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CONTENTS
02738
SPECIFICATIONS
MODEL 615
SPECIFICATIONS
AS A VOLTMETER: GENERAL:
RANGE: 100 millivolts full scale (100 microvolts. least sig DISPLAY: 4 digits from 0000 to 1999 on 0.1, 1.0, and 10.0
nificant digit) to 100 volts in four decade ranires. sensftlwty settings; from 0000 to 999 on the 100.0 sensi-
ACCURACY: +0.290 of reading +1 digit on all ranges exclu. tivity setting.
sive of noise and drift. POLARfTV SELECTION & OVERLOAD INDICATION: Auto-
ZERO DRIFT: Less than 1 millivolt in the first hour or subse- matic.
quent 24.hour periods after l.hour warmup. Less than OVERRANGING: lOO%overrangingon all ranges exceptwhen
150 mliCrOYOlt* pm "C. "Sing Se"sltl"lty setting of 100.0.
NOISE: * 1 digit with input shorted on most sensitive range. DISPLAY RATE: 24 readings per second maximum (20 per
INPUT IMPEDANCE: Greater the" 10" phms shunted by second on 50 Hz models); adjustable to tw, readings
35 picofarads. Input resistance may aIs0 be selected in per minute.
decade steps from 10 to 10" ohms. PRfNTER OUTPUTS AND OUTPUT CONTROLS: Model 4401
NMRR: Greater than 60 d8 on the most sensitive range de. accessory provides BCD output and external cpntmls.
creasing to 40 dB on the lOOwIt range at line frequency. ISOLATION: Circuit ground to chassis ground: Greater than
AS AN AMMETER: IO6 ohms Shunted by 0.2 microfarad. Circuit ground may
be floated up to 100 volts with respect to chassis ground.
RANGE: lo-`2 ampere full scale (1O-L5 ampere, least sig.
nificant digit) to 0.1 ampere in 12 decade ranges. CMRR: For high open-circuit CMRR. residual unshielded
capmtance between input high and chassis ground is less
ACCURACY: b-0.5% of reading, -tl digit on 0.1 to l@' than 0.1 picofarad.
ampere ranges using optimum sensitivity control setting;
*2% of reading *I digit 0n l@a and lo-3 ampere ranges ANALOG OUTPUTS:
and 14% of reading *1 digit on 1O-Lo to lo.`1 ampere Unity gain: At dc. Output is equal to input within 100 ppm.
ranges exclusive of noise and zer0 drift. exclusive of noise and zero drift. for Output currents of
NOISE: f-4 digits with input open and shielded on most 100 microamperes or fess.
sewitive range. 1 mA: fl milliampere at up to 1 volt for full scale input,
OFFSET CURRENT: Less than 5 x IO-l5 ampere 100% overrange capability except on 100.0 sensitivity
setting.
AS AN OHMMETER: 1 V: *l volt at up to 0.1 microampere for full scale input.
RANGE: 10,000 ohms full scale (10 ohms. least significant 100% pverfange capability except M 100.0 sensitivity
digit) to 10" ohms in eleven decade ranges. setting.
ACCURACY: &0.5% of reading. hl digit on 10' to lOa ohm CONNECTORS: Input: Tefkxvinsulated triaxial. Analog wt.
ranges using optimum sensitivity control setting; *4% of puts: Unity Gain: Binding Ppsts. 1 mA; Switchcraft Nl13B.
reading + 1 digit from 109 to 10'" ohms exclusive pf noise 1V; Amphenol 80 PC 2F. Printer output &controls: 50.pin
and zero drift. Amphenol Micro-Ribbon.
DIMENSIONS, WEIGHT: 5%" high x 19" wide Y 10" deep
AS A COULOMEMETER: (132 x 433 x 280 mm); net weight. 20 pounds (9.1 kg).
RANGE: 10." coulomb full sca1e (lo-" coulomb. least POWER: 105.125 or 210.250 volts (switch selected), 60 HZ:
significant digit) to 10'5coulomb in seven decade ranges. 50 Hz models available. 35 watts.
ACCURACY: +5% of reading 3~2 digits on all ranges. Drift ACCESSORIES SUPPLIED:
due ta offset c"rrent does not exceed 5 x lO-`I coulambs, Made1 6011 Input Cable: 30" triaxiel cable with triaxial
secpnd. connector and 3 alligator clips.
ii 0372R
MODEL 615 ELECTROMETEX
SECTION 1. GENERAL DESCRIPTION
l-l. GENERAL. imizes zero offset with high source resistance.
a. The Keittlley Model 615 Digital Eleceromeeer is a d. A front panel ZERO CHECK Switch permits check-
fast, accurate and sensitive Electrometer with digital ing zero-offset without disturbing the tneasurement
display. It is a versatile, comp'letely solid-state CiX"iC.
instrument which measures a wide range of d-c voltage,
current, resistance and charge. Thy4Electrometer's e. Operarion up to *lOO voles above case ground is
input resistance of greater than 10 ohms is the re- possible without affecting the reading. Isolatio"~
sult of extensive instrument development with high in- from csrcuit low to case ground is greaeec than 106
put impedance transistors. The Model 615 has all the ohms shunted by 0.2 microfarad.
capabilities of conventional VTVMs, but it can also
make many more measurements without circuit loading. f. Analog output provided for 1 mA full scale re-
corders such as the Keiehley Model 370 Recorder or
b. The Electrometer has four decade voltage ranges other floating instrument.
from 0.100 volt full scale to 100 volts, 12-decade
CUrrent ranges from 10-12 ampere full scale tcl 0.1 am- g. Digital display enables voltage'measurements to
pere, 11 decade linear resistance ranges from lo4 ohms l O.Z% of reading *I digit.
full scale to 1OL4 ohms, and seven decade charge rang-
es from lo-11 coulomb full scale to 1O-5 coulomb. h. Polarity is automatically indicated on the dis-
Pk+,
C. The Model 615 employs matched insulated-gate
field-effect ~ransiseors followed by a transistor dif- i. Display rate 1s adjustable from 24 readings per
ferential amplifier and complimentary outpue stage. second to two readings per minute LO acconmadate the
A large amount of negative feedback is used for sta- mode of data retrieval.
biliey and accuracy.
j. Analog-to-digital converter is a dual slope in-
1-2. FEATURES. tearaeing type circuit to pro"ide inaounity to line
power frequency pickup.
a. Unique input circuit provides overload profec-
tion up eo 500 volts on most ranges without damage. k. Model 4401 Printer Output.Cards are available
for factory or user installation. This option pro-
b. Time stability is better than 1 millivolt/day vides BCD outputs far significant digits, range, pol-
after l-hour warmup. Less than 150 microvolts per `=C arity, sensitivity and overrange. Various remaee
zero drift with temperature. control lines are also provided. The Output Buffer
cards are easily inserted into prewired, premouneed
C. Offset current less than 5 x 1O-L5 amperes min- card-edge connectors an the Model 615 chassis.
04728
OPERATION WDEL 615 ELECTROMETER
TABLE 2.
Model 615 Front Panel Controls and Terminals (Figures 1 & 3).
contra1 F""ctio"*l Description Par.
SENSITIVITY Switch Selects full-ecsle voltage sensitivity; slso used to mulriply 2-2,2-3
current, resietance and charge ranges on the Range Switch.
Automatically eelecrs the proper decimal point position.
RANGE Switch Selects the mode which ia to be measured: voltage, current, Z-2,2-3
resistance or cherge.
FEEDBACK Switch Selects either NORMAL or FAST modes of operation. 2-2,2-4,2-5
POWERSwitch Controls e-c line power to instrument (an/off). 2-2
DISPLAY RATE Control Determines number of analog-to-digital conversions per second. 2-3
ZERO caner01 Provides fine zero control adJuseme"e. 2-2
ZERO CHECK Switch Provides zero offset check without disturbing the source circuit. 2-2
INPUT Receptacle Connefts wurce to input. ~ecepeacle is a Teflon insulneed 2-l
triaxia1 connector.
LO TERMINAL Provides connection to input low. 2-l
*Display Lights Indicates polarity of input signal. 2-3
Numerical Readout Indicates magnitude of input signal. 2-3
TABLE 3.
Model 615 Rear Panel Controls end Terminals (Figure 2).
Control Functional Description Psr.
COARSE ZERO Switch Provides extended adfustment cepabflity of the front panel 2-2
ZERO Control.
1 MA OuTPuT Receptacle Connect[i analog output to monitoring device. 2-9
PRINTER/CONTROL 50 pin connector for BCII digital output: provldea printer 2-10
CO""eCtOC control and remote control when Model 4401 printer ootput
cards ere installed.
SPARE Receptacle Blank hole with cover plate for mounting edditional 50 pi" __-
CO""BCtOC.
Xl OUTPm and Provides extremely linear unity gsi" operation. Also used 2-9
G"m.tl Terminals for guerded reeFstance a.easureme"te.
CASE GROUNDTerminal Connected to Model 615 cabinet and outside shell of input 2-6
Connector.
LO Terminal Pravidea connection to input low end front panel LO connection. 2-6
1 VOLT OWPIPI Provides l'volt output for calibration purposes. 2-9
Line Cord connecta line power to inatroment. 2-2
F"M 3 AD Slow Blov. 117 volt - 314 A. 2-2
234 volt - 3/g A.
117-234V Switch Sets lnatrument for either 117 or 234 volt a-c power operation. 2-2
2 0470
MODEL 615 ELECTROMETER GENERAL DESCRIPTION
RANGE Switch ZERO CHECK
SENSITIVITY Switch
(S1203) (51201) (S1202)
POWER DISFLAY ZERO FEEDBACK LD INPUI
Switch PATE CONTROL Switch (S1204) BINDING RECEPTACLE
(S102) CONTROL (R1222) POST (51209)
(R1201) (51202)
FIGURE 1. Model 615 Front Panel Controls and Terminals.
(9102)
1 VOLT ODTPW Transistor Transformer
COARSE ZERO
switcn (S1205)
Xl ouepur
(51203)
FIGURE 2. Model 615 Rear Panel Controls and Terminals.
0570 3
OPERATION MODEL 615 ELECTROMETER
SECTION 2. OPERATION
2-l. INPLPI CONNECTIONS. d. Carefully shield the input connection and the
source being meaaured, since power line frequencies
8. The INPUT Receptacle of the,Model 615 is a Tef- are well within the pass band of the Electrometer o"
lon insulated triaxial connector. The center termi- a11 ranges. Unless the shielding is thorough, pickup
nal is the high impedance terminal: the inner shield may cause definite readout disturbances.
is the low impedance terminal; the outer shield is
case ground. (See Figure 3). e. "se high resistance, low-loss materials - such
as polyethylene, polystyrene or Teflon - for insula-
b. The front panel LO Terminal is connected to tion. The insulation resistance of test leads and
the inner shield or low impedance terminal. The LO fixtures should be several orders of magnitude higher
Terminal is connected to the rear panel LO Terminal. than the source resistance. Excessive leakage will
When the shorting link o" the rear panel is connected, reduce accuracy. "se a law-noise type cable which
the LO is connected to case ground. employs a graphite coating between the dielectric and
the surrounding shield braid.
f. Any change in the capacitance of the measuring
circuit to ground will cause disturbances in the read-
ing, especially on the more sensitive ranges. fake
the measuring setup a.s rigid as possible, and tie
down connecting cables to prevent their movement. If
a continuous vibration is present, it may appear at
INPUT the output as a sinusoidal signal and other precau-
tions may be necessary to isolate the instrument and
the connecting cable from the vibration.
NOTE
Clean, dry connections and cables are very
important to maintain the value of all in-
sulation materials. Eve" the best insula-
tion will be compromised by dirt, dust,
solder flux, films of ail or water vapor.
A good cleaning agent is methyl alcohol,
which dissolves most common dirvwithout
chemically attacking the insulation. D=Y
the cables or connections after washing
with alcohol or dry nitrogen if available.
If available, Freon is a" excellent clean-
FIGIRE 3. Model 615 Triaxial Input Receptacle. ing agent.
g. The accessories described in Section 7 are de-
c. The Model 6011 Input Cable (provided) is a 30" signed to increase the accuracy and convenience of
triaxial cable with triaxial connector and 3 alligator input connections. "se them to gain maximum capabil-
clips. See Table 4 far color coding of the alligator ity of the Model 615.
clips. The high impedance terminal is shielded by the
inner braid of the eriaxfal cable up to the miniature h. Far low impedance measurements - below lo*
alligator clip. ohms or above 10-S ampere - unshielded leads may be
used.
TABLE 4. i. When the Model 615 is used on the most sensi-
Color Coding of Alligator Clips for Model 6011 Input tive ~"rrent range with the FEEDBACK Switch at FAST,
Cable. same insulators - such as Teflon - may produce ran-
dom signals which show up as erratic readout deflec-
Lead tions. Insulation used in the Model 615 is carefully
selected to minimize these spurious signals.
heavy wire with Input high C*llt*r
red clip cover j. It is advantageous to connect the Model 615 in-
thin wire with Input low Inner Shield put to the source only when a reading is to be made.
black clip cover "se a high impedance transfer switch and well shield-
thin wire with Case Ground Outer Shield ed chamber if available.
green clip cO"er
4 04728
MODEL 615 ELECTROMETER OPERATION
NOTE f. The Model 615 may have excessive drift or zero
offset after long periods of storage or after an over-
In some cases, the offset current can charge load. This my be corrected with the zero controls
the external test circuitry. One example of although drifting may continue for several hours.
this occurs when measuring a capacitor's
leakage resistance by observing the decay of NOTE
the Germinal voltage. If the leakage current
is less than the offset c"rrent (less than 5 If the Model 615 has been stared for a long
x lo-l5 ampere), there may be no decay of the time, the offset current may exceed the
terminal voltage when the Electrometer is specification when first used, but should
left connected across the capacitor's termi- decrease to below the specified amo"nt
nals. after one or two hours of "se. This is an
inherent characteristic of the input tran-
k. The Model 6012 Triaxial-to-Coaxial Adapter en- sistors; the instrument is not faulty.
ables using coaxial cables and accessories with the
Model 615 by adapting the triaxial INPUT connector to g. Although the offset current of the Electrometer
the UHF coaxial type, is much below that found in conventional voltmeters,
it cm be observed on the readout since the offset
CAUTION currene charges the input capacitance, the Electrome-
ter appears to drift when the input is open. Use the
The Adapter connect? circuit law to case ZERO CHECK Button to discharge the charge build-up,
ground. The Model 615 cannot be used off-
ground when using the Adapter. The instru- h. Follow the particular procedures in paragraphs
ment cabinet will be at the same potential 2-3 co 2-7 for measuring voltage, current, resistance,
as the input law. and charge.
NOTE 2-3. DIGITAL READOUTOPERATION.
Keep the shield cap (provided) on the INPUT a. Valtmecer Digital Readout.
Receptacle when the Electrometer is not in
use co prevent overloads due to external 1. When the RANGE Switch is placed in the VOLTS
noise pickup. position, ehe Electrometer digital readout desig-
nates the actual voltage measured using four numer-
2-2. PKECMINARY OPERATING PROCEDURES. ical digit readouts.
a. Check the 117-234V Switch for the proper AC line 2. The SENSITIVITY Switch has four positions
voltage. which control the lighted decimal point location
and therefore the full scale voltage range. The
b. Check for proper rated fuse. full scale voltage range far each SENSITIVITY Switch
position is shown in Table 5.
C. See the front panel controls as follows:
ZERO CHECK Button TABLE 5.
RANGE Switch
SF.NSItI"ITY Switch
wise- Position SENSITIVITY Switch Decimal Point
FEEDBACK Switch NORMAL Position msi.cion
POWERSwitch OFF
I -~-
0.1 Positicm 1 (full" .xXxX
I
d. Connect the power cord. Place POWERSwitch to counterclockwise)
ON position. After one-half hour warm-up, adjust the 1 Position 2 x.xXx
ZERO Conerol if necessary. Zero is indicated by con- 10 Position 3 xX.xX
tinuously flashing * polaricy lights. 100 PosFtFon 4 (fully xXx.x
clockwise)
NOTK
The rear panel COARSE ZERO Control may be
adjusted if a large zero offset is indicated. 3. The fourth (left most digit) readout permits
a.* averrange display. The largest reading that can
e. After a few moments increase the voltage sensi- be displayed "sing all four digit readouts is 1999.
tivity by advancing the Switch to one position CLIUIIC- If there is'an overload condition, then all read-
erclockwiae. Continua zeroing with the FINE ZERO outs will blank (none of the digital readout tubes
Control. will be lighted). The polarity (*) display indica-
0570 5
OPERATION MODEL 615 ELECTROMETER
tars remain lighted during an overload condition ac~rately knovn capacitor since the Electrometer
indicating the correct polarity. Thus the Electrom- is sensitive to the integral of the current applied
eter display will indicate correctly within specifi- from the external unknown source.
cations with no ambFguous overload display.
2. The coulomb measurement is determined by mul-
4. To remove the overload condition, change the tiplying the RANGE Switch setting times the digital
SENSITIVITY Switch setting or decrease the input readout display.
signal magnitude.
e. DISPLAY RATE Control. (This control is a con-
b. Ammeter Digital Readout tinuously variable control that permits the user to
select the rate of analog-to-digital conversion).
1. When the RANGE Switch is placed in the AMMETER That is, the control determines the number of times
position, the Electrometer digital readout desig- a new reading will be recomputed per unit of time.
nates the voltage across an accurately known self- Thts is useful for sampling a continuously varying in-
contained resistor. The RANGE Switch selects the pllt current as well as for controlling slower external
calibrated range resistor for current measurements devices such as paper tape punches and printers. With
from 10-l to lo-11 amperes. The range resistor is the DISPIAY Control in the MAX Position the display
the reciprocal value of the Range setting. The rate is 24 times per second (20 for 50 HZ models).
readout indicates the voltage across the Range re- When the control is varied clockwise, the rate de-
sismr. creases to a minimum of about 2 per minute in the ex-
treme clockwise position. The front panel DISPLAY
2. The full scale current range is determined by SATE Control applies to the digital circuitry only.
multiplying the Range setting times the digital
readout display. The SENSITIVITY Switch operates 2-4. VOLTAGE MEASUREMENTS.
in the same fashion aa for voltmeter measurements.
(Refer to preceding paragraph 2-3, a). a. The Model 615 can meas,,re an unknown voltage
when the low impedance terminal is up to 100 volts
3. The full scale current range far various front off case ground. Safe operation of the Electrometer
panel control settings is shown in Table 6. is insured by grounding the case. To use the Model
615 for off ground voltage measurements, disconnect
the shorting link between LO and CASE GND Terminals
TABLE 6. on rhe rear panel. (Refer t.3 Figure 2).
Full Scale RANGE SENSITIVITY I CAUTION
Switch
Operating the Model 615 at more than 100
volts off ground may permanently damage
the instrument. The isolation between
circuit low and ground could break dawn
making the instrument unusable far safe
off ground measurements.
Refer to Paragraph 2-6 far complete instructions for
making off ground measurements.
C. Ohmmeter Readout. b. The Model 615 has been designed to meas"re valt-
ages up to 100 volts from very high resistance sources.
1. When the RANGE Switch is placed in the OHMS However, the Model 615 can also be used for meaaure-
position, the Electromerer digital readout desig- ments from low sr,urce resistance and voltages up to 30
nates the actual voltage across the unknown resis- kilovolts with high voltage divider probe.
tor as an accurately known current (internal to the
Electrometer) is applied to the unknown. 1, The input resistance can be decreased in or-
der to reduce the effects of stray pickup with low
2. The RANGE Switch selects the current for Olw sou*ce resistances. Refer to Paragraph 2-4, f for
lll~ClS"C~lU~"t~. The current is the reciprocal value complete instructions.
of the OHMS range setting from 105 to lo12 ohms.
The SENSITIVITY Switch operates in the same fashion 2. ear measurements of voltage up to 30 kilovolts
aa for voltmeter measurements. refer to Paragraph 2-4, g which describes various
divider probes available from Keithley.
3, The actual resistance measurement is deter-
mined by multiplying the RANGE Switch setting tFmes c. The Model 615 can measure voltages in two modes:
the digital readout display. Normal Mode and Fast Mode.
d. Coulombmeter Readout. 1. Normal Mode. In the Normal Mode - FEEDBACK
Switch at NOWAL - the unknown voltage is connected
1. When the RANGE Switch is placed in the CO"- to the INPW Receptacle. Input impedance with th
LO"BS position, the Electrometer digital readout RANGE Switch in VOLTS position is greater than 1084
designates the actual voltage across a self-contained ohms shunted by 35 picofarsds,
0570
2. Fast Mode. 1" the fast Mude - FEEDBACK NOTE
Switch at FAST - the effects of inp"t cable capaci-
tance may be reduced for measurements fcum very high To make off ground measurements. refer to
source resistances. Guarded valtage measuremenr~ Paragraph 2-6.
may aiso be made.
d. normal lode voltage Measurements
ZERO CHECK ButtOn LOCK
RANGE Switch VOLTS
SENSITIVITY Switch Fully Cluckwise
FEEDBACK Switch NORMAL
TO make aff graund measureme"zs, refer 'CO
Paragraph 2-6.
2. connect the Modei 6011 Trianial Input Cable
eo the unknown voltage as fallows:
a) the heavy wire with red clip cover should
be connected to the source high potential.
c) The thin wire wirhgrceaclip cover should
not be connecred when the shorting link between
LO end CASE Terminals on the rear panel is con-
nected.
3. ""lock the ZERO CHECK Button eo make a mea-
surement
4. Adjusr the SENSITIVITY Switch c~unrercL~ckwie.e
LO increase the Model 615 sensitivity. Readjust rhe
ZERO control as necessary after each change in sen-
sitivity.
5. The voltage measured is indicated directly 0"
the digital display with the decimal poinr automat-
ically indicated. The poiarity is auLomatical,y
indicated corresponding CO Lhe potential of the
Electr~merer input high with respect to input low.
NOTE
The Model 615 has 100% overranging on all
ranges except for rhe 100 volt full range
sensitivity. An overload on any range is
indicated by a blanked digital display, a
feature which averts erroneous readings
when 200% of full range Is exceeded. The
digital display is Lighted when the over-
load is removed.
e. ~aat Mode voltage Measurements
1. set the frant panel controls as follows:
ZERO CHECK Butfc'n LOCK
RANGE Switch VOLTS
SENSITIVITY SWitCh Fully Clockwise
FEEDBACK Switch FAST
0470
OPERATION MODEL 615 ELECTROMETER
2. Model 6103A Divider Probe for measurements up below 10-S ampere range - a self contained resistor
to 30 kilovolts. This probe permits meas"rements is connected between the electrometer amplifier in-
with overall accuracy of Cg%. Input r**i*t**c* is put and output (in the feedback loop). This method
1012 ohms maximum. The actual voltage is obtained permits faster response speed since the effect of
by multiplying the Electrometer digital display input capacitance is minimized. The input volcsge
times the divider ratio. drop is reduced to less than 100 microvolts on any
range. Refer to Table 7 for typical Response and
NOTE Noise performance for various values of input capac-
itance.
The Model 6012 Triaxial-to-Coaxial Adapter
must be used with Models 6102A and 6103A C. Normal Mode Current Measurements.
sF"ce tile probes are termFnated with a LW
connector. When using the Model 6012, the 1. Set the front panel controls as follows:
case ground is connected to inp"t law so
that the Electrometer may not be used for ZERO CHECK nutron LOCK
off ground measurements. - RANGE Switch 10-l AMPERES
SENSITIVITY Switch Fully Counterclock-
2-5. CURRENT MEASUREMENTS. wise
FEEDBACK Switch NORMAL
a. The Model 615 can measure an unknown current
when the low impedance terminal is up to 100 volts off NOTE
case ground. Safe operation of the Electrometer is
insured by grounding the case. To "se the Model 615 To make off ground measurements, refer to
far off ground current measurements, disconnect the Paragraph 2-6.
shorting link between LO and CASE GND Terminals on the
rear panel. (Refer co Figure 2). 2. Connect the Model 6011 Triaxial Input Cable
for meeauring s,, unknown current as follows.
CAUTION
a) The heavy wire with red clip cover should
Operating the Model 615 at more than 100 be connected to the source high potential.
volts off ground may permanently damage
the instrument. The isolation between b) The thin wire with black clip cover should
circuit low and ground could break down be connected so as to place the Electrometer in
making the instrument unusable for safe series with the c"rrent to be measured.
off ground meawrements.
c) The thin wire with green clip cover should
Refer to Paragraph 2-6 for complete instructions for not be connected when the shorting link between
making off ground meas"eements. LO and CASE GND Terminals an the rear panel is
connected.
b. The Model 615 can meas"re currents in two modes:
Normal Mode and Fat Mode. 3. Unlock the ZERO CHECK Button to make B mea-
surement.
1. Normal Mode. In the Normal Mode - used on
eny renge - the cwrent is determined by measuring 4. Adjust the RANGE Switch to increase the Slec-
the voltage drop across a self-contained reeistor emmeter sa"siti"ity for CUrrent measurements.
shunting the electrometer amplifier input. This
method permits a minimum noise m~as"rement when re- 5. The full range c"rrent for the Electrometer
sponse speed is not.critical. is determined by multiplying the digital display
times the RANGE Switch setting. The best accuracy
2. Fwt Mode. I" the F.ast Mode - for "se only for current meas"rements is obtained by "sing a
TABLE 7.
Typical Effects of External Inp"t Capacitance on Response Speed and Noise Performance in C"rre,,t Measurements
with the Model 615.
i-l**** Rise Time (seconds) Output Noise (Peak-Co-Peak)
No C 2eE 5000pF No
- C x 5000pF
$;to -2.0 2.0 2.0 6 x lo-l5 1.5 x 10-14 7 x 10-13
$" .07
.45 .07
.45 .45'
.07 8.5 x 10-14 $5; i.2 ;,!p;"
10-S ,015 ,015 ,015 ;.i ;,m;l3 ;.": 2 x 10-10
10-7 ,003 .003 ,003 s'x 10-11
10-6 .003 ,003 ,003 3.3 x 10-10
s
MODEL 615 ELECTROMETER OPERATION
SENSITIVITY Switch seeting which permits the use of
the smallest value rage resistor. The rsnge resis-
tor value is equivalent CO the reciprocal of the The ZEN, CHECK Sutt~" provides a short
RANGE Switch setting. The input voltage drop across across the feedback of the Electrometer
the shunt resistor is indicated directly on the Amplifier to enable zero adjustment.
Electrometer digital display. Do not apply a short circuit ecross the
Electrometer input terminals since this
NOTE will creete ""stable amplifier operation
The SENSITIVITY Switch settings permit sn 4. Adjust the RANGE Switch to increase the Slec-
input voltage drop af O.i, 1, 10, and 100 tr"meCer seneitivity for current measurements.
volts for current measuremenfs in the
mrmsl Mode. on the LO-9 to 10-l' AMPERES 5. The full range current for the Electrometer
settings of the RAN E Switch, the resistors is determined by multiplying the digital readout
(109, 1010, and 101E ohms) used have a volt- times the RANGE Switch setting. The best accuracy
age coefficient uf .O*% per vale (naminal). for current measurements is Obtained by using a
1f the SENSITIVITY Switch is adjusted far a SENSITIVITY switch setting which permits the use of
100 v"lt input drop, then a" additional the smallest value range resistor. The range cesis-
error of 2% occurs for the current messure- t"r value is equivalent to the reciprocal of the
lS**t. `rherefore ie is reconrmended t" select RANGE Switch settine. The input voltane drop, across
the smallest input drop possible to minimize ehe shunt resistor Is indicated directly on the
voltage coefficient errors. EiectromeLer digital display.
d. Fast mde Current Weasurements (for current be- NOTE
low 10-5 amperes).
The source resistance of the circuit eo be
1. Set the front panel controls es follows: measured should not be Less than 0.1 rimes
the range resistar used since adequate
ZERO CHECK Button LOCK feedback voltage cannot be developed at the
RANGE Switch 10-6 AMPERES input and zero stability is adversely af-
SENSITIVITY Switch Fully Councerclock- fected. The range resistor is the recip-
wise rocal of the AMPERES range in ohms.
FEEDBACK Switch FAST
CAUTION
NOTE
Foe measurement of capacitor leakage cur-
TO make aff graund measurements refer ta rents using the Pest Mode, a very stable
Psragraph 2-6. voltage supply must be used. With a ~a-
pacitor connected across the input, the
2. Connect the Model 6011 Triaxial 1"put Cable electrometer is exCrem*ly sensitive to
for measuring an unknow" current ae in 2-5, c-2. voltage transients with a resultant in-
crease in readout noise.
3. unlock the ZERO CHECK Sutton t" make e mee-
surement
I I I I
I I
I `f I
I-
a-7
: ME)WJ&NG I
I 1 readout
I X __ __
_
I 1
I SOURCE I I AMMETER I
L--------l L------------l
R+Ri"
1 = ' readout R
FIGURE 4. Error Due to Ammeter Resistsnce.
0470 9
OPERATION MODEL 615 ELECTROMETER
e. Galvanometric current Measurement Method. b. Normal Mode Measurements. D`sconnect the short-
ing link between LO and CASE GND Terminals on the rear
I. operate the Electrometer in the Fast Mode as panel. Connect the Model 615 case securely to earth
described in Paragraph 2-5, d. ground for maximum operator safety. Operate the Alec-
trometer 8s described in Paragraphs 2-4 or 2-5.
c. Fast Mode Measurements. Disconnect the shorting
link between LO and CASE CND Terminals on the rear
panel. Connect the Model 615 case securely eo earth
ground for maximum operator safety. Operate the Alec-
trometer as described in Paragraphs 2-4 or 2-5.
3. Adjust the Current Source co obtain a null on
the Electrometer digital readout. Increase the WARNING
Electrometer sensitivity as needed. The value of
the current which is suppressed is indicated o" the The 1X4 analog outp"f can only be used with
current source setting. a recorder which will operate off ground
such as the Keithley Model 370.
NOTE
NOTE
The connections for the Galvanometric Method
require the following accessories. The Model 615 ca"""t be operated off ground
if the Model 6012 Adapter is used since the
1 - Model 261 Current Source input Low and chassis ground are connected.
1 - Model 6012 Adapter
1 - UHF tee fitting, Part No. cs-171 2-7. RESISTANCE MEASUREMENTS.
1 - Low noise coaxial cable, Model 2611
1 - Low noise coaxial cable, Part No. 19072C. a. The Model 615 ca" be used to measure resistance
since the Electrometer permits accurate voltage or
2-6. OFF GROUNDMEASUREMENTS. current measurements from high resistance sources.
ResFstance can be measured F" the following three ways.
a. `fhe Model 615 can be used for measurements when
the low impedance rerminal is up to IO0 volts off case 1. Normal constant CurrenL Technique.
ground. Safe operation of the Electrometer is insured 2. Fast Constsne Current Technique.
by grounding the case. To use the Model 615 for off 3. Volt-Ammeter Method.
ground measurements, disconnect the shorting link be-
tween LO and CASE GNC Terminals a" the rear panel. b. Normal Constant C"rre"t Resistance Measurement.
(Refer co Figure 2).
1. I" the constant current method, the Electrom-
CAUTION eter meas"res the voltage drop across the unknown
resistance when a constant current is applied. The
Operating the Model 615 at more than 100 voltage drop is the" proportional to the resistance
volts off ground may permanently damage of the unknown.
the instrument. The isolation between
circuit low and ground could break down 2. The Normal mode is recommended f r measure-
making the instrument unusable for safe ments from 100 to 1O'l ohms. Above 10Pl ohms use
off ground measurements. the Fast constant current technique.
10 0470
MODEL 615 ELECTROMETER OPERATION
3. Set the front panel controis as fallows: 2. set the front panel controls as follows:
ZERO CHECK SULLO" LOCK ZERO CHECK Button LOCK
RANGE Switch 1011 OHMS RANGE Switch 1011 OHMS
SENSITI"ITY Switch Fully Counterclock- SENSITI"ICY SWFtch Fully Counterclock-
wxse wise
FEEDBACK switch NORMAL FEEDBACK Switch FAST
4. Connect the unknown resistance between the 3. connect the unknown resistance between the
electrometer input high and low as for normal Mode Electrometer input high and GUARD Terminal as for
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