Keithley 616 User manual

INSTRUCTION MANUAL
MODEL 616
DIGITAL ELECTROMETER
©COPYRIGHT 1
^ITsT S-T
28775 AURORA ROAD CLEVELAND,
TELEX; 98-5469
IINTC
44139 •[phone]
KEIT H LEY
PRINTED IN U.S.A.

SPECIFICATIONS MODEL 616
SPECIFICATIONS
AS AN AUTORANGING VOLTMETER
RANGE: ±10 microvolts -per digit (lOinV full range) to
rlOO volts full range in five decade ranges. 100%
overranging to 1999 on all ranges.
ACCURACY (lO^C to 30°C): ±(0.2% of reading +0.1% of
range)
.
READING TIME: Less than 4seconds to within 0.1% of
final reading, except where limited by source char-
acteristics .
ZERO DRIFT: Less than (50 microvolts +0.01% of range)
per ®C, and less than 100 microvolts per 24-hour
period after two hours warm-up (during which drift
does not exceed 500 microvolts)
.
NOISE: ±10 microvolts with input shorted.
INPUT IMPEDANCE: Greater than 2x10^^ ohms shunted
by 20 picofarads. Input resistance mav also be
selected in decade steps from 10 to 10^^ ohms.
NORMAL MODE REJECTION RATIO;
R/UNGE NMRR MAX. AC
lOmV 94dB 2V p-p
lOOmV 80dB 2V p-p
1V80dB 20V p-p
10 V60dB 20V p-p
100 V60dB 200V p-p
For voltage of line frequency and at least 10% of
full range dc reading. Maximum total input 200
volts peak ac +dc.
COMMON MODE REJECTION RATIO: Greater than 140 dB at
line frequency with 300 volts peak-to-peak from cir-
cuit Lo to chassis ground, up to 10^1 ohm source re-
sistance, and at least 10%of full range dc reading.
AS AN AMMETER
RANGE: ±10~-6 ampere per digit (10”13 ampere full
range) to ±0.1 ampere full range in 13 decade
ranges. 100% overranging to 1999 on all ranges.
ACCURACY (20“C to 30°C) :
Range Switch Setting Accuracy
10-1 to 10- /A ±(0.5% of reading +0.1% of range)
10-8a±( 2%of reading +0.1% of range)
10“^ to 10“^\a ±(5% of reading +0.1% of range)
NOISE: 2X10-15 ampere peak-to-peak on the most sen-
sitive range, exclusive of alpha particle disturbance.
OFFSET CURRENT: Less than 5x10“15 ampere.
COMMON MODE REJECTION: 300 volts peak-to-peak at line
frequency from circuit Lo to chassis ground on any
range and with at least 10% of full range dc reading
will not degrade accuracy more than 0.3% of range.
(Equivalent to 140 dB CMRR)
.
AS AN OHMMETER
RANGE: 1ohm per digit (1000 ohms full range) to
ohms full range in 12 decade ranges. 100% overrang-
ing CO 1999 on ail ranges.
ACCURACY (lO^C to 30*0:
Range Switch Setting Accuracy
108 to lO^il ±(0.5% of reading +0.1% of range)
±(2% of reading +0.1% of range)
10^to 10^2j
-2 +( 5 % of reading +0.1% of range)
METHOD: Two-terminal constant-current. Current equals
reciprocal of OHMS range.
AS ACOULOFEBMETER
R^\NGE: ±i0“^8 coulomb per digit (10"^2 coulomb full
range) tO' ±10”^ coulomb full range in 8decade
ranges. 100% overranging to 1999 on all ranges.
ACCURACY (lO^C to SO^C) :±(5% of reading +0.1% of
range) on all ranges.
ASACONSTANT CURRENT SOURCE
RANGE: 8currents in decade steps from 10“5 to 10“L2
ampere using OHMS ranges. Hi terminal is positive.
COMPLIAxNCE: Up to 200 volts.
ACCURxiCY (lO^C to SO^C): ±0.5% from 10“5 to 10“'
ampere, ±2% at lO”® ampere. ±5% from 10"^ to
]_ 0“12 ampere.
LOAD REGULATION; Better than 0.1% for loads up to
10 11 ohms.
GENERAL
DISPLAY: 3digits plus 1overrange digit; decimal
position, polarity, and overload indication; 5
readings per second. Depending on ser.sitivity
setting, 3least-significant digits blink or blank
when overload condition exists.
POLARITY SELECTION: Automatic
SENSITIVITY SELECTION: Automatic: Voltage sensi-
tivity selection is fully automatic. Sensitivity
selection is automatic two decades above and be-
low range switch setting for resistance, charge,
and most current measurements. Manual: Front
panel switch. Remote: Programmable with the Model
6162 Output/Control (optional) .
ISOLATION: Circuit Lo to chassis ground;, greater
than 109 ohms shunted by 500 picofarads (decreas-
ing to 108 ohms at 30°C and 70% relative humidity).
Circuit Lo may be floated up to ±1000 volts with
respect to chassis ground.
ANALOG OUTPUTS: Unity Gain: For dc inputs, output
is equal to input within 20 ppm for output currents
of 1mA or less. In the fast mode output polarity
is opposite input polarity. 1volt; ±1 volt at
up .to 1mA with respect to circuit Lo for full range
input; 100% overrange capability. In the normal
mode the output polarity is opposite input polarity.
OPER.ATING ENVIRONMENT: 20°C to 30^C, 0% to 70% re-
lative humidity. lO’C to SO^C with derated spec-
ifications. Storage: 0“C to 70®C.
CONNECTORS: Input: Teflon-insulated triaxial.
Analog Outputs: Unity gain, 1volt chassis, Lo,
and guard; binding posts. BCD Output: Internal
connectors for interfacing the Model 6162 Isolated
Output/Control.
DIMENSIONS; WEIGHT: Style M3-1/2 in. half-rack,
overall bench size 4in. high x8-3/4 in. wide x
15-3/4 in. deep (100 x220 x400 mm); net weight,
11 pounds (4,8 kg)
.
POWER: Line Operation: 90-125 or 180-250 volts
(switch selected), 50-60 Hz, 9watts.
ACCESSORIES SITFLIED: Model 6011 Input Cable: 3ft.
dm) triaxial cable with triaxial connector and 3
alligatorite-ips
.
NOTE: All accuracy and gam specifications are exclusive of noise and zero offsets.
Accuracies include temperature coefficient. On the 5% accuracy ranges as an
Ammeter, Ohmmeter, and Constant Current Source the coefficient is less than
0.2% per 'C.
LV 0374

i-'-'i:
<>

MODEL 616 GENERAL INFORMATION
NFORMATION
1-1, INTRODUCTION. The Model 616 Digital Electro-
meter is an automatic ranging, multipurpose electro-
meter featuring sensitivity to 10 microvolts per
digit. Its 3-1/2 digit LED display provides 0.2%
voltage accuracy for awide range of measurements.
The Model 616 is essentially adigital multimeter
optimized for measurements from high source impe-
dance. The 616 provides wide range capability when
measuring current, resistance, and charge in addition
to voltage
.
1-2. WARRANTY INFORMATION. The warranty is stated
on the inside front cover of the manual.
1-3. CHANGE NOTICE. Improvements or changes to
the instrument not incorporated into the manual
will be explained on ayellow Change Notice sheet
attached to the inside back cover.
0773 1

GENERAL INFORMATION MODEL 616
TABLE 1-1.
Front Panel Controls
Control Functional Description Paragraph
Power ON Controls line power.
SENSITIVITY Sets voltage sensitivity and decimal point. 3-4a
ZERO Adjusts zero offset. 3-4a
RANGE Sets range on a chosen function. 3-3
FAST/NORMAL Sets instrument for either Feedback or Shunt Mode. 3- 7b
ZERO CHECK Places instrument in ZERO CHECK mode. 3-6
INPUT Triaxial input receptacle. 3- 2a
FAST/NOSMAL
S103
ZERO CHECK I
S102
POWER ON SENSITIVITY ZERO
S202 SAOl RL19 RANGE
SlOl
TRIAXIAL
INPUT
JL20
FIGURE 2. Front Panel Controls and Display.
20773

FIGURE 3. Rear Panel Connectors.
TABLE 1-2.
Rear Panel Controls
.
MODEL 616 GENERAL INFORMATION
Control Functional Description Paragraph
Line Switch Sets instrument for nominal 117V or 234V. 2-3a
Line Receptacle Mates with 3-wire line cord. 2-3c
FUSE 117V: 3/16A 2~3b
234V: 1/lOA
XI CWHITE) Unity-gain Output, 200V @1mA maximum. 3-2c
IV (RED) Recorder Output, IV @1mA full range. 3-2c
GUARD (BLUE) Guard Output. 3-2c
LO (BLACK) Circuit Low. 3-2c
GROUND (GREEN) Chassis ground. 3-2c

INITIAL PREPARATION MODEL 616
SECTION 2. INITIAL PREPARATION
2-1. GENERAL. This section describes procedures for
incoming inspection and preparation for use.
2-2. INSPECTION, The Model 616 was carefully in-
spected both mechanically and electrically before
shipment. Upon receiving the instrument, check
for any obvious damage which may have occurred dur-
ing transit. Report any damages to the shipping
agent.
2-3. PREPARATION FOR USE.
Line Voltage. Before power Is applied check
the position of the LINE switch (S201) on the rear
panel. Select the 117V position for operation from
50-60 Hz line voltages over the range 90V to 125V
rms. Select the 234V position for operation from
50-60 Hz line voltages over the range 180V to 250V
rms
.
b. Fuse Installation. After the line voltage
range is selected check for the proper fuse, type
and rating as follows:
1I7V: 3/16 amperci ,type SAG SLO-ELO
234V: I/IO ampere, type 3AG SLO-BLO
c. Line Connections. This instrument requires a
three-wire line cord (Keithley part no. CO-7) which
provides connections to line voltage (high, common)
and chassis ground. For operator safety, the
chassis ground pin should be connected to earth
ground.
CAUTION
If the instrument input LO is to be floated,
above chassis ground, make certain that the
"link" between LO and GROUND on the rear
panel is removed.
40773

OPERATING INSTRUCTIONS
3-1 .GENERAL. This Bection describes the proce-
dures for operating the Model 616 as avoltmeter^
aiKmetet^, ohnfflieter, and coulcmibmeter.
3-2. CONNECTIONS.
a. Input Receptacle. This receptacle is a
Teflon insulated trlaxial connector. The center
terminal is the high impedance input; the inner
shield is the low input; and the outer shield ia
case, ground,, The ma,ting connector is aKeithley
part no. CS-141 trlaxial plug.
b. Model 6011 Input Cable .This cable is a30
inch long triaxial cable terminated with 3color-
coded alligator clips. The input high is Identified
by the heavy wire with red insulator. The input
low is identified by the thin wire with black in-
c. Rear Panel Terminals. The rear panel has
six binding posts which are used for making special
connections to the Model 616,
1. XI Terminal (White). This terminal provides
an analog signal at unity gain.
2. IV Terminal (Red). This terminal provides
an analog signal with ascale factor of 1volt for
full range input.
3. LO Terminals (Black). These terminals
provide aconnection to input low. Either
terminal may be used for system connections.
4. GUARD Terminal (Blue). This terminal pro-
vides aconnection to the amplifier feedback
when in the FAST mode.
5. GROUND Terminal (Green). This terminal
provides aconnection to chassis ground. A
shorting link is provided for easy connections
between low and chassis.
3-3. FUNCTION SELECTION. The Model 616 provides a
single front panel rotary switch for selection of
function and range. The RANGE .Switch (SlOl) permits
manual selection of any of four functions, namely,
VOLT, OHMS, COULOMB, and AMPERE.
3-4„ VOLT FUNCTION. The Model 616 provides five
decades of voltage sensitivity from .01000 volts
to 100 volts full range. Ihe VOLT function is
selected by setting the. RANGE switch to VOLT.
a. Manual Sensitivity Settings. The front panel
SENSITIVITY switch has si,x positions. As the switch
is rotated counter clockwise, the seiiBitivity is
increased. These positions correspond to full range
sensitivities of 100,0V, lO.OOV, l.OOOV, .lOOOV, and
.OlOOOV as in Table 3»1- Position six is the
AUTO sensitivity mode which enables either auto-
matic sensitivity or remotely selected sensitivity
(when used with the Model 6162)
.
TABLE 3-1.
\Sensitivity
jSetting Full Range
Disolav Maximum
Display
110 mV .01000 V±.01999 V
100 mV .1000 V ±.1999 V
11V1.000 V±1.999 V
10 V10.00 V±19.99 V
1100 V 100.0 V±199.9 V* 1
*The display indicates 000. OV at 200,0 volts input.
The three least significant digits will flash on
and off (blinking action) to indicate an over-
voltage condition. The display will continue to
read up to ±201.7 volts with blinking action. Be-
yond ±201.7 volts the display will indicate 001.7
volts with blinking action.
CAUTION
Voltage inputs greater than ±200 volts are
not recommended since damage to the Instru’
ment may result
.
FIGURE 5. Typical Display on 10 mV Sensitivity.
0374 5

OPERATING INSTRUCTIONS MODEL 616
b. Automatic Sensitivity Operation. In the AUTO
mode, the Model 616 automatically selects the pro-
per sensitivity in accordance with the following
rules
.
1. Upranging. If the display reading is be-
tween 0-1-8-0 and 1-9-9-9 and the input signal
is increased beyond 1-9-9-9, the Model 616 auto-
matically up-ranges to the next higher (less
sensitive) range. The three least significant
digits are blanked during range changing so as
to prohibit incorrect readings from being dis-
played. If the input; signal exceeds +199.9 volts
the display will continue to indicate up to :+201.7
volts but the three least significant digits will
flash on and off to indicate an over voltage
condition.
2. Dcrton ranging.. If the display reading is
at least d-l~8-0 and the input signal is decreased,
the Model 616 automatically down ranges to the next
lower (more aensitive) range.
To interpret areading on OHMS, COULOMB, or AMPERE
ranges both the digital display (with decimal location)
and the RANGE setting (powers of ten)should be consi-
dered. For example, given adigital reading of 17.32
and aR^INGE setting of 10“^ AMPERE, the actual_meas-
ured value would be interpreted as 17.32 xlO"'" ampere.
Since the decimal point is moveable, it is important
to notice the position of the dcraimal point to deter-
mine the full range of Che instrument. See Table 3-3
for typical range settings in the AMPERE function.
TABLE 3-3.
Typical Current Range Settings*
Input Range Sensitivity Digital
Current Setting Setting Display
10_i^A
10
1
10_ -A
10_. A
10 ^-^A
10 mV .00010
10 mV
10 mV .00100
.01000
100 mV
1V.1000
1.000 1
c. Remote Sensitivity Selection. When the Model
61.6 is used with the Model 6162 Isolated Output/
Control ,the 616's voltage sensitivity may be re-
motely selected. The output connector on the rear
panel of the 6162 provides four isolated control
lines for the purpose of remote sensitivity pro-
gramming. The lines are coded as shown in Table
3-2. The 616’® front panel SENSITIVITY switch
must be set to AUTO position.
TABLE 3-2.
Remote Sensitivity Programming Logic
Sensitivity
^0
Control
"a
Lines
^2
.01000 V000 0
,1000 V0100
1.000 V0101
10.00 V01 1 0
100.0 V0 1 1 1
*The current reading is interpreted by multiplying the
display reading times the. range setting. Other cur-
rents not shown can be measured by selecting the
appropriate RANGE switch setting in decade steps from
10"^^A to ,10*^A.
3-b. OPERATION AS A VOLTMETER. The Model 616 can be
used to measure voltages from ±10 microvolts to +200
volts. Although the Model 616 is useable as agener-
al purpose digital voltmeter, it has certain, charac-
teristics which enable reliable measurements from
very high source resistances. When used in the VOLT
mode, the Model 616 has an input resistance greater
than 2xlO^'^ft. As aresult, the loading of the
source circuitry is relatively insignificant when
compared to typical digital voltmeters having 10°
ohms input resistance. The Model 616 has 20 pico-
farads of shunt capacitance (not including the input
cable capacitance) .Since alarge amount of capaci-
tance causes aslowing of response, the Model 616
input capacity is kept as small as possible.
NOTE
The remote enable line Ry is used to defeat
the automatic sensitivity feature. WTien Rq
is open, the 616 returns to automatic opera-
tion. Logic L=» open.
3-5. RANGE SELECTION. The front panel RANGE switch
(SlOl) provides selection of four functions, VOLT,
OHMS, COULOMB, and AMPERE as described in paragraph
3-3. For each function, awide selection of ranges
is. provided; 8ranges on OHMS, 4ranges on COULOMB,
and 11 ranges on AMPERE. Since the SENSITIVITY
switch is used in conjunction with the RANGE Switch,
the actual number of useable spans is 12 decades on
OHMS, 8decades on COULOMB, and 11 on AMPERE.
NOTE
On the 10“^A to 10“^A ranges, the voltage de-
veloped must not exceed 2volts, otherwise,
overheating of arange resistor could result.
As aresult, the 10 volt and 100 volt sensi-
tivity settings are not recommended for 10“^A
to 10“'^A ranges.
a. Measurements From Very High Source Resistance.
To use the Model 616 as avoltmeter, set the front
panel controls as follcwsj
RANGE —VOLT
SENSITIVITY —AUTO
FAST /NORMAL —NORMAL
(A complete explanation of the use of the FAST/NORMAL
switch is given in paragraph 3-7b)
Make connections to the Model 616 using ashielded
triaxiai cable. Keep cable length as short as poss-
ible to reduce the slowing effects of cable capaci-
tance. The zero control may need occasional adjust-
ment to reduce any voltage offset which may occur
due to temperature variations. To rezero the Model
6.16, set the ZERO CHECK switch to CHECK position
and adjust the front panel ZERO control for aO-O-O-O
display. (The recommended warm-up time for the Model
616 is two hours although it is useable Immediately
after power is turned on.) The Model 616 provides a
direct reading voltage display with automatic decimal
point position and polarity.
60374

MODEL 616 OPERATING INSTRUCTIONS
%ERROR =IQQ R
R+Rxn
Figure 6.Operation As aVoltmeter in NORMAL Mode..
b. Measurements From Low Source Resistance. To
use the Model 616 for voltage measurements from low
source resistances, set the RANGE switch to the 10“^^
AMPERE position. In this mode, the Model 616 input
resistance is reduced to lOH ohms; as a result the
electrometer will be less sensitive to electrical
noise pickup and input cable vibration. Voltage
measurements can be made by following the same
procedure given in paragraph 3-6a. The Model 616
can be used with the RANGE set at any position be-
tween 10^11 AMPERE to 10-1 ampere. The Model 616
input resistance can be determined by taking the
reciprocal of the AMPERE setting. Significant load-
ing error may result if the input resistance is
reduced to less than lOOx the source resistance.
c. Measurements Above 200 Volts. The Model 616
can be used with accessory divider probes to measure
voltages up to 30 kilovolts. Range must be set to VOLT
1. Model 6102A Divider Probe (10:1). This
accessory extends the voltage measuring capability
of the Model 616 to 1000 volts. The input resis-
tance is 10^*^ ohms. The divider accuracy is ±4%
to 1000 volts. (To use the Model 6102A an access-
ory Model 6012 Adapter Is needed to mate the triax-
ial input with the UHF connector on the probe.)
2. Model 6601A Divider (100:1). This accessory
extends the voltage measuring capability of the
Model 616 to 5000 volts. The input resistance is
10^ ohms. The divider accuracy is ±0.01%.
3. Model 610 3A Divider Probe (1000:1). This
accessory extends the voltage measuring capability
of the Model 616 to 30 kilovolts. The input re-
sistance is 10^^ ohms. The divider accuracy is
±57o to 30 kilovolts. (To use the Model 6103A
an accessory Model 6012 Adapter is needed to mate
the triaxial input with the UHF connector on the
probe.)
NOTE
The Model 616 may exhibit alarge amount of
zero offset or drift Immediately after an
overload or along period of storage. In
addition, the offset current may exceed the
specification for ashort time until the
Model 616 is sufficiently stabilized.
Although the offset current of the Model 616
is well below offset found in, conventional
voltmeters, the effects of the offset current
charging the input capacitance may be noticed
when the input is open. Use the ZERO CHECK
switch to discharge the offset charge.
CAUTION
The Model 616 .should not be operated with cir-
cuit Icrw floating by greater than 1000 volts
with respect to chassis ground. If the Model
616 is to be used with circuit lc« floating
make certain that no connection is made be-
tween the LOW and GROUND terminals on the
rear panel. Do not connect agrounded re-
corder or other instrument to the XI or IV
outputs when the Model 616 is floated.
d. Voltage Measuremeriits in FAST Mode .Whe;n the
FAST/NORMAL Switch is set to FAST, the Model 616 is
connected in a"FEEDBACK" amplifier configuration.
In this configuration, the Model 616 requiress special
connections. To measure voltage, connect the source
between input HI and GUARD. An easy way to accom-
plish this connection is to connect the link (on the
rear panel) between "GUARD" (blue terminal) and
"GROUND" (black terminal). Then use the triaxial
cable for input connections with the input voltage
applied between the "red" clip lead and the "green"
clip lead. NOTE
In this special voltage connection, the LO
input (black clip lead) is not used since
the voltage amplifier configuration has been
changed. This "FAST" method significantly
0374 7

OPERATING INSTRUCTIONS MODEL 616
3-7. OPERAT ION AS mAWTER. The Model 616 can be
used to aeaKure currents from 110-25 ampere to 200
milliamperes Although the Model 616 is useable as
ageneral purpose pico--iEimeter, it hits certain charac-
teristics which enable reliable measurements of very
small currents with fast response.
a. Korpsal Mode Cu rrent Measurements
»
]!n t..his mode,
the Model 616 measures current over awide range.
When the FAST/NORMAL switch Is set to NORMAL, the
Model 616 operates as ashunt-type picoammeter in
which aresistor is connected directly across the
input teruiinals. The Model 616 measures the volt-
age drop across the shunt resistors where Vj-jj =Ij^
XRg. This method of measurement is typical of
most multimeter current measuring techniques. To
use the Model 616 as ashunt-type picoammeter, set
the front panel controls as follows:
range —10 ^AMPERE (or appropriate range)
SENSITIVITY —AUTO
EAST /NORMAL —NORMAL
NOTE
Full range is determined by the
sensitivity setting and the AMPERE
range setting.
Make connections to the Model 616 using ashielded
triaxlal cable. Keep cable length as short as pos-
sible to reduce the slowing effects of cable capaci-
tance. The zero control may need occasional adjust-
ment to reduce any voltage offset which may occur
due to temperature variations. To rezero the Model
616, set the ZERO CHECK switch to CHECK position
and adjust the front panel zero control for aO-O-O-O
display. (The recommended warm-up time for the
Model 616 is two hours although it is useable immediat-
ely after power is turned on.)
NOTE
The Model 616 may exhibit alarge amount of
zero orfset or drift immediately after an
overload or along period of storage, in
addition, the offset current laay exceed the
specification for ashort time, until the
Model 616 is sufficiently stabilized. A.i-
though the offset current of the Model 616
is well below offset found in conventional
voltmeters, the effects of the offset current
charging the input capacitance may be nociced
when the input Is open. Use the ZERO CHECK
switch to discharge the offset charge.
CAUTION
Do not use the 10 volt and 100 volt sensi-
tivity settings for RANGE switch settings
of 10 ,10 ,10“5, and 10“^ ampere. If
the voltage exceeds 2volts on these ranges
,
overheating of the resistors could result
with subsequent degradation of accuracy in
tlie AMPERE mode.
1
1
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dr "
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niivvv
1T{
1Measuring |
1
Points 1
1
}I1
1rrveter
IX1
jSOURCE !1AMMETER i
t
1
1=Imeter R%error in reading due to circuit loading =—lOO
if Rin «R, 1Imeter and %error 3^0
Rin
R+Rin
FIGURE 9. Loading Effects in Ammeter Function.
0374

MODEL 616 OPERATING INSTRUCTIONS
b. Fast. Mode Current Measurements, (Useable for
currents from lO^^A and smaller.) in this mode, the
Model 616 measures very small currents with fast
response. When the FAST/NOEMAL switch is set to
FAST, the Model 616 operates as a feedback-type
picaommeter in which the current flows through the
feedback resistor of the voltage amplifier. The
Model 616 indicates the voltage developed across
the range resistor where Vp xRy. This
method of me.asurement provides fast response since
the effect of the input capacitance from lengthy
cables is diminished. To use the Model 616 as a
feedback-type picoammeter, set the front panel
controls as follows:
RANGE —10"^^ AMPERE
SENSITIVITY ~AUTO
FAST/NORMAL —FAST
Make connections to the Model 616 using ashielded
triaxlal cable. The zero control may need occasion-
al adjustment to reduce any voltage offset which
may occur due to temperature variations. To rezero
the Model 616, set the ZERO CHECK switch to CHECK
position and adjust the front panel ZERO control
for aO-O-O-O display. (The recommended warm-up
time for the Model 616 is two hours although it is
useable immediately after power is turned on.)
NOTE
The Model 616 may exhibit alarge amount of
zero offset or drift immediately after an
overload or along period of storage. In
addition, the offset current may exceed the
specification for ashort time until the
Model 616 is well below offset found in
conventional voltmeters, the effects of the
offset current charging the input capaci-
tance may be noticed when the input is open.
Use the ZERO CHECK switch to discharge the
offset charge.
S) Considerations When Measuring Current. When
using the Model 616 in either the NORMAL or FAST
modes, there are certain considerations which ensure
optimum performance. In general, it is advantageous
to use the smallest possible value of shunt resis-
tance for apicoammeter. First, small value resis-
tors are of higher quality compared to large values
with respect to accuracy, time stability, tempera-
ture, and voltage coefficient. Second, ideal plco-
ammeters require very small input resistance so that
source loading does not affect the overall accuracy
of the measurement. Since the input resistance
inashunt picoammeter is determined by the range
resistor, the RANGE multiplier should be set at the
lowest value. Third, the use of alow value resis-
tor reduces the input RC time constant and results
in faster response. However, since noise and zero
drift become more significant when the voltage
amplifier sensitivity is set to 10 or 100 millivolts.
the appropriate range multiplier should be selected
with aone volt full scale sensitivity. The use of
the Model 616 in the FAST mode enables measurements
of very small currents while reducing the source
leading and input RC time constant. Since the range
resistor is connected in the feedback of the volt-
age amplifier, the effective input resistance is
determined by the open-loop gain where =Ry tA.
(The value of Ais typically 10,000.) Another ad-
vantage of the feedback mode is Che reduced effect
of input capacitance since the input RC time con-
stant is decreased by the gain A“RC ^
A). As aresult, the measurement speed is governed
by the feedback time constant which is afunction
of the feedback resistor and stray capacitance across
the resistor (usually afew pF). Thus, when compar-
ing shunt versus feedback modes, it is evident Chat
Che feedback measurement offers superior performance
for most applications.
TABLE 3-4.
Current Settings
Input Range Sensitivity Digital Typical
Current Setting Setting Display Accuracy*
10"^A
lO'I^A “;S
10
10 mV
10 mV
.00010
.00100
+
+
2d
6d
10 :^A
io"::a 10 mV .01000 +51 d
100 mV .1000 +51 d
1V1.000 ±51 d
10"J^A lo-f 1V1.000 ±51 d
10"^ 1V1.000 ±51 d
10-® A10"® 1V1.000 ±21 d
10 'A10"^ 1V1.000 ±6d
loi A10-^5 1V1.000 ±6 d
10 ,A1V1.000 ±6d
lO-A A10"^ 1V1.000 ±6d
10" ^A1V1.000 ±6d
10-2 ^10"^ 1V1.000 ±6 d
10 A10 1V1.000 ±6 d
*exclusive of noise, zero drift, and loading error.
NOTE
The use of the FAST mode for current measurements
is subject to certain restrictions as follows:
1. The range resistor value should not be
greater than the source resistance, otherwise
feedback division results In zero instability at
the output.
2. The largest value of current measured
should not exceed 10“^ ampere, otherwise the
full feedback current cannot be developed.
The NORMAL mode should be used for currents
from 200 mA to 10~^A.
0374 9

OPERATING INSTRUCTIONS MODEL 616
FIGURE 10. Operation As An Ohnmeter in NOSM/i.L Mode
3-8. OPEFaTION asA.N OHMMETER. The Model 616 can
be used to measure resistance from 1ohm to 2x
ohms. Although the Model 616 is useable as ageneral
pxirpose chmmeter. ;lr. has certain characteristics
which enable rellahlt' Tseasurements of very large
resistances with fast response,
a. Normal Mode OhmsMeasurements. In this, mode ^the
Model 616 measures resistance over awide range. The
use o:t the NOPM/U. mode is recommended for measurements
up to 10^^' ohms (use the FAST mode for larger resis-
tances). The Model 616 uses aconstant current method
i'or seasuriiig resistance. Therefore, the digital
Make connections to the Model 616 using ashielded
triaxial cable. Keep cable length as short as
possible to reduce the slowing effects ot cable
capacitance. The nero control luay need occasional
adjustment to reduce any voltage offset, which may
occur due to the temperature variations,. To rezero
the Model 616, se't the ZERO CHECK Switch to CHECK
position and adju.st the front panel ZERO control
for aO-O-O-O display. (The re^commended war-mup time
for the Model 616 is two hours, although it .is useable
immediately after power is turned on.) Tfic Model 616
provides adirect reading display with automatic
decimal point position.
the input terminals where V=IxR(the current Iis
selected in decade steps using the RANGE Switch) .To
use the Model 616 as an obrnmeter, set the front panel
controls as follows:
RANGE —10^ OHMS (or other appropriate range)
SENSITIVITY —AUTO
FAST /NORMAL —NORMAL
TABLE 3-5.
Ohms Settings
Source
Res is tance Range Setting Sensitivity
Setting Digital
Distlav Typical Accuracy* i
lo?-^ 100 V100.0 ±51 d
io“ 10 V10.00 +51 d
lojf 1V1.000 +51 d"
lof^ 1V1.000 +51 d
ioi° loH 1V1.000 +51 d
lo! 10^ 1V1.000 ±51 d
10° 1V1.000 ±21 d
lol 1V1.000 ±6d
IQ? 10? 1V1.000 +6d
10? 1V1.000 ±6d
iS 10^ 1V.1000 +6d
10^ 10c 100 mV .01000 +6d
10^ 10^ 10 mV .00100 ±2 d
*exclusive of noise, zero drift, and loading error.
Fast Ohms Measurement. In this mode, the
Model 616 measures very large, resistances with
7-esponse (use this mode for resistances larger than
10^^ ohms). When the FAST/NORMAL switch is set to
FAST, the unknown resistance (Rx) is floating
with respect to the low side of the voltage ampli-
fier. The unknown resistor is connected across the
feedback so as to reduce the effects of capacitance
and therefore speed up the measuring time. To use
the Model 616 for FAST ohmmeter measurements, set
the front panel controls as follows:
12
RANGE —10 OHMS
SENSITIVITY “AUTO
FAST/NORMAL —FAST
Connect the unknown resistance between Input HI and
GUARD (on the rear panel)
.
NOTE
When the FAST mode is used for resistance meas-
urements, the unknown resistance sample is con-
nected in feedback around the electrometer
amplifier. Therefore the resistance must be
floating and not referenced to LO.
10 0374

MODEL 616 OPERATING INSTRUCTIONS
mm tmm tmm mm mm mm rnmaa mam"i
SOURCE ELECTROMETER
V«1/C /i dt
FIGURE 11. Operation As ACoulombmeter in FAST Mode .
3-9. OPERATION AS ACOULOMBMETER. The Model 616 can
be used to measure charge by means of acurrent inte-
gration technique. When the Model 616 is set to any-
one of the 4coulomb ranges, an accurately known capa-
citor is connected in the feedback loop of the volt-
age amplifier so that the voltage developed is pro-
portional to the integral of current where V «Q/C
or V=1/c/idt. The Model 616 can also be used with
accessory Models 2501 or 2503 for measurement of
static charge on adielectric surface. Adiscussion
of static charge measurement is given in section 3-lOc.
To use the Model 616 as acoulombmeter, set the front
panel controls as follows:
RANGE —10“^° COULOMB
SENSITIVITY —AUTO
FAST /NORMAL —FAST
Make connections to the Model 616 using ashielded
triaxial cable. Keep cable length as short as
possible to reduce the slowing effects of cable
capacitance. .The zero control may need occasional
adjustment to reduce any voltage offset which may
occur due to the temperature variations .To rezero
the Model 616, set the ZERO CHECK Switch to CHECK
position and adjust the front panel ZERO control
for a0~0“0-0 display. (The recommended warmup
time for the Model 616 is two hours although It is
useable Immediately after power is turned on.)
The Model 616 provides adirect reading display
with automatic decimal point position.
NOTE,
3-10. ALTERNATE MEASUREMENTS. The Model 616 can
also be used with Keithley accessories which ex-
tend the measuring capabilities of the electrometer.
a. Null Method for Current Measurements. The
Model 616 can be used with an accurate current
source such as Keithley Model 261: to measure
small variations of current. When using this method,
the Model 616 is operated as acurrent null detector
in the FAST mode. The current source should be ad-
justed to obtain anull reading on the Model 616
(the electrometer should be set to an appropriate
range and sensitivity depending on the magnitude of
current variation)
.
b. Volt-Ammeter Resistance Measurements. The
Model 616 can be used with an accurate voltage
source such as Keithley Models 240A, 244, 245, or
246. When using this method, the Model 616 is
operated as apicoairaneter so that the current
through the unknown resistance is measured by the
electrometer. The resistance is then calculated in
terms of the known voltage impressed and the re-
sultant current measured on the electrometer.
e. Static Charge Measureiaents
.
The Model 616
can be used with Models 2501 or 2503 Static Detector
Probes for measurement of static charge on adielec-
tric surface. When using this method, the Model 616
is operated as avoltmeter with areading directly
in volte. (Do not attempt to measure static charge
with the Model 616 in the COULOMB mode.)
NOTE
The input offset current of the Model 616
contributes acharge of 5x10“15 coulomb
per second and should be subtracted- from
the actual reading.
For more information about Static Charge
Measurements, request the Keithley Product
Notes entitled "Electrometer Static Charge
Measurements".
0374 11

OPERATING INSTRUCTIONS MODEL 616
FIGURi: 12 .Null Method lor Curreii tMe as ureinent
.
3-n .RECORDER OUTPUTS. The Model 616 provides
several outputs for monitoring an analog signal.
±. XI Ou tput (Unity Gain). This output can be
used for monitoring the input signal in applications
requiring abuffer amplifier.
1. NORMAL MODE. In the NORMAL MODE, the signal
at the XI OUTPUT (with respect to LO) is equal to
the input within 20 ppm at dc. The XI OUTPUT can
deliver up to 1inilliampere for outputs up to 200
volts ,
2. FAST MODE. In the FAST MODE, the XI OUTPUT
terminal is connected to input LO. For unity gain
applications when in FAST mode the GUARD terminja
should be used. Typical rise times for various
current ranges is shown in Table 3-6. This data
is representative of instrument response for unity
gain operation.
c. GUARD OUTPUT. This output can be used with
the XI output for recording purposes or special
measuring techniques such as guarded resistance
measurements.
1. NORMAL MODE. In this mode, the GUARD terminal
is connected to the LO terminal.
2. FAST MODE. In this mode, the GUARD terminal
can be used to monitor the input current when the
Model 616 is used as aFAST mode picoarnmeter. The
output of the GUARD terminal is proportional to
the Input current where Vq =' linput ^^range* The
GUARD terminal is also useful for making guarded
resistance measurements. For this type of measure-
ment, the unknown resistance is connected between
input HI and GUARD. The voltage developed at the
GUARD terminal is proportional to the unknown re-
sistance, where xR^.
TABLE 3-6.
Response at GUARD (Unity Gain) OUTPUT for Fast Current*.
b. 1VOLT OUTPUT. This output provides a1volt
analog output at up to. 1milliampere corresponding Range
Setting Rise
]. VTime 10-907,
10 V100 V
to a full scale input. 1X10-5 A50 pS 100 pS 500 yS
1X10 ^A
1X10 ^A300 pS 500 yS 1mS
1. NORMAL MODE. In the NORMAL mode, the out- 2mS 3mS 5mS
put polarity is opposite the input polarity. 1X10 A10 mS 12 mS 15 mS
1X10 ^A
1X10“:^; A
1X10' A
60 mS 60 mS 60 mS
2. FAST MODE. In the FAST MODE, the output 300 raS 300 mS 300 mS
polarity is the same as Input. 3S3S3S
*Typlcal instrument performance (may vary from unit
to unit)
.
Tin'¥rtiTTr~r]iriiiiiii>iifiitiitiiri iiimn i
FIGURE 14. Unity-Gain (XI) Measurement .
12 0773

MODEL 616 OPERATING INSTRUCTIONS
3-12. DIGITAL OUTPUT CONTROL.
a. General. The Model 6162 Isolated Output/Control
provides isolated BCD outputs, remote controls, and
remote programming lines for systems use of the Model
616. The Model 6162 has 32 bits of measurement in-
formation provided in parallel format. Strobe lines
permit data transfer in 4bit multiples which are
compatible with 8, 12 ^or 16-bit data systems.
Strobing of the "open collector" outputs also permit
multiplexing of data from 2or more 6162’ son a
single data bus. Print rate can be adjusted from
1/5 second to 7seconds per reading to permit atrans-
fer rate compatible with the speed of measurement
and/or the acquijsition system. Isolated Remote Con-
trols are provided for Zero Check, Sensitivity, Dis-
play Hold, Output Hold, as well as Strobe. The 616’s
low to chassis ground Isolation is maintained by the
6162 (greater than 10^® ohms). Digital output low
is also isolated from chassis ground by 10° ohms.
b. Installation. The 6162 circuitry is housed in
aseparate 3-1/2 in. high half-rack chassis. It can
be used on the bench adjacent to the 616 or rack
mounted side-by-side in astandard 19 inch rack width
using rack hardware provided (Model 1007).
1. Bench Mounting. Position the Model 6162 on
the left side of the Model 616 as shown in Figure
19 since the interconnecting cable has been de-
signed to mate with the 616 in this configuration
only. Remove the "side dress" panels (Item 11) on
the sides which are adjacent. Loosen the socket
head screws (Item 24) and slide the panels to the
rear of the instruments. After both panels are
removed install the "mounting clamp" (Item 23)
PRINT RATE POWER
R115 S402
FIGURE 16. Front Panel of Model 6162.
using the original hardware. Remove two screws
on one of the instruments and insert the mounting
clamp behind the corner bracket as shown in Figure
17. Replace and tighten the two screws to hold
the clamp in place. Next, insert the open part of
the clamp behind the corner bracket on the second
instrument. Attach a1-1/8" long Phillips head
screw (Item 25) and kepnut (Item 26) to secure the
two instruments together.
2. Rack Mounting. Proceed as described in the
above paragraph for bench mounting. Then attach an
"angle bracket" (Item 21) on each instrument using
hardware (Item 22) in place of original hardware.
The bottom corner feet and tilt bail assemblies
may be removed If necessary. The original hard-
ware, side dress panels, feet and tilt bail assem-
blies should be retained for future conversion back
to bench mounting.
0773 13

OPERATING INSTRUCTIONS MODEL 616
FIGURE 18. Rear Panel of Model 616 and 6162 .
c. Connection.9 .Asingle prewired cable plugs
into the 616 ’s chassis to provide all necessary
conanunication between units. To install the cable,
remove the 616's top cover, place rubber grommet
within the rear panel slot, insert cable, and plug
the three mini-connectors into their respective
pc-board locations as shown in Figure 19. Aseparate
50-pin AMP type 205211-1 connector provides isolated
outputs and control lines. Amating 50-pin connector
is furnished with the 6162 (Keithley Part No. CS-271 ).
e. Summary of Digital Information .Table 3-7
identifies the data lines available at the 6162
output connector. The data is grouped in 4-bit
bytes with acorresponding Strobe line. The strobe
(or enable) line permits serial data transfer from
asingle 6162 or multiplexing of the data output of
anumber of 6162 's onto acommon data bus. Conven-
tional parallel data transfer is obtained when all
strobe lines are at Logic ”0" (closure to output LO
within 0.5 volt).
d. Power Requirements .The 6162 is powered from f. Print Rate. The basic 616 has areading rate
50-60HZ line voltage and has aseparate power switch of 5readings per second. The front panel RATE
and fuse. Line voltage is selected using the rear control on the 6162 varies the print rate in 1/5
panel switch. Fuse type is 3AG SLO-BLO, 1/4A(117V) or second increments.
1/8A(234V).
14 0773

MODEL 616 OPERATING INSTRUCTIONS
TABLE 3-7.
Pin-Out for 50-Pin Connector
Pin No. Name Function Pin No. Name Function
1Strobe #4 Buffer Control 26 4 X 10^ Data //3
2Output Hold Control 27 FLAG
4Xloj-
2X10^
Timing Output
3Strobe i)l Buffer Control 28 Data #2
4Output Lo GND 29 Data in
Cl DP3 (1.000) Decimal Point 30 1 X 10 Data #3
6DP4 (10.00) Decimal Point 31 MANUAL RANGE Range Control
7DPI (.01000) Decimal Point 32 Rl Range Control
8DR Down-range 33 Range Control
9UR Up-range 34 EXP 8X10^ Output
10 FLAG Timing Cutout 35 EXP 4X10^ Qiltpii£
11 4X10^ Data y/1 36 Strobe #3 -
EXP 1XlOn
Buffer Control
12. 2X10° Data #1 37 Output
13 ZERO CHECK Output 38 EXP 2X10“^ Output
14 R2 Range Control 39 Strobe #9 Buffer Control
15 ZERO CHECK Remote Control 40 "0" (10 mV range) Outnut
16 8XlO^^’ Data //i 41 EXP POL Output
17 1X10° Data ifl 42 EXP 1XlOi Output
18 Strobe #5 Buffer Control 43 POLARITY Output
19 Strobe #6 Buffer Control 44 Function
20 Strobe #8 Buffer Control 45 F2 ^Function
21 1X10° Data #4 46 8X10} Data in
22 DP 2(.1000) Decimal Point 47 1X10^ Data #2
23 DPS (100.0) Decimal Point 48 Strobe #1 Buffer Control
24 8X102 Data #3 49 Strobe #2 Buffer Control
25 2X10^ Data #3 50 Display Hold Control
g. Data Transfer .Conventional parallel data
transfer is accomplished through parallel connections
with one bit of information per conductor. Strobing
allows data to be grouped into word lengths (bytes)
appropriate to the acquisition device, thus simpli-
fying. the interfacing between the 6162 and 8, 12, or
16-bit devices. When all STROBE lines are at Logic
”0", the 6162 data outputs are enabled and are avail-
able in parallel form. Individual strobe lines may
be used to connect to acommon data bus in multiples
of 4-bit words. The 6162 "open-collector" outputs
are "open" unless the respective strobe lines are
at Logic "0". The use of "open-collector" config-
uration allows the parallel connection of 2or more
6162 units since none of the outputs will conduct
unless strobed. The 6162 outputs are TTL and DTL
compatible. The "open collector" output switches
between ahigh and low impedance level rather than
specific voltage levels. This permits the user to
determine the voltage level defined by logic state
"1". The output "1" state may be selected from any
voltage over the range of +2 and +12 volts. The "0"
state is 0.5V at +35 mA Cmaximum)sink current.
h. Word Sequence .The particular sequence in
which the words appear in serial data transfer is
determined by the way the "STROBE" lines are grouped
and the order of activation, In addition to the
wiring of the data blocks.
i. Control Features.
1. Flag (Flag) .This output provides alogic
level which can be used to indicate the proper
time interval for transfer of data. Alogic "1"
occurs from 50 milliseconds to 7seconds depending
on the Print Rate control setting. No change in
the Digital Output is made during this interval.
On some digital devices, it may be necessary to
trigger off the leading edge of the Flag or Flag
waveform by differentiating or other wave shaping,
2. Display Hold. This control line retains the
last reading on the display (except polarity) when
closure is made to digital LO (Pin 4). Neither the
a/d conversion nor digital output are affected by
this control.
3. Output Hold .This control line retains the
last reading at the Digital Output when closure is
made to digital LO (Pin 4). Neither the a/d con-
version nor digital display are affected by this
control.
4. Zero Check.This control line actuates the
616’s zero check solenoid to permit monitoring of
the electrometer amplifier offset. When the line
is released (Logic "1") the 616 returns to normal
operating configuration. The front panel ZERO
CHECK switch must be set to OFF position to permit
remote zero check control.
1. Remote Programming .Remote lines are provided
at the 50-pin connector to permit remote, selection
of sensitivity over five decades. When the 616's
SENSITIVITY Switch is set to AUTO position, the
sensitivity may be remotely programmed or allowed
to function automatically. When the MANUAL RANGE
line on the 6162 is at Logical "0" the coded range
lines are enabled, and the LSI range lines are
disabled.
0374 15

OPERATING INSTRUCTIONS MODEL 616
Name Pin No. Remarks
Strobe #1 48 Buffer Control
F.1
F2 44 uCoded function lines
43 ^See Table 3-11
ia.P POL 41 Logic "1" »+
EXP 1X10^ 42
Strobe.in
EXP 1. X 10
EXP 2X10
EXP 4X10
EXP 8X10
Strobe 1^2
1X10°
2X10°
4X10°
8X10°
Strobe #4
1 X 10^
2Xlo::
4X10|
8X10^
Strobe #5
1X10^
2X10,
4X10,
8X10
Strobe #6
TABLE 3-8.
Cross-Reference for Digital Outputs.
Name
Strobe #7
FLAG
Buffer Control
Used on OHMS, AMPERE
COULOMB ranges
Buffer control for
Data #1
Data //I (BCD)
Buffer control for
Data #2
Data #2 (BCD)
Buffer control for
Data #3
Data #3 (BCD)
Buffer Control
Down Range
Up Range
Strobe #9
The following are no
Output Hold
Display Hold
MANUAL RANGE
r2
^4
Digital Lo
Zero Check
Zero Check
Buffer Control
.0000= 100 mV
0.000= 1V
00,00= 10 V
000.0 =100 V
Remote Control
Remote Control
Sensitivity lines
See Table 3-12
Ground Reference
Indication
Remote Control
FIGURE 20. Identification of Pins on Digital Output Connector.
16 0374