Keithley 150R, 150 Service manual
MODEL ‘150
and
MODEL l5OR
DC MICRO VOLT-AMMETER
INSTRUCTION MANUAL
’ .
KEITHLEY INSTRUMENTS, INC.
CLEVELAND, OHIO
“‘1,
SECTION
INTRODUCTLON
SPECIl~ICA~IONS
OPJ3RATION
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Operating Controls
A.
Preliminary Set-up
B.
General Precautions
C.
1.
2.
3.
4.
5.
Meaouring Voltage
D.
1.
2.
3.
Measuring Current
E.
1.
2.
Other Applications
F.
1.
2.
source Reoistance
Shielding
Thermal EMF
Input Noise
Checking the Zero Point
Direct Moaswement
Small varib.tions
Differential Voltages
Dire&
14oasurcment
Small Variations
Null Indicutor
Megohmwter
1 .'
II
III
’
CIRCUIT DESCRIPTION
Input Circuit
A.
AC Amplifier
B.
DC Amplifier
C.
Zero Supprension
D.
Other Controls;
E.
Power Supply
F.
MAINTENANCE
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General Notes
Trouble Shooting
Volta&c-Renistance Diagram
Circuit Schematic Diagram
Replaceable Parts List
Iv
V
SECTION I - INTRODUCTION
The Model 150 Micro Volt-Ammeter is a stable, versatile instrument
for measuring extremely low level DC signaln. It functions a6 a
voltmeter i9‘om one microvolt to one volt full scale, and as an
ammeter from one milliampere to one hundred micro-microampere8
full scale., It aloo opcratev as a DC amplifier with gains up to
ten million for driving recordertl.
The very low noise level
of
the Model 150, together with ite long
term stability rrake it ideal for many meaouromcnto requiring c;:treme power nensitivity.
Typical applications include mca,suring the output from strain gages,
thermopilos,
oclntillation countors,
thermocouples,
and barrier layer cells. Other applications
bolometers, phototubes, ionization chanlbtirs,
are found in cell studies, measurement of electrochemical potcn-cials,
electrolytic corrosion studies, molecular weight analysis and Hall
effect studies.
In addition to its use as a direct indicator of minute potentialo
and currents, the Mod01 150
Wheatstone or Mueller bridges,
may
also be used as a null detec~tor In
or with an external voltage source
ao a meg-me&ohmmeter. .
An important feature of the inritrument is zero supprenoion up to
100 times full scale,
in place of the usual more limitod~ meter zero.
This permits measurements of small oignala in the presence of large
thermal EMF's or other masking DC signals.
-1
I
SXTION II - SFXIFICATIOPIS
VOLTXTX~ SrPECIFICATIONS
13
RANGES:
overlapping ranges in lx and
microvolt to 1 volt full wale on n zero-cqnt.cr mster.
3x
sI;cps from 1
Zl<RO STADILITY:
NOISE :
‘2ccuRAcY:
INPUT AhTD SOURCE RXSISTANCE: As tabulated bclov unless
RANGE:
Aftor n one hour warm-up within + 0.1
microvolt + 2 x lo-5 R
o~icrovolts
per day, -&rc i7 Is
the sourcerasiotancc in ohms.
b!ith the input shdrted, less than 0.03 !?!.crovolt
peak to peak (0.006 microvolt RW). At variol+s source
impcdlances the noiw is given by E =
6.5 Y
IO-+ (II +
2000); microvolts peak-to-peak since the ohmic input
reoistanco is added to R, the source resisfence.
_ .
25 of full scale on all rsngco.
resistors
shunting ths input are requested, in which
case the input resistance i3 1OOK on the micrcvclt rxgcc
and 1 megohm on tho millivolt rangee. The rw~xilwn sowcc
res-lstanco specificatisns on the 1 and 3 n:crovolt ranges
hold with or without shuntine input resistance.
.
Input Resistance
Greater thsn
Maximum
Source Hssistanca
1 microvolt
3 microvolts
10 microvolts
30 microvolts
100 microvolts
and above
F?ESPONSE SPEED: (10 to p@$ of full scale.). With maximum
specified source resistance, less than one second
ranges except the 1 microvolt renge whore it is two seconds.
b!ith source resistances less than 10% of maximw source
resistnnco,
except the 1 microvolt range where it is within 1 second.
1 me&ohm
3
megohms
10 megohms
30 megohms
90 megohms
10~ ohms
30~
ohms
1OOk ohms
300k ohms
1 megohm
on
all
response io within 0.5 second on all ranges,
.I1 -1
VOLTAGE ZERO SUPPRESS: Rnngos, Off, plllo or minus 10, 100,
lOQ0 and 10,000 microvolto; and 0.1, 1.0, 10.0, 100.0
m~~l.:~vo.ltn corresponding to tho MICROVOLTS and
MILLI-
VOLTS positions on tho function switch. Thu accuracy
of the
oupproooion rangco
1s approximately 2C$ and the
stability is such that 100 times full scale may be
suppressed.
RANGES: 15 overlapping ranges in lx and 3x steps frown lo-lo
to 10-3 ampere full scale on a zero center meter.
-.i
STARILITY:
After one hour warm-up,
lo-11 ampere per day.
NOISE:
ACCURACY:
VOLTAGE DROP:
INPIJP RESISTANCE:
Less than 2 x lo-12 ampere peak to peak.
Plus or minus 3% of full scale on all rangon.
100 microvolts on the millimicroampero ranges,
1
millivolt
on the microampere ranges.
Equal to 1 x 10m4 divided by current range
on microamperes. (Input resistance on the 10-j range Is
one ohm, rising to one megohm on the 10-l' ampere range).
RESPONSE SEZD :
'One second except on the 10-l'
it is two seconds.
CURlGNT ZERO SUPPRESS:
suppression on any range. Accuracy and stability are tho
same as for voltage zcrc suppress.
GENERAL SFECIFICAT';IONS
RECORDER OUTPUT:
Plus or
for full-scale deflection on any range.
within plus or minlui 2 x
'
range vhere
A maximum of 100 times full scale zero
minIA
10 volts at five milliamperes
OUTPUT IMPEDANCE:
60 ~7.5 RFJECTION:
INPU!I' ISOLATION:
Less than 10 ohms belou 1 cps.
Greater
than 5O:l.
Negative terminal may be grounded or floating
up to plus or minus 400 volts with respect to the case.
A link is provided for grounding the negatlvo terminal to
the case.
POWER REQUIREMWI'S: 11-f/230 volts, 30 watts, 60 cps only.
50 cps mod&s on special order.
II - 2
SECTION III - OPERATION
A. OPI?RATII:G COF!TROI.S
The controlo of the Modal 150 are simple and conveniently
placed. 'Their functions are as follo7m:
ON-OFF svitch is located to the right of the panel
motor.
FUNCTION switch selacto the function which is to be
used;
millivolts, microvolts, ;r.icromporco or
mlllimicroampores.
RANGX switch selects the full scale c!ultiplier of
the function selected by the FUNCTI@N switch.
Noto that the 0.3 and 0.1 positions are to be
used in current measurement only.
ZERO SUPPRESS controls consist of the ZERO IiANCX
switch which selects the course range of suppressing voltage in discreet steps and the ZERO
SET potentiometer which gives continuously
variable fine control including settings through
zero I
.
_ _
PREIJMINAPY SST-UP
B.
Connect the instrument to the power line. Unless othcrvioc
marked the unit nay be used on 117 volt, 60 cps line.
convert to 220-volt operation, refer
t0
the MAINTZ?!ANCE coctioll.
A three-wire line cord is furnished, which grounds the cabinet.
If a three-wire receptacle is not available, use tho two-pin
adapter furnished, and ground the third lead to an external
ground.
Set controls as follows:
Function:
Millivolts
Range: 1000
Zero suppress: OFF
Input:
Short the inputloads together.
TO
III - 1
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