Keithley 620 Instruction Manual
INSTRUCTION MANUAL
MODEL 620
MULTI-PURPOSE ELECTROMETER
AND ACCESSORIES
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, transistors, fuses, and batteries, which,
within a year after shipment to the original buyer, proves defective on examination.
DAMAGE IN SHIPMENT
Be sure to include the instrument model num-
ber and serial number in all communications.
If the instrument is damaged when received,
or fails to operate properly, a claim should be
filed with the carrier. Upon receipt of the claim
agent’s report, we will inform you regarding
repair or replacement.
REPAIRS
When returning an instrument for repair or
recalibration, it should be securely packed
against shipping damage and sent to the fac-
tory, freight prepaid. A brief letter describing
the difficulty should accompany the instrument.
CONTENTS I
-___SIWION
INTRODUCTION
...............................................
SPECIFICATIONS
.............................................
OP&RATION
..................................................
A.
B.
C.
D.
E.
F.
0.
Prel-iminary Steps
Voltmeter
Ammeter
(1) Normal
(2) Fast
Ohmmeter
(1) Normal
(2) External Voltage
Battery Check.
Using External Indicators
Miscellaneous Applications
(1) Current Source
(2) Static Charge Detector
CIRCUIT DISCUSSION
..*..**.....,r.*....,....**.*.....*..,...
A.
Voltmeter
EL
Ammeter
(1) Normal
(2) Fast
C.
Ohmmeter
(1) Normal
(2) EXternal Voltage
ACCESSORIES
. . . . . . . . . . . ..*........*............*...*........
MAINTENANCE
. . . . . . . . . . . . . ..*...~*.....*.*....*........*...*.
A.
Trouble-Shooting
B.
Schematic
?*
Voltage-Resistance Diagram
D.
Replacement Parts List
I
IT
III
IV
V
VI.
in
KEITHLEY INSTFiUMEXTS
620
CLEVELAND, OHIO
SECTIOI\T
I
- INTROiXJCTION
The Keithley Model 620 Electrometer
is an
ultra-high impedance volt-
meter with full-scale ranges of 0.1,
0.3, 1.0, 3.0
and
10 volts.
The maximum input resistance is greater than 1014 ohms;
in additi
the input resistance may be varied in decade steps from 106 to
n
10
YOO,
ohms by means of the shunt resistors built into the instrument.
Thus, the 620 is not only appropriate for measurement in high-impedance
circuits, but also can be used with decreased input impedance where
a high input impedance would merely introduce unwanted pickup.
The 620 may be used as a direct-reading ammeter from 10-5 to-lo-11
amperes full scale.
This (j-decade range is covered in overlapping
3x and 10x scales.
Two current measuring methods are available to
the user of the 620.
Normally, current is determined by measuring
the voltage drop across7a resist&r
shunted from input to ground.
Alternately, on the ,lO to 10 ampere ranges, negative feedback
can be applied.to the input of the voltmeter through the current
measuring resistor.
This largely eliminates the input drop and in-
creases measuring speed, particularly on the more sensitive ranges.
The 620 measures
105 to 10"
ohms full scale with a two-terminal
input.
Unlike conventional ohmmeters, the resistance is read on
the same linear scales used for current and voltage,
As a dc preamplifier, the 620 has gains of 0.1,
0.3,
1,
3,
and 10.
Continuing gain stability is assured by a large feedback factor on
all ranges.
The output is 1 volt, open circuit, with an internal impedance of
16.67K for fW.l. scale input on all ranges. Thus, the output may
be used for driving oscilloscopes or pen recorder amplifiers, or
the output may be shunted down to provide lo- or
50-1~
outputs
for
servo-rebalance recorders. Note that a phase reversal occurs from
input to output.
620
I-l
SECTION II
- SPECIFICATIONS
Ranges:
II
b”
Voltage: 0.1
0.3,
1
3,
10-5 to 10-11
and 10 volts full
scale.
Current:
amperes full scale in lx and 3x
overlapping ranges.
(c) ohms:
105
ohms to lo"
ohms full scale on linear lx and 3x
(d)
overlapping ranges.
Meter Scales:
Left Zero 0 to 3 and 0 to 10.
Accuracy:
Voltage:
Current:
2%
of full scale on all. r3nges.
3%
of full scale
fz$m 10 amperes to 10-Y amperes.
(c) $of full scale from 3 x 10
0 t LO-l1 amperes.
4%
of full scale from 10
ohms to 109 ohms.
5s
of
full. scale from 3 x 109 ohms to LOU ohms.
Resistance Standards:
109 and lOlo ohms, 2% accuracy.
oh~resistors may be expected to decrease in
value at about & per year.
Input Impedance:
On the VOLTS position, the input impedance is greater than 1014
ohms resistive,
shunted by approxiasteu
30
micromicrofarads.
Drift:
Less than 3 millivolts per hour after 2 hours warm-up.
Recorder Output:
one volt for fur. scale meter deflection,l6.6m source impedance.
Amplifier:
Frequency response is Cc to 100 cycles on all ranges. Maximum
gain is 10.
Noise is less than 2% peak to peak of fWl scale.
Front Panel Controls and Terminals:
INWJ! comector is a teflon insulated. UHF type receptacle. An
accessory binding post which plugs into the cente?Z of the connector is furnished.
A ground binding post is mounted on the
panel above the input connector.
RANGE switch is located in the center of the front panel. This
control selects VOIIp9, OHMS, or AMPERFS. On the AMPERES position,
620
II - 1
a shunt resistor whose value is the rec%procal of the designated
range may be used to decrease the input resistance as well as to
measure current.
MULTIPLIER switch, located in the center of the front panel above
the RANGE switch, determines the voltage sensitivity of -the dc
amplifier,
and sets the voltage range when the RANGE is set on
VOLTS.
On OHMS or AMPERES, the setting of this knob multiplied. by
the OHMS or AMPIXES setting gives the full scale meter reading.
ZERC control, located at the left under the meter, is used to set
the meter to zero.
METER-BATTERY switch, at the right under the
meter, turns
the
instrument on, determines meter polarity, and tests the batteries.
ZERO CHECK-OPERATE switch, located at the bottom right, shorts the
input terminal through 5 megohms while the amplifier input is shorted.
Rear Panel Controls:
OIJTPCT receptacle for external recorders, Amphenol 8opC2F; Mat-
ing plug Amphenol 8oPC2M.
Normal-Fast control is locked in NORMAL position. In FAST positition, current measurements are made with feedback around the shunt
resistor.
COARSE ZERO is used to bring the front panel ZERO control in range
if the aaplifier is quite badly unbalanced.
Tubes:
one
5886, two 6418
Cabinet:
@" wide by &' high by
6 314"
deep. Weight
5 314
lbs.
Batteries:
Battery
!422.?
Expected Life
Bl
Mallory FMl2R or
350
hours
equivalent
(3
req'd)
E, B3, B4
tieready- #4l2 or
500 hours
equivalent
620
II - 2
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