a accuracy, the user should select the lowest

full range for best possible accuracy. Table 2-l.

shows the total accuracy for typical dial settings.

(The accuracy on the lOOkA range is +.05% of 1000 or

o.s”A plus 2.5%

Output

lhrL-elLt setting

1 x lo-6A 1 x lo-6A O-1-0 100 $ + .055 NA 1 x

104A

1 x lo-6A

When the OUTPUT SELECTOR is set to + or - and VOLTAGE When the OUTPUT SELECTOR is set to + or - and VOLTAGE COMPLIANCE is set to 100, up to 100 volts will be COMPLIANCE is set to 100, up to 100 volts will be present at the output terminals. present at the output terminals.

b. Stability. The stability is specified in terms of the front panel dial setting or reading as well as the full range selected. specification is the e of the readinR stability and the full range stability, the user should select the

lowest full range for best possible stability.

c. Line Regulation. as +..005% of full range for a corresponding 10% change in line voltage.

d. Load Rezulation.

ified a8 2.005% of full range far a change from no load to full load.

tion corresponds to an output compliance voltage change

from 0 volts to 100 volts.

to

“0” position to obtain the stated

of 1000 or %A

for a coca1 of 5.5nA.)

TABLE 2-l.

Accuracy

Decade Dial

For Typical Dial Settings

RANGE

Setting

Total Accuracy

(FINE c0ntr01

set to “0”)

o-o-1 1000 &k4 + .505 VA

1-o-o

10-O-O 1000 UA + .0055 p.4

10 @

+ .OlO *

CAUTION CAUTION

Since the m stability

The line regulation is stated

The load regulation is spec-

The no load to full load varia-

FIGURE 4. Co”*ectm”s.

e. Output Impedance.

The effective output impedance of the Model 225 is a function of the load regulation specification and the high to low insulation

resistance. The output impedance for each Range setting is given in Table 2-2. The insulation resistance is 2 x 1012 ohms with the FILTER Switch OFF, but is 1 x lOlo

ohms with the’FILTER Switch ON. There-

fore the maximum output impedance is 2 x lOl2 on 100 nA and 1OOOti ranges with the FILTER Switch OFF. The effective output impedance R. ~a” be decermtned by the

following equations.

0676

MODEL 225

TABLE 2-2.

Output Impedance

Range setting

100 m.4

10 mA

1000 liA

100 ,,A

O”tput Impedance*

2 x 10; n 2 x log n 2 x lOlOG 2 x 1OlI R

10 UA

1000 nA

100 nA

2 x l0l2 “, “, : :;12 n

*With Filter switch set to off. I

For the 100 mA range,

R,, = 103n and % regulation = 0.005%

since I regulation = 100 x

RL

qq

I 1

Then % -

The Model 225 will deliver the dialed current for a load resistance from 0 ohms to WK. The val’ue of w is determined by the dialed current I and the compliance voltage setting VC where Rw.K =

WI.

If the load resistance exceeds RMAx then

the Mcdel 225 will automatically switch into Volt-

age Limit mode indicated by the LIMIT lamp (DSlOl)..

f. Floatiw Operation. The instrument can be floated

“I) to +500 volts off chassis nround with less than 5

ppm of-full range change in &put current per volt off ground. on the rear panel m,,st be m.

For floating operation, the shorting link

In this case, two

coaxial cables should be used to connect to output

high and low.

The outer shell of the front panel O!Jf and LOW receptacles are always at chassis ground for safety when flokting the instrument.

A

filter capaci-

tor C217 (,05 ~0 is connected between the LOW and

GROUND binding posts to minimize line frequency pickup. The LOW to GROUND isolation is approximately lo7 ohms.

A

typical example of floating operation is shown in

Fig”re 9. In this example, the Model 225 can be used

with a voltage supply such 8s Keithley Model 240A

to

extend the maximum compliance voltage to +600 volts.

The Model 225 can be adjusted for a compliance voltage

of +500 2100 volts de. The maximum current is 10 milliamperes (for the Model 24OA).

c. contra1 setti”*s.

The output current is selected by three decade switches and a seven position Range Switch. Refer to the discussion of the fronr panel concrok in paragraph 2-4 before power is turned on.

2-4. FRONT PANEL CONTROLS.

a. Power Switch (S2022. This switch controls the

line-power to the instrument.

b. OUTPUT SELECTOR Switch (SlO5). This switch has four positions designated “-“, and “+“. polarity.

The + and - positions set the output current

The two “STANDBY” positions divert ehe out-

“STANDBY”,

put current as shown in Figure 5. The output load is

not disconnected at any position of the switch. (The

shunting effect should be considered, since a small

voltage can be developed across the lo-milliahm shunt and therefore across the output terminal.)

c. VOLTAGE COMPLIANCE Control (R1171. This control

is a continuously variable potentiometer which can be

see for a compliance voltage from lo~volts to 100

volts.

d. Range Switch (SlOl). This switch selects the

full scale ranpe from 10-7 BmDePe to 10-l amoere.

The dial is deiignated in re&s of engineering Airs; that is, nA, IJA, and mA. The full range is determined by the position of the lighted decimal point end the designated engineering unit.

e. Selector Switches (SIOZ, SlO3. S104L. These switches select the magnitude of ‘the o”tput current in three decades. The position

of

the dials determines

the significant digits from O-O-O to V-9-9.

f. FINB Control (Rl38)-. This control is the inner

dial of a dual concentric control. The fully clock-

wise position “10” represents 1 digit added t., the

right-hand dial (S104). The fully counter clockwise position is the “0” or off position. When the FINE Control is

set

to “0”. the output current is determined

only by the calibrated dials within rated specifica-

tion. This control cm be used to “trim” the output

current to within +.02% of full range, although the

trim dial is adjustable t., within 2.005% of full range.

NOTE

For example, if the three decade dials were set

for

9-9-9 on the 1000 !,A range, then the FINE control could be set to 1500 clockwise to obtain a current .Y”tp”t of approximately 999.5 +4.

2-3. PRELIMINARY PROCEDURES.

a. Power.

Check the 117-234V Switch for proper linevoltage setting. Check the fuse for proper rating. Set the Power Switch to off before connecting the power

card.

b. Connections.

The output load should be cwnected

as described in paragraph 2-l.

0972B

Since the stabilitv specification is +.02% (or better) of reading, the useebie resolution w&d be ~i.2 ,,A. If the FINE control was set to “O”, then the output would be 999.0 ti 2.5 ,JA.

g. FILTER Switch (S106). This switch should be

used whenever the Model 225 must deliver current to

an inductive load.

10

5

OPERATION MODEL 225

OPERATING CHARACTERISTICS. The Model 225 Current

2-5.

Source has a bipolar output, a constant cnreent up to the maximum compliance setting, and automatic crossover to constant voltage mode.

a. Bipolar Output.

accept current and as such it has a bipolar output.

1. Current Source. The instrument can be used as a current source with a resistive load as shown in Figure 5. current set by the front panel controls. Tbe voltage developed across the load resistance IO x RL.

2.

a current sink as shown in Figure 6. In this case.

the polarity of the current is such that cw’eent

is flowing into the Model 225. The output voltage “0 = E - IORL, where IC is selected by the front panel dials, E is the external voltage source, and RL is the load resistance.

b. Constant Current Mode. Tbe Model 225 will de-

liver the dialed current for resistive, capacitive, and inductive loads unless the voltage required at the output terminals exceeds the compliance voltage.

1. Resistive Load. deliver current to a resistive load from 0 ohms to w where k = VC/IO and VC is the compliance

voltage

In this case, the

Current Sink.

setting.

The

Model 225 can deliver 0’

Model 225 delivers B

RL is V, =

The instrument can be used as

The instrument can be used to

-‘Iff!?++iJ ___----------

FIGURE 5.

I

Resistive Load.

RI

I

FIGURE 6.

Current Sink.

2.

Capacitfve Load. The instrument can also be

used to charge a capacitive load as shown in Figure

7.

The capacitor will be charged to the compliance

voltage set on the front panel.

3.

Inductive Load. The instrument can

deliver current to an inductive load. When the ratio

of load inductance than 10-6, the FILTER Switch m”st be set to “ON” for stability. citor across the output as shown in Figure 8.

:I I I

I

The FILTER Switch connects a 1 pF cap*-

L to load

FIGURE 8.

resistance R is greeter

Inductive Load.

be

used

to

FIGURC 7.

FIGURE 9. FIGURE 9.

Capacitive Load.

Floating Supply. Floating Supply.

6

0972

11

MODEL 225

OPERATION

C. constant “Oltsge Mode.

jwted for a compliance voltaza from 10 to 100 volts. The voltage limiiing will o&r if the load resistance is such that IORL - "C.

marically switch into a constant voltage mode (the LIMIT lamp will be lighted) such that the output volt-

age will not exceed the compliance setting. If the

Mcdel 225 is used as a current sink, a,, output voltage

of 130 volts could be developed regardless of the con-

pliance setting. The voltage limiting characteristic can be shown as in Figure 10.

2-6.

M!JDULATION. For convenience in making dynamic

measurements, the Model 225 has a MODULATE input (JlOl)

so that the current can be modulated in the 50 to 500

HZ range.

a. Circuirry. The Model 225 uses a transformer

coupled input with 500 ohms impedance.

b. Characteristics. The peak-to-peak modulation

can be adjusted up to a maximum of 40% of full range from 50 CD 100 Hz decreasing to about 8% of full range at 500 Hz (with a 10 volt rms sine wave input). The modulation circuit is not calibrated so that the user

m"st check with a knwn load resistance. Within a

selected w the modulation is independent of decade

dial setting.

can affect the modulated current signal so that the

modulation calibration should take into account this

CapC.CitaWX.

C. "Olcage Complia*ce.

compliance can cause clipping of the modulated cur-

rent as shovn in Figure 11.

The capacitance of the output cables

The Model 225 can be ed-

The instrument "ill auto-

The serring of the voltage

t

1.3

,

I

F1mP.E 10.

RL-+

Volt Limit Characteristic

I

FIGURE 11.

Modulation.

I

NOTE

When the 225 output is modulated the average

value or dc level is determined by the dial set-

rings. The outpllt is essentially a sine-wave at the input drive frequency. The peak-to-peak

modulation amplitude depends on both the magni-

tude and frequency of the drive signal so that the exact modulation waveform will have to be

checked tith an actual output load connected. Clipping of the output signal may occur depending on the compliance voltage setting. The modulation feature is especially useful when making dynamic impedance measurements on semiconductor devices, etc.

0972

12

7

CIRCUIT DESCRIPTION

MODEL 225

3-1.

GENERAL.

SECTION 3.

The Model 225 is an all solid-state

CIRCUIT DESCRIPTION

current source which is composed of varicus circuits

as shown in Figure 12. These circuits include the

following types.

a. High Gain Operational Amplifier “A3”. b. Differential Voltage Sensing Amplifier “Al”. c. Kelvin Divider with Precision l-volt Reference. d. Voltage Compliance Amplifier ‘A2”.

Compliance Voltage Control.

e.

f. Compliance Voltage Suppies 2130 V. g. Series Regulators.

Range Resistor Controls.

h.

Power Supplies.

i. j. Modulation Circuit.

3-2.

THEORY OF

OPERATION.

The Model 225 can deliver

currents from 10-7 to 10-l amperes with a compliance

voltage up t0 100 volts. The current source utilizes a high gain differential amplifier “A3” which controls the current through the range resistor “R”. The

differential voltage sensing amplifier

“OUT” voltage with respect to a voltage reference.

‘Al” senses

the

A

kelvin-varley divider network permits adjustment of current in decade steps. The voltage compliance

amplifier ‘AZ” eenses the voltage at a point ahead of

the range resistor with respect to

the

compliance

voltage contra1 patenrial. The compliance voltage

supplies allw a 2100 volt compliance at the output.

These supplies deliver power to the load up to B mex-

imm of 10 watts (100 V x 0.1 lators are driven

by the

lifier ‘A3”. The range resistor is selected

A).

The series regu-

high gain differential amp-

by the

RANGE Switch for currents of 10-7 ta 10-l ampere full

w.

The remaining power supplies are used to bias

the operational amplifiers and reference zener.

3-3.

CIRCUITRY.

a. High Gain Operational Amplifier ‘A3”. This

amplifier is composed of matched emitter followers

(4111 and Q114). e differential rpn gain stage (transistors Qlli and Q113), a differential npn gain stage (transistors QlOS and QllO), an emitter follower transistor Q115 and a second npn gain stage (Q116 and

Ql17).

b. Differential Voltage Sensing Amplifier “Al”.

This amplifier is composed of a marched pair of FET’S

(transistors Q118A and Q118B). These devices have a

low temperature coefficient (5 ppm/W) and low typical offset-current (less than 10 pA). The offset-current however, doubles every 10°C approximately. Potentiameter R144 provides zero adjustment for the differen-

tial pair.

c. Kelvin-Varley Divider with Precision l-Volt

Reference.

1. l-Volt Reference. The voltage reference utilizes a S-volt zenee diode (D116). (The zener is stable to 20 ppm). An accurate divider, composed of

R181 and R183, divides the 9 volts down to l-volt. Potentiameter R182 is used to adjust the reference voltage ta precisely l-volt.

2. Kelvin-Varley Divider. This divider is composed of three decade dials and

a potentiometer

fine control. The Selector Switches 5102, S103, and

S104 and PINE Control Rl38 permit adjustment of the voltage drap across the Range resistor R. The divider resistors are designated R148 through R18D.

(These resistors have 0.1% accuracy and a temperature coefficient of 25 ppmlW.)

FIGURE 12. Block Diagram.

0676

MODEL 225

CIRCUIT DESCRIPTION

d. Voltage Compliance Am”lifier ‘A2”. This ampli-

fier is comwsed of a differential

nain

staee: transistors Q107’and QlO8. The fr”“t p&e1 compii&ce control R117 sets the maximum compliance voltage desires

up to +100 volts. The bias reference for transistor QlO8 is provided by a divider string camposed of re-

sistors Rl15, R116, R117, and R118. Potentiometer

R116 provides a” internal compliance voltage edjustment. The amplifier is biased “off” in the constantcurrent mode of operatian. When the voltage at the

“series regulator output” reaches the preselected CMI\pliance limit, the amplifier “A2” is t”rned “ON” and the Model 225 automatically changes to a voltage limit

made.

The LIMIT indicator US101 is turned on a”t”-

matically when in the “valtage limit mode”. F”r pos-

itive polarity, transistor QlO8 turns on in the volt-

age limit mode while 4107 is turned aff. The difference voltage is buffered by emitter-follower stage, Q201 and Q204. Transistor Q202 is turned on and chere-

fore drives transistor Q207. (The LIMIT indicator is

cannecced in series with Q207.) Transistor Q2D2 provides valtage level translation. Far negative polar-

ity, the difference voltage between Q107 and Q108 is such that transistors 4205 and QZO6 are driven. (Transistors Q201 and 9204 act as buffer stages.)

Transistor Q206 provides voltage level translation and drives Q208. The LIMIT indicator is connected in series with Q208 and is turned an. Potentiometers R203 and R207 provide control of the LIMIT indicator turn-on

for + limit and - limit respectively.

e. Compliance VoltaRe Control. This control adjusts

the maximum compliance voltaee from +lO volts t” cl00

Volts. This is’accomplishedwby “sing a linear 5D-kilohm potentiometer designated R117. A constant c”rrent

is driven through the resistor divider. The polarity is controlled by the ODTPIPT SELECTOR Switch S105.

i. Power Supplies.

The remaining power supplies provide power to the amplifier stages and voltage references.

1. 510 volts.

Diodes D211 tbr” D214 form a fu.ll-

wave rectifier which provides unregulated voltages

for the 210 vole regulator stages. Capacitors C207 and C2D8 provide filtering, Transistors Q209 and Q210 and reference zeners D205 and D206 form the 210 volt regulators.

This supply provides bias

voltages for the voltage LIMIT indicator circuit.

2. 212 volts.

This supply provides power t” the amplifier stages and reference diode D116. The supplies consist of a full-wave rectifier (Diodes

D215 thru D218), a” integrated circuit QA201, and

a linear operational amplifier QA202. The voltage

developed by QA201 is 24 volts. This output is

split to form separate 212 volt supplies.

(These supplies are referenced to the output high.) Potentiometer R226 provides adjustment af the 24 volt OUCPUL.

j. Modulatian Circuit. The modulation circuit

consists of transformer TlOl which is connected so

that the voltage feedback to amplifier “Rl” can be modulated by an external source. Therefare the currentoutputwill likewise be modulated. The primary of TlOl is connected between the center terminal of JlOl and chassis graund.

f. Compliance Voltage Supplies. These voltage

suoolies orovide unresulated +130 volts for the series

.~

regulatarb. transformer T201.

wave rectifier.

AC

pover”is obe&ed fram a secondary of

Diodes D207 thru D21D form a full-

Capacitors C203 thru C206 provide

filtering of *c ripple.

g. Series Resulators.

form a comolimentarv-svmmetrv 0”tp”t staw.

Transistors QlOl and 9105

(These transistor; are rated at 300.vol&, 35 watts.) Transistors Q103 and 9106 are c”rrent limiting transistors

which shut down the output transistors during a change

in the selected polarity.

h. Range Resistor Controls. The Range Switch SlOl selecees full range current fram lop7 to 10-l amperes. Range resistors R184 thr” R190 are selected such that,

for each selected current, the voltage drop across

the Range resistor R is 1 volt for full range.

3-4. SWITCHING. The 0lppP”T SELECTOR Switch S105 has four positions labeled “-“, “STANDBY”. “STANDBY”, and

,a+,,

. The “-” and “+” positions connect the internal

circuitry such that the polarity of the current at the

“OVP” terminal can be changed with respect to “LOW”. This is accomplished by reversing the polarity of the voltage references since amplifier ‘A3” is a bipolar amplifier. The two “STANDBY” positions permit a

change of polarity to be made without developing large

transients. The “STANDBY” positions connect the high output LO “LOW” through a 10 milliohm shunt as shown

in Figure 5. Since the selected c”rrent will be shunted thraugh the 10 milliohms, up t” 10 millivolts can be developed between the “OUT” and “LOW” terminals

with no load. Resistor R193 limits the voltage drop

to 1 millivalt for a 1 ahm laad.

0571

9

14

MorJE?. 225

SECTION 4.

GENERAL.

4-1.

be used with the Model 225 to provide additional con-

The following Keithley accessories can 4-2. OPEBAlmG 1NSTK"CTlONS. A separate InstrUction

ACCESSORIES

Manual is supplied with each accessory giving complete

venience and versatility. operating information.

Model 1004 Rack Mounting Kit

Description: The Model 1004 is a rack mounting kit with overall

dimensions 5-l/2 inches high x 19 inches wide x 10

inches deep.

Application: The Model 1004 converts the instrument from bench to

rack mounting.

It is suitable for mounting one instru-

ment in one-half of a standard 19-inch rack.

Parts Litit:

item

NO. Description

1

Top Cover 1

2

Panel 1

3

Angle 1

4

screw 4

5

Plate

6

Screw 4

7

Angle 1

Qty. Per Assembly

1

Keithley Part NO.

200168 174528

17476A

_--

191266

__-

146248

10

0571

15

SERVICING MODEL 225

SECTION 5.

5-l. GENERAL.

checkout and servicing the instrument. Follow the

step-by-step procedures for complete servicing.

5-2. SERVICING SCHEDULE. This instrument requires no periodic maintenance beyond the normal care required

for high-quality electronic equipment,

5-3. PARTS REPLACEMENT. Refer Parts List, Section 7, ponent specifications and part numbers. Replace cornponents as indicated using replacement parts which

meet the listed specifications.

Code

Letter

Multimeter, Digital Voltage: 20.1% of reading. Current:

A

This section contains procedures for

to

for information regarding corn-

Instrument Type

the Replaceable

20.2% of reading except 50.3% of reading on 100 mA, 1 A ranges.

TABLE 5-1.

Test Equipment.

Specification and Model No.

SERVICING

5-4. TROUBLESHOOTING.

a. Test Equipment.

mended test equipment for servicing and calibrating

this instrument.

b. Troubleshooting Guide. Refer to Figure 16 for

voltages and test points.

If the instrument problem cannot be readily located or repaired, contact a Keithley representative or the Sales Service Department.

Cleveland, Ohio.

Keithley, Model 160

Refer to Table 5-l for recom-

NOTE

Manufacturer

Use

Accuracy check, General.

Electrometer

*

Voltmeter, Differential 0.5 V to 500 V 100 VV null.

C

Voltmeter, True RMS 0.1 mV to 300 V rmm8 Freq. Resp.

D

Oscilloscope

E

Variae O-130 ” lms.

F

Power Line Monitor 105-130 V nos.

G

Oscillator 100 Hz, sine wave.

H

Recorder

.I

Load Pixture

K

Indwtive Load Fixture 1 mH Inductance

L

.OOl V to 100 V lo’“0 input resist- Keithley, Model 610C

enee

10 to 4 MHZ. DC-450 kllz, 1 mV/div.

1 WA for full-scale deflection. 1 kC/lO 0 - Resistors See Text.

Keithley, Model 662 Keithley, Model 124

Tektronix, Model 503 Genersl Radio

Wavetek. Keithley, Model 370.

See Text.

General.

General

General Line Regulation. General

Modulation Check

Drift Check. Load Regulation.

Inductive Load

Check.

0571

16

11

CALIBRATION

MODEL 225

SECTION 6.

GENERAL. This section contains procedures for

6-1. checking the instrument in order to verify.aperation within specificetions.

TEST EQUIPMENT.

6-2. mended test equipment for servicing end calibrating this instrument.

CALIBRATION PROCEDURE.

6-3.

step-by-step procedures for calibrating this instrument.

Par*.

6-3

a.

Accuracy.

115V. Amb. Temp: 25OC. Rel. Humidity: 50%. Link between LOW end CROWD. FILTER: OPP.

Refer to Table 5-1 for recom-

Refer to Table 6-l far

Specification or Adjustment

NOTE: Line voltage

Performance Check

Verify the accuracy on each fullscale range.

Set OUTPUT to STANDBY. Connect the Digital Multimeter (A) to OUT receptacle es shown in Figure 17. Set COMPLIANCE to 100. Set FINE to 0 (calibrated position).

CALIBRATION

TABLE 6-l.

Description

NOTE

If proper facilities end equipment ere not

available, contact a Keithley representative or the Sales Service Department, Cleveland, Ohio.

Keithley Instruments, Inc. maintains a complete repair end calibration facility with equipment traceable to the National Bureau of Standards.

Measurement

Figure

17

100 mA Range: Set decade dials to 9-9-9. Set range to 100 mA.

Current reading should be

99.9 CA +o.l35 u&4.*

Set OUTPUI to +. Measure current.

Repeat for - OUTPUT.

10 18~4 Range: Set decade dials to 9-9-9. Set range to 10 mA. Set OOTPOT to +.

Measure

current.

Current reading should be

9.99 EA +.075 !“A.**

Repeet for - OUTPUT.

1000 pA Range: Set decade dials

to 9-9-9. Set range to 1000 pA.

Current reading should be

999. “A 27.5 WA.** Set OUrPUT to +. Measure current. Repeat for - OUTPUT.

100 pi Range: Set decade dials to

9-9-9. Set range to 100 @.. Set

Current reading should be

99.9 LLA 20.75 PA.** OOTPDT to c. Measure current. Re peat for - ODTPW.

10 @ Range: Set decade dials to 9-9-9. OUTPUT to f.

Set range to 10 @. Set be 9.99 fi 20.075 )rA.**

Measure current.

Current reading should

Repeat for - ODTPW.

1000 nA Range:

to 9-9-9. Set ODTPL’I to +.

Set decade dials Current reading should

Set range to 1000 nA.

Measure

current.

be 999. nA 27.5 “A.**

Repeat for - OWIPOT.

100 nA Range: Set decade dials

Current reading should

to 9-9-9. Set range to 100 “A. be 99.9 nA LO.75 nA. ** Set OLTPUT to +. Measure current. Repeat for - OUTPDT.

12

* Includes 33.3% accuracy of the Model 160 (see Table 5-I).

** Includes 20.2% accuracy of the Model 160 (see Table 5-l).

0972

17

MODEL 225

CALIBRATION

TABLE 6-1. (Cont'd)

pera.

6-3

b.

C.

Specification or Adjustment

Line Regulation. NOTE: Line voltage: 115V. Amb. Temp:

25W. Rel. Humidity:

50%. Link between LOW end GROUND. FILTER: OFF.

Lasd Regulation. NOTE: Line

voltage: 115". Amb. Temp:

25%.

Rel. Humidity: 50%. Link between LOW end GROUND. FILTER: OFF.

Description

Verify line regulation. Set OUIPb"f to STANDBY. Set decade

dials to 9-9-9. Connect load resistor between front panel Loh( and Om es shown in Figure 18. Set COMPLIANCE to 100. Set

FINE

to

0.

Set renge to 100 mA. Set line voltage to 105 V. Set

0uT'pvT to +. Measure voltage at

load.

Repeet for - ODTPDT.

Set line voltage to 125V.

Verify load regulation.

Set ODTPDT to STANDBY. Set decade

dials to 9-9-9. Set FINS to 0. Set

range to 100 s&i. Set COMPLIANCE to

100. Set line voltage to 115 V. Connect load resistor between front

panel LOW end ODT es shown in Figure

18. Set ODTPUT to l . Measure voltage et load. Repeat for - OUTPUT.

Measurement

Voltage change should not exceed 50

pV.

Voltage change should

not exceed 50 uV.

Voltage change should

not exceed 50 WV.

18

d. Noise Check.

e. Modulation.

Inductive Loading.

Drift Check.

Set OUl'PuT to STANDBY. Set decade dials to 9-9-9. Set FINE to 0.

Set range to 100 mA. Set COMPLIANCE

to 100. Connect load resistor. Set ODTPlrr to +. Measure cm* noise using Voltmeter (D). Repeat for - ODTPUT.

Set range to 100 mA. Set decade dials to 5-O-O. Set FINS to 0. Set

COMPLIANCE to 100. Connect Oscilla-

tor (H) to MODDIATE input. Connect Oscilloscope ( ) end loed resistor

to OUT es shown in Figure 19. Set Oscillator (H) for 30 V p-p @ 100 Hz. Waveform should be e 400 mV p-p mcd-

ulated "eve.

Set range to 100 mA. Set decede

disls to 9-9-9. Set FINE to 0.

Set COMPLIANCE to 100.

to ON.

Connect inductive load.

Set FILTER

(1 mH in series with 1 kG) es shown

in Figure

20.

Set OUTPUT to +.

Connect Oscilloscope (H) and measure

ripple. 100 mv p-p.

Voltage should be less than

Set FILTER to OFF. No

oscillations should occur. Set range to 1000 PA. Set decade

dials to 9-9-9. Set FINS to 0. Set

OUTPUI to STANDBY, Warm-up 225 for

1 Hr. Connect Recorder to OUT. Set

OUTPUT to +.

Adjust FINE for 1 V

deflection on recorder. Total drift

for 1st hour should not exceed 2250 mV

with less then 100 mV/W.

Noise should be less

then 10 m" rms.

400

mv p-p.

19

20

0676

18

15

CALIBRATION

MODEL 225

TABLE 6-2,

Calibration Procedures

Para. Specification

6-4

a.

or Adjustment

Power Supplies.NOTE: DC voltmeter and os-

cilloscope must be

floated for measure-

ment of 12v supplies.

Line Voltage: 117v. Link between LOW and CRODND. LINE SWITCH:

117v.

Description Me~S”r~tlEtlt

Calibrate power supply.

-12 VOLTS DC: Measure -12V supply

with respect to range switch shaft.

(cnmnon). Adjust pcaentlometer B226 for -17.v +o.o1v.

+12 VOLTS DC: Measure +lZV supply

with respect to range switch

shaft, (common).

NOTE: If 234V power 1s used, set

LINE SWITCH to 234V.

-10 VOLTS DC: Measure -lOV with respect to LOW. Ripple should be

less than 20 mV p-p.

+lO VOLTS DC: Measure +lOV with respect to LOW. Ripple should be

less than 20

SIV

p-p.

Sub-

Assembly Figure Point Part No.

Ad~just for volt- PC-228

ag; of -12v + O.OlV. Ripple

should be less

potentiometer R226.

than 3 mV p-p.

Voltage should

PC-228 be +12V +o.ZW. Ripple should be less than 3 mv p-p.

Voltage should

PC-228 be -lOV +lV.

Voltage should

PC-228 be +lOV +‘V.

Test Schematic

14,16 -12V

14.16 +12V

14316 -lOV

14,16 +lOV

24203E

242038

242032:

24203E

Amplifier Zero

b.

Reference

e.

Bias

d.

Set range to nA. Set decade dials

to O-O-O. Set OUTPUT to STANDBY. set COMPLIANCE to 100. COnnecc Digital Voltmeter (A) between test points shown in Figure 16. Adjust

potentiometer R144 for zero. Set range to mA. Set decade dials

to 9-9-9. Set FINE to 10. Set OUT-

PUT to + STANDBY. set COMPLIANCE

to 100. connect Digital Voltmeter

(A) between test points ehown in Figure 16. Adjust potentiometer R182 for +1.0 LO.5 mv.

Set OIJCPCT to - STANDBY.

Set rsn~e to nA. Set decade dials

to 9-9-G. Set FINE to 10. Set

COMPLIANCE to 100. Set OUTFliT to

- STANDBY. Connect Digital Volt-

meter between test points shown

in Figure 16. Adjust potentiometer

X121 for voltage between 27 mV to

40 mV. (This sets current thru transistors QlOl, Q102).

Adjust for 0

20.1 mv.

Adjust for

+,.ov 20.5

SIV.

Voltage change

must not exceed

1 mv.

Adjust for

voltaSe be-

tween 27 mV to 40 mv.

PC-228

Potenriometer

R144.

PC-228 Potentiometer

RlS2.

PC-228

14.16 -

24204E

242043

16

0571

19

MODEL 225

CALIBRATION

TABLE 6-2. (CONT’D)

Para. Specification

6-4 or Adjustment

Compliance

Voltage Limit Lamp

Description

Set range to mA. Set decade dials Adjust for to 9-9-9. Set FINE to 10. Set

Measurement

Assembly Figure Point Part No.

PC-228

voltage Of potan-

COMPLIANCE to 100. Set OUTPm to 1Ol.V +10 tiorseter

Sub-

+

STANDBY.

Connect Digital Volt-

mV. R116.

meter (A) between range switch

shaft (12V eonrmon) and LOW.

Connect load resistor. Adjust

potentiometer R116 for 1Ol.V +lO mv.

Set range to mA. Set decade dials

to 9-9-9. set FINE to 10. set COMPLIANCE to 10. Set OUTPUT to + STANDBY. Connect Oscilloscope

(E) to OUT. Oscilloscope settings:

2mVldiv SmS/div

Trigger

Input

Connect load resistor. Set OUTPW

to +. Adjust potentiometer R203 such that the LIMIT lamp turns an when the 225 changes from current

= INTERNAL

=

AC

COWLED

PC-228 Potentiometer R203.

mode to voltage mode. NOTE: To determine the crowover

point between current and voltage

modes, adjust the COMPLIANCE con-

trol until the oscilloscope ripple

waveform changes as shown in Figure 21.

Test

14,16 COMNON

14,16 -

Schematic

24204E

24203E

Set

OUTPCT

to -.

Adjust

potentiometer R207 such that the LIMIT lamp turns on when the 225 changes from current mode to voltage mode.

PC-228 Potentiometer R207.

24203E

0571

17

20

i

CALIBRATION

MODEL 225 -

I

MILLATOR

XIVPP ‘L

IOOHz

FIGURE 17.

225

?A00

07

FIGURE

19.

Accuracy Check

~- I

OSCILLOScOPE

OUT

0

OUTPUT IS 40%

OF F.S.

&J-P)

m

Modulation Check

225

m

FIGURE 20.

FIGURE 18. Regulation Check

I LLOSCOPE

osc

OUTFUT

<ImnY PP

A

Inductive Load Check

FIGURE 21.

18

Current Mode Vs Voltage Mode Waveforms

21

0676

MODEL 225

KKPLACKAStE

PARTS

SECTION 7.

REPLACEABLE PARTS

7-l. REPLACEABLE PARTS LIST: This section contains a list of components used in this instrument for user reference. The Replaceable Parts List describes the

individual parts giving Circuit Designaticn, Descrip-

tion, Suggested Manufacturer (Code Number), Manufac-

Abbreviations and symbols

A

CbVar CerD Ceramic Disc CerTB Cer Trimmer Camp

ampere Carbon Variable Ceramic Tubular

Ceramic Trimmer Composition

F Fig

GCb k

!-I

DCb Deposited Carbon Desig.

Designation

M

Mfr. F.AL Electrolytic, Aluminum ETB ETI

Electrolytic, Tubular Electrolytic, Tantalum

MtF

MY

NO. Number

turer.‘s Part Number, and the Keithley Part Number.

Also included is a Figure Reference Number where

applicable.

Manufacturer is listed in the CODE-TO-NAME Listing

following the parts list.

TABLE 7-l.

farad

Figure Glass enclosed Carbon kilo (103) micro (10-6) Meg (10%

Manufacturer Metal Film Mylar

The complete name and address of each

0

ohm

pica (10-12) FC Paly

Ref.

Printed Circuit

Polystyrene

Reference

TC” Tinner COpperweld V VOlL

” mi War

watt Wirewound Wirewound Variable

7-2.

ELECTRICAL SCHEMATICS AND DIAGRAMS. Schematics and diagrams are included to describe the electrical circuits ss discussed in Section 3. Table 7-2 ldenti-

fies all schematic part numbers included.

7-3. HOW TO USE THE REPLACEABLE PARTS

LIST.

This Parts List is arranged such that the individual types of camponencs are Listed in alphabetical order. Main Chassis parts are listed followed

by

printed circuit

boards and other subassemblies.

7-4. HOW TO ORDER PARTS.

a. Replaceable parts may be ordered through the

TABLE 7-2. Schematics

Description Assembly No. Schematic No.

Amplifier

Power Supply

Sales Service Department, KeithLey Instruments, Inc. or your nearest Keithley representative.

b. When ordering parts, include the following in-

formation.

1. Instrument Model Number

2. Instrument Serial Number Part Description

3.

4. Schematic Circuit Designatian

5. Keithley Part Number

c. All parts listed are maintained in Keithley

Spare

Parts Stock.

available upon request.

Any

part not listed can be made

Parts identified by the Keithley Manufacturing Code Number 80164 should be ordered directly fram

PC-227, PC-228

PC-228

Keithley Instruments, Inc.

242048

24203E

0571

22

19

REPlACEABu3 PARTS

MODEL 225

series

100 Amplifier

200

De*CdptiD”

1) Chassis

11) Front Panel Top Cover Assembly

12)

Cover, Sheet Metal

13) screws

Cfrcult Designation series

TABLE l-3.

Description

Power supply

TABLE 7-4.

Mechanical Parts List

Circuit Designation

PC-227, PC-228

Quantity

Per Assembly

1 240218 1

--1

4

PC-228

K.Sithley

Fart No.

2339%

245630

24561D

_--

Page No.

22 27

Fig. NO.

22

Handle Assembly

14) Handle 1

15) Screws 86-32 x 3/S”

R.H. Slotted

Bottom Cover Assembly

2) cover 1

3) Fastener 2

Feet Assembly

4) Feet

5)

Ball

6) Screws OS-32 x 3/S” Phillips, Pan Head Tilt Bail Assembly

7)

Bail

8) Right

Assembly

9) left Assembly

10) Screws 06-32 x l/4”

Phillips, Pan Head

_-- __-

m-18

2

_--

--- 17148C

17149c

FA-54

-_- ---

4 4 4

FE-5

FE-6

--_

_-- ---

1 171478

1 192068 1

2 ---

19205B

23

20

23

0972

MODEL 225

REPlACEABLE PARTS

FIGURE 22. Top Cover Assembly.

0571

Botkm Cover Assembly.

24

21

REPLACEABLE PARTS

MODEL 225

REPIACEABLE PARTS LIST

AMPLIFIER, “100” SERIES, PC-228

CAPACITORS

CiCC”if Desig.

Cl01 Cl02 Cl03 Cl04 Cl05

Cl06 Cl07 cl08

Cl09 Cl10

Value

Raring

.0068 fl 6OOV .0022 p 600~ .22 &dJ 501) .02 $2 600~

4.7 pF 2ov

4.7 @ 2ov lllF zoov lP 2oov

.OZuF 33PF

600” 1ooov

Cik-C”it Desig. Description

3101 Receptacle, BNC, MODUuTE 5102 Not Used 3103

Receptacle, BNC, Front Panel om

(Mil. No. W-1096/U) 02660 31-221 cs-15 2

5106

Receptacle, BNC, Rear Panel OLPP (nil. ii*. UG-1094kl) 02660 31-221 cs-15 2

J105

Receptacle, SNC, Front Panel LOW

(Mil. No. UG-1094/U) 02660 31-221 cs-15 2

Mfr.

Type Code

Mfr. Desig.

Keithley

Part No.

&L-D 72982 ED-.0068 C22-.006SM 14 CerD 72982 ED-.0022 C22-.0022M 14 MY 84411 601PE C61-.22M 14

CerD 72982 ED-.02 C22-.02M 14 ETT 17556 TSDl-20-475

C179-4.7M

ETT 17554 TSDl-20-475 C17Y-4.7M 14 MY 13050 107-21 C66-1M 14 MY 13050 107-21 C66-1M 16

CerD 72982 CerD

71590

ED-.02 c-22-.02 DD-330 C-64-33~

CONNECTORS

Mfr. Code

(Mil.

NO. UG-1094/u) 02660 31-221 cs-15 2

Mfr. Desig.

Keithley

Part No.

Fig. Ref.

14

Fig.

Ref.

J201 5202

Circuit Desig. Type

DlOl 0102 D103 D104 D105

0106 0107 0108

D109

DllO Dill

0112 D113

0114 D115

0116 D117 0118 Ill19 D120

n121*

Binding Post, GROUND

Binding Post, Rear Panel LOW

Not Used Silicon Silicon Silicon Not Used

s11icon Silicon

Silicon Silicon 01295

Silicon 01295

Silicon Silicon Silicon

Not Used Not Used

Zener, 6.2V, 1/6W Si 1 icon Silicon Silicon Silicon

Mfr. Mfr.

Code

01295

01295 01295

01295 01295 01295

12956 01295

01295 01295 01295

. . .

*Selected from Keithley Part No. TG-39, NPN transistor,

58474 DF21BC BP-118 58474 DF21GC BP-11G

DIODES

Desig.

lN645 lN645 lN645

lN645 lN645 lN645 lN645 lN645

18645 lN665 lN645

lN827A lN916 lN914 lN914 lNY14

connected base to emitter

2 2

Keithley Fig. Parr NO.

RF-14 RF-14 RF-14

RF-14 RF-16 RF-14 RF-14 RF-14

RF-14 RF-14

RF-l&

DZ-68 RF-28

RF-28 RF-28 RF-28

26555A*

Ref.

14 14 14

14 14

14 14 14

16 14 14

14 14

14

22

0675

25

MODEL 225

RRPIACFABLE PARTS

MISCELIANEOUS PARTS

Circuit

Desig.

DSlOl

DS201 DS202 OS203

FZOl(117V) FZOl(236V)

P201

_-_

QA201

QA202

TlOl

Description Pilot Light, LIMIT Pilot Light, Decimal

Pilot Light, Decimal Pilot Light, Decimal

Fuse, 3AG slow Blow, 1/4A

Fuse, 3AG slow Slow, 1/8A /1600 Fuse

Holder

Power Cord, 6 feet Strain relief for P201

Integrated Circuit 07263 Linear Integrated Circuit

Modulation Transformer 80164

Mfr.

Code

91802

91802 91802

91802

75915 75915 342012

93656 28520

04713

T201 Power Transformer 80164

Mfr.

Desk. 2100 2140

2140 2160

313.250

MDL

4638-13 SR-SP-1

65R7723393A723C

MCl639G

TR-125 TR-124

Keithley

Part No.

Fig.

Ref. PL-38 2 PL-47 2

PL-47 2 PL-47 2

FU-17 2 FU-20 2 FH-3 2

co-5 2

cc-4 2

IC-14 2

IC-13 2

TR-125 2 TR-124 2

circuit Desig.

Mfr. Mfr.

Code Desig.

80164

04713 9103 07263 Q106 04713 Q105* 80164

Q106 07263 Q107 04713 QlO8 04713 Q109 04713 QllO 04713

Qlll** 80164 Q112 07263 Q113 07263 Q114** 80164 Q115 07263

Q116 07263 Q117 07263 QllSA*** 80164 QllsB*** 80164 Q119 04713

* Specially selected transistor: order singly. ** Matched pair; order as a pair. ***Matched pair with heat sink; order as a pair.

TRANSISTORS

40318 MM3003 2N3565 MM6003 40318

2133638 2N3905 283905 2N3905 2N3905

A-642L

2N3565 2N3565

A-642L 2N3565

2N3638 2N3638 2N5652 2N5452 2N3903

Keithley

Fig.

Part No. Ref.

2456011 TG-58 TG-39 TG-59

26560A TG-33

TG-53 TG-53 TG-53

TG-53 TG-64

TG-39 TG-39

TG-64

TG-39

,TG-33

TG-33

24670~

24671X TG-49

14 14 14 14 16

14 14 14 14 14

0972

26

23

REPlACEABLE PARTS

MODEL 225

RESISTORS

circuit

Oesig. RIO1 12 k*

RI02 3.9 n R103 RI04 100 n RIO5

RlO6 RI07 RI08 R109 RllO

Rlll

R112 402 !-I R113

Value Rating

IO%, l/2 w 10%. l/2 w

18 R

10%, l/2 w 10%, l/2 w

180 n 470 n

3.9 n 27 R

lO%, l/4 w lO%, l/2 w

lO%, l/2 " lO%, l/2 "

Not USed

37.4 k0

l%, l/8 W

402 c-t I%, l/8 W

l%, l/8 W

100 R lO%, l/2 w Rl14 15 kil I%, 1/a w Rl15

~116 RI17 Rl18 Rll9 RI20

R121 R122 R123 R124 R125

5.49 k0

2 k0

50 kn

5.1 kfl

22 k0

10 kR

1 kIl

8.2 k0

390 n

4.7 kfl

l%, l/8 w 20%, 2w

10%. 3w

5%, 3w

10%, l/2 w IO%, l/2 w

20%, 2w lO%, l/2 W

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

Type

camp camp camp camp comp

camp camp

camp MtF MeF

MCF

camp MtF MCF

WWVX WW"ar ww

camp

camp wwvar

camp

Mfr.

Code 01121

01121

01121 01121

01121 01121 01121

07716 07716

07716

01121 07716 07716

71450 12697

44655 01121 01121

71450 01121 01121 01121

01121

Mfr.

Des&.

88 EB EB ER cs

E8 RR EB

CEA CEA

CEA E8 CEA CEA

INS 115 58 200

EB EL3

1NS 115 EB EB ES RR

Keithley Fig.

Part NO. Ref.

Rl-12K 14 RI-3.9 RI-18 Rl-100 R76-180

RI-470 RI-3.9 RI-27

15 15 14 14

14 15

15 R88-37.4K 14 R88-402

R88-402 RI-100

14

14 R88-15K 14 R88-5.49K 14

RP50-2K @.,,~,~'K 14

RP80-50K 14 Rl73-5.lK

14 Rl-22K 14 RI-1OK

14 Rp!&=TKw1'-il: 14

RI-8.2K

14 RI-390 14 Rl-390 14 RI-4.7K

14

R126 R127 RI28 R129 R130

Rl31 R132 R133 R134 RL35

~136 R137 R138 R139 R140

R141 R142 R143 RI44 R145

RI46 R147 RI48

R149 R150

Rl51 RI52

20 kQ 20 kn 20 kR 20 k0

2.2 kR 20 kR

20 kn

49.9 ks-, 20 kQ 20 kR

1%. l/8 w 1%; l/8 w I%, l/8 W I%, l/8 W IO%, l/2 W

l%, l/8 W 1%, l/8 W l%, l/8 W MY3 l%, l/8 W l%, l/8 W MCF 07716

MfF MtF

MtF

camp

MtF MW

MtF

100 kl? l%, l/8 W MtF 499 n 1%, l/8 w ?-RF 500 n

95.3

n

100 n

182 k0 182 kR 10 kn 500 0

49.9 kt?

49.9 kfi 10 kR

40.2 0

40.2 i?

40.2 0

40.2 R

40.2 0

l%, l/2 W

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

l%, 1/a w

l%, l/8 w lo%, l/2 w 20%, 314 w

l%, 1/a w I%, l/8 w

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

l%, l/2 " l%, l/2 W

l%, l/2 w I%, l/Z w

"ar 71450

MtF MtF

Camp cermee 73138

MtF MfF

COUIP MCF MfF MeF

MtF me

07716 07716 07716

07716 01121

07716 07716 07716 07716

07716 07716

07716

01121 07716

07716

01121

07716 07716

01121 07716 07716 07716

07716 07716

CEA

CEA CEA CEA EE

CEA CEA CEA cl?* CEA

CEA CEA

GC-T450 CRC ES

CEA CEA E8

77PR500 CEA

a.4 ES CEC CRC CEC

CRC CEC

R88-20K 14

R88-20K 14 R88-20K 14 R88-20K 14

Rl-2.2K R88-20K

14

14 R88-20K 14 R88-49.9K 14

R88-20K

14 R88-20K 14

R88-LOOK 14 R88-499 RP91-500

R94-95.3 13

RI-1OOK R88-182K

R88-182K Rl-LOK

14

15

14

RP64-500PP.!1?~." 14 R88-49.9K

14

R88-49.9K 14 RL-1OK R94-40.2

R94-40.2

14 13 13

R94-40.2 13 R94-40.2 13

894-40.2 13

24

0571

27

MODEL 225

REPLACEABLE PART’S

RESISTORS (Conc’d.)

circuit Oesig.

RL53

Rl54 40.2 1 R155 40.2 :

RI56

R157

Rl58

Ri59 Rib0

RI61 RI62 Rl63

RI64

R165 RI66

RI67 RI68

Rib9

Rl70 Kiil

Rii?

RI73

R174

R175

40.2 ?

40.2 :!

40.2 0

40. 2 ‘5 200 2 200 :I

200 ? 200 I 200 ? 200 : 200 1

200 ‘1 200 ,2 200 ? 200 ‘2

1 k-i 1 k,?

1 k.1 1 k’l 1 kl 1 kl

Rating

I%, l/2 w I%, l/2”

I%, l/2 w

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

1%. 112 w l/4%, 1/z W l/4%, 112 W

l/4’/., l/2 w 1/a, l/2 w l/4%,

112 l/4%, l/2 l/4%, L/2

w w w

l/4%, l/2 w

l/4%, l/2

w l/4%. l/2 w l/4%,

1/z

w

O.l%, l/2 w

O.l%, 112 w O.l%, l/2 w

O.l%,

O.l%, l/2 w

l/2 w

TYPe

MtF MtF

l-lee MfF MtF MtF

MtF MtF MtF MtF MfF

MtF MCF MCF MtF MtF

MW MW MtF MW MtF

Mfr. Mfr. Code

07716 07716 07716

07716 07716 07716 07716 07716

07716 07716

07716

07716 91637

91637 91637 91637

91637

oesig.

CEC CEC CEC

CEC CEC R94-40.2 CEC R94-40.2 CEC-TO CRC-TO

CEC-TO CEC-TO CEC-TO CEC-TO CEC-TO

CEC-TO CEC-TO CRC-TO

CEC-TO

MFF MFF R169-IK

MFF MFF MFF Rl69-lK MTF

Keichley

Part NO.

R94-40.2 R94-40.2 R94-40.2

R94-40.2

Rl27-200 R127-200

RL27-200 KL27-200 R127-200 R127-200 Rl27-200

RL27-200 R127-200 R127-200 R127-200

Rl69-1K

R169-1K Rl69-lK

RL69-1K

Fig.

Ref.

13 13

13 13 13

13 13

13

13 13

13 13 13 13

13 13 13 13 13

RI76 KL77 8178

K179

Ri80 11181

K182 Rl83 R184 RI85

RI86 R187 Rl88 R189

Ii190 RI91

RI92 RI93

RI94

Ri95

1 k.! 1 k.3 , k(l 1 k:! 1 k!-l

1 kn

200 2

4.99 kn 10 R 100 2

I k:! 10 k? 100 k? 1 w: 10 M:l

681 3

100 k:! 10 ,)

220 > 220 :?

O.l%, l/2 W O.l%, l/2 W o.l%,

L/2

w

O.l%, l/2 w

l%, l/8 W

20%, 2 w

l%,

l/8

W O.l%, l/4 w O.l%, l/2 w

0.1%. l/2 w O.l%, 1/z W O.l%, l/2 w O.l%, 112 w

114%. 2

w

1%. l/8 W lo%, l/2 w

lO%, l/2 w

lo%, l/2 w

lo%, l/2 W

MtF lee MtF MtF MfF

MtF ww”a r MtF ww

MLF

MtF MtF

MCF

MtF

MCF

91637 91637

91637

9,637

91637

07716

71450 07716

01686 7009

91637

91637 91637

91637 91637 91637

07716 01121

01121 01121 01121

MFF R169-1K MFF Mm R169-1K Mm R169-lK MFF

CEA

INS 115

CEA MTF MFF

MFF MFF MFF MIT-2

CEA EL3

EB EB E8

L3

R169-1K

Rl69-1K

R88-lk

RP50-200RP.iG'+i)o 14 R88-4.99K

R95-10 Rl69-100

R169-1K Rl69-1OK R169-100K Rl69-lM

RL61-1OM R88-681

RI-100K ill-10 RI-220

KL-220

13 13 13 13

14 14

15

15 15 15

15 15

16 16 16 14 14

0774

25

28

REPLACEABLE PARTS

MODEL 225

SWITCHES

circuit

Desig. Description SlOl

---

5102

___

s103 __-

SlO4

_-_

SlO5

--5106

5201 Slide Switch, LINE s202 Toggle Switch, Power 80164

Rotary Switch less components, Range Knob Assembly, Range Switch Rotary Switch less components, first Decade Switch Knob Assembly, first Decade Switch Rotary Switch less components, second Decade Switch

Knob Assembly, second Decade Switch

Rotary Switch less components, third Decade Switch

Knob Assembly, third Decade Switch

Rotary Swifch, DDTPDT SELECTOR Switch

Knob, OUTPUT SELECTOR Switch Toggle Switch, FILTBR

Mfr.

Code 80164 SW-284 80164 80164 SW-282 80164 80164 80164 80164 80164 80164

80164

8016L

Keithley

ear-t No.

23 bti3

2360311 SW-282

23603.4 SW-282 23603A

SW-283

SW-309

SW-151 SW-4

Fig.

Ref.

2 2

26

23

0571

MODEL 225

REPlACEABLE PARTS

POWER SUPPLY, "200 SERIES

CAPACITORS

Circuit Desig. Value

C201 c202 C203 C204

C205 C206 140 p 15ov EMC 56289

C207 C208 C209 c210

C211 c212 C213 c214

C215

C216 c217 .05 p 600"

C218

C219

Not Used

.5 P .OOl !AF

.OOl pF 140 NF

100 &IF 100 p ,001 g 600" ,001 fl

100 pF

4.7 &J 100 PF .02 pF 10 w

10 IrF 150 pF

470 pF 1ooov

Rating Type

_----

400 " 600 " 600 "

150 "

4ov EAL 73445 4ov SAL 73445

600V cero 72982 4ov

zov 600" 600"

2ov 2ov 600~

_--_MY

CerD CWD EMC

CerD 72982

EAL ETT CerD cerD ETT

ET-r 17554 TSDZ-20-106

MY

&k-D tern

Mfr.

Code

13050 72982 72982 56289

73445 17554 72982 72982

17554

56289 72982

71590 DD-471

DIODES

Mfr.

Desig.

-____

SMl.4 ED-.001 ED-.001 Type 630

Type 630 C437ARfGlOO C437ARfGlDO ED-.001 ED-.001

C437ARfGlOO TSDl-20-475 ED-100

ED-.02 TSD2-20-106

6PS-550 ED-150

Keithley

Part No.

-----

Cll7-.5M C22-.OOlM czz-.OOlM 14 Cl83-14OM 14

C183-140M 14 Cl50-1OOM 14 c150-IOOM 14 c22-.OOlM c22- .OOlM 14

Cl50-100M Cl79-4.7M c22-LOOP C22-.02M c179-low

C179-10M C62-.05M C22-150P

C64-470P

Fig. Ref.

-14

14

14 14 14 14 14

14 14 14

0201 0202 0203 0204 D205

D206 0207 0208 D209 D210

0211 D212 Silicon 0213 Silicon 0214 0215

D216 Silicon D217 D218

zener

Rectifier, IA, 800V

uectifier,~ -fit,-8mv

-ReeEGieer,. lA,~-800V Rectifier, 1.4, 800V

Silicon

Silicon Silicon

Mfr. Code

01295 01295

12954 12954 IN709 12954 IN715 DZ-22

12954

~04713

04713

04&&L 04713

01295 01295

01295 01295 01295

Mfr. DesiF,.

lN645 lN645 lN709

lN715

lN4006

-----B14006-IN4006

lN645 lN645 IN645

lN645

lN645 113645 lN645

Keiehley

Part No. Ref. RF-14

RF-14 DZ-21 DZ-21

DZ-22 RF-38

RF-38 RF-38 RF-38

RF-14 RF-14 RF-14 RF-14 RF-14

RF-14 RF-14 RF-14

Fig.

14 14 14 14 14

14 14 14

0777

27

30

REPlACEmLE PARTS

MODEL 225

Circuit

Desig.

Value Rating Type

R201 4.7 kR R202 6.8 kR R203 2

kfi R204 4.7 k0 R205 2.2 k0

R206 R207 RZOS R209 R210

It211 R212 R213 R214 R215

R216 R217 R218 R219 R220

R221 R222 8223 R224 R225

1 k0

kn

2

2.2 kft

56 kfl

10 kfl 10 kfl

47 kfl 56 ktl 47 kC

kn

1

1 kC

Not Used

1.8 kfl

12

6.04 k0

Mfr.

Mfr. Keithley

Fig.

Code llesig. Pare NO. Ref.

lO%, l/2 w

O.l%, l/2 w

lG%, l/2 w

lO%, l/2 w

C0Uip Comp

hw

camp camp

10%. l/2 w

O.l%, l/Z w

lO%, l/2 w

10%, l/2 w

10%. l/2 w lO%, l/2 w

ww’

camp camp C0mp

Come lO%, l/2 " 10%. l/2 w lO%, l/2 w lO%, l/2 w

Comp camp Camp

lO%, l/2 w

10%. l/2 w camp

n

lo%, l/2 w camp l%, l/S w MtF

01121 ES Rl-4.7k 14 01121 EL3 Rl-6.8k 14 54294 SP23DlS

R6L2k RF.'Il-Jx 14 01121 E8 Rl-4.7k 14 01121 EB Rl-2.2k

01121 54294 01121 01121 01121

01121 01121

01121 01121 01121

RI-lk 14

R67;Zk RF- 5-e sr. 14

Rl-2.2k 14 RI-56k 14 Rl-lOk 14

Rl-1Ok 14 Rl-47k 14 Rl-56k 14 Rl-47k 14 Rl-lk 14

I4

01121 E8 RI-lk 14

01121 01121 07716

ES

CEA

Rl-l.Sk

14 Rl-12 14 RES-6.04k 14

kfl

R226 R227 R228 R229 R230 R231 R232

CiTC”if

_

"IZSLR.

1

2.21 kfl kfl

ii kR

10 kfl 120 R 100 kC

Q201 Q202 Q203

Q204 PNP, TO-92 Case

Q205 9206

Q207 QZOS 9209 Q210

20%, 2 w I%, l/S w 1%. l/S w l%, l/8 W lO%, l/2 w lo%, l/2 w

lO%, 1/z w

ww MtF MtP MtF Comp Camp

ComP

71450 07716 07716 07716 01121 01121 01121

TRANSISTORS

Mfr. Code

04713

MOT

04713

02735

04713

02734

lNS115 CR.4 CSA CEA EL3 E8 RR

Desis.

2N3905 MM4003

2N3905

2~5087

2N3905

40346

MM4003

40317

40319

RPSO-lk R~-'17-Iti 14 R88-2.21k 14 RSS-20k

14

RS8-20k 14

Rl-lOk 14 Rl-120 14 Rl-100k 14

Keithley Fig.

Pact No. Ref.

l-G-53 14

TG-59

14

TG-53 14

TG-61 14

TG-49 14 TG-44 14

TG-44 14 TG-59 14 TG-43 14

TG-50 14

28

0675

31

r

0

P

G

1

P

e

I

r

I I

I @)I I I

I Oi

t I

L

.O

/

/n I .& I

1’

0 I

‘7 /

-i

I

I I I I I I I I

-

I I

I I I I

I

I I

I

SERVICE FORM

Model No. Name

Company Address City

List all control settings and describe problem.

Show a block diagram of your measurement system including all instruments connected (whether power is turned on or not). Also describe signal source.

Serial No.

State

P.O. No.

Phone

(Attach additional sheets as necessary.)

Date

Zip

Where is the measurement being performed? (factory, controlled laboraton/, out-of-doors, etc.1 What power line voltage is used?

Frequency?

Variation? OF. Rel. Humidity?

Any additional information. (If special modifications have been made by the user, please describe below.)

*Se sure to include your name and phone number on this service form.

Ambient Temperature?

35

Variation?

OF.

Other?

Keithley 225 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual