Keithley 150B Service manual

INSTRUCTION MANUAL

MODEL 15OB

MICROVOLT AMMETER

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 (except
tubes and batteries) which, within a year after
shipment, proves defective upon examination.
We,will pay domestic surface freight costs.

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

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

ance and shipping instructions.

REPAIRS AND RECALIBRATION

Keithley instruments maintains a complete re-

pair service and standards laboratory in Cleve-

land, and has an authorized field repair facility
in Los Angeles.

To insure prompt repair or recalibration serv-

ice, 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 150B MICROVOLT AMMETER

TABLE OF CONTENTS

TABLE OF

Section

MODEL 150B SPECIFICATIONS. .... .ii 4. MAINTENANCE. . . . . . . . . . . 19

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

l-1.

l-2. As a Microvoltmeter. ..... 1

l-3.

l-4 .. As an Ammeter. ........ 1

2. OPERATION. ............. 3

2-1.
2-2.
2-3.

2-4,.
2-5.

2-6.
2e7.
2-8.
2-9.

2-10.
2-11.
2-12.
2-13.
Z-14,.
2-15.

2-16.

CIRCUIT DESCRIPTION. ., . . . . . . .13

3.

General. ...........

As a Null Detector ...... 1

Mode of Operation. . . . . .

Battery Operation. . . . . .

Microvolt and Null Detector

Operating Procedures . . . .

Ammeter Operating

Procedures . . . . . . . . .

Zero Suppress Operation. . .

Filter Switch. . . . . . . .

Recorder Outputs . . . . . .

Synchronizing Terminals. . .
Differential (Floating)
Measurements . . , . F . . .
Accuracy Consideration . . .

Thermal Noise. . . . . . . .

Input Resistance . . . . . .

Therinal Emf's. . . . . . . .

Shielding. . . . . . . . . .

Operating From Source Other
Than 117 Volts, 60 cps . . .
Accessories For Input

Connections. . . . . . . . .

Page

.3
.3

. 4,
.6

.6
: 7

.7
.8

.8
: 9

. 9
.lO

.ll

.ll

CONTENTS

1
1

7

0

Section

4,-l.
4-2.
4,-3. Mechanical Chopper

4,-4,. Troubleshooting. . . . . . . 20

4-5.
4,-6. Check Out and Calibration
4-7.
4,-a. Amplifier Check Out

ACCESSORIES. . . . . . . . . . . . 35

5.
5-l.
5-2. Model 4007 Dual Rack

5-3.

6. REPLACEABLE PARTS. . . . . . . . . 41

6-l.

6-2. How to Order Parts . . . . . 41

General. . . . . . . . . . . 19

Parts Replacement. . . . . . 19

Replacement. . . . . . . . . 19

Preliminary Troubleshooting

Procedures . . . . . . . . . 20

Procedures . . . . . . . . . 20

Power Supply Check Out

and Calibration. . . . . . . 22

and Calibration. . . . . . . 25

Model 4,006 Rack

Mounting.Kit . . . . . . . . 37

Mounting Kit . . . . . . . . 37

Model 370 Recorder . . . . . 39

Replaceable Parts List . , . 41
Model 150B Replaceable

Parts List . . . . . . . . . 42

Models 14,83, 14.84
Replaceable Parts List . . . 50

Schematic Diagram 20350E . . 53

Schematic Diagram 20357D . . 55

Page

3-1. General. . . . .

3-2.
3-3.
3-4..
3-5.
3-6.
3-7.
3-8.

0667R

Input Circuit. .

AC Amplifier . . .....

Demodulator. . . ... * ..

DC Amplifier . .

Zero Suppression .....

Power Supplies . .....

Battery Charging

, ......

.......

......

Circuit .. .17

13
13

. .14.

.15

.15
. .15
. .15

* Change Notice Last page

* Yellow Change Notice sheet is included

only for instrument modFfications affect-

ing the Instrument Manual.

i

GENERAL DESCRIPTION

MODEL 150B MICROVOLT AMMETER

TABLE 1.

Model 1SOB Specifications.

AS A VOLTMETER AND NULL DETECTOR:

RANGE: 0.3 microvolt (3 x 10-’ volt) full scale to 1 volt on a

Zero-centw meter. 14 overlapping ranges in Ix and 3x
steps.

ACCURACY:

Meter:

*2g Of full scale on all ranges.

I-Volt Output Terminals: *I%.

100.Millivolt Output Terminals: Adjustable to ~1%.
Note: Accuracy specifications excluie noise and drift.

ZERO DRIFT: Less than 0.1 microvolt per 24 hours after I-

hour warmup with reasonably constant ambient tempera.
ture. Long-term d!ift is ncwcumulatlve.

INPUT NOISE: ‘With input shorted, less than 5 nanovolts

rms (25 nanovolts peak-to-peak) on the most sensitive
range.
With a 10,000.ohm source resistance. lessthan 14 nanovolts
rms (70 nanovalts peak-to-peak) on the most sensitive
range.

INPUT RESISTANCE:

Range

0.3 IN 1M
1 P”

3,

10 pv 30 M
30 IN 100 M

100 #v and above 100 M

Note: ‘Source resistances higher than the recommended

maximum will increase noise and rise time.

ZERO SHIFf WITH SOURCE RESISTANCE: Less than

volt

per ohm.

LINE FREQUENCY RUECTION’: A voltage of power line

frequency which is 75 db (p.p/dc) greater than full scale
affects reading less than 2% on the most sensitive range
(decreasing to 60 db on the 10.microvolt range and to 20
db on the l-volt range).

COMMON MODE RLIECTIDN*: Greater than

frequencv or dc.

RISE TIME (10% to 90?&)? Using up to 1wO ohms source

reSistanCe, less than 0.5 second on the 30.mlcravolt and
higher ranges. increasing to 3 seconds on the 0.3.microvolt
range.

Using maximum source resistence up to 100 kllohms, rise

times increase to approximately 3 seconds on the 30.

microvolt and higher ranges. 6 seconds on the lo-microvolt

and lower ranges.

ZERO SUPPRESSION: Up to 10 millivolts available. Stability

is such.that

‘Note: All specifications are measured with filter in. With

filter out. rise times forany source resistance up to maxi.
mum are less than 0.5 second on the 30.microvolt and
higher ranges. increasing to 3 seconds on the 0.3.microvolt
range. With filter out, the rejection ratios are reduced
about 30 db.

Input Resistance Maximum Source*

Greater than,

ohms

3M

10

M

100

times full scale may be suppressed.

Resistance,

Ohms

10 k

30 k
100 k
300 k

1M
IM

180

db at line

1o-‘o

AS AN AMMETER:

RANGE: 3 x lOLo ampere full scale to

center meter. 14 overlapping ranges In lx and 3x steps.

ACCURACY:

Meter: a3% Of full Scale on ali ranges.

I-Volt Output Terminals: *2%.

100.Mllllvolt Output Terminals: Adjustable to +2q6.
Note: Accuracy specifications exclude noise and drift.

ZERO DRIFT A2

werm.up.

INPUT NOBE: Less than 3 x 10’12 ampere peak.to-peak on

the most sensitive ran,~e,

INPUT VOLTAGE DROP: 100 microvolts on the nsnoampere

renges, 1 millivolt on the microampere ranges..

INPUT RESISTANCE: On the microampere ranges. the input

resistance is equal to lo” divided by the range in
On the nanoampere ranges, it is equal to
the range in

x lo’”

amperes~

ampere per 24 hours after

1W3

empere on zero.

lo”

divided by

l.hour

amperes.

GENERAL:

ISOLATION: Circuit ground ,to chassis ground: Greater than

1O’O ohms shunted by 0.001 microfarad. Circuit ground
may be floated up to ~400 volts with respect to chassis
ground. On battery operation. may be completely isolated
from power line end ground.

RECORDER OUTPUT (1 volt):

Output: ztl Volt dc et up to 1 milliampere for full-scale
meter deflection on eny range.

Resistance: Less than 5 ohms within the amolifiar oass
band. band.

Noise: Input noise times gain plus modulation products. Noise: Input noise times gain plus modulation products.
Modulation Products: Less than 4% peak.to-peak of full Modulation Products: Less than 4% peak.to-peak of full
Scale with input shorted. Scale with input shorted.

RECORDER OUTPUT

Output: ztlO0 mv adj;stabi;&er a
meter deflection on eny range.
Output Rsslstancs: Less than 1000 ohms.

Noise: Input noise times gain plus modulation products.
Modulation Products: Less than ‘/z% peak.to.peak of full

scale with input shorted.
Using this output, response time is at least one second on

any IB”B.3.

CONNECTORS: Input: Special Kelthley Model 1485. Output:

Amphenol BOPCZF Receptacle.

POWER:

Line Dperatlon: 105125 volts or 210.250 volts, 60 ops. 25
watts. 50.cps mode18 available.

Battery Operation: Rechargeable nickel-cadmium &volt

battery pack. Ov?r 7 hours continuous operation from full
charge: recharges in less than
ing circuit.

DIMENSIONS. WEIGH(T: 7 inches high x 8% inches wide x

10

inches deep; net weight, 16 pounds.

ACCESSORIES SUPPLIED: Model

Cable (4 feet, low-thermal triaxial cable, alligator clips).
Mating output connector. Length of lowthermal solder.

Internally mounted nickel.cadmium battery pack. Model

1499.

1100

1100

mv): RECORDER OUTPUT

mv):

10%

spa” for full-scale

16

hours from built.in charg.

1506

Low.Therma, Input

ii

0267R

MODEL 150B MICROVOLT AMMETER

GENERAL DESCRIPTION

SECTION 1.

l-l.

instrument which measures voltages from 0.3 microvolt to 1 volt and currents from 0.3
nanoampere
with either battery or line power operation.

l-2.

thermopile and thermocouple potentials, Hall effect, contact resistances, biologically
generated emf's, electrochemical potentials and strain guages emf's.

sistance and loti zero shift; excellent zero stability;
and common mode rejection; battery operation; zero suppression;
circuitry;

ment accuracy even from high resistance sources; is ideal for long-term measurements; de-

tects dc signals in the presence of large ac voltages and is virtually insensitive to nc
or dc voltages applied between circuit and chassis ground;

for improved isolation; measures small changes in dc signals: reduces temperature and shield­ing problems; provides outputs where either filtering is needed or fast response or greater

output power is needed.

GENERAL.

AS A MICROVOLTMETER.

a. The Model 150B is ideal as a microvoltmeter for measuring semiconductor resistivity,

b. The Model 15OB has input noise less than 25 na,novolts peak-to-peak; high input re-

c. With these features, the Model 150B permits excellent resolution; maintains measure-

The Keithley Model 150B Microvolt Ammeter is an extremely sensitive

to

1 milliampere. It can be used as a voltmeter, null detector or an ammeter

two available outputs.

GENERAL DESCRIPTION

very high line-frequency rejection

special low-thermal input

disconnects from power lines

l-3. AS A NULL DETECTOR.

As a null detector the Model 15OB is excellent for use in ratio measurements and in

a.

potentiometer and bridge circuits.

b. The Microvolt Ammeter's outstanding features as a null detector are:
solution; high line frequency and cormnon mode rejection; isolation from chassis ground to
input terminals; battery operation; high input resistance; floating capability; low zero
shift;

C.
usable resolution of most potentiometers and bridges; may be simply connected to the ter­minals of a null circuit; is very insensitive to commnn mode voltages developed in the
null circuit; can be used in most potentiometer and bridge circuits without off-null load-

ing; accurately detects a null regardless of the setting on most potentiometers and bridges;
compensates for thermal emf's generated in the null circuit.

1-4. AS AN AMMETER.

It is useful for making low voltage drop,
output of radiation detectors,

.._

b.

low zero drift for measuring long-term current; excellent floating capabilities for measur­ing ungrounded sources;

zercl suppression.

Because

a. The Model 150B has general use in research,

The instrument has low voltage drop for measuring currents in very low-voltage circuits;

of these features the Model 150B has resolution comparable to the maximum

design and production test facilities.

in-circuit measurements as well as measuring the

phototubes and other current generating transducers.

and low input noise,giving excellent resolution.

very good re-

'.

0667R

1

OPERATION MODEL 150B MICROVOLT AMMETER

Control
JEER SUPPLY Switch
4NGE Swi.tch

UNCTION Switch

ERO SUPPRESS Controls Determines the amount of zero suppression
LLTER Switch Connects or disconnects a lfne frequency filter

gPLIT Receptacle Connection for input cable 2-16

TABLE 2.

indicates the paragraph which contains instructions on the use of the control.

Model 150B Front Panel Controls.

Control

Controls mode of operation for power supply
Se.lects the full scale voltage or current which

is to be measured

Determines whether the Model 150B measures voltage or 2-3,2-

current;

at the input

Functional Description

selects input resistance on voltage ranges.

The table briefely describes each control, and

Functional Descriotion Par.

Par.

2-1,2-

2-3,2-

2-5
2-6

LINE VOLTAGE Switch
BATTERY FUSE
Line Fuse

Power Cord

1V OUTPUT Receptacle

1OOMV OUTPUT Receptacle

1OOMV ADJUST
GND Terminal
LO Terminal

SYNCHRONIZING Jacks

Sets Model 150B for 117 or 234-volt ac power line

Quick-Acting, .3/4 amp 3AG or MDL fuse

117-volt: Slow-Blow l/4 amp 3AG or MDL fuse

234-volt: Slow-Blow l/8 amp 3AG or MDL fuse
Provides ground connection for cabinet; 3-wire power

cord with NEMA approved 3-pronged plug

Power output; provides ?l volt at up to one.milliampere

for a full-scale meter deflection.
Recorder output; provides >OOmv, adjustable within

1Omv span, for full-scale meter deflection. Filtered.

Adjusts 1OOMV OUTPUT within 1Omv span

Connection to chassis ground
Connection to circuit low; circuit low will not

be at chassis ground unless LO is linked to GND

Eliminates any interaction between two ad~jacent

Fast response.

2-16

__

--

--

2-7

2-7

2-7
2-3,2-9,2-14
2-3,2-9,2-14

2-8

TABLE 3.

indicates the paragraph which contains instructions on the use of the control.

2

Model 150B Rear Panel Controls.

The table briefly describes each control, and

0567K

MODEL 150B MICROVOLT AMMETER

OPERATION

SECTION 2.

2-l.

and the red dot cannot be seen through the switch knob.

in the AC position, or from its battery with the Switch in BATTERY position.
sition the red dot can be seen.

battery operation, however, if the ac power line will create ground loop or isolation prob-

lems.

is'disconnected; it is greater than 101" ohms shunted by .OOl microfarad with the power
cord connected.
8 cps) which may appear at the output for certain low-level measurements. (See paragraph

2-14,.)

2-2.

MODE OF OPERATION,

a. When the POWER SUPPLY Switch is in the OFF position, the Model 150B will

b. The Model 150B operates either from an ac power line when the POWER SUPPLY Switch is

For most uses the instrument functions well from ac. use

Isolation from low to ground is complete for battery operation when the power cord

Also, battery operation is useful to reduce modulation products (usually

Before using the battery operation,
battery operation can damage the battery pack and lead to inaccurate measurements.

BATTERY OPERATION.

thoroughly read paragraph 2-2.

OPERATION

not operate,

In either po-

NOTE

Improper

The Model 150B is supplied with a rechargeable 6-volt,

battery pack. Do not use the battery more than seven consncutive hours without recharging.

4, ampere-hour nickel-cadmium

,FIGURE 1.

Circuit designations refer to Replaceable
Parts List and schematic diagram.

0667R

Model 150B Front Panel Controls.

FIGURE 2.
Circuit designations refer to Replaceable
Parts List and schematic diagram.

Model 150B Rear Panel Controls.

3

OPERATION

..~

-.,

-.

MODEL 150B MICROVOLT AMMETER

NOTE

Permanent damage to the battery pack may occur if it is used for
secutive hours witbout recharging.

gycles is greatly reduced.

Before using the Model 150B, check the state of the

At this discharge rate, the number of recharge

more

than 8 con-

battery charge.

Check the battery charge before making a measurement. Hold the POWER SUPPLY Switch

b.
in the BATT. TEST position; the red dot will show.
the state of the battery charge directly on the meter.

In this position the Model 150B shows

The minimum acceptable charge is

a meter indication of approximately +6 on the upper meter scale.

Tine terminal voltage of a nickel-cadmium battery changes very little from full

1.

charge to almost crmplete discharge.

minal voltage will vary a few minor divisions for different batteries.

The +6 meter indication for minimum charged ter-

After a few

charge-discharge cycles, the exact value of the charged terminal voltage for any in-

dividual battery wil.1 be apparent.

Recharge the battery if needed.

2.

Otherwise, battery operation is the same as for

the ac power line operating mode; refer to paragraph 2-3.

NOTE

When the battery is used beyond its capacity, two effects are seen.

a large shift in zero offset from ac to battery operation.

Also,

There is

the power

supplies do not regulate and high ripple voltages appear at the supply outputs.

C. To recharge the battery,

SUPPLY Switch t,o AC or OFF.

connect the power cord to an ac power line.

The battery will be automatically charged in either of these

Turn the POWER

positions. The charging circuit is such that the battery cannot be overcharged.

d. It is suggested that the battery be used during the day and be recharge& at night.
Leave the instrument always connected to the ac power line; then turn the POWER SUPPLY
Switch to OFF at night.

After a fully charged

it will recharge within 16 hours.

Leaving the power cord connected has little effect on

battery is used icor

the isolation: loLo ohms with the low-ground link disconnected.
longer than eight hours,

2-3.

MICROVOLT AND NULL DETECTOR OPERATING PROCEDURES.

it may take considerably longer than 16 hours to recharge.

_ .

seven

ConseCutiVe Hours,

If the battery is used

a. Set the front panel 'controls as follows:

POWER SUPPLY Switch
RANGE Switch

FUNCTION Switch

OFF

1oooMV

INPUT R lOOK

ZERO SUPPRESS COARSE Control OFF

FILTER Switch

-IN

NOTE

Make sure rha ZERO SUPPRESS COARSE Control is OFF.

voltage is introduced,

which may cause an error in measurements.

If it is not, a suppression

See paragraph

2-5 for zero suppression.

.-

-

4

0667R

MODEL 150B MICROVOLT AElMETER

b. Check the voltage shown on the rear panel LINE VOLTAGE Switch; connect the Model

150B to the ac power line. The battery will now be charging.

If the circuit low is to be at ground, put the low-ground link between the LO and GND

c.

terminals on the rear panel. The ground terminal (GND) is connected to the chassis and the

third wire of the power cord. The low terminal (LO) is connected to circuit ground and the

low side of the INPUT Connector.

OPERATION

d. Turn the POWER SUPPLY~Switch to the desired mode of operation, AC or BATTERY.

moat stable operation, allow the Model 150B to warm up for 1 hour.

Connect the unknown voltage to the INPUT Receptacle using a Model 1506 or 1507 Low-

e.

Thermal Input Cable.

f. Set the FUNCTION Switch to INPUT R OPEN if high input resistance is desired.

position the Model 150B input resistance varies bv range (See Table 4,). If the input is

left completely open circuit,

onds.

ings as the input circuit is opened.

age with 100 kilohms shunting the INPUT Terminals.

g.

shows the greatest on-scale deflection.

specified for the range being used. (See Table 4). If the maximum is exceeded, the

Model 150B may not perform within its specifications.

circuit's thermal construction.
to the Model 15OB INPUT Receptacle, offset should be less than 0.5 microvolt.

Set the FUNCTION Switch to INPUT R 1OOK if it is desired to maintain on-scale read-

Increase the sensitivity of the Model 150B with the RANGE Switch until the meter

Check the source resistance to make sure'that it is within the maximum value

1.

Zero offsets with the ZERO SUPPRESS Controls off will vary with the quality of the

2.

(See paragraph 2-16)

the meter mav drift off scale on any range within a few sec-

In this position the Microvolt Ammeter measures volt-

When a Model 1488 Low-Thermal Shorting Plug is connected

For

In this

-~

Input Resistance

Range

0.3 microvolt
1 microvolt

3 microvolts
10 microvolts
30 microvolts

100 microvolts
300 microvolt8

1 millivolt

I

through 100 MR

TABLE 4.

quency Rejection by Range.
frequency (50 or 60 cps) voltage at input to the indicated dc voltage. The above line
frequency rejections are reduced about 30 db on all ranges with the filter out.

0667R

Model 150B Input Resistance, Maximum Source Resistance, and Minimum Line Fre-

Greater Than Resistance Rejection

1 Ma 10 kQ 55OO:l

3 Ma 30 kR ---

10 MQ 100 kR --­30 Ma 300 kR 1OOO:l

00 MO 1 Ma ---

1

00 MR 1 MR ---

1

00 MO 1 MR ---

1

The rejection is the ratio of impressed peak-to-peak line

Maximum Source

1 MR

Minimum

Line Frequency

3O:l

5

-

OPERATION

__;

I

Shifts in source resistance may also affect the zero offset, if the source resis-

3.

tance approaches the maximum value given in Table 4.

source resistances less than 10% of the maximum value.

MODEL 150B MICROVOLT AMMETER

This effect is negligible for

h. At low levels,

leads and the circuit under test.

spurious emf's may be generated simply by conta.ct between the input

These may be compensated for by the zero suppression

circuit. If possible, always leave the instrument connected, Andy adjust the zero after

estabLishing a zero reference in the apparatus under test.

For example, in bridge measure-

ments, disconnect the bridge, exciting voltage, or with a phototube, shield the tube from,

light.

2-4.

AMMETER OPERATING PROCEDURES.

the range using the RANGE Switch.

Set the FUNCTION Switch to the AMPS position.

Make sure low resistance leads are used to connect the
source to the Model 150B input to minimize input voltage drop.
rent overload on any range is 100 mii'liamperes.

put voltage drop is exceeded (see specifications),

If this is exceeded,

the current-sensing resistor may be dam-

The maximum allowable cur-

or if the maximum in-

Select

aged. The Model 150B rise time (10% to 90%) as an ammeter is less than 1 second on the 3­nanoampere and higher ranges, increasing to 3 seconds on the 0.3-nanoampere range.

2-5.

ZERO SUPPRESS OPERATION.

a. Purpose:

The zero suppression circuit cancels any constant voltage in order to use

a more sensitive range to observe a superimposed signal. Stability is such that up to

100 times full scale may be suppressed. For example,

the Model 150B can measure changes

of less than one microvolt in a lOO-microvolt steady signal on its l-microvolt range.

b. Suppression Voltages Available:

one of four maximum values. (Refer to Table 5).

The COARSE Control sets the suppression voltage to

The FINE Control continuously adjusts the

voltage between the positive and negative value of COARSE Control setting. For example, if

the COARSE Control is at 3 for a maximum suppression voltage of l 1.2 mv, the FINE Control

adjustment span is from -1.2 mv to +1.2 mv.

Operation:

~C.

Maximum

ZERO SUPPRESS COARSE Suppression

1.

Keep the COARSE Control in OFF

position.

Adjust the RANGE Switch to
the range that gives the closest to a
full scale meter deflection.

Control Setting Voltage

1

2

.*3.6 microvolts

*120 microvolts

3 t1.2 millivolts

2.

Completely turn the FINE Control

4.

*12 millivolts

in the direction opposite to the meter

deflection (counterclockwise for posi­tive deflections and clockwise for neg­ative deflections).

TABLE 5.
Settings. The zero suppression voltage
shown is the maximum value, *15%, for each

Suppression Voltage by Control

COARSE Control setting. The Level of sup-

3.

Increase the COARSE Control set-

ting until the meter needle passes

pression voltage for each setting is the
same on every voltage range.

through sero. Adjust the FINE Control

for zero deflection.

..,

-,

I

-

4.

Set the RANGE Switch to a more sensitive range,
than the original range (four RANGE Switch positions).
zero, if necessary.

6

up to 100 times more sensitive

Readjust the FINE Control to

-J

0667R _;

MODEL 150B MICROVOLT AMMETER

OPERATION

2-6.

FILTER SWITCH.
The input filter is adjusted at the factory for 60 cps line frequency, unless 50 cps

a.

is indicated on the rear panel of the Model 150B.

b. When the FILTER Switch is at the IN position, a line frequency (Twin-Tee) filter is

used at the INPUT. With the Switch at the IN position a higher level (about 3~0 db) of 60

cps

can be tolerated at the INPUT without affecting the accuracy or the sensitivity of the

Model 150B.

Nomally ,

it is best to leave the FILTER Switch at the IN position for all

cases except where the source resistance exceeds 300 kilohms.

c. The filter has a 5-microfarad capacitor.

capacitor is in use and produces an RC time constant.

ohms or greater,

the rise time of the Model 150B is affected by the RC time constant and

When the FILTER Switch is set to IN, this

For a source resistance of 300 kil-

increases above that given in the specifications.

With the Switch set to OUT, the capacitor is not in use.

d.

If rise time is important,

set the FILTER Switch to~the OUT position for source resistances greater than 300 kilohms.

HOWeVer, with the filter out, the line frequency rejection is reduced 30 db on all ranges.

2-7. RECORDER OUTPUTS.

The Model 150B has two'recorder outputs; fl volt at up to 1 mil-

liampere and a filtered *lOO millivolts.

The *l volt, 1 milliampere output is accurate to i-l% of full scale. Output resis-

a.
tance is less than 5 ohms within the amplifier pass band.
eithef battery or ac operation.

I'f the Model 150B is used for differential measurements,

This output may be used during

do not ground the recorder connected to the output.

When recording with the 1 volt 1 milliampere output, the Keithley Model 370 Recorder

1.

offers complete compatability with the Model 150B.

This output is sufficient to drive

the Model 370 without the use of any recorder preamplifiers. The Model 370 allows maxi-

mum capability of the Model 150B.

to 1500 volts off ground.

Using the Model 370 with the Model 150B avoids interface

It has 1% linearity, 10 chart speeds and can float up

problems which may be encountered between a measuring instrument and a recorder.

The Model 370 is very easy to use with the Model 150B.

2.

All that is necessary is
connecting the two units and adjusting an easily accessible control for full-scale re­corder deflection.
on the Model 150B.

an 8 cps beat may appear..

The furnished Model 3701 Input Cable mates with the output connector
On the most sensitive ranges of the Model 150B, under some conditions,

This condition can be eliminated by mounting a lOO-microfarad

capacitor across pins 14. and 17 in the back of the Model 370 Recorder.

The other recorder output is ilO0 millivolts.

b.

with servo balance recorders.

The 1OOMV ADJUST, which is a screwdriver adjust potentiom-

eter on the rear panel of the Model 150B,

millivolt span.

The resistance of this recorder output is less than 1000 ohms.

is used to adjust the 1OOMV output over a lo-

This output can be used in conjunction

The 1OOMV

output Receptacle is filtered to provide less than l/2% peak-to-peak ac voltages in the

output signal.

may be used during either ac or battery operation.

The rise time will be no less than 1 second on any range. This output

If the Model 150B is used for differ-

ential measurements, do not ground the recorder connected to the output.
2-8. SYNCHRONIZING TERMINALS.

When two or more Model 150Bs are close together,

due to the slight difference in their chopper frequencies.

All Model 150Bs have nearly the same chopper frequency.

a beat may develop between the instruments

To eliminate this interaction,

0667R

7

OPERATION

/

I

MODEL 150B MICROVOLT AMMETER

7

.,

use the two synchronizing terminals on the rear panel of the instrument.
synchronize the chopper, frequencies.

No polarity is necessary; just connect leads from the

These terminals ~'

terminals of one Model 150B to the same terminals on an adjacent Model 150B.
2-9. DIFFERENTIAI. (FLOATING) MEASUREMENTS.

a. The Model 150B will measure the difference between two voltages, neither~ of which is

at power line ground.

It can be floated up to *400 volts off ground.

CAUTION

The instantaneous voltage between circuit low and case ground must not exceed *400
volts at any time.

If the power cord is unplugged,

case may be at any voltage.

For best results in making differential measurements, follow the steps below:

b.

The front panel controls are electrically conne,cted to the case.

and the off-ground voltage exce'eds *400 volts, the

Use necessary safety precautions.

-

1. Remove the link from the LO terminal on the rear panel.
Connect the source to the input.

2.

Make ,measurements as described in- paragraph 2-3.

The zero suppress controls may be used for differential measurements.

If power line frequency pickup is a problem, use battery operation.

3.

-

When recording from the Model 150B with the LO to GND link removed, be sure to

4.

-use a recorder which also has LO isolated from GND by a high imp&dance, and is also
capable of withstanding the necessary voltage with respect to ground.

The Keithley

Model 370 Recorder meets these requirements.

Z-10.

ACCURACY CONSIDERATIONS.

other considerations besides the instrument affect accuracy.

working with higher voltages are very important with microvolt signals.

For sensitive measurements - 10 millivolts and below -

Effects not noticeable when

The Model 150B

reads only the signal received at its input; therefore, it is important that this signal

be properly transmitted from the source. The following paragraphs indicate factors which

affect accuracy:

thermal noise,

input resistance, thermal emf's, shielding and circuit

connections.
2-11. THEIU@L NOISE.

a. The lower limit in measuring small potentials occurs when the Johnson noise, or
thermal agitation, becomes evident. The amount of noise present in the source is shown
in the following equations.

Thermal noise in any ideal resistance can be determined from the Johnson

1.

noise equation:

E2

rms

- 4kTRF Equation 1

where E,, is the rms noise voltage developed across the voltage source;

T is the temperature in degrees Kelvin;
R is the source resistance in ohms;
F is the amplifier bandwidth in cps;

k is the Boltzmann constant (1.38 x 10mz3 joules/OK).

8

0667R

MODEL 150B MICROVOLT AMMETER OPERATION

For an ideal resistance at room temperature (300°K), equation 1 simplifies to

Erms

2. Peak-to-peak meter indications are of more interest than the rms value.

mentally, the peak-to-peak Johnson noise is about five times the rms value.

temperature, equation 2 becomes

EPP

where Epp is peak-to-peak noise voltage developed across the voltage source.

3. The Model 150B bandwidth, F, can be estimated from the response speed, tr, by:
F = 0.35/t, Equation 4

The response speed varies with the range used and the source resistance. On the l-

microvolt range when the source resistance is less than 33 kilohms, for example, the

bandwidth is greater than .07 cps.
ation is 6 seconds, so the .07-cps bandwidth is a minimum value.

b. In general,

tars, and equations 2 and 3 are nearly correct. If the source resistance is composed of

other materials, it may be necessary to include other terms in the equations to account

for flicker, l/f, and current noise over and above the thermal noise.

c. As seen in equations 2 and 3, the noise of even low resistance values becomes signi­ficant in the microvolt region. The noise in non-ideal resistors is even greater. There­fore, keep the source resistance as low as possible. Other effects of very high source

resistance are decreased response speed and added pickup of extraneous voltages.

good wirewound or low-noise metal-film resistors approximate ideal resis-

= 1.29 x 10-l' (R F)1/2

= 6.4,s x 10-l' (R F)l/2

The maximum specified response speed for this situ-

Equation 2

Experi-

At room

Equation 3

Z-12.
obtained using high feedback factors. When the source resistance exceeds the amplifier's
physical input resistance - amplifier input resistance without feedback - the feedback

is partially destroyed.
exceed the maximum source resistance listed in Table 4,.
but noise, offsets, slow response and instability may result. On the most sensitive ranges,

the maximum specified source resistance is consistent with Johnson noise considerations.
2-13.

a. Thermal emf's (thermo-electric potentials) are generated by thermal gradients be-

tween any two junctions of dissimilar metals. These can be large compared to the signals

which the Model 150B can measure.

b.

Model 150B can have some offset (paragraph 2-3).

touching the circuit, by putting a heat source near the circuit, or by a regular pattern
of instability,

INPUT RESISTANCE.

THERMAL EMF'S.

Thermal emf's can cause the following problems:

Meter instability or zero offset much higher than expected.

1.

Meter is very sensitive to ambient temperature differences.

2.
corresponding to heating and air conditioning systems or changes in sun-

light.

The Model 150B is a feedback amplifier; its input resistance is

Then the instrument may not operate properly. Normally, do not

Higher resistances can be used,

Note, though, the

This is seen by

9

OPERATION

To minimize the drift caused by thermal emf's, use the same metal or metals having

C.

MODEL 150B MICROVOLT AMMETER

the same thermo-electric powers in the input circuit. Gold, silver and low-thermal solder

have a thermo-electric power within about to.25 pv/“C of copper. This means a temperature

inbalance of l°C between these metals would generate a thermal,emf of about 0.25 microvolt.
At the other extreme, germanium has a thermoelectric power of about 320 nv/oC, and silicon
will develop about 420 nvv/'C against copper. Standard physical handbooks contain tables

of thermoelectric powers of materials. Since the Model 150B input circuit is made of pure

copper, the best junction is copper to copper. However, copper oxide in the junction will

cause thermal emf's on the order of 100 nanovolts per oC or less. Also, differences in
processing of two pieces of copper can cause thermal emf's of up to 0.2 microvolt per "C.
The Model 1483 Kit contains all necessary equipment to make very low thermal copper crimp

joints.

d.
temperatures.
lar sources which vary temperature.

See paragraph 2-16.

Besides using similar metals, thermal emf's can be reduced by maintaining constant

Keep all circuits from open windows, fans,

air conditioning vents and simi-

Minimize thermal gradients by placing all junctions
physically close on a large heat sink. Thoroughly c,lean all copper leads before making a
connection.

Crimp together the ends of each copper wire; bolt the lugs for each connectior
point together; mount all stacks of lugs on a thick metal plate having high thermal conduc­tivity. Thermal conductivity between the junctions and the heat sink can be kept at a high

level by using mica washers or high conductivity ceramics for electrical insulation.

e. Several other techniques will reduce the effects of thermal emf's. Use the zero sup­pression circuit to buckout constant voltages.
cadmium-tin low-thermal solder, such as supplied in the Model

If connections must be soldered, use only

1483 Kit.

If cadmium solder

is used for connections, make sure the soldering iron used is clean and that it has not

been used with regular solder before. Use only Rosin solder flux.

all cadmium,-soldered joints together to reduce thermal emf's.

Unlike metals - including

If possible, heat sink

regular solder - may be used and low thermal emf's obtained if a well-controlled oil bath

or a good heat sink is used.

Thermal voltages may be calculated from the thermoelectric
power of the materials in the junction and the possible temperature difference between the
junctions.

2-14.

a. Due to its narrow bandwidth and filtering,

voltages superimposed upon a dc signal at the input terminals.

SHIELDING.

the Model 150B is quite insensitive to ac

However,

ac voltages which
are large compared with the dc signal - thousands of times greater on the more sensitive
ranges - may drive the Model 150B ac amplifier into saturation, increasing the noise and
erroneously producing a dc output at the demodulator. Therefore,

the circuit should be

shielded and the shield connected to the Microvolt Ammeter ground, particularly for low-

level sources.

Improper shielding can cause the Model 150B to react in one or more of the following

b.

ways:

Needle jitter or instability,

1.

from 10% to 20% of full scale.

2. High offset (dc bias). Changing the power cord polarity or the connection between

the LO and GND terminals may affect the amount of offset.

3. Slow response time, sluggish action and/or inconsistent readings between ranges.

c. To minimize pickup, keep the voltage source and the Microvolt Ammeter away from

strong ac magnetic sources.

Connect all shields together at the low side of the input or

10

0467R

MODEL 150B MICROVOLT AMMETER

OPERATION

at the LO terminal.
of the loop.

Therefore, minimize loop areas in the shield connections as well as the in-

The voltage induced due to magnetic flux is proportional to the area

put circuitry. Connect the shield at only one point. Run all wires in the circuit along

the same path,

so the loop area is only the small difference in position of two adjacent

wires.

Strong third harmonic magnetic fields - 180 cps for 60-cps units - may create an

d.

8-cps beat at the Microvolt Ammeter output and meter. To reduce this effect, turn off all

possible nearby sources, such as heavy-duty transformers. Remove the Model 150B and the

measuring circuit as far as possible from the magnetic field. If removal does not greatly

reduce the beat, magnetic as well as electrostatic shielding around the circuit may be
necessary. The ratio of the 8-cps amplitude to the dc output level may be reduced by

nearly 1 decade using the 1OOmv filtered output.

2-15.

OPERATING FROM SOURCE OTHER THAh' 117 VOLTS, 60 CPS.

If the ac power source is 234 volts, use a screwdriver to change the Line Voltage

a.

Switch on the back panel, Change the fuse from l/8 ampere to l/16 ampere. Use only 250-

volt MDL fuses. No other adjustment is necessary.

The Model 150B can operate satisfactorily from 60 or 50-cps sources, but the best ac

b.

reiection is achieved when the filteris set for the line freauencv.

For 50-CDS ac Dower

sources, change the two resistors in the input filter R14~7 and R14~8 (Figure 18). use

Keithley part Rl32-1273 (R147 and R14,8)

for 50 cps. Some units are, per special
order, modified at the factory for 50-cps ac
power sources. The filter in these cases is
adjusted for SO-cps,

and this fact is indi-

cated on the re.ar panel of the Model 150B.
2-16.

ACCESSORIES FOR INPUT CONNECTIONS.

The easiest way to connect the volt-

a.

age source to the Model 150B input is with

the Model 1506 Input Cable supplied with

the instrument.

ary setups, for measurements at several
points, and when fast connections are needed.

Use the Cable for tempor-

FIGURE 3.
Cable.

Model 1506 Low-Thermal Input

The Model.1506, which has alligator clips,

connects directly to the INPUT Receptacle.

Where more permanent setups are needed,

b.

use the Model 1507 Input Cable. It is

similar to the Model 1506, except it has spade lugs instead of alligator clips.

Use crimp connections with copper wire and lugs for the best low-thermal joints.

C.

The Model 14,83 Low-Thermal Connection Kit contains a crimp tool, shielded cable, an assort-

ment of copper lugs, copper wire,

cadmium solder and nylon bolts and nuts. It is *

com-

plete kit for making very low-thermal measuring circuits. The Kit enables the user of

the Model 150B to maintain the high thermal stability of the Microvolt Ammeter in his
own circuit.

0667R

11

OPERATION

The Model 1486 male low-thermal input

d.

connector is for connecting custom-made

circuits to the Model 150B.

e. Other available accessories are:

The Model 1484 Refill Kit, which contains

replacement parts for the Model 1483; The

Model 1485 female low-thermal input con-

nector to use with the Model 1486 for
building shielded low-thermal circuits;

Model 1488 Low-Thermal Shorting Plug, which

is helpful in testing the Model 150B; Model

1489, which is a replacement nickel-cadmium

battery pack.

Model 1481 or Model 1482 Input Cable,

f.
supplied with the Keithley Models 147 and
148, may be-used with the Model 150B. The
shielding in these cables, however, is not

as good as the shielding in the Models 1506
and 1507 Input Cables.

Shielding problems

occur with the Models 1481 and 1482 Cables

at source resistances greater than 10

kilohms.

WODEL 150B MICROVOLT AMMETER

FIGDRE 4.

Model 1483 Low-Thermal

Connections Kit..

12

0667R

-

MODEL 1508 MICROVOLT AMMETER

CIRCUIT DESCRIPTION

SECTION 3. CIRCUIT DESCRIPTION

3-1. GENERAL.

The Model 150B consists of a chopper demodulator system followed by a dc amplifier.

a.

Feedback is applied to the whole loop. (See Figure 5).

A mechanical chopper converts the dc input signal to a 94-cps signal. The ac signal

b.

is amplified, demodulated,

back network samples the signal at the output and compares it to the input.

dc amplified and applied to the meter and the output.

The dc input

signal and the feedback signal are compared in the input transformer primary.

former increases the voltage-difference signal between the two.

the difference signal.

The ac signal is then demodulated by a saturated transistor switch

The ac amplifier amplifies

and enters a dc amplifier, which has a feedback capacitor td filter out the demodulator

ripple.
feedback network.

The dc’amplifier output is connected to the meter, the output terminals and the

The feedback resistors determine full-scale range.

The zero suppress

signal is connected to the feedback point in the input circuit.

A feed-

The trans-

94 CPS CIIOPPTR DRIrn

I

I 1

FIGURE 5.

f

I

Block Diagram of Model 150B Amplifier Circuits.

LNMRTER

I I1 I

c. The power source for the Model 150B is either line voltage or the rechargeable bat-

tery .

Voltage from either’ source is applied to a regulator, then to an inverter, then to
two supplies (which provide large amounts of filtering) and a demodulator and chopper drive.
The two supplies furnish power to the amplifier circuits. There is also a battery charging
circuit to charge the battery when the line voltage is connected.

NOTE

The circuit designations referred~to in this section are for Schematic Diagrams
203503 and 20357D found at the back of the manual.’

3-2. INPUT CIRCUIT.

The dc input signal is connected through the high terminal of the INPUT Receptacle,

a.

5104, through the input filter to the center contact of the mechanical chopper, GlOl.

(see Figure 6).

The feedback signal is applied to the center tap of the input transformer,

03678

13

CIRCUIT DESCRIPTION

._

~~_

MODEL 150B MICROVOLT AMMETER

Input

Chopper

. ”

Transformer

FIGURE 7. Model 150B Input Circuit. The dc input signal, Vin, is applied to the mechani-

cal chopper.

The feedback signal, Vf (the dc amplifier output voltage, Vo, times &he

feedback ratio, b ), is applied to the transformer primary. The signal, Vd~> stepped up

by the transformer is the difference between the two, Vd = Vin - Vf. When the dc input

signal is initially .applied to the Model 150B,
primary is entirely vin. As the output voltage rises,
a small value, vf = fin. or 4 V, = vin.

Vf is zero and the voltage across the

Vf increases and vd decreases to

Only L? I

which depends upon the RANGE and

FUNCTION Switch settings, determines the amplifier gain.

T101. The chopper alternately applies a positive and a negative square-wave signal across
each half of the primary. The magnitude of the square wave is proportional to the dif-

ference between the dc input and the feedback signal.

TlOl increases the magnitude of

this signal and applies it to the grid of tube VI.

b. The input compartment is designed to insure high thermal stability and to minimize

internal ac pickup.

1. Thermal stability is obtained in part by using only copper wire interconnections

in the input circuitry. Connections between components are made with low-thermal cad=.

mium solder.

section of the feedback loop.

Special low-thermal resistors are used in the filter and in the low-level

The switches "se standard contacts and rotors, gold

plated for low thermal emf's and high reliability.

The input compartment is shielded against magnetic and electrostatic pickup on all

2.

sides.

The wires are physically placed to maintain minimum loop area, further minimiz-

ing pickup.

C.

The feedback network is formed from the output of the dc amplifier back to the

center tap of the primary of transformer TlOl.

The RANGE Switch, S104, selects the

feedback rati.: used for each range.

3-3.

AC AMPLIFIER.

a. The ac ampiifi;?:: circuit amplifies the 94-cps difference signal which

to

the dc inpui signa,.

The signal is applied to the grid of tube Vl and amplified.

14

corresponds

0367R

MODEL 150B MICROVOLT AMMETER

CIRCUIT DESCRIPTION

Transistor QlOl acts as a cc~nstant current source for tube Vl, with field effect transistor
Q102 providing a high impedance level following the first stage. Transistor Q103 is for

impedance matching.

justs the gain to compensate for beta variations.

by transistors QlO4 through Q107.

Potentiometer R112, between the Q103 emitter and the QlO4 base, ad-

The difference signal is then amplified

Transistors 9106 and Ql07 also form a full wave signal

for demodulation.

The tube type of Vl and the bias of Vl with transistors QlOl and Q102 are selected

b.
for low-noise operation at 94, cps.
quency to be amplified by the first stage is selected to be 94 cps (TT ADJ Controls,

A narrow bandwidth around 94 cps is provided. The fre-

Poten-

tiometers R140 and R143) by a notch filterin a feedback loop around the first stages.
3-4. DEMODULATOR.

switch demodulator.

with ripple component.
wave rectified signal.

Transistors QlO6 and QlO9 in inverted configuration form a transistor

They convert the 94,-cps wave from the ac amplifier into a dc voltage

Resistors Rl.27 and Rl28 sum the voltages from each to form a full­The secondary of the inverter transformer, T201, furnishes a

square-wave drive for the demodulator.
3-5. DC AMPLIFIER.

a. The demodulator signal is amplified by two low-drift,

QllO and Qlll,

in differential configuration to compensate for temperature drift.

high gain silicon transistors,

Silicon

transistors Qll2 and Q113 form the second amplifier stage. Total gain is about 500.

Diode D102 limits the output current,

A feedback loop with capacitors Cl09 and Cl20 around the dc amplifier acts as an

b.
integrator, filtering the ripple component of the demodulated waveform.
capacity,

which is approximately the value of Cl09 and Cl.20 times the dc amplifier gain,

protecting output transistor 9114.

The effective

and the feedback factor (or open-loop gain) of the entire amplifier, Vl to Q114, determine
the response speed of the system.

The capacitive feedback also reduces the noise in the

amplifier outside the system bandpass.
3-6. ZERO SUPPRESSION.

The zero suppress circuit provides a regulated voltage from the

power supplies to buckout steady background potentials in the input signal. The lo-turn FINE

Control, potentiometer R307, is connected between -12 and +12 volt outputs. The rotor of
potentiometer R307 is connected to a resistive divider R187, R301, R302 and R303 in the

COARSE Switch which further divides the voltage. The suppression voltage is applied direct-

ly to the feedback resistor, RT65, whic'h acts as another divider in conjunction with R149.

3-7. POWER SUPPLIES (See Figure 7.)

The power supply for the Model 150B consists of a

regulated supply which operates from the power transformer or a rechargeable battery.

The output of this regulator feeds an inverter, two highly filtered supplies with outputs
of +12, -12 volts and a drive circuit for the chopper and demodulator. These power all
the other Model 150B circuits.

The line power, battery and battery charging circuits are controlled through the

a.

POWER SUPPLY Switch, S201.

When the switch is in AC, the battery is charged and the power

supply operates from the power transformer, T202. When the switch is in OFF, the battery

charges; all other circuits are off.

When the switch is in BATTERY, the power supply

operates from the battery; the power transformer is disconnected at its primary windings.

The regulated supply is prefiltered with a large capacitor, C211. The supply con-

b.
sists of a series regulator with a darlington pass arrangement made up of Q218, Q212 and
Q214.

Any variation across the output is referenced by resistors R234 and R238 with zener

0467R

15

CIRCUIT DESCRIPTION

MODEL 150B 'MICROVOLT AMMETER

FIGURE 7. Block Diagram of Model 150B Power Supplies.

diode D211 and compensated for by the amplifier consisting of Q215, Q216 and Q217.

The

output of the supply is adjustable around -5 voLts.

Voltage from the regulated supply is applied to the inverter circuit.

Transistors
92:; and Q202 form a switching network to supply a square-wave voltage to transformer
T201.

The switching frequency is 94 cps,

T201 has a saturable ferrite core.

The inverter circuit supplies voltages to the two

the same as the carrier frequency. Transformer

regulated supplies and the chopper demodulator circuit.

The +12 volt supply is a highly filtered voltage taken from the secondary windings

d.

of the inverter transformer, T201. Diodes D201 and D202 furl wave rectify the signal

from the transformer.
lington configuration,
supply output.

A current limiting circuit, transistor Q205, protects the pass transistor

This signal is filtered by the RC filter, R204 and C203.

A Dar-

transistors Q203 and Q204, maintains the low-ripple voltage at the

if the output of the supply is shorted.

The -12 volt supply operates in 9 similar manner to the +12 volt supply.

e.

One secondary of the inverter transformer drives transistors Q209 and Q2LO through

f.

a phase compensating network made up of resistors R220 through R224 and capacitor C210.

This phase compensation network compensates for the chopper phase shift.

Transistors

Q209 and Q210 are alternately cut off and driven into saturation, forming a square wave
drive to the demodulator.
ary of the inverter transformer that is used to drive the demodulator.

The drive for the chopper is taken from one-half of the second-

Capacitor C213

"rounds off" the square wave to produce a more acceptable chopper drive wave form.

-..

.-

-

MODEL 150B MICROVOLT AMMFTER

CIRCUIT DESCRIPTION

3-8.

BATTERY CHARGING CIRCIIIT.

a. The battery circuit operates when the POWER SUPPLY Switch, 5201, is in the AC or

OFF position.

b. A charging currant from transistor T20.. is applied to the battery through a half

wave rectifier and a series resistor, RZ28. A fuse is incorporated in this circuit to

protect the instrument and the battery.

Note, however,

that the battery can be damaged

if it is used far beyond its capacity. A polarity reversal of a crll may occur, causing

heavy circulating currents within the battery.

,..

1266~ 17

MAINTENANCE MODEL

I.508

._

MICROVOLT AMMETER

.,.

,-

Instrument

Hewlett-Packard Model 200 CD

Oscillator, 5 cps to 600 kc,

*2% accuracy.
Hewlett-Packard Model 5512A

Electronic Counter, 300-kc counting

rate, 10.1% accuracy.

Keithley Instruments 1488

Low-Thermal Shorting Plug.
Keithley Instruments Model 1507

Input Cable.

Keithley Instruments Model 260
Nanovolt Source.

Keithley Instruments Model 261
Picoampere Source.

Keithley Instruments Model 370

Recorder.

Use

TT adjust and Filter adjust
calibration.

Minitor oscillator frequency.

Short Model 150B INPUT Receptacle.

Connecting cable for Model 260 and

Model 150B.

Signal source for calibrating Model

150B.
Signal source for calibrating Model

150B.

Monitor drift.

,_.

7

<~_

.-

.-

_.

.-

Keithley Instruments Model 6lOB

Check plate voltage of tube VI.

Electrometer.
Keithley Instruments Model 662

Check voltage at output terminals.

Guarded DC Differential Voltmeter,

l

O.Ol% to 1 millivolt.

RCA Model WV98B Senior Voltohmyst,

Check dc voltages throughout circuit.

11 MD input resistance, *3% accuracy,

0 to 1500 volts dc.
Tektronix Type 503 Oscilloscope, dc Check wave forms for troubleshooting

to 450 kc.

TABLE 6.

Equipment Recormsended for Troubleshooting and Calibrating the Model 150B. Use

and calibration.

these instruments or their equivalents.

18 0667R

MODEL 150B MICROVOLT AMMETER

SECTION 4.

4-l. GENERAL.

Section 4 contains the maintenance,

a.

the Model 150B.

to maintain the instrument's specifications.

The Model 150B requires no periodic maintenance beyond the normal care required of

b.
high-quality electronic equipment.
cipal maintenance is an occasional chopper replacement. (See paragraph 4-3.) Occasional
verification of meter calibration (paragraph 4-7) should show any need for

4-2.

Microvolt Ammeter.
ments which meet the specifications.

the components listed in Table 7.

List are purchased only from Keithley Instruments or its distribtitors.
4-3. MECHANICAL CHOPPER REPLACEMENT.

PARTS REPLACEMENT,

a. The Replaceable Parts List in Section 6 describes the electrical components of the

It is recommended these procedures be followed as closely as possible

Components operate well below maximum ratings. Prin-

Replace components only as necessary, and use only reliable replace-

The Model 150B uses no special critical parts except

Make sure parts coded 80164 in the Replaceable Parts

MAINTENANCE

troubleshooting and calibration procedures for

adjustment.

The mechanical chopper is designed for long life.

a.

it will eventually wear and become noisy.

~em0~1 Procedures.

b.

Disconnect the chopper drive coil at connector 5105 (Figure 11).

1.

the chopper lugs from the studs mounted on the bottom of the input compartment.

Remove the four mounting screws from the bottom of the input compartment. Remove

2.

the old chopper.

Replacement Procedures.

c.

Mount the chopper with the four furnished screws.

1.

!

Battery pack assembly

Mechanical chopper assembly and input connector

assembly (See paragraph 4.-3.) GlOl & J105

Input transformer assembly

Dress the leads and draw the lugs down on the studs.

2.

component Desig.

At this point, replacement is necessary.

However, since it is mechanical,

Carefully remove

Circuit

BT201

TlOl

Keithley
Part No.

Model 1489

20139B

20137B

.

.

TABLE 7.

the proper lead length.

0667R

Model 150B Pre-assembled Components.

These parts have lugs crimped on them and

Use only Keithley parts for replacement.

19

MAINTENANCE

MODEL 150B MICROVOLT AMMETER

Connect

3.

4. Check the instrument for proper operation.

the chopper drive coil at connector JlO5.

Follow paragraph 4-8, subparagraph b,

steps 1, 2 and 3.

4-4.

TROUBLESHOOTING.
The following procedures give instructions for repairing troubles which might occur

a.

in the Model 150B. Use these procedures to troubleshoot and use only specified replacement

parts.
readily Located or repaired,

b.

checking out the power supply and amplifier circuits.

Table 6 lists equipment recomsrended for troubleshooting._ If the trouble cannot be

contact Kqithley Instruments or your Keithley field engineer.

Paragraphs 4-6, 4-7 and 4-8 give step-by-step procedures for troubleshooting and

Follow these in the order given.

Tables 9 and 12 are troubleshooting tables for these circuits. Also refer to Section 3 to

find the more crucial components and to determine their function. The Schematic Diagrams,
203503, and 20357D, contain the voltages at certain points in the circuit, measured with
a Model WV98B Voltohmyst.

NOTE

Before troubleshooting inside the Model 150B, check the external circuits (para­graph 4-5). Always check out the power supply circuit before touching the ampli-

fier circuits.

The amplifier circuits often appear faulty only because of a de-

fect in the power supply.

­.-

.-

4-5.

PRELIMINARY TROUBLESHOOTING PROCEDURES.

a. Before troubleshooting, check the outside circuits to the Model 150B. Isolate the

Microvolt Aaraeter from all external effects:

1.

Disconnect all outside circuits from the INPUT and OUTPUT Receptacles, and CND

and LO terminals.

Connect a low-thermal short across the INPUT Receptacle.

2.

The best connector is a

Model 1488 Low-Thermal Shorting Plug. The next best is a Model 1506 Input Cable with

the clips connected together or the Model 1507 Input Cable with the .lugs connected to-

gether. Keep the cable as far as possible from ac sources, and avoid a loop where the

alligator clips or lugs are connected.

3. Set the ZERO SUPPRESS COARSE Control to OFF.

b.

If the battery charge is acceptable (paragraph 2-2), set the POWER SUPPLY Switch to

BATTERY.

Disconnect the power cord from the power Line. Battery operation eliminates

many ground-Loop connection problems with the test equipment.

c.

If ac operation is used, check the Line Voltage Switch for correct position and the

Fuse for correct rating.
4-6.

CHECK OUT AND CALIBRATION PROCEDURES.

a. TO ascertain whether the Model 15OB is operating

of the voltage ranges and current ranges,

20

properly, perform a-~ accuracy check

0667R

MODEL 150B MICROVOLT AMMETER

MAINTENANCE

1. To check the accuracy of the voltage ranges,

2-3.

150B using the 1507 Input Cable.

a nine-tenths full-scale signal with the Model 260 (i.e.

the 10 microvolt range; 27 microvolt signal for the ~Omicrovolt range, etc.). Check

each range for both positive and negative polarity. The meter accuracy of the Model 150B

is specified to be f2% of full scale exclusive of noise and drift.

2-4,. Use the Model 261 as the current source and connect the Model 261 to the Model 150B
using the 1507 Input Cable.
nine-tenths full-scale signal with the Model 261 (i.e.

10 nanoampere range; 27 nanoampere input signal on-tKe 30 nanoampere range, etc.),

each range for both positive and negative polarity.

is specified to be “3% of full scale exclusive of noise and drift.

calibration (paragraph.4,-7~).
to be within specification, check the indicated resistors in Table 11.

b. The following procedures give the steps to check out and calibrate the Model 150B
circuits.
shooting table.

Table 6.

Use the Model 260 as the voltage source and connect the Model 260 to the Model

Check each voltage range on the Model 1508 by applying

2. To check the accuracy of the current ranges,
Check each current range on the Model 150B by applying a

3. If any range. fails to be within specifications, check to see if the meter is in
If the meter is in calibration and any range still fails

If a circuit fails to check out at any point, refer to the circuit’s trouble-

Continue as Long as the points check out. Use the equipment listed in

follow the procedures of paragraph

9 microvolt input signal for

follow the procedures of paragraph

9 nanoampere input signal for the

Check

The meter accuracy of the Model 150B

c. Procedures are given for the power supply and amplifier circuits.

principal adjustments to bring the instrument within specifications.

d. If the Model 150B is not within specifications after performing these checks and
calibrations, return the unit to Keithley Instruments for further checkout, or follow the
troubleshooting procedures to find the fault.

I

VL Bias adjust
Gain control

TT adjust
Filter adjust

Meter Cal.

Frequency adjust

Current Coma. adiust

TABLE 8.

picturing the location,

Make sure the power supply circuit is operating correctly before checking the

amplifiers.
taken out of ourder,

Control

Model L50B Internal Controls.

All circuits depend upon properly functioning power supplies. If

Circuit
Desig.

R107 LO 4-7, 4,-8
R112 15 4-8
Rl4,O and R14,3 15 4-8
~14,6 18 4-8
R193 17 4-7
R235 13 4-7
R304, 10 4-7

The table lists all the controls, the figure

and the paragraph describing the adjustment.

NOTE

the resulting adjustment may be faulty.

Fig.
Ref.

These cover the

Refer to
Paragraph

0667~

21

MAINTENANCE

-

MODEL 150B MICROVOLT AMMETER

TROUBLE

No voltage.at the blat'

and white wire attache1
to la$t pin before

strdon S103 (point G
Fix. 10).

Irregular wave form at
pin 8 or 9 (Fig. 8).

Incorrect 1-12 volt
supply voltage, or
ligh ripp,le on this

SUPPlY.

PROBABLE CAUSE

k

Blown fuse.

i

II209 or D210 open.

Regulator circuit not

functioning nomally.

I

Check for shorted transformer T202
or wiring;

I

Check components; replace if faulty

I

Refer to Section 3 to determine the

components in the regulator circuit.

SOLUTION

then replace fuse.

Check these components and replace

if faulty.

Defective Q203 and/or

Check components; replace if faulty.

Q204

Defective C203 and/or

Check components;

replace if faulty.

c204

-5 volt regulator

Change the value of R204; increase the
not supplying enough value if the t12 output is low; de­voltage to inverter

for 94 cps.

crease it (not below 3.9 kR) if the +l

output is high.

Incorrect -12 volt
supply voltage, or

Defective Q207 and/or
Q208

Check components;

replace if faulty.

ligh ripple on this
'upply.

Defective
c209

-5 volt regulator not

Check and/or

components;

replace if faulty.

I

Change the value of R219; increase the
supplying enough volt- value if the -12 output is low; de­age to inverter for
94 cps.

w.3 9.

4-9.

Troubleshooting Table for

Power

SUPP

POWER SUPPLY CHECK OUT AND CALIBRATION.

‘1Y.

a. All circuits depend upon the -5 volt regulated supply.

crease it (not below 3.9 kR) if the -1

output is high.

This supply drives the in-

verter transformer which, in turn, supplies the -12 and cl2 volt outputs.

-5 volt supply must be operating correctly before further checks are made.
suppLy fails to check out at any point, refer to Table 9.

After clearing the trouble,

continue the check.

Therefore, the

If the power

Procedures for Checking Regulated Power Supplies.

b.

Connect the Model 1488 Low-Thermal Shorting Plug to the INPUT.

1.

controls as follows:

22

Set the Model 150B -

0667R

:

MODEL 150B MICROVOLT AMMETER

POWER SUPPLY Switch OFF
RANGE Switch 1 MICROVOLT
FUNCTION Switch INPUT R OPEN
ZERO SUPPRESS COARSE Control OFF
Line Voltage Switch Set to line voltage
FILTER Switch

Turn the FREQ ADJ Potentiometer, R235 (Figure 13) and Vl BIAS Potentiometer, R107

2.

(Figure 10) completely counterclockwise.

This ensures that the tube in the first stage

IN

and the chopper will not be damaged.

Plug in the power cord.

3.

4,. Measure the voltage at the red wire on the POWER SUPPLY Switch front deck. It

should be -11 volts dc *2 vdc.

MAINTENANCE

Turn the POWER SUPPLY Switch to AC.

5.

Use the Type 503 Oscilloscope to check the

wave form at pin 8 or 9 of connector 5201 on the bottom of PC-120 (Figure 11). Wave

form should look like Figure 8.

The dc voltage at pin 8 or 9 should be -5 volts *0.3 vdc.

a)

This voltage will be

present at pin 8 or,9 if the chopper frequency is 94 cps.

b) Check the chopper frequency by connecting the Type 503 Oscilloscope differential-

ly at pins A and D on connector X05 (Figure 11).

with the Model 5512A Electronic Counter set at 94 cps.

Measure the oscillator frequency

Connect the oscillator to the
horizontal channel of the Type 503 Oscilloscope and obtain a lissajous pattern. The
wave form of the chopper drive should resemble that in Figure 9.

FIGLJRE 8.

Correct -5v Regulated Supply

Wave Form at Pin 8 or 9 of Connector 5201.

See paragraph 4-7.

Form was obtained on

the 1 pv range with the FILTER Switch set

The

to IN.

scale is 0,2v/cm verticle, 2

msec/cm horizontal.

0667R

FIGURE 9.

at Pins A and D of 5105.

Correct Chopper Drive Wave Form

See paragraph

4-7. Form was obtained on the 1 NV range

with the FILTER Switch set to IN.

The

scale is 5v/cm vertical, 2 mseclcm horizon­tal.

23

MAINTENANCE

T

~'

..,

._

..~

Measure the signal levels and ripple with respect to low of the +12 and -12 volt

6.

supplies. Table 10 gives the values.

MODEL 150B MICROVOLT AMMETER

a) To measure the +12 volt supply,

connector 5201, Figure 11.

b) To measure the-12 volt supply,

connector 5201, Figure 11.

c) To find the ripple on the supplies connect the Type 503 Oscilloscope to pin 19

or 6. The ripple should be less than 2 mv peak-to-peak.

Regulated

Power

SUPPlY

+12 volt pin 19, 5201 11 to 12.5 1;5 850 *lOO

-12 volt p'in 6, 5201 11 to 12.5 2.0 460 *70

TABLE 10.

c. Meter Noise Check.

Model 15OB input with the Model 1488 Shorting Plug or some other suitable device.

the meter noise.

not, then possible sources of noise are transistor QlOl, tube Vl, the chopper, power sup-

PlY,

and cadmium solder joints.

Signal Level, Maximum Ripple and Resistance for Regulated Power Supplies.

Test Point, Signal Level;

Figure 11 Volts dc

Set the Model 150B RANGE Switch to 0.3 MICROVOLT.

The meter noise should be less than 25 nanovolts peak-to-peak.

connect the Model WV98B Voltmeter at pin 19 of

connect the Model WV98B Voltmeter ta pin 6 of

Maximum Ripple, Resistance

Millivolts to Ground,

Peak-to-Peak

Ohms

Short the

Check

If it is

-

d. Meter Calibration.

Set the Model 150B front panel controls as follows:

1.
POWER SUPPLY Switch

RANGE Switch 100 MICROVOLTS
FUNCTION Switch

ZERO SUPPRESS COARSE Control OFF

ZERO SUPPRESS FINE Control

FILTER Switch IN

2. Short the Model 150B input with the Keithley Model 1488 Shorting Plug or s~ome

other suitable device.

Zero the meter with the Mechanical Zero Control.

3.

4. Turn the POWER SUPPLY Switch to ON and set the ZERO SUPPRESS Control to position 2.

5. Adjust the Model 15OB 1V Output to within fO.l% of full scale as read on the

Keithley Model 662 Differential Voltmeter.

6. Adjust the Meter Calibration potentiometer (Rl93, Figure 17) for a reading of 10

on the Model 150B meter scale.

OFF
VOLTS (either position)
Approximately-centered

24

e.

Current Compensation Calibration.

0667R

MODEL 150B MICROVOLT AMMETER

1. Set the Model 150B front panel controls as follows:

MAINTENANCE

POWER SUPPLY Switch

OFF
RANGE Switch 10 MICROVOLTS
FUNCTION Switch
ZERO SUPPRESS COARSE Control

VOLTS, INPUT R 1OOK

OFF

ZERO SUPPRESS FINE Control Approximately centered

FILTER Switch

IN

2. Short the Model 150B input with the Keithley Model 1488 Shorting Plug or some

other suitable device.

Turn the POWER SUPPLY Switch to ON,

3.

Allow the Model 150B to warm up for 10

minutes and reach thermal equilibrium.

4. Zero the Model 150B using the ZERO SUPPRESS Controls.
Remove the short from the input.

5.
Adjust the Current Compensation Adjust (R304,, Figure 10) for null. A few tenths

6.

of a microvolt instability is to be expected.$

4-8. AMPLIFIER CHECK OUT AND CALIBRATION.

The check cut and calibration of the amplifier circuits is divided into these parts:

a.
operational check, gain calibration,
dtift verification.

The operational check does not have to be followed by gain calibration.

Use this to check the Model 150B operation.

point,

refer to Table 12. After clearing the trouble, continue the check.

TT Adjust calibration, Filter Adjust calibration and

If the amplifiers fail to check out at any

NOTE

If

Check the power supply circuits before adjusting the amplifiers.
changes are made,

Operational Check Procedures.

b.

Connect the Model 14,88 Low-Thermal Shorting Plug to the INPUT RECEPTACLE.

1.

the amplifier circuit may need recalibration.

extensive

Set the

front panel controls as follows:

POWER SUPPLY Switch AC
RANGE Switch 1 MICROVOLT
FUNCTION switch

INPUT R OPEN

ZERO SUPPRESS COARSE Control OFF

ZERO SUPPRESS FINE Control

FILTER Switch

On the l-microvolt range, the meter offset should be less than 0.5 microvolt (50%

2.

of full scale).

Connect the Model 610B Electrometer to'the plate of tube Vl (point E, Figure 11).

3.

It may be higher if the shorting plug (Model 1488) is not used.

Adjust the Vl BIAS Potentiometer (R107,

*0.1 volt.

the Vl BIAS Potentiometer,

If the plate voltage is high and cannot be adjusted down to 7 volts with

then decrease the value of resistor R102;

Figure 10) until the Model 610B reads 7 volts

Approximately centered

IN

If the plate vol-

tage is low and cannot be adjusted up to 7 volts with the Vl BIAS Potentiometer, then

0667R

25

MAINTENANCE

_-

MODEL 150B MICROVOLT AMMETER

increase the value of

Remove the Model 1488 Siwrting Plug and leave the Model 150B input open. Set the

4.

FUNCTION Switch to ;I?;PUT R 100%.

1v OUTPUT.

Set the oscilloscope amplifier to dc coupling, 0.2 volt/cm, time base to 1

second/cm. Set the Model .!5OB LO the 3-microvolt range.

Control to 1 and adjust the

reli3tor

X102. Disconnect the Model 610B.

Connect the Type 503 Oscilloscope to the Model 15OB

Set the ZERO SUPPRESS COARSE

ZERO SUPPRESS FINE Control to obtain a 3-microvolt signal.
The response time (from 10% t.3 90% of final value) should be approximately 6 seconds.
Adjust Gain Control potenriometer Rl12 (Figure 15) for this value.

c. Gain Calibration Procedures.

1. Connect the Model 260 Source to the Model 150B input with the Model 1507 Input

Cable.

Connect the Model 662 Differential Voltmeter to the Model 150B 1V OUTPUT Receptacle.

2.
Before turning the Model 260 POLARITY Switch to + or -, adjust the ZERO SUPPRESS

3.

Controls for zero output at the output terminals.

Set the Model 662 to the 5-volt range.

Use the Model 662 to determine the zero output.

For a given full-scale input signal, measure the output voltage. Check each range

4,.
and rezero the output using the ZERO SUPPRESS Controls before each check. The output
should be 1 volt dc *l% for all ranges. If for any range the output is not 1 volt *l%,
refer to Table 11 and check the resistors for that range.

Replace any faulty resistor.

7

.

d. TT Adjust Calibration.

1. Set the Model 150B front panel controls as follows:
POWER SUPPLY Switch

OFF

RANGE Switch 1 MICROVOLT

,FUNCTION Switch

VOLTS (either position)
ZERO SUPPRESS COARSE Control OFF
ZERO SUPPRESS FINE Control

Approximately centered
FILTER Switch IN

Apply 10 volts peak-to-peak to the input of

2.

the 94 cps filter (pin 3 to pin 1 of

PC-119, Figure 15) with the Model 200CD Oscillator.

Adjust TT ADJ potentiometers R140 and R143 (figure 15) for minimum signal at the

3.

output, pin 6 of PC-119.

Monitor the output signal with the Model 503 Oscilloscope. The
output signal should be about 25O:l less than the input, typically 40 mv or less, and
contain very few 94 cps voltages.

Filter Adjust Calibration.

e.

Keep the Model 15OB front panel controls the same as in subparagraph d.

1.
1

Apply 10 volts peak-to-peak,

2.

60 cps (or 50 cps if designated on rear panel) to the

Model 1508 INPUT Receptacle with the Model 200CD Oscillator.

Adjust FILTER ADJ potentiometer R14.6 (Figure 18) for minimum voltage at the output

3.

of the filter (junction of resistor R14.8 to low).

Monitor the output with the Model 503

26 0667B

MODEL 150B MICROVOLT AMMETER MAINTENANCE

Voltage Resistors used
RANGE

0.3 p"
1 K"

3 I-rv

10 I.r" Rl64, R165, R167, R170

30 K"

100 pv

300 WV R164, R165, R167, R173 300 *a

1 rn" R165, R168

3 rn" R165, R169
10 mv R165, R170 10 pia R165, R168, R181
30 Ill" R165, R171

100 rn" Rl65, R172 100 va
300 ln" R165, R1~73

IV R165 1000 pa

TABLE 11. Range Checkout.

Oscilloscope.
peak or less. The output may still contain some live frequency signal.

Drift Verification.

f.

put with the Model 1488 Low-Thermal Shorting Plug.

0.3 MICROVOLT.
the drift should be less than 0.1 microvolt per 24 hours.
tive of a faulty battery.

R164 through Rl67
R164, R165, R167, R168 1 *a
~164, R165, R167, R169 3 na

~164, R165, R167, R171
R164, R165, R167, R172

in RANGE Switch

If any ranges fail,

The filter rejection ratio should be about 300:1, typical1 30 mv peak-to-

Make sure the Model 150B mver is on. Short the Model 150B in-

Connect the Model 150B to the Model 370 Recorder.

current

RANGE

0.3 na R172, ~164, R165, R167, R174
Rl72, R164, R165, R167, R175
Rl72, R164, R165, R167, R176

10 na

30 *a

100 na

1 w

3 w

30 I.La R165, R168, R182

300 pa Rl65, R168, Rl84

check the listed resistors.

Set the Model 150B RANGE Switch to

R172, ~164, R165, R167, R177
Rl72, Rl64, R165, R167, R178
R172, Rl64, Rl65, R167, R179
R172, Rl64, R165, R167, R180
R165, Rl68, RI.79
R165, R168, R180

R165, R168, R183

R165, R168, Rl85

Excessive drift may be indica-

Resistors used

in RANGE Switch

After a l-hour warm-up

0667R

27

High zero offset

-.

I

Short in feedback network. Make sure lugs do not touch each other o

Random zero drift, one hundreds
of nanovolts or more, somettmes

reduced if the cabinet 1s slap­ped. Response speed 1s within
specification.

t very temperature

sensitive.

esponse spee
possibly offset also high.
Cannot adjust to specifications
with R112.

OOK across the input,

Noisy chopper. Replace chopper; see paragraph 4-3.

Contaminated

INPUT Receptacle, Clean INPUT Receptacle with
shorting plug, or connection
in input compartment.

Low ac amplifier gain,

due to

bad active element.

If contamination goes below

plated surface, replace connector. Clean

Set to l-microvolt range, ZERO SUPPRESS

COARSE to 1, FINE to an easfly readable

non-metallic

With oscilloscope, check for

square wave at Vl grid, and sine wave at

input and output of each succeeding stage

Reduce zero suppression as necessary to

revent saturation. Check dc voltages,

schematic.

see

TABLE 12 (Sheet 1).

Amplifier Troubleshooting Table.

This table assumes that the Model 1508 has a Model 1488

Shorting Plug on the input, and that only test instruments are connected to it.

I

TROUBLE PROBABLE CAUSE

SOLUTION

Response speed very slow,

Low gain in dc amplifier.

Unsolder and lift one end of R127, Rl28
possibly offset also high. and clO9. See points M and N, Figure 15.
Cannot adjust to specifi­cations with R112.

Apply 1 to 1OOmv to base of QllO to zero

meter. Change input by 1 millivolt; out-

put should shift 0.5 to 1 volt. If not

or if more than 1OOmv is required to zero
check,transistors, beginning with QllO ar
Qlll.

QllO and Qlll are matched for off-

set. Replace only with parts purchased

from'Keithley.

Leaky or shorted Cl09 and/or

Check; replace if faulty.

c120.

Demodulator does not "clamp"
during one-half cycle.

Defective 9108, 9109, QZOV Check for square wave

at

collector of

or Q210. Q209 and Q210 and base of Q108 and QlOV.

Replace faulty components.
All microvolt ranges out of R164 or R165 out of tolerance.

-Check resistors; replace if faulty.
calibration. The millivolt
ranges are good.

All ranges are out of cali- R165 out of tolerance. Check resistor; replace if faulty.

bration.
One range out of calibration.

Corresponding resistor in Check resistor; replace if faulty.
Table 11 out of tolerance.

When connected in measuring Too much 60 cps at input.

circuit, meter needle oscillates

in ac and/or battery operation,

Reduce 60 cps appearing at the input by

shielding and grounding as described in
paragraph 2-14,.

even with filter in.

TABLE 12 (Sheet 2). Amplifier Troubleshooting Table. This table assumes that the Model 1508 has R Model 1488
Shorting Plug on the input,

and that only test instruments are connected to it.

MODEL 150B MICROVOLT AMMETER

!Fiqa. 1$&l:) jFiZS. 14,515)

FIGURE 10.

Top View of the Model 15OB Chassis.

Front panel faces right.

components, printed circuits and switches is shown.
schematic diagrams for circuit designations.

Figure 11 shows the bottom view.

30

Location of

Refer to Replaceable Parts List and

0667R

MODEL 150B MICROVOLT AMMETER

FIGURE 11.

Bottom

View of the Model 150B Chassis.

components, printed circuits,

switches and test points is shown.

Front panel faces down.

parts List and schematic diagram for circuit designations.

0667R

Location of

Refer to Replaceable

Figure 10 shows the top view.

31

MAINTENANCE MODEL 1508 MICROVOLT AMMETER

Q216 cmi

FIGURE 12.

c21:

Capacitor, Diode and Transistor Locations~ on PC-121.

Refer to Figure 13 for resistor locations.

izo9

32

FIGURE 13.

capacitor,

Resistor Locations on PC-121. Refer to Figure 12 for

diode and transistor locations.

0667R

MODEL 150B MICROVOLT AMMETER

MAINTENANCE

FIGURE 14.

Capacitor, Diode
and Transistor Locations on
PC-119.

Refer to Figure 15
for resistor locations and
test points M and N.

FIGURE 15.

Resistor and' Test

Point Locations on PC-119:

Refer to Figure 14. for capa-

citor, diode and transistor

locations.

0667R

33

MAINTENANCE

D202-

MODEL 150B MICROVOLT AMMETER

FIGURE 16. Capacitor,

17 for resistor locations.

Connector and Diode Locations in PC-120. Refer to Figure

FIGURE 17.

Resistor Locations in PC-120.

connector and diode locations.

34

Refer to Figure 16 for capacitor,

Ob67R

MODEL 150B MICROVOLT AMMETER

MAINTENANCE

FIGURE 18.

I

Component Locations on PC-118.

35

MODEL 150B MICROVOLT AMMETER

ACCESSORIES

SECTION 5.

5-1.

dimensions are 7 inches high x 19 inches wide x 10 inches deep.

converts to half-rack size,

screws at the bottom of each side.

Attach in this order: cover (Z),

adapter (g), and chassis connecting plate (3).

Use the 10 inch size with the Model 150B. Use the 13-inch size for 13-inch deep Keithley

instruments.
for the lo-inch cover.

I

I

MODEL 4.006 RACK MOUNTING KIT.

The Model 4,006 Kit converts the Model 150B from a bench model to rack mounting. Rack

a.

and the Kit contains a half-rack adapter panel.

Procedures. Remove the wrap-around cover on the Model 150B by removing the two corner

b.

Add the rack mounting parts as shown in Figure 19.

rack angle (5), panel support angle (7), rack panel

c. Notice that the cover assembly comes in two sizes, a 13-inch size and a lo-inch size.

The rest of the procedure for the 13-inch size is the same as given above

Item Keithley

(See Fig. 19) Description Part No.

1
2

3

4.
5

6
7
8

Cover Assembly (13 inch)
Cover Assembly (10 inch)
Chassis Connecting Plate

Screw,
Rack Angle
Screw, slotted, #lo x l/2
Panel Support Angle
Rack Adapter Panel

round head, hex socket, /ilO x l/2

ACCESSORIES

The Microvolt Ammeter

Quantity

20015B
200160
191548

----

1914.7B

----

19157A
19158A

TABLE 13. Parts List for Keithley Model 4006 Rack Mounting Kit.

5-2. MODEL 4007 DUAL RACK MOUNTING KIT

The Model 4.007 Kit converts the Model 150B to rack mounting.

a.
two lo-inch deep instruments, one each lo-inch deep instrument and 13-inch deep instrument,
or two 13-inch deep instruments. The Model 150B is a lo-inch deep instrument. Dimensions
of the Kit are 7 inches high x 19 inches wide x 10 or 13 inches deep.

Procedures. Remove the wrap-around cover on each instrument by removing the two

b.

corner screws at the bottom of each side.

Figure 20. Attach as follows when rack adapting two lo-inch instruments or two 13-inch

instruments:

chassis connecting plate (3).
instrument and one lo-inch deep instrument:

bracket (E),

0667~

cover (1 or 2), two rack angles (5),

Attach as follows when rack adapting one 13-inch deep

chassis connecting plate (7) and chassis connecting plate (3).

Assemble the rack mounting parts as shown in

chassis connecting plate (7), and

cover (1 or 2), two rack angles (5), zee

The Kit will contain

37

ACCESSORIES

MODEL 150B MICROVOLT AMMETER

item 6

FIGURE 19.

Exploded View of Keithley Model 4,006 Rack Mounting Kit. Refer to Table 13

for parts List.

Item

(See Figure 20)

Description Part No.

1 Cover (13 inch) 19059c 2
2 Cover (10 inch) 19152B 2
3 Chassis Connecting Plate 19154.A 1

4 Screw, round head, hex socket, 810 x l/2 ---- 8

5 Rack Angle 19147B 2
6 Screw, slotted, i/10 x l/2 ---- 4
7 Chassis Connecting Plate 19700A 1
a Zee Bracket

TABLE 14.

Parts List for Keithley Model 4007 Dual Rack Mounting Kit. Two extra covers

are included in kit (see paragraph S-2).

Keithley

19167A

Quantity

1

38

0667~

MODEL 150B MICROVOLT AMMETER

A"

I"

+- item 1

ACCESSORIES

item 7 -

\ item 4,

---_-- ^^ - . . . _..

FLti”Kls L”.

&xpLoaea view or KelcnLey MooeL quvI UuaL KacK Mounrmg K1C.

7 . . . . . 1 ., * .

I_,.-.. -.. . . . . _... ..,

wrer to

Table 14, for parts list.

5-3. MODEL 370 RECORDER.

a.. The Model 370 Recorder is uniquely compatible with the Model 150B as well as other

Keithley microvoltmeters,

electrometers and picoammeters.

The Recorder is a high quality

economical instrument that epitomizes the performance of the Model 150B, and any other

Keithley instrument,

even 'in the most critical applications.

The Model 370 can be used with

the Model 150B to record dc potentials and currents over the Model 150B's entire r.snge.

b. The Model 150B has the output necessary to drive the Recorder directly (1 volt,

1 milliampere),

volts off ground,

thus eliminating the need for a pre-amplifier.

enabling the Model 150B to be used to its specified off-ground voltage.

Th.e Recorder is specially shielded to avoid pickup of extraneous signals.
time of the Model 370 Recorder is 0.5 second; linearity is fl% of full scale.
speeds
controls.
self-priming inking system.

- from 314, inch per hour to 12 inches per minute ­The 6-inch chart has a rectilinear presentation.

Chart paper and ink refills are easy to install.

The Model 370 floats *500

The response

Ten chart

are selectable with front panel

The Model 370 Recorder has a

c. The Model 370 is very easy to use with the 'Model 15OB. Just connect the Model 150B's

1V OUTPUT Receptacle to the Model 370 with the furnished 3701 Input Cable and adjust an

0667R

39

ACCESSORIES

MODEL 150B MICROVOLT AMMETER

easily accessible control for full-scale recorder deflection.
of the Model 150B, under some conditions, an 8-cps beat may appear.

On the most sensitive ranges

This condition can be

eliminated by mounting a one microfarad capacitor across pins 14, and 17 in the back of the

ode1 370 Recorder.

IGURE 21.

Especially Designed for use with Keithley Microvoltmeters and Other Instruments.

Maximum Recording Convenience is Obtained Using the Keithley Model 370,

The Model

370 can be directly connected to the,Model 1508 l-volt output with the Recorder's accessory
cable.

Response time, floating capability and other specifications of the Model 370 Re-

corder are completely compatible with those of the Modal 15OB Microvolt Ammeter.

4.0

0667R

MODEL 150B MICROVOLT AMMETER

REPLACEABLE PARTS

SECTION 6.

6-1. REPLACEABLE PARTS ,LIST.

Model 150B (and~its accessories).

cription,

Number.

a suggested manufacturer,

The last column indicates the figure picturing the part.

of the manufacturers listed,in the "Mfg.

The &Replaceable Parts List describes the components of the

The List gives the circuit designation, the

the manufacturer's part number and the Keithley Part

REPLACEABLE PARTS

part

The name and address

Code" column are in Tablc14.

6-2. HOW TO ORDER PARTS.

For parts orders, include the instrument's model and serial number, the Keithley

a.

Part Number,

the circuit designation.,and a description of the part. All structural parts
and those parts coded for Keithley manufacture (80164) must be ordered through Keithley
Instruments, Inc. or its representatives.
able Parts List,

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

b.

completely describe the part, its function and its location.

In ordering a part not listed in the Replace-

ment, Keithley Instruments, Inc.

.CerD

camp
DCb
EAL

ETB
ETT

ampere
Ceramic, Disc

Composition
Deposited Carbon
Electrolytic, Aluminum

Electrolytic, tubular
Electrolytic, tantulum

Mfg.
MtF

MY

ti

P
Ref.

req'd

Manufacturer
Metal Film
Mylar

ohm
pica (10-12)
Reference

r~equired

des-

f

Fig

k
M or meg

farad

Figure
kilo (103)
mega (106) or megohm

in milli (10b3)

0667R

TABLE 15.

u

v

w

ww
WWVar Wirewound Variable

Abbreviations and Symbols.

micro (10m6)

volt
watt

Wirewound

41

REPLACEABLE PARTS MODEL 150B MICRCVOLT AMMETER

WDEL 150B REPLACEABLE PARTS LIST

(Refer to Schematic Diagrams 20350E and 20357D for circuit designations.)

CAPACITORS

Circuit

Desig. Value
Cl01 10 pf 20 v

Rating

TYPO

ETT
Cl02 100 pf 600 v CerD
Cl03
Cl04

1 Pf
100 pf 15 " EAL 56289 89D217 C93-100M

200 "

MY

Mfg.

Code Part No.

0539’7

72982

Mfg. Keithley

Part No.

KlOJ20K C80-10M
ED-100 c22-1OOP

13050 107-21 C66-1M
Cl05 10 pf 15 " EAL 56289 89D159 c93-lop1
Cl06 100 pf

15 "
Cl07 10 pf 20 "
Cl08
Cl09

10 pf

20 " ETT 05397 KlOJ20K cao-10M

422 ;If 10 "

Cl10 .047 iJ.f 200 "
Cl11

Cl12
Cl13

1 Pf

,033 I.rf
,068 pf 100 "

200 v

100 v

Cl14 .033 I.rf 100 "
Cl15

Cl16

2.5 IJ.f 200 "

5 Kf

200 "
Cl17 2.5 pf 200 "
Cl18 100 vf 6v
Cl19

100 pf

15 v ETB
Cl20 "27 wf 10 v

EAL 56289 89D217 C93-100M
ETT

ETT

MY
MY

MY
MY
MY
MY

MY
MY
EAL

ETT

05397 KlOJ20K cao-1OM
05397 K33JlOS C78-22M

13050
13050

88480
88480
88480
99120

99120
99120

56289

72699

80164

SMLA
107-21

3FR 333-lE C146-.033M
3FR 683-1E
3FR 333-1E

AZ2-255X
A22-505X

AZ2-255X

89D

TDLOO-15

C143-.047M

C66-1M

C146-.068M
C146-.033M
C145-2.5M

C145-5M
C145-2.5M
C147-100M
Cll-100M 10

C78-27M

Fig.
Ref.

18
14,

14.

14.
14~

14
14
14
14,
14

14
14

14.
14,
18

18
18
16

14~

c201
c202 500 pf
C203
c204 100 Kf

500 af

100 pf

15 v EAL

15 v

15 v EAL 56289 89D217

15 v EAL 56289 89D217
C205 0.1 i.rf 200 v

C266
C207
C208
c209
c210

c211 500 I.rf
c212 500 pf
c213
C214 .0033 pf

Not used

500 /.lf
100 IJ.f

100 I.lf

0.1 IJ.f

2 Pf

15 " EAL 56289 89D222

15 v EAL

15 " EAL

200 "
25 v EAL

15 v EAL 56289 89D222

200 v

600 v CerD 72982

*Nominal value, factory adjusted

42

EAL

MY

MY

MY

56289 89D222
56289

89D222 C93-500M 12

C93-500M

C93-100M

12
12

C93-100M 12

02777 P-12M C66-.lM 16

12
12
12
12

12

12
12
12

56289
56289

13050

89D217 C93-100M
89D217 C93-100M

SMlA
56289 89D231
99120 AZ2-205X

ED-.0033 C22-.0033M

C93-500M

C47-.lM
C94-500M

C93-500M

C120-2M

0667R

MODEL 150B MICROVOLT AMMETER

REPLACEABLE PARTS

DIODES

Circuit

Desig.
DlOl

Dl02

TYPO

Silicon

Number

1~645

Silicon lN645

Mfg. Keithley
Code

01295
01295

Part No. Ref.
RF-14

RF-14

Fig.

18
14

D201 Silicon 1~645 01295 RF-14 16
D202 Silicon lN645 01295 RF-14 16
D203 Silicon lN645 01295 RF-14 16
D204 Silicon lN645 01295 w-14 16
D205 Silicon lN645 01295 RF-14 12

D206 Silicon lN645 01295 RF-14 12
0207 Silicon lN645 01295 RF-14 10
D208 Silicon lN645 01295 RF-14 10
D209 Silicon lN645 01295 RF-14 16

D210 Silicon lN645 01295 RF-14

16

D211 Zen‘2r lN7Q9 12954 DZ-21 12

D212 ZeIler lN709 12954 DZ-21 12

MISCELLANEOUS PARTS

Circuit

DeSiX.

Description

Mfg. Keithley Fig.
Code

Part No. Ref.

BT201

Battery assembly

F201 (117V) Fuse, slow blow, 314, amp, 3AG (Mfg. No.

313.750)

F201 (234V) Fuse,

slow blow, 318 amp, 3AG (Mfg. No.

313.375)

F202 (117V) Fuse,

slow blow, l/4, amp, 3AG (Mfg. No.

313.250)

F202 (234,V)

Fuse, slob blow, l/8 amp, 3AG (Mfg. No.

313.125)

---

GlOl

Fuse holder, 2 req'd (Mfg. No. 34.2012)

chopper Assembly

JlOl Connector, 15 pin (Mfg. No. PSC4SS 15-12)
J102 Receptacle, Microphone, 1V OUTPUT (Mfg. No.

80-PC2F)

---

(F)Plug, Microphone,~Mate of 5102 (Mfg. No.

80-MC2M)

J103

Receptacle, Microphone, 1OOM V OUTPUT (Mfg.

No. 80-PC2F)

---

(F)Plug, Microphone, Mate of 5103 '(Mfg. No.

80-MC2M)

80164

75915

75915

75915
75915

75915

80164

03612

02660
02660

02660
02660

Model 1489

10

FU-14

PU-18

FU-17
FU-20

FH-3
20138B 10

cs-175 16

CS-32
cs-33

CS-32
cs-33

2

2

2

(F) Furnished accessory.

0667R

4.3

REPLACEABLE PARTS MODEL 150B MICROVOLT AMMETER

MISCELLANEOUS PARTS (Cont'd)

Circuit
Desig.

3104

-_-_

JlO5*"

Receptacle, INPUT
Plug, Special, Mate of JlOl

Receptacle

Description

, Locking Ring (Mfg. No. 126-1430) 02660
. Receptacle (Mfg. No. 126-1429) 02660
. Body (Mfg. .No. 126-1425)

J105?dd<

Plug

. Nut (Mfg. No. 41-153) 02660

Lock Ring (Mfg. No. 126-1428)

: Plug~(Mfg. No. 126-1427)

5201

Connector, 22 pin (Mfg. No. PSC4SS22-12)

5202 Banana Jack, 2 req'd (Mfg. No. 108-903)

---

---

---

Binding Post, LO (Mfg. No. DF21BC)
Binding Post, GND (Mfg. No. DF21GC)

Shorting Link (Mfg. No. 938-L)

Mfg. Keithley Fig.

Code Part No. Ref.
80164

80164

cs-133
Model 1486

1

12
CS-165
CS-163

02660

CS-161

12
CS-160

02660
02660

03612

74970

58474
58474

24655

CS-164

CS-162

CS-182
BJ-6B

BP-11B
BP-11G
BP-6

16

2
2
2

M201 Meter 80164

P201

---

SlOl
s102

--_
s__

s103

Cord Set, 6 feet (Mfg. No. 4638-13)

93656

Cable Clamp (Mfg. No. SR-5P-1) 28520

Slide Switch, FILTER

Rotary Switch less components, FUNCTIOh
Rotary Switch with components, Function
Knob Assembly, Function Switch

80164
80164

80164
80164

Rotary Switch less components, ZERO

SUPPRESS COARSE 80164

-I-

-_-

__D

-_-

5104

_-_

---

Rotary Switch with components, Zero

suppress coarse

Knob Assembly, Zero Suppress Coarse Switch

Rotary Switch, Potentiometer, ZERO

SUPPRESS FINE

Knob Assembly, Zero Suppress Fine Switch
Rotary Switch less components, RANGE

Rotary Switch with cotiponents, Range
Dial Assembly, Range Switch

80164
80164

80164
80164 16995A

80164
80164
80164

?c:c Schematic Diagram 20350E

-'-$c;* Schematic Diagram 20357D

ME-14 10

co-5

2

cc-4

SW-45

2

SW-214 11
20147B

14838A

SW-219 10
20135B

18070A

RP42-10K

SW-215

1,lO

11
20145B
19713A

4.4

0667R

MODEL 150B MICROVOLT AMMETER

MISCELLANEOUS PARTS (Cont'd)

REPLACEABLE PARTS

Circuit

Desig.

Description

s201 Rotary Switch less components, POWER SUPPLY

---

--­s202

5203

Rotary Switch with components, Power Supply
Knob Assembly, Power Supply Switch

Not used

Slide Switch, 117-234 v
TlOl Transformer Assembly
T201

Transformer

T202 Transformer

RESISTORS

Circuit
Desig. Value Rating

RlOl 100 kR
R102

*390 R
R103 220 kR
R104 10 kR

R105 680 kR

lO%, l/4 w
lo%, 112 w
lo%, l/4 w
lO%, l/4 w
lO%, l/4 w

TYPO

Comp
camp

Comp

Comp

camp

Mfg. Mfg.

Code Part
01121

01121
01121
01121
01121

CB
EB
CB R76-220K
CB R76-10K
CB R76-680K

Mfg. Keithley

Fig.

Code Part No. Ref.

80164

SW-218

10
80164 20133B
80164

80164
80164
80164

80164

NO.

18393A

SW-151

20J37B
TR-93

TR-95

Keithley

Fig.

Part No. Ref.
R76-100K

Rl-390

2
10
10

10

18
18
18
18
18

RlO6 15 n
R107 20 n
R108 47 kfi
Rl09 *3.9 kn
RllO 47 ~k.fl

Rlll 33 kfl
R112 750 kR

R113 150 kR

Rll4 39 kR
R115 3.9 kQ

Rl16 100 kfl
R117 10 kR
R118 470 n
R119 3.9 kn
R120 4.7 k&-l

Rl21 18 kR
R122 18 kfl

Rl23 100 R

R124 10 k0
R125 10 kSl

lO%, l/4 w
lO%, 5 w
lO%, l/4 w
lO%, l/2 w
lO%, l/4 w

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

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

lO%, l/2 w

lO%, l/2 w

lO%, l/2 w

lO%, l/2 w

lO%, l/2 w

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

* Nominal value, factory set.

Comp
WWvar

Comp
Comp
camp

camp
DCb
Comp
camp
Comp

Comp
Comp
Comp
camp
camp

Comp
Comp
Comp
camp
camp

01121

71450
01121
01121
01121

01121

79727

01121

01121

01121
01121

01121
01121
01121
01121

01121
01121
01121
01121
01121

CB 8 R76-15
AW
CB

RP34-20

R76-47K
EB Rl-3.9K
CB

EB

R76-47K

Rl-33K
CFE-15 RPlZ-750K

EB Rl-150K
EB Rl-39K
EB Rl-3.9K

EB Rl-100K
EB Rl-1OK
EB Rl-470
EB Rl-3.9K
EB Rl-4.7K

EB Rl-18K
EB Rl-18K
EB

Rl-100
EB Rl-1OK
EB

Rl-1OK

18
10
18
18
18

15
15

15
15
15

15
15
15
15
15

15
15
15
15

15

0667R

45

REPLACEABLE PARTS MODEL 150B MICROVOLT AMMETER

RESISTORS (Cont'd)

Circuit Mfg. Mfg.

Desig.
R126

R127
R128
R129
R130

K131
R132
R133
R134
R135

R136
R137
Rl38
R139
R140

R141
R142
R143
R144
R145

Value Rating

4.7 kQ
10 kQ
10 kR

50 k;2
250 s2

120 kR
120 kn

50 kR

12 kR
12 kR

470 n
25 kQ

1.8 kR

47 R

10 kR

*47 k:!

50 kn
10 kR

25 kR

"560 n

TYPO

camp
DCb 79727 CFE-15
DCb 79727 CFE-15
DCb 79727 CFE-15 RlZ-50K
DCb 79727 CFE-15

DCb 79727 CFE-15
DCb 79727
DCb

Comp

camp

Comp
DCb 79727 CFE-15
Comp

Comp
ww

DCb
DCb 79727 CFE-15 Rl2-50K
ww 714.50 1NS 115 RP50-1OK
DCb 79727 CFE-15 Rl2-25K

Comp

Code Part No.

01121

EB

WE-15
79727 CFE-15 R12-50K
01121
01121

01121
01121

01121

71450

79727

01121

EB

EB Rl-12K

EB Rl-470

EB

EB R1-47

lNS-115

WE-15

CB R76-560

Keithley Fig.
Part No. Ref.

Rl-4.7K
RlZ-10K
RL2-1OK

15
15
15
15

RlZ-250
Rl2-120K

RlZ-12OK

15
15

15
15

Rl-l2K

15
15

15
Rl2-25K
RI-1.8K

15

15

15
RP50-1OK

RlZ-47K

15

15

15

15

15

18

R146
R147
R148

R149
R150

R151
R152
R153
Rl.54
R155

Rl56
R157
R158
R159
Rl60

R161

R162

R163

R164
R165

10 kR
**LO60 2
**lo60 n

300 kR

Not used

Not

used

Not used
"1.5 kR
"150 R
"100 R

"8.2 MO
"2.7 MR
"1 MR
"680 kfi
"56 kR

"27 k0
"100 n

68 9.

300 kQ

300 2

lO%,

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

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

lO%, 1/z w
LO%, l/2 w
lO%, l/2 w
l/4%, l/2 w
l/4%, l/3 w

ww 71450

1NS 115 RP50-lOK
ww 01686 7010 R132-1060
ww 01686 7010
DCb

Comp 01121
camp
Comp

Comp 01121
Comp 01121
Comp 01121
camp

Comp 01121

camp

Comp 01121

Comp 01121
MtF 07716
ww 01686

79727 CFE-15

CB
01121
01121

CB Rl-150

CB Rl-100

CB Rl-8.2M

CB Rl-2.7M

CB
01121

CB

CB

01121

CB

CB Rl-100

CB Rl-68

CEC-TO

7010

Rl32-1060
Rl2-300K

Rl-1.5K

Rl-1M
Rl-680K
Rl-56K

RI-27K

Rl27-300K

Rl32-300

18
18
18
10

11
11
11

11
11
11
11
11

11
11
11
11
11

* Nominal value, factory set.
** Keithley part number Rl32-1273 is used for R147 and R148 in units adjusted for 50 cps.

4,6

0667R

MODEL 150B MICROVOLT AMMETER

REPLACEABLE PARTS

RESISTORS (Cont'd)

Circuit Mfg. Mfg. Keithley Fig.
Desig. Value

Rating

TYPO

Code Part No.

Part No.

Ref.

R166
R167

R168
R169
R170

R171
R172
R173

R174

R175
R176

R177
Rl78
R179
R180

Rl81
R182
R183
Rl84
R185

R186
R187
R188
Rl89
R190

1 Ma

300.6 il
300 kfi

99.7 kQ

29.7 kfi

9.7 kR

2.7 kR
700 R
333 kR
100 kR

33.3 kfl
10 kR

3.33 kQ
1 kfl
333 n

100 R

33.3 n
10 i-l

3.33 cl
1 cl

100 kR

3 kS1

8.6 kfi

4.99 kn
1 kn

MtF 07716 CEC-TO Rl27-1M
MtF 07716
MtF
MtF
MtF

07716
07716
07716

CEC-TO
CEC-TO R127-300K
CEC-TO Rl27-99.7K
CEC-TO R127-29.7K

R127-300.6

MtF 07716 CEC-TO Rl27-9.7K
MtF
MtF 07716 CEC-TO
MtF
MtF

MtF

07716
07716

07716
07716

CEC-TO R127-2.7K

R127-700
CEC R94-333K
CEC R94-100K

CEC

R94-33.3K

MtF 07716 CEC R94-10K
MtF
MtF
MtF

MtF
MtF

07716
07716
07716

CEC R94-3.33K
CEC R94-1K
CEC R94-333

07716 CEC R94-100
07716

CEC

R94-33.3

00327 A20 R126-10
00327 A20

Rl26-3.33

00327 A20 R128-1

DCb 79727 WE-15

R12-100K

DCb 79727 CFE-15 Rl2-3K
DCb 79727 CFE-15

R12-8.6K

MtF 07716 CEC R94-4.99K
WWvar 71450

AW RP3-1K

11
11
11
11
11

11
11
11
11
11

11
11
11
11
11

11
11
11
11
11

11
10
17
17

2,ll

R191

R192

R193
R194
Rl95

R196

R197

Rl98

Rl99

R201
R202

R203
R204
R205

3.33 kQ
1 kn

2 kS1
Not used
Not used

Not used
Not used
Not used

100 kn

330 n

330 n

4.7 cl

*10 kR

470 R

l%, l/2 w

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

lO%, l/2 w

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

Jc Nominal value, factory set.

0667R

MtF

07716 CEC R94-3.33K
MtF 07716 CEC R94-1K
ww

DCb CFE-15

Comp
camp
Comp
Comp

camp

71450

79727

01121

01121

01121

01121

01121

1NS 115 RP50-2K

Rl2-100K

EB

R1-330
EB Rl-330
EB
EB
EB

Rl-4.7

Rl-1OK

Rl-470

17
17
17

10

17
17
13
13
13

47

REPLACEABLE PARTS

MODEL 150B MICROVOLT AMMXTER

REr;:STORS (Cont'd)

Circuit
Desig.

R206

R207
R208
R209
R210

R211
R212
R213
R214
R.215

R216

R217
R218
R219
R220

R221
R222
R223

R224
R225

ValW

10 kR
100 R
12 kR
100 kQ

Not used
Not used

Not used
Not used

27 R

470 R

10 ldl
12 kR
100 kn

*lo k0

15 k0
15 kfl

15 k0

Not used

15 k0

820 9

Rating

Mfg.

Type Code

01121
01121
01121

camp 01121

camp
Comp

Comp
Comp
Camp
Comp
Comp

Comp
Comp

Comp

Comp

01121
01121

01121

01121

01121
(31121
01121

01121
01121

01121
01121

Mfg.

Part No.
EB Rl-1OK 13

EB Rl-100 13
EB Rl-12K 13
EB Rl-100K 13

EB
EB

EB
EB
EB
EB
EB

EB
EB

EB
EB

Keithley
Part No. Ref.

Rl-27
Rl-470

Rl-1OK

Rl-12K

Rl-100K

Rl-1OK

Rl-15K
Rl-15K

Rl-15K
Rl-15K

Rl-820

Fig.

13
13

13

13
13
13
13

13
13

13
13

R226

R227

R228

R229

R230

R231

R232
R233

R234

R235

R236

R237

R238

R239

R240
R241

R242

X243

R244
R245

22 kR
22 kfl
56 s1

2.7 kR

2.7 kQ

1.8 kfi
390 5-l

2.73 kR
30 k0

1 kR

1.4 k0

3.3 kR
20 kQ
680 n

47 R
Not used

1.8 kR

1 k0
Not used
Not used

Comp
Comp

ww

Comp
Comp

Comp

Comp
DCb
DCb
ww

DCb

Comp
DCb

Comp

Comp

DCb

DCb

01121
01121
94310 Val-10
01121
01121

01121
01121

79727
79727
71450

79727

01121

79727
01121
01121

79727
79727

EB
EB

EB
EB

EB
EB
WE-15
CFE-15

lNS-115

CFE-15
EB

CFE-15
EB
EB

CFE-15
WE-15

Rl-22K
Rl-22K
R133-56
Rl-2.7K
Rl-2.7K

Rl-1.8K
Rl-390
R12-2.73K

Rl2-30K

RPSO-1K
R12-1.4K

Rl-3.3K
RL2-20K
Rl-680

Rl-47

R12-1.8K

R12-1K

13
13
10
13
13

13
13
13
13
13

13
13
13
17
17

13
13

9~ Nominal value, factory set.

4.8

0667R

MODEL 150B MICROVOLT AMMETER

REPLACEABLE PARTS

RESISTORS (Cont'd)

Circuit
Desig.

R246
R247
R248

R301 10 Mfl
R302 300 kR
R303 27.3 kSl

Value Rating

600 Cl

l%, l/2 w

Not used

2.2 kfi

lO%, l/2 w

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

112

w
R304 10 kfi lO%, 5 w
R305 47 kcl

R306 a470 0
R307 10 kn
R308

yc470 R

R309 47 kfi

R310 20%, l/2 w

109 R

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

5%, 2 w

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

Circuit

Desig.

Number Code

Mfg.

TYPO

Code

DCb 79727

Comp

01121

DCb 79727
DCb 79727
DCb 79727
WWvar 71450

Comp 01121
Comp 01121

WWvZ.r 12697

Comp 01121
Comp 01121

Comp 75042

TRANSISTORS

Mfg.

Mfg. Keithley Fig.

Part No. Part No. Ref.
CFE-15

EB

CFE-15

R12-600

Rl-2.2K

Rl2-1OM
CFE-15 R12-300K
CFE-15 R12-27.3K

AW RP34-10K

EB Rl-47K

EB

Rl-470

62.~~ RP42-10K

EB

Rl-470

EB Rl-47K
GBT R37-109

Keithley

13
13

10
10
10
10
17

17
10

17
17

11

Fig.

Part No. Ref.

QlOl
0102

Q106
Q107
0108

$09

QllO ?+6

517638

u-147
Al380
A1380

S17638

S17638 07263

Sl7638

2~1381 01295

2Nl381
Al380

07263

73445
73445

07263

07263
01295

73445

I m-4@

Qlll%

Ql12 517638
Q113 Sl7638
Q114

Q201

A1380 73445

07263
07263

2Nl381

2Nl535

01295

04713

Q202 2N1535 04713

Q203

2N1381
Q204 517638
Q205

4206
Q207

517638

517638

2~1381

01295
07263
07263

07263
01295

TG-33 18
TG-38

18
TG-32 14
TG-32

14
TG-33 14

TG-33
TG-33
TG-8
TG-8
TG-32

TG-32
TG-33
TG-33
TG-8

14
14
14
14
14

14
14
14
14

TG-7
TG-7
TG-8
TG-33
TG-33

TG-33
TG-8

12
12
12

12
12

* Nominal value, factory set.

0667R

49

REPLACEABLE PARTS

MODEL 150B MICROVOLT AMMETER

TRANSISTORS (Cont'd)

Circuit

Desig.

Q208
Q209
Q210

Q211

Q212
Q213
Q214
Q215

Q216
Q217

Q218

Circuit
Desig.

Vl

Number

S17638
2N398A
2N398A

Not used

2Nl381
2~1381
2Nl381

S17638
S17638

S17638
2N1535

Number

512Ax

Mfg. Keithley

Code
07263 TG-33

02735 TG-13
02735 TG-13

01295 TG-8
01295 TG-8
01295 TG-8

07263 TG-33
07263 TG-33

07263 TG-33
04713

VACUUM TUBES

Mfg.

Code
80164

Fig.

Part No.

TG-7

Keithley
Part No. Ref.

EV-512AX 18

Ref.

12

12
12

12
12
12
12

12
12

Fig.

MODELS 14.83, 1484 REPLACEABLE PARTS LIST

Description

Crimp Tcol for Copper lugs

ii8 Nylon Screws

ii8 Nylon Hex Nuts

Copper Bolt-on Lugs
Copper Spade Lugs
Copper Hook Lugs
Copper Splice Tubes
Low-Thermal Cadmium-Tin Solder

Copper Alligator Clips (Mfg. No.

60051
Shielded Cable
Insulated 1120 Copper Wire

Non-metalic Abrasive

Mfg.

Quantity

1
50
50 80164,

100 80164

100 80164,
100 80164,
100

10 feet

10

10 feet

100 feet 80164

3 pads 80164,

Code

80164,

80164

80164
80164

76545
a0164

Keithley
Part No.

TL-1

-

-

LU-19
LU-21
LU-22
LU-23

-

AC-9 14~83, 14,84

SC"5 1483, 14.84

ws-1 1483, 14.84,

17774,A X83, 1484

Used on

Kit Model

1483
14,83 ) 14,84

14.83, 1484
X83, 1484

14.83, 14,84

14.83, 1484
1483, 14~84,
1483, 1484

50

0667R

MODEL 150B MICROVOLT AMMETER

REPLACEABLE PARTS

00327

01121 Allen-Bradley Corp.

01295 Texas Instruments, Inc.

01686 RCL Electronics, Inc.

02660 Amphenol-Borg Electronics Corp.

02735

02777 Hopkins Engineering Co. 73445 Amperex Electronic Co. Division oi

03612 Burndy Corp.

04713

Welwyn International, Inc.

Cleveland, Ohio

Milwaukee, Wis. Kenilworth, N. J.

Semiconductor-Components Division North Adams, Mass.

Dallas, Tex.

Riverside, N. J.

Broadview, Chicago, Illinois
Radio Corp.~ of America

Commercial Receiving Tube and

Semiconductor Division
Somerville, N. .J.

San Fernando, Calif.

Lynwood, Calif.

Motorola, Inc.

Semiconductor Products Division

Phoenix, Arizona

24655 General Radio Co.

West Concord, Mass.

28520 Heyman Mfg. Co.

56289

58474 Superior Electric Co., The

71450

72699 General Instrument Corp.

72982

74970 Johnson, E. F., Co.

75042 International Resistance Co.

Sprague Electric Co.

Bristol, Corm.

CTS Corp.

Elkhart, Ind.

Newark, N. J.
Erie Technological Products, Inc.

Erie, Pa.

North American Philips Co., Inc.
Hicksville, N. Y.

Waseca, Minn.

Philadelphia, Pa.

05397

07263

07716

12697

12954

13050 potter co.

TABLE 16.

facturers, Cataloging Handbook H4-1).

Union Carbide Corp.
Linde Division
Kemet Dept.
Cleveland, Ohio

Fairchild Camera & Instru. Corp.

Semiconductor Division

Mountain View, Calif.

International Resistance Co.

Burlington, Iowa

Clarostat Mfg. Co., Inc.

Dover, N. H.
Dickson Electronics Corp.

Scottsdale, Ariz.

Wesson, Miss.

Code List of Suggested Manufacturers.

75915 Littelfuse, Inc.

Des Plaines, Ill.

79727 Continental-Wirt Electronics Corp.

Philadelphia, Pa.

80164

88480 Mid-West Abrasive Co.

93656 Electric Cord Co.

94310 Tru-Ohm Products

99120 Plastic Capacitors, Inc.

Keithley Instruments, Inc.
Cleveland, Ohio

Detroit, Mich.

Caldwell, N. 3.

Memcor Components Division
Huntington, Ind.

Chicago, Ill.

(Based on Federal Supply Code for Manu-

0667R

51

-

I ,

I
L

-

-

-

,I+

r-

CHANGE NOTICE

September 12, 1967

MODEL 150B MICROVOLT AMMETER

Pane ii. Change the ISOLATION specification to:

ISOLATION:
microfarad.

Circuit ground to chassis ground:

Circuit ground may be floated up to -400 volts with respect to chassis ground.

Gqater than 10' ohms shunted by 0.001

On battery operation may be completely isolated from power line and ground.