Service Manuals, User Guides, Schematic Diagrams or docs for : Keithley 603 603A(Model603)
<< Back | HomeMost service manuals and schematics are PDF files, so You will need Adobre Acrobat Reader to view : Acrobat Download Some of the files are DjVu format. Readers and resources available here : DjVu Resources
For the compressed files, most common are zip and rar. Please, extract files with Your favorite compression software ( WinZip, WinRAR ... ) before viewing. If a document has multiple parts, You should download all, before extracting.
Good luck. Repair on Your own risk. Make sure You know what You are doing.
Image preview - the first page of the document
>> Download 603A(Model603) documenatation <<
Text preview - extract from the document
INSTRUCTION MANUAL
MODEL 603
ELECTROMETER AMPLIFIER
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 factory, DDD 216.
795.2666. You will be given assistance 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 representa-
tkve or the plant directly before returning the
instrument.
Estimates for repairs, normal recalibration?.,
and calibrations traceable to the National Bureau
of Standards are available upon request.
MODEL 603 ELECTROMETER
AMPLIFIER CON'I'ENTS
CONTENTS
SECTION
INTRODUCTION . , . . . . . ............... . I
SPECIFICATIONS . . . . . . . . . . . . . ............... . . II
OPERATION . . . . , . . . . . . . . . ............... . III
A.) Operating Controls
B.) Input Output Connections
C.) Preliminary Set Up
D.) Use of Model 603 as a Differential
Amplifier
E.) General Precautions
CIRCUIT DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV
A.) Detailed Description of Amplifier
B.) power Supply Voltages
C.) Operation of Power Supply
MAINTENANCEAND TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . V
A.) Maintenance
B.) Trouble Shooting
REPLACEABLEPARTS LIST . . . . . . . . . . . ............... , . . 6
VOLTAGERESISTANCE DIAGRAM . . . . . . . . . ............... , . .
SCHEZ4ATIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1165R i
SECTION I INTRODUCTION
--
The model 603 Electrometer Amplifier is a high gain amplifier
and voltmeter for the frequency range of dc to 50 kilocycles.
Its outstandinp characteristics are an input impedance of
greater than lOl& ohms shunted by 10 micromicrofarads, a grid
current of less than 5 x lo-lh amperes, a maximum full scale
sensitivity of 2.5 millivolts, differential input, low drift
and a remote probe containinp the first stage electrometer
tubes. The remote probe allows the input grids to be located
as far as 21r feet from the main amplifier. By employing this
feature the input capacitance may be kept to a minimum so that
it is possible to achieve fast voltaee and current measurements
in high impedance circuits., Current measurements, either dif-
ferential or single-ended are made by inserting high megohm
resistors in the place provided in the remote probe.
The outnut capability of the Model 603 is 10 volts sinale
ended or 20 volts pushnull at a maximum current of 10 milli-
amperes. The output is therefore suitable for driving mil-
liamnere recorders as well as nen amplifiers and oscillo-
scopes.
I-l
MODEL 603 ELECTROMETER
AMPLIFIER SPECIFICATIONS
SECTION II SPECIFICATIONS
AS A VOLTMETER:
RANGE: Differential input from .0025 volt full scale to 1 volt in nine lx, 2.5x and 5x
ranges.
ACCURACY: *2% of full scale on all ranges exclusive of drift.
ZERO DRIFT: Less than 2 millivolts per hour after l-hour warm-up.
INPUT IMPEDANCE: Greater than 1014 ohms shunted by 10 picofarads each input to ground.
AS Aiv METER (WITH MODEL 6033 SHUNT RESISTORS):
GRID CURRENT: Less than 5 x lo-l4 ampere.
TYPICAL RISE TIMES: 10% to 90% for selected current ranges.
Rise Time with Rise time with
Voltage Shunt No External 20 pf
Range > Resistance, Capacitance, Across Input,
millivolts ohms milliseconds milliseconds
2.5 x LO-12 2.5 109 60 125
2.5 x LO-l2 25.0 10 10 500 1000
2.5 x LO-10 2.5 107 0.6 1.0
2.5 x LO-10 25.0 108 6.0 12.0
2.5 x 10-g 2.5 105 0.03 0.04
2.5 x 10-s 25.0 10'5 0.05 0.1
AS AN AMPLIFIER:
GAIN: With single-ended input and output, 4000, 2000, 1000, 400, 200, 100, 40, 20, and
10 for meter ranges of .0025 to 1 volt full scale.
FREQUENCY RESPONSE(Within 3 db): From 1-kilohm SOUL-ceresistance ox less, dc to 10 kc
on the .0025-volt range, rising to 50 kc on the l-volt range.
NOISE: Less than 25 microvolts rms referred to the input on the .0025-volt range, in-
creasing to 2 millivolts rms on the l-volt range.
COMMON MODEREJECTION: More than 1OO:l at dc. Input grids must be within one volt of
ground for minimum grid current; can be run at maximum of i3 volts.
INPUT IMPEDANCE: Greater than 1014 ohms shunted by 10 picofarads each input to ground.
OUTPUT: f20 volts differential or i-10 volts single ended at up to 10 milliamperes for
full-scale input.
1165R 11-l
MODEL 603 ELECTROMETER
AMPLIFIER SPECIFICATIONS
GENERAL:
INPUT HEAD: Contains input section of amplifier and may be connected directly to front
panel or operated remotely through cabling at distances of up to 24 feet from the ampli-
fier.
INPUT SWITCH: Located on remote head and shorts each side of the input through 1 megohm
to ground.
ZERO SUPPRESSION: up to one volt.
POLARITY: Zero-center scale.
CONNECTORS: Input: BNC type; Output; Amphenol 31-PC3F; binding posts on front panel.
POWER: 105-125 or 210-250 volts, 50-60 cps., 120 watts.
DIMENSIONS, WEIGHT: Amplifier: 5-l/4 inches high x 19 inches wide x 10-l/2 inches deep.
Input Head: 2-l/4 inches high x 3-l/2 inches wide x 3-l/2 inches deep. Net weight, 21
pounds.
4CCESSORIESSUPPLIED: Mating input and output connectors; binding post adapter; Model
6031 Connecting Cable, 12 feet long.
II-2 1165R
SECTION III - OPERATION
A. OPZRATING CONTROLS
The operating controls for the Model 603 are all located on the
front panel. Their location and functions are as follows:
ON - OFF switch is located below and to the left of the
panel meter.
COARSEBALANCE is the first of three large knobs starting
from the left of the panel. This control is a 19 posi-
tion switch. Moving the switch by one position changes
the meter zero by approximatelv 100 millivolts.
FINE BALANCE is the knob following the coarse balance con-
trol. It is a ten-turn potentiometer and each turn shifts
the zero by approximately 10 millivolts.
MILLIVOLTS is the third knob in the row. This control
selects the full scale sensitivity or the amplifier Cain
as stated in the specifications.
OUTPUTLEVEL is a screw driver adjustment located below
the meter and to the right of the output. Its function
is to adjust the output dc, so that the output terminals
are at ground potential when the panel meter reads zero.
B. INPUT AND OU'PPUTCONNECTIONS
Input connections are made via either BNC input connector
in the remote probe. If the cover is removed and the
interior exposed as shown in Figure I, it is seen that a
place is provided for two input resistors between the
input grids and ground. If it is desired to use the in-
strument only as a single ended device, the other grid
is shorted to ground by placing a length of wire between
the diode clips furnished to hold the resistor. The re-
maining pr'd may be left open or shunted with the appro-
priate resiStor as desired. The cover is then replaced
and either a BNC connector is used to mate with the BNC
receptacle on the probe or the binding post adapters fur-
nished may be used. If particularly low capacity is de-
sired, it is possible to force a pin into the central
oortion of the connector, employing the binding post for
the ground connection.
The input head is either plugged directly into the panel
of the main amplifier or plugged in at the end of a cable
not to exceed 2b feet in length. The instrument should
be turned on only if the input head is connected to the
amplifier.
0163 III - 1
Outnut connec~tions are furnished either on the panel with bind-
ing posts or at the rear of the instrument with a three pin con-
nector. The two red binding po.+,s are connected to the balanced
output cathode followers and output is exactly 180 degrees out of
phase between the two signal outputs. AT NO TIME SHOTTLDEITHER
OUTPUTBE GROUNDED THE CHASSIS.
TO
C. PRELIMINARY SET-UP
1. Plug in input head either directly at the panel or at the
end of the cab1.e.
2. Observe the instructions about input connections in section
III-B.
3. Connect the instrument to the power line. Unless otherwise
marked the unit may be used on 117 volt 50 to 60 cps power only.
To convert to 2'20 operation refer to the schematic DR 12669-D at
the rear of this manual. A three wire cord is furnished which
grounds the cabinet. If a three wire receptacle is not available,
use the two pin adapter furnished and ground the third lead to an
external ground.
IL. Set the controls as follows:
a. Coarse and Fine Balance: To center of their range.
b. Range: 1000 millivolts.
C. Input: Short Inputs to ground.
5. Turn on instrument and wait approximately 60 seconds. The
instrument should now indicate on scale. Bring the meter to zero
by adjusting the Balance Controls as necessary. To increase the
sensitivity, turn the Millivolt switch to the desired range and
rebalance as necessary. It should be realized that on the more
sensitive ranpes (about 25 millivolts and below) that the warm-up
drift will be apparent. It is therefore recommended that on the
most sensitive ranges about one hour warm-up be allowed before
use.
6. Driving of Recorders: The model 603 furnishes an output of
10 volts sinple ended (one output terminal to around) or 20 volts
push-pull (across both output terminals) for full scale meter de-
flection at a maximum current of 10 milliamperes. This output
may be used directly with oscilloscopes and pen amplifiers.
Milliampere recorders and galvanometers must be connected to the
output in series with the appropriate resistance to limit the
output current.
D. Use of the Model 603 as a Differential Amnlifier:
The basic circuit of the Model 603 incorporates a differential
amulifier with an in-phase rejection of 1Wk. Differently stated
this means that a signal applied to one input grid with the other
grounded will produce an output signal which is 100 times greater
than the output signal produced if the innut is applied to both
grids in parallel. However in the Model 603 t&E is a basic
0662~ TIT - 2
restriction that the DC potential between the grids and ground
must not exceed one volt plus or minus with respect to around
if the grid current specifications are to be met.
Nevertheless, where the balanced input can be used, it will give
considerable improvement in spurious signal rejection if it can
be arranged that the desired signal appears across the input
grids while any spurious signal is picked up equally and in
phase at the two grids. In this way the snuri~ous signal will
be discrimi.nated against and the desired sivnal will be ampli-
fled.
If the balanced input is used, it should be remembered that each
input grid must have a DC return to ground and it is not suffici-
ent to connect between the two input terminals. Very often the
resistance of the surroundings will provide the return path to
ground. However if a sufficient return path does not exist it
can be provided by shunting resistors to ground in the place pro-
vided in the input head. (See section IIIB.) If this precaution
is not observed the input will rapidly charge up due to grid cur-
rent flow and the amplifier will be inoperative until a return
path is provided. The value of resistance to ground will best
be determined by considering the impedance that, in the first
place, is necessary and the permissible voltage that can be al-
lowed to build up at the grids due to grid current.
E. GENERALPRECAUTIONS:
1. Input wires should be as short as possible and well shielded
in order to reduce power line pickup as well as the pick-up of
stray electrostatic fields. When the Model 603 is used at its
maximum input impedance, electrostatic pick-up must be carefully
eliminated. In some cases it may be necessary to shield the
entire test object.
2. If the high input resistance of the Model 603 is to be
realized in practice, careful attention should be paid tothe
quality of insulation used in the input circuit, Ordinary rubber
and plastic insulation should be avoided in favor of teflon or
polystyrene. Insulation for switches, standoffs and bushings in
contact with the signal lead should be made of polystyrene, poly-
ethylene, ceramic, teflon or other high quality insulation ma-
terial. If cables are necessary, most types of polyethylene or
teflon insulated cable will be satisfactory. However if critical
work at low levels is contemplated, a very substantial reduction
in cable noise will be obtained with a coaxial cable using a
graphite-coated dielectric. One satisfactory type is Amphenol
21-537.
3. Avoid leaving the input grids floating and unshielded.
Large signals can be induced at the input of the amplifier.
Although no permanent damage will occur, some temporary loss
of DC stability may be experienced.
III - 3
4. If the power line is especially unstable 8om.e improvement
in stability can be obtained with a line regulating transformer.
5. Some attention should be given to providing adequate venti-
lation for the amplifier since the power dissipation is about
120 watts. If it is used with end-frames in the open air no
precautions are necessary. However, if the instrument is used
with rack mounting, it will pay dividends in longer instrument
life if forced air ventilation is provided. Several blowers
for rack mounting are available such as Bud Radio Type B25.
FIG. 1
SECTION IV -- CIRCIJIT DESCRIPTION
The Model 603 is a direct-coupled DC amplifier with a balanced
electrometer input followed by three stages of balanced pentode
amplification and two output cathode-followers which drive the
output stage and the balanced feedback loops.
The amplifier derives a high degree of DC stability by the use
of balanced circuitry and close regulation of all critical plate
and filament supplies.
A. Detailed description of the Amplifier (refer to DR 12669-D the
circuit schematic):
The input tubes, Vl, V2 and V3 are contained in the remote input
head. Vl and V2 are type 5886 electrometer tubes and V3 is a
cathode follower used to transmit the signal at a relatively low
impedance to the main amplifier. The filaments of Vl and V2 are
supplied from the regulated R'+ supply via R105 and R106. The fila-
ment current then flows through RlO3 and RlOk. The drop across
these resistors furnishes the bias for the electrometer tubes.
A bias voltage of five volts is used to allow some measure of
input voltage variation around ground when operating the ampli-
fier with a balanced input. Resistors R103 and RlOh also serve
as the return point for the negative feedback voltage from the
cathodes of VlO and Vll, the output cathode-followers. This feed-
back voltage is attenuated by R159, R160, R161, R162 and resistors
R176 through Rl93. Resistors R176 to R193 are chosen to set the
gain of the amplifier.
Due to the fact that the input tubes are filamentary types, it is
not convenient to float the filaments above ground. Therefore in
order that some measure of in-phase rejection is obtained, local
feedback from the cathodes of V& and V5 to the screens of Vl and
V2 is used to provide rejection against common mode signals.
The principle of operation is as follows: If a signal.of the same
magnitude and phase is received at each input grid simultan&ouslyi
equal signals are transmitted to each grid of Vh and V5 via cathode
followers V3a and V3b. Since Vii and V5 form a differential ampli-
fier, an equal in-phase signal received at each input grid will
cause the cathode of the stage to move nearly as far as the grids.
This cathode signal is fed back to the screens of Vl and V2 via
R107 through R128. It will be found that the direction of the
feedback signal is such as to cancel the input signal. On the
other hand if the signal to the two input grids is equal but the
signal each input grid receives is 180◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo