Service Manuals, User Guides, Schematic Diagrams or docs for : Keithley 410 410C(Model410_252C410C)
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MODEL 410
and
MODEL 410C
MICRO-MICROAMMETER
KEITHLEY INSTRUMENTS, INC.
CLEVELAND, OHIO
CONTENTS
SECTION
.............................
INT'ROD'JCTION .. ....... .....
..............................
DESCRIPTION .. ....... .....
Currznt ranges
Input Impedance
Input connectors
Input Switch
Grid Current
Zero Drift
Zero Control
Rocordor Output
Response Speed
Amplifier Noise
Circuit Description
Calibration
OPERATION................................ .. ..... .. .....
Input Connections
Input Connections Using Direct Leads
Grid Current
Recording
Speed of Response
MAINTENANCE.............................. .. .*a...,
Maintenance Adjustments
Insulation
Connector Caps
SPECIAL INSTRUCTIONS THE MODEL
FOR 41OC.. .. ,..#....
KEITHI. INSTRUMENTS CZWELAN3, OHIO
SECTIONI INTRODUCTION
Model 410
The Keithley Model 410 Micro-microammeter is a line operated
vacuum tube electrometer designed and constructed especially for
measuring small currents. Full scale ranges are from 10-3 to
j x 13-13 ampere,
The fsaturos include full-scale voltage drop at the lnptit of
less than five millivolts, zero drift of less than 2% of full scale
in eight hours, good accuracy and calibration stability, and simpli-
city of operation. It also has an output which will drive a O-l
or 0-3 milliampere recorder as weli as the numerous potentiometer -
rebalance recorders; one output terminal is at ground, making it
convenient to connect cathode ray oscilloscopes or pen-driving
amplifiers, similar to the Brush and Sanborn equipment.
The major panel controls are the rsngo switch (amperes full-
scale) and the zero. Minor controls are the Zero Check, used to
short circuit the input and in setting the zero, Meter Polarity
Tar providing up-scale readings for currents flowing in either di-
rection, and an ON-OFFpower switch. The mater dial is illuminated,
and these bulbs serve as the pilot light.
Model 41OC
The Keithley Model 41OC is identical to the Model 410, except that
the panel meter is provided with contacts which can be set to
close at any predetermined meter pointer deflection. The delicate
contacts of the meter operate a relay in the 410~7, and the relay
contacts (SPDL') are available for external switching functions
through an AN connector on the rear of the chassis.
- I-1 -
KEITHI,EY TNSTRUMENTS CZVELAND, OHIO
SECTIONII DESCRIPTION
Tw3nt.y ovorlapging current ranges, from 10 x. 10-Y qsre. to
3 x lnmpers are selected by the Amperes Full 3rraJ.e s&t&, :ccm&eB
left of the Meter. The accuracy of the ranges from 1C;x 1S-" throm@
3 x 10-7 is within 25, 10 x 10-g through 3 x lo-]? is wJtiLn il$`,.
Iqut Impedance is controlled by negative fee&%=$ f~>rm Cra ,:`rqmn
so that the voltage drop across the input terminslr 0 &raw than 5,
millivolts for full-scale meter deflection. TX3 3s .c&sedi2n ~rr&Iprl'
zero setting; if the meter needle is not set at `1,erq -nzzH zero 3ztqrti
c urrznt , about 3 millivolts constant potential per ReroenJ of 5;:
scale are added to the five millivolts.
The Input Connector is located on t.he back :s.ce c3 $Be, s.%ssi~,
It is~UHE'nnector. with tafldn insulation, and sagas a s,tanda&
tzf ion insulated mating plug. The plug and 1es.dwarsa, cm' c&bLe sfamz&a
be extremely well insulated to prevent the leakage zrl C&a am&!1 `:3-s.
A cap is provldod for kasping dirt out when tha in&rumenm iy szore&
Input Switch Labelled----
ZEROCKSCKis located ta, tihe Irf5 of %ltm
RangeSwitch. When depressed, it effectively sbn?a $ti >npun ?a, re+-
move spurious charges, and p&Ides tho scro inp.Xi cnrwlid. rsfersnnn
for zeroing the meter with the Zero Control.
I-. Grid Current is less than 5 x lo-l4 ampere, amdJ
limitofmeasurement
vs. 3&s
of a vacuum tube electrometzr.~ Twla is &mti: 1%:
of full-scale on the most sensitive range.
1 Zero Drift is less than 25 of full scale im e&~&mhourn on a~Il?lrmrqes
exceptxx ampere where it is less than 4%03 s?tiI sa.?im ;nz &@&
hours. These drifts include warmup from a cold s%xd. M' * *;ro iiL.mm74lmml-
I Up can be provided, the drift will be one half to ammf:oUHib @ z&ams
amounts ,
1 Zero Control- The Zero knob is located to t&s r&g&t ti She stemerra&
is Usedor zeroing thexer with zero input cur&. EtY3ec*~&e%,7~ wxm
input current can be obtained by depressing the Ee.mm: ~%mti bu%?,onl,. %e
I input must not be short-circuited. This upsets thm neg@5ve fmsd&m& pti
and makes it impossible to zero ths meter.
1
t
t
I'- - u-1 -
L KEITmY INSTRUMENTS
411, &
t A
4'OC
It is recommendedthat the meter pointer not be set anywhere but zero
on the meter scaie with zero input current, because with the feedback used,
a dc potential is developed across the input whenever the output and the
panel meter are not zero for zero input current. Recorders, of course, can
be biased to any part of their seals for zero Volts at the Model 410 o-utput.
Output is provided for driving rscorders. The amplifier will develop
5 volts for full-scale meter deflection, and 5 milliamperes can be drawn
without upsetting the circuits. The OUTiVT connector is at the rear of
the chassis, The connection details and suitable outp,Jt attenuators
are discussed in OPERATION, Section III.
Response Speed of the 410 depends upon the current range being used and
also upon ths capacitance of the external circuitry. On the less sensitive
ranges the speed is limited by the amplifier respons which is from dc to
approximately 1,000 cps. On thi, ranges from 3 x lo- 8, to 10 x 10-l* ompereo
i
I
the speed has been reduced to about 1.0 second by the addition of capacitors
I
across the range resistors. On the three most oenoitivo ranges, shunt cap-
acitance across the input limits the response speed. Because of the method
of application of tim negative feedback, the slowing effects of capacitance
from the high input terminal to ground hs.ve been greatly reduced, but are
still significant. Tnble I below gives typical response speeds; viz; the
time constant of the response t,o a step functior..
TABLE I
r
TYPICAL BESPONSE
SPEEDS (to read 67% of final value)
I
I `-
Rang.3
s No significant external capacitance I with 5000 mmf across
I
Undamped Damped Undamped Damped
3 x 10-13 2.2 seconds 2.2 seconds 4 seconds 4 seconds
1
1 x 10-q 1.0 " 1.0 " 2 I' 2 `I
1 x 10-11 0.15 " 1.0 " .5 :; 1.0 I'
! : x" ~~-~
1 x 10'-8
0.10
0.05
0.01
"
"
"
0.5
0.5
0.5
0
I'
u
.2
.l `I
.05 I'
1.0 "
1.0 `I
1.0 `I
If the maximumspeed of response is desired, the capacitors shunting the
range resistors may be removed; however the increased response to spurious
I ac signals may interfore with recording, as mentioned in Section I.
Amplifier Noise is principally power frequency, and is 30 millivolts
ITM max at the OUtpUt t.smhISh, irrespective of the current range. From
t the most general point of view, grid current and amplifier zero drift are
also background noise; these have already been discussed,
t
- `l-I-2 -
c
t KEITBLEY INSTRUMENTS CLEVETELAND,
OHIO
Circuit Description
The circuit diagram DR 10867-c is enclosed at the back. The amplifier
consists of two 58% electrometer tubes operated as a long-tail pair, with
a substantiel amount of in-phase rejection. Further in-phase rejection is
obtained by supplying Vl and V2 screens from 7.3 and Vk. A triode connected
&X6 is used as the cathode follower output stage.
Negative feedback from the output (directly, or through a low impedance
divider) is accomplished through the shunt resl.star to the grid of the in-
put electrometer tube. It is this feedback which keeps the input voltage
drop low.
Tho open loop volts.g~o gain of ths amplifier, meas'ired from the first
stage grid to the feedback connection which would normally be connected to
the low impedance end of the shunt resistor, is about 2500 on the 1~~s
sensitive ranges, alternates between 1500 and 500 on the middle ranges,
and is 150 on the 3 x lo-13 ampere range. This assures a low input drop.
To insure low drift, the feedback-voltage (the voltage drop across
the high resistance range resistors) is made large and alternat s between
1.0 volt and 3.0 volts for most of the ranges. On the 10 x 10- 8 ampere
range and those less sensitive it is 5.0 volts, while on the 3 x lo-13
ampere range (the instrument's most sensitive) it is 0.3 volt. The alter-
nation of the feedback voltage is used to economize on the very expensive
high megohmresistors, so that only one Is used for every decade of
m*as;ired current. Table II, below, gives the value of Ep and RS for
each current range.
TABLE:II
Range Resistor
Ampares Full Scale RS Accuracy $
10 x 10-4 0.1
3 x 10-4 Z67K 1
10 x 10-5 5OK I.
3 x 10-5 166.7~ 1
10 x 10-6 500K 1
3 x 1~6 1.667 Meg 1
10 x 10-V 5 Meg 1
3 x 10-7 16.67 Meg 1
10 x 10-g 1
3 x 10 -a ::aMeg 1
10 x 10-g 108
3 x 10-9 109 :
10 x 10-10 109
3 x 10-10 1010 :
: 1010
;Oxxl,'!;: 1011
3 ;
10x10-12 1 1011 3
1012
~"xx':;~:3 1012 ;
3 x 10-13 0.3 1012 3
KEIT'LUXYINSTRUMENTS - 11-3 -
CLEVELAND,
OEIO
410 &
4lOC
The power supply is regulated by a Sola transformer. Half -wave
selenium rectifiers supply the B+ and B- potentials. The filtering
is conventional.
Calibration is determined by the value of the high resistance range
resistors and the value of the feedback resistors. From 10-3 t0 10-a
the overall accuracy is better than 2$. From 3 x 10-g to
amperes, the accuracy is better than 4%.
The meter is connected between the output terminal and ground.
When the range resistor is shorted In zeroing the instrumnt, the meter
measures the voltage existing between the input terminal and the output
terminal (which are connected together when the shorting button is
pressed) and ground.
The balancing of the amplifier, with the Zero control, is done in
the filament circuit of K?. This is a convenient low-impedance point and
does not disturb the electrode potentials or' the low grid current elec-
trometer tube,
- II-4 -
f
L"
KEITELEY INSTRuMEmTS CLEVELAND,
OHIO
41!l &
t
4lOC
SECTIOll III OPERATION
Simplicity of operation is an outstanding characteristic of the Model
413. First ccnnect the input to a current source, and the output to a re-
corder or external indicator, if desired.
Then: a) Plug the power cord into a 110 volt 60 cps outlet. Not-2
that because a Sola resonant regulating transformer is used, the power fre-
quency, as weil as voltage, must be the proper value.
b) Turn the amperes Full Scala to the 10 x 10-k position.
c) Turn the power` switch to ON.
d) After a few minutes warmup, set the panel meter to zero with
r
I
ths ZEROcontrol.
e) Advance the instrument's sensitivity with the re.nge switch,
until a usable deflection is obtained on the panel meter. The current is
read directly. Attention should be paid to the METERpolarity switch, so
that an up-scale deflection is obtained.
T
L f) Pariodically check the zero setting by operating the ZERO
CEXCKswitch and receroing the meter if necessary.
Input,
-- using cabling
i
The current source should be connected to the input connector wit,h the
- high impedance side of the current source associated with central conductor
i, .* of the connector. The lead-in cable should be polyethylene, polystyrere, or
teflon insulated coaxial cable, and the connector should have teflon insula-
tion. Amphenol type 83-756 or equivalent is recommended. During preparation
i of cable and connectors, it is essential that all high impedance surfaces be
, kept scrupulously clean to avoid leakage. With graphite coated cable, it is
necessary to avoid tracking graphite onto the high impedance surfaces of the
cut end of the insulation and the teflon surface of the connector. Movement
1 of the cable during measurement should be avoided since this will cause
Spurious needle movements, because of capacitance changes and generation
of static charges.
CBID CUPBFXT the Model 410 is less than 5 x lo-14 ampere - usually
in
. about= X@Gnpere . It can be read directly on the 3 x lo-13 ampere range
after carefully shielding the high impedance input conductor such as by
screwing the connector cap on.
The grid current can be subtracted algebraically from the total current
read on the meter to give the correct current in the circuit being measured -
on the most sensitive ranges.
. PBCOPDING: The Model 410 is provided with a connector on the rear of
the chassis for recording. The output for full-scale meter deflection is
+5'volts. The maximum current that may be drawn from the output terminals
is 5 milliamperes. This output is suitable for driving one and five mil-
liampere recorders as well as recorders employing an amplifier. Cinch-Jonas
S-202-B is the chassis connector, P-202~CCT is the mating plug. Terminal
#l is ground.
- III-1 -
KEITHL?lXINSTBDMgNTS cmLAND, OHIO
Tsblc III gives resistance to be used in series with one and five
milliampere recording milliammatera, to make the recorder full-scale de-
flection equal the panel meter full-scale deflection.
TABLE TII
Recorder Serisa Resistance
1 m.a. 3.3 to 3.7K
5 m.a. 323 to 940
The exact aeriss reaiatanco varies from recorder to recorder, and a
portion of the series resistance should be adjustable ao that the recorder
may be calibrated exactly against the panel mater.
A suitable voltage divider for more sensitive recorders can easily be
made, keeping in mind that 5 volts appear at the output terminal.3 for full-
, scale deflection of the panel meter, and that a 1000 ohm divider will not
draw too much output current and will be sufficiently low impedance to con-
nect to amplifier inputs.
I
The Speed of Reaponae, or the time constant of an input transducer
and mico-nio%%ueter, depend8 upon the speed of response of the cir-
s
cuitry of the instrument find also upon the capacitance of the current
, source and its connecting cable. Because of the wag the negative feed-
.~ back ia applied in the Model 410, the external Input capacitance is not
nearly a.8 important aa in systems using a voltmeter acroaa a shunting
. resistor, and quite large capacitances can be tolerated without having an
impossibly slow response. Thus, a cable run from an ion chamber to the
micro-microammeter is permissible.
The internal time constant of the Model 410 depends upon both the
frequency response of the amplifier stages and the time constanta of the
high megohin range reaiatora and the associated distributed capacitancea,
These change from range to range on the 410, the speed decreasing aa the
sensitivity is increased. Table I in Section II, Description, gives
quantitative values.
t216 Volta. A connector has been mounted on the back face of the
chaaa& to provide 4216 volts for polarizing an ion chamber, The poton-
tial ia derived from 2 bB2 voltage regulator tubea, and is well filtered,
The supply can be short circuited without damaging it, The chaaaia con-
nector ia Cinch-Jones SlOl, and PlOl is the mating plug.
- III-2 -
K!CITELEf INSTRTJMgNTS CLEVELAND,
OHIO
SECTICNIV MAINTENANCE
-
The Keithley Model 4.10 Micro-microammeter has been designed to give
Lang, trouble-free service. ILigh quality components have been used
throughout, and the circuits are stabilized by a substantial amount of
negative feedback.
DR 10867-c, at the back, is the detailed circuit schematic diagram
of the Plodal 410. The circuit operation was discussed in Section II,
Description.
Maintenance Adjustments
One maintenance control is provided. It is accessible from the to!,
of the chassis, and is located behind the meter.
3138, ,ME?%RCALq3RATION,is in series with the Mater. To recalibrate,
use the 13 x 10-j ranSe and, with 7 x 10-b ampere through the input cir-
cuit, adjust ~138 so the meter reads exactly 7.0. Since the shunt resistor
cn this range is accurate to 0.1s of its nominal value the overall accuracy
can be adjusted to about 1% of full scale. Cn the 3 X ID 4 to 10 x 10-9 amper*
rengc tha range resistors are act` ate to 1% and, providing the calibration
was accurately done on the LO x lr T range, the overall accuracy will be 2$,
From 3 x 10-g to 3 x lo-13 anpares the range resistors are accurate to 34
and the overall accuracy will be 476.
,/
i. Vacuum Tubes Vl and V2 are the two electrometer tubes, and are located in
an aluminum can which plugs onto the top of tha chassis near the input
terminals. The tubes have been selected, matched and labelled; Vl is
Keithley part EV5886-5 and V2 is ~~5066-6. The difference between the two
is that EV>886-6 does not have to hnve low grid current. It is recommended
tiiat the complete Input Tube assembly Model 4102, be kept for replacement
purposes.
The other tubes are standard receiving tubes and need no special selec-
tion to assure satisfactory performance of the Model 410.
INSULATION: All insulation for the high impedance conductors Is made
of teflon, as are the contact insulators on the range switch. This should
give satisfactory service in all humidities. Occasionally, the high im-
pedance insulators should be inspected to insure that they are free from
dirt and dust.
CONNECTORCAP: The cap for the input connector should be kept in
place whenever the connector Is not being used. In storage and in trana-
port, it keeps the insulation from accumulating dust and dirt. Before
screwing the cap back onto the connector, be certain that it is clean, so
the insulation will not be contaminated.
t
/
k- - Iv-1 -
I KEITHLEY IKSTRIJMENTS CLEVELAND,
OHIO
i10 &
I 4mc
SECTION SPECIAI INSTBUCTIONS THE MODEL
V FOR 410C
DB 11165-c is the circuit schematic diagram of the Model 410~.
It differs from the 410 in providing the meter contacts, and
the relay which is controlled by them.
The meter-relay is manufactured by Assembly Products, Inc.,
of Chesterland, Ohio, Model 461-c. Its contacts will close
vhen the black meter pointer coincides with the red index
pointer. The index can be set easily to any point on the
meter scale by rotating the black knob on the front of the
meter.
To obtain reliable contacting of the meter, the contacts are
locked together electrically. Unlocking can be accomplished
by operating the FZSZT button on the panel, or by a remote
switch.
To complete the locking path, it is necessary that contacts A
and B of the AN connector be connected. This can be done
within the mating male plug, if resetting is to be done only
with the panel button, or leads can be run to a remote reset
relay or switch.
The one AN connector, it will be seen on the schematic diagram,
is used for the resetting circuit, control relay contacts, and
the output to a recorder.
. The relay contacts are rated 5 amperes at I.10 volts AC, or
24 volts DC.
- V-l -
KEITBLEY INSTRUMENTS CLErnLAND, OHIO
This report is intended to SUP ,ly data on performance in addition to
or outside of our published specifications. Measurements are made on
stock instruments and are to serve as a guide rather than a limitation
or guarantee of Performance of any particular instrument.
Pour Pests are inciuded:
1) @verload characteristics
2) Linearity
31 Response Speed
4) Drift
MODFL 410
Pigute 1 shows the performonce of the output signal with several full
scales overload. Curves are shown for no load and for llC load.
and the input signals used were both positive and negative.
t
/ Figure 2 shows the linearity between negntive full scale and positive full
scale, 11s may be seen, it is so good it is hard to r*eaSureo This is
the anplifier output only and has nothing to do with meter linearity.
i Please note that the range used employs one volt feedback, The
linearity may be expected to be 3 times a8 good on ranges using 3 ~.~lte.,
5 times as good on ranges using 5 Mlta and onlyd times as good on the
most sensitive range.
Chart 3 is a listing of response speeds for all decade ranges and ths most
sensitive `range with small input capacity and with 5000 mmf input
capacity, for the standard unit and for the standard unit with range
switch capacitors remvad.
On some ranges, overshoot is encountered. Por these, the overshoot in
percent of full scale is recorded.
The times given are to reach 90% of final value. Conversion to standard
eLectriCa *`the constant" is made by dividing by 2.3. For example,
the Standard unit on the 10 x 10-12 range has a 90% reSPoMe time of
2.3 secoxxls. This means a "time constant" of 1 second.
Figure 4 shows the 3uday drift record
of a "typicsl" unit. Remember that,
e
-. on any iang~s, the drift record will be ftbes *s good as the record
.3
, shown
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