Service Manuals, User Guides, Schematic Diagrams or docs for : Keithley 153 153(Model153MicroAmmeter)
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INSTRUCTION MANUAL
MODEL 153
MICROVOLT-AMMETER
@COPYRIGHT 1974
J+ZEITHLEY INSTRUMENTS. INC.
MODEL 153
CONTENTS
SECTION PAGE
SPfTCIFICATIONS __-_-_____---__________________-- iv
1. GENERAL DESCRIPTION _____--______-______----
2. (-,pE~TION _______-__---______--------------- 3
3. APPLICATIONS __-______-__-_______----------- 12
4. CIRCUIT DESCRIPTION ___-_______________----- 13
5. SERVICING __-_____-___________------------- 17
6. C&IBuTION _--_________--________--__-_--- 23
7. ACCESSORIES -_--___________--_______________
33
8. REpuCpygjLE PARTS ------------------------- 37
SCHpJ.fATIC _____-_______-__-------------------
45
1174
MODEL 153 ILLLlSTRATIO!&
ILLUSTRATIONS
'i . Vo .
. Title Pap*
1 Model 153 Front Panel. ______________-_-_-_------------------- 7
2 Front pane1 Controls. -______----_---___--_---------------------- 4
3 Rear panel Terminals. --___----_________--_____---------------_- 5
4 Thermal Sink Construction. _--___-_______-_____------------------ 10
5 Using Model 153 with 4-Terminal Connections. ----_--------__----- 11
6 Null Circuit and Leeds and Northrup K3 Potentiometer. ----------- 1:
7 Diagram Showing Currents in Solid State Circuits. --------------- 12
8 Circuit for Semiconductor Resistivity Measurements. ----- -------- 12
9 Model 153 Block Diagram. ____-___-___________________________ 13
10 Wave Form at Junction of Diodes D301 and 0302. ----------------- 16
11 Wave Form at Junction of Resistor R302 and Capacitor C302B. ------ 18
12 Wave Form at -13 Volt Supply. __--____________---_---------------- 18
13 Divider Connection for Multivibrator Frequency Adjustment. ------- 20
14 Wave Form of Multivibrator Output. -------------------------- 20
15 Wave Form for Tuned Multivibrator Output Across Resistor R121. --- 20
lb Wave Form for Input Modulator ElOl. ---------------------------- 20
17 Demodulator Wave Form for Full-Scale Input on l-Volt Range. ----- 21
18 Typical Model 153 Drift Chart. _____-_-_____-___-__----------- 25
19 Model 153 Interior. ----__--------_-_-------------------------- 26
20 Model 153 Inter&,=. __-_______--______-___----------------------- 27
21 Capacitor, Tube, Battery, and Modulator Locations on PC-lob. ----- 28
22 Resistor Locations on Printed Circuit Board PC-lob. ---- - ----- -- 29
23 Component Locations for Printed Circuit Board PC-107. _--_____- 30
24 Component Locations on Model 153 Rear Chassis Panel. ---- ----- -- 30
25 Component Locations on Range Switch Sl. -_------__------------- 31
26 component Locations on Range Switch Sl. _____-______-_-___-_--- 31
27 Component Locations for Model 153 Power Supply and Multivibrator. 32
28 Keithley Instruments Model 1531 Gripping Probe. -_--_---_-e-s-- 33
29 Keithley Instruments Model 1532 Test Leads. ----___------------ 33
30 Keithley Instruments Model 1533 Mating Connector. -------------- 33
31 Model 1483 Low-Thermal Connection Kit. _____-______________---- 34
32 Keithley Instruments Model 6012 Triaxial-to-Coaxial Adapter. _---- 34
33 Exploded View of Model 4005 Rack Mounting Kit. ___-_____-____---- 35
1174 iii
MODEL 153
SPECIFICATIONS
KEITHLEY INSTRUMENTS. I LN c.
INSTRUCTION MANUAL
CHANGE NOTICE
MODEL 153 MICROVOLT-AMMETER
INTRODUCTION: Since Keithley Instruments is continually improving pro-
duct performance and reliability, it is often necessary to make changes
to Instruction Manuals to reflect these improvements. Also, errors in
Instruction Manuals occasionally occur that require changes. Sometimes,
due to printing lead time and shipping requirements, we can't get these
changes immediately into printed Manuals. The following new change in-
formation is supplied as a supplement to this Manual in order to provide
the user with the latest improvements and corrections in the shortest
possible time. Many users will transfer this change information directly
to a Manual to minimize user error. All changes or additions are indi-
cated in italics.
Page 41, Replaceable Parts, Resistors should read as follows:
R172 9.9kn O.l%, 1/3w w 15909 1250-9.9KR R-110-9.9?? 22
R173 100 n O-l%, 1/3w w 15909 1250-100R R-110-100 22
Pages 38 s 39, Replaceable Parts, Diodes, should read as follows:
D303 Rectifier, l.OA, 8OOV lN4006 MOT RF-38 27
D304 Rectifier, l.OA, 6OOV IN4006 MOT RF-38 27
MODEL 153 GENERAL DESCRIPTIO1i
SECTION 1. GENERAL DESCRIPTION
l-l. GENIZAL.
a. The Keithley Model 153 Microvolt-Ammeter is a versatile dc instrument with high inp,:t
impedance and low noise for measuring a wide range of voltages and currents. Its voltage
ranyes are from 5 microvolts full scale to 1000 volts, and its current ranges are from
lo- ?l ampere full scale to 0.1 ampere. The Model 153 has zero-center and zero-left meter
scales.
b. Accuracy for the voltage ranges varies from 21% of full scale on the 3-millivolt a-.?
higher ranges to ?3% of full scale on the 10 and 30-microvolt ranges. Accuracy for tjle
current ranges varies from +2% of full scale on the 3 x 10v9 ampere and higher ranges to
24% of full scale on the 3 x lo-11 ampere and lower ranges.
c. Input resistance is 200 megohms for the l-millivolt and higher ranges. Input resis-
tance for the lo-microvolt range is 20 megohms. If a lower resistance is wanted, a front
panel switch control allows shunting a 2-megohm resistor across the input.
d. Input noise on the most sensitive voltage range with the input shorted is less thar.
0.06 microvolt rms. In ut noise on the most sensitive current range with the input open
is less than 0.1 x lo- 13 ampere rms.
1-2. FEATURES.
a. The Model 153 has excellent resolution for potentiometric null detector applications.
Line frequency rejection is good; a power line or twice power line frequency which is 40 db
(p-:~"c) greater than full scale affects readings less than 0.5%. Isolation greater than
10') -..,~s from ground permits use in floating circuits.
h The Model 153 uses the voltage drop method to measure currents. Input resistance
a:: .in ammeter varies from 1 megohm on the lo-L1 ampere range to 1 ohm on the O.l-ampere
range. Voltage drop varies from 10 microvolts to 100 millivolts, depending upon the
range used.
=. Recorder output is fl volt dc at up to 1 milliampere for full-scale meter deflection
on any range. The l-milliampere capability permits use with recording galvanometers.
Output resistance is less than 10 ohms with the output potentiometer set for maximum out-
put. Drift is less than +2 microvolts per 24 hours.
l-3. APPLICATIONS.
a. As a voltmeter, the Model 153 is ideal for measuring a wide variety of voltages such
as contact potentials, vacuum tube electrode potentials, biologically generated emf's,
electro-chemical potentials, and power supply voltages. Other applications include use
with various voltage generating transducers such as piezo-electric generators, Hall effect
generators and strain gauges.
b. The Model 153 is also ideal for most null detector applications. On the three most
sensitive ranges, power sensitivity is better than 5 x lo-21 wtt. High ac rejection and
~iloating capability make the Model 153 an ideal null detector for any bridge or potentio-
meter.
1174 1
I GENERAL DESCRIPTION MODEL 153
FIGURE 1, Model 153 Front Panel.
2 1174
MODEL 153 OPERATION
SECTION 2. OPERATION
2-1. FRONT PANEL CONTROLSAND TERNINALS.
a. METER Switch. The METER Switch has four positions. POWEROFF shuts off the in-
strument; this also short circuits the meter, allowing accurate mechanical zero adjust-
ment. METER + and METER - determine meter polarity. CENTER ZERO sets the instrument
for center zero operation (lower meter scales).
b. FUNCTION Switch. The FUNCTION Switch has three positions, two for voltage inputs
and one for current inputs. In the VOLTS INPUT R-2M position, input resistance is ap-
proximately 2 megohms. In the VOLTS R-OPEN position, input resistance is at the maxi-
mum for the range being used. (See Table 1.) In the AMPS position, the Model 153 func-
tions as an ammeter.
c. RANGE Switch. The RANGE Switch selects the full-scale instrument sensitivity for
one of 17 voltage and 21 current ranges. The 10 or 3 of the top meter scale corresponds
to full-scale deflection for the range selected with the RANGE Switch.
d. ZERO Control. The ZERO Control allows precise meter zeroing. Its range is about
20 microvolts, so it is most effective on the microvolt ranges. Since the II-volt and
higher ranges use a 1OOO:l divider, the Control is also somewhat effective on the 3-volt
range. It has much less effect on other ranges.
e. INPUT Receptacle. The INPUT Receptacle is a Teflon-insulated Triaxial type con-
nector. Its center terminal is the circuit high; the inner shield is circuit low (cir-
cuit ground); the outer shield is chassis ground.
2-2. REAR PANEL CONTROLSAND TERMINALS.
a. DC OUTPUT ADJ Control. This Control sets the amplitude of the output voltage.
Both the output voltage and reszstance vary wxtn the control setting. Voltage span is
from 0 to 1.05 volts; output resistance varies to 7.5 kilohme maximum.
b. Output Binding Posts. Three posts are used for the l-volt recorder output. G is
f;r case ground; LO is circuit ground; HI is the output connection. The furnished short-
!-:: link is for connecting the LO Post to the G Post.
C. 117-234 Switch. The screwdriver-operated slide switch sets the Model 153 for 117
or 234-volt ac power lines.
d. FUSE. For 105-125 volt operation, use a l/2 ampere, 3 AG Slow Blow fuse. For
210-250 volt operation, use a l/4 ampere, 3 AG Slow Blow fuse.
e. Power Cord. The 3-wire power cord with the NEMA approved 3-prong plug provides a
ground connection for the cabinet. An adapter for operation from 2-terminal outputs is
provided.
NOTE
The Model 153 INPUT Receptacle is a Triaxial connector. Any attempt to con-
nect bnc-type connectors to it may damage both.
1174 3
OPERATION MODEL 153
-MECHANICAL
ZERO
FUNCTION METER
SWITCH - -SWITCH
(S1) .(S3)
INPUT ZERO
RECEPTACLE- -CONTROL
(Jl) (R155)
I
RANGE SWITCH
I
(S2)
FIGURE 2. Front Panel Controls.
I MODEL 153 OPERATION
- ..-. ,.
3
FIGURE 3. Rear Panel Terminals.
OPERATION MODEL 153
2-3. PRELIMINARY PROCEDURES.
a. Check the 117-234 Switch and the Fuse for the proper ac line voltage.
b. Set the controls as follows:
METER Switch POWEROFF
RANGE Switch 1 VOLT
FUNCTION Switch VOLTS INPUT R-2M
Check meter zero. If necessary, adjust with the meter mechanical zero.
C. Connect the power cord and set the METER Switch to +. Within one minute, the meter
needle should be at zero with the input shorted. If the meter is not exactly at zero
with the input shorted after approximately 20 minutes, adjust the internal BIAS ADJ Po-
tentiometer, R125 for exact meter zero. (See paragraph 5-5.) For maximum accuracy, al-
low the Model 153 to warm up approximately 30 minutes.
d. To cancel any zero offset, short the input high to low and reduce meter sensitivi-
ty. Adjust the front panel ZERO Control.
2-4. VOLTAGE MEASUREMENTS.
a. Voltage measurements can be made with either of two input resistances: 2 megohms
for all ranges, or a higher resistance, from 20 megohms to 200 megohms depending upon
the range.
1. Generally, it is better to use the higher input resistance (obtained by setting
the FUNCTION Switch to VOLTS OPEN). To maintain the accuracy of measurements, the in-
put resistance should be 100 times the source resistance. (See Table l-l for input
resistance by ranges.
2. With the higher input resistance, soma meter deflection may occur with the input
open due to extraneous sisal pickup. To reduce this pickup and also to speed recovery
from input overloads when measuring low impedance sources, use the 2:megohm input resis-
tance (obtained by setting the FIJNCTION Switch to VOLTS (R-2M).
b. Connect the voltage source to the INPDT Receptacle. Use properly shielded and
grounded leads. Refer to paragraphs 2-8 and following for suggestions and cautions.
c. Set the RANGE Switch to the highest voltage range. Turn the METER Switch to CENTER
ZERO for the correct polarity for the input signal. Increase the Model 153 sensitivity
until the meter shows the greatest on-scale deflection. On the 3-volt and higher ranges,
the Model 153 will withstand overloads to 1000 volts without damage. On the lower ranges,
momentary overloads to 1000 volts will cause only temporary instability and zero offset.
Prolonged overloads will damage components and cause increased noise and slower response
speeds.
I 6 1174
MODEL 153 OPERATION
TABLE 1. Model 153 Voltage Input Resistances and Current Input Resistance, Voltage Drop
and Maximum Current Overload by Ranges. Maximum Current Overload is tllc p,r~'atcst curr~p.t
for the ralli;e xliich will not damage tliti range resistor.
vo1tag e Inpur Rcsistancc current Input Voltage Maximum
Range :~tll FLTC'rION Renfie Resistance Drop GUI-rent
..:itcll sft to Overload
OPEN R-211 (milliampcr:
10 microvolts -20 Mu -1.8 M. 10 picoamps 1 M. 10 ,I" 0.5
30 micro\~i,lts -50 M -1.9 x 30 picoamps 1 ?1 30 ,.v 0.i
100 microi~olts -200 hl~ -2 El 100 picoamps 1 T.1 100 ,:v 0.5
300 microvolts -200 )I. -2 Mu 300 picoamps 1 bl, 300 ;i" 0.5
1 millivolt -200 M -2 M 1 nanoamp 1 hl 1 m\ 0.5
3 millivolts -200 K -2 M. 3 nanoamps 1 x 3 rn" 0.5
10 millivolts -200 M. -2 M. 10 nanoamps 1 Mu 10 mv 0.5
30 millivolts -200 Mu -2 MY 30 nanoamps 100 k:~ 3 mv 1.6
100 millivolts -200 Mu -2 M. 100 nanoamps 100 k~. 10 mv 1.6
300 millivolts -700 Mu -2 M' 300 nanoamps 10 k:: 3 mv 5
1 volt i -200 M: -2 M? 1 microamp 10 k:. 10 mv 5
3 volts 200 MT -2 MC 3 microamps 1 kl. 3 rn" 16
10 volts 200 M: -2 MS 10 microamps 1 k:: 10 mv 16
30 volts 200 Mu: -2 I-Ii: 30 microamps 100 1. 3 mv 50
100 volts 200 M: -2 w 100 microamps 100 :. 10 mv 50
300 volts 200 M1 -2 Ml? 300 microamps 10 1. 3 mv 160
1000 volts 200 M? -2 I% 1 milliamp 10 7. 10 mv 160
3 milliamps -1 n 3 mv 500
10 milliamps -1 R 10 mv 500
X rnil.~icatupS 21 R 30 mv 500
100 milliamps -1 r! 100 mv 500
2-5. CURRENT MEASUREMENTS. Set the FUNCTION Switch to AMPS. Select the range using the
RANGE Switch. Make sure low resistance leads are used to connect the source to the Model
153 input to minimize input voltage drop. Refer to Table 1 for the voltage drop by ranges
and for the maximum allowable current overload which will not damage the instrument. On
all ranges momentary overloads will only cause temporary zero offset end instability.
Prolonged overloads exceeding the values in Table 1 may damage the current-sensing resis-
tars.
2-6. FMATING OPERATION
a. The Model 153 can be connected Qetween two potentials, neither of which is at powr
line ground, It can be floated up to -500 volts off ground. Triaxial connectors are
especially useful when operating the low terminal at a different potential from the ground
terminal.
1174 7
OPERATING INSTRUCTIONS MODEL 153
b. For best results with floating operation, follow the steps below:
1. Remove the shorting link from the LO or GND Post on the rear panel.
2. Connect the unknown source to the Model 153, connecting the lowest impedance
paint to the input low. Operate as described inparagraph 2-4. Do not ground any re-
corders used with this operation, since the low of the Model 153 output is no longer
grounded.
3. Use triaxial cable and connectors for floating operation. A complete outer shield
protects the operator.
4. Make sure the chassis is grounded. Use the G Post on the rear panel or the ground
pin of the power cord.
2-7. RECORDEROUTPUT.
a. Model 153 output for full-scale meter deflection on any range is adjustable from 0
to *1.05 volts at up to 1 milliampere. Output polarity is positive. Output resistance
is less than 10 ohms with the DC OUTPUT ADJ Control set for maximum output; resistance varies
with the Control setting to 7.5 kilohms maximum. If the Model 153 is used for floating
measurements, do not ground the recorder connected to the output.
b. When recording with the Model 153 "se the Keithley Model 370 Recorder. The output
of the Model 153 is sufficient to drive the Model 370 without the "se of any recorder
preamplifiers. The Model 370 allows maximum capability of the Model 153. It has 1% line-
arity, 10 chart speeds and can float up to ?500 volts off ground. Using the Model 370
with the Model 153 avoids interface problems which may be encountered between a measuring
instrument and a recorder.
c. To "se the Model 370 with the Model 153 connect the high and low binding posts on
the Model 153 rear panel to the sama posts on the Model 370. Do not ground the Model 370
if differential measurements are being made. Adjust the easily accessible Calibration
Control on the Model 370 for full-scale recorder deflection.
2-8. INPUT CONNECTIONS.
a. The Model 153 INPUT Receptacle is a triaxial type; its mating connector is the
Keithley Model 1533. For input leads to the Model 153, Keithley Instruments, Inc., has
the Model 1534 Special Low-Thermal Triax Cable which can be connected directly to the
Model 1533 Connector. The Connector is made to acconrmodate the 0.145-inch outer diameter
of the Cable.
b. For best connections to the input, use the accessory probes and leads described in
Section 7. This will enable the Model 153 to be used under the best conditions. Other
considerations for making sure the Model 153 is properly connected are listed in the
following paragraphs.
c. Carefully shield the input connection and the source being measured. Unless the
shielding is thorough, any alteration in the electrostatic field near the input circuitry
will cause definite meter disturbances.
8 1174
MODEL 153 OPERATING INSTRUCTIOXS
d. Use high resistance, low-noise materials - such as Teflon (recommended), polyethy-
lene or polystyrene - for insulation. The insulation leakage resistance of leads shx*Jld
be greater than 500 megohms to maintain the Model 153 input resistance. Excessive lea;:-
age reduces the accuracy of readings from high impedance sources. Voltage breai:d3jm of
the cable must also be high: 1000 volts center conductor to inner shield; 500 volts be-
tween shields. The Model 1534 Cable meets these requirements. Triasial cables used
should be a low-noise type which employ a graphite or other conductive coating brt!ieen
the dielectric and the surrounding shield braid.
e. Any change in the capacitance of the measuring circuit to ground will cause extran-
eous disturbances. For instance, cable flexture changes the cable capacitance and thus
affects meter readings. Make the measuring setup as rigid as possible and tie down connec-
ting cables to prevent their movement. If a continuous vibration is present, it may ap-
pear at the output as a sinusoidal signal and other precautions may be necessary to iso-
late the instrument and the connecting cable from the vibration.
f. For low impedance measurements, unshielded leads and the Model 6012 Adapter ma)
be used. Since the circuit low and ground are connected with the Adapter, do not use it
for off-ground measurements.
NOTE
Keithley Instruments, Inc., has several booklets available on low voltage measure-
ments and low current high resistance measurements. A list is available from
Keithley Instruments, Inc., or its representative.
2-V. ACCURACY CONSIDERATIONS. For sensitive measurements - 100 millivolts and below -
other considerations besides the instrument affect accuracy. Effects not noticeable when
working with higher voltages are very important with microvolt signals. The Model 153
only reads 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 emf's, shielding and circuit connections.
2-10. THERMAL EMF'S.
a. Thermal emf's (thermo-electric potentials) are generated by thermal gradients be-
tween any two junctions of dissimilar metals. These can be significatn compared to the
signals which the Model 153 can measure.
b. Thermal emf's can cause the following problems:
1. Metal instability or zero offset much higher than normal. Note, though, the
Model 153 may have some offset (paragraph 2-3).
2. Meter is very sensitive to ambient temperature VariStiOnS. This is seen by touch-
ing the circuit, by putting a heat source near the circuit, or by a regular pattern of
instability, corresponding to heating and air conditioning systems or changes in sun-
light.
1174 9
OPERATING INSTRUCTIONS MODEL 153
c. To minimize the drift caused by thermal emf's, use the same metal or metals having
low thermo-electric powers in the input circuit. Gold, silver and low-thermal solder
have thermo-electric owers within about *0.25 wv/'C of copper. This means even a tempera'-
ture difference of 10 1 C between one of these metals and copper will generate a thermal
emf of 2.5 microvolts. At the other extreme, germanium has a thermo-electric power of
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