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Instruction Manual
Models 6106, 610BR
Mul_tl&flqnge. ElecVpeters
Keithley Instruments. Inc.
26775 Aurora Road/Cleveland. Ohio 44139A216) 248-0400
MODELS 61013, 610BR ELECTROMETERS
TABLEOF CONTENTS
Section Page Section ? :I '22
1. GENERAL DESCRIPTION ........ 1 4-6. Calibration Procedures. . . . 31
4-J. Grid Current Check. 33
l-l. General ........... 1 4-a. DC Amplifier Adjustment 31
l-2. Features. .......... 1 4-9. High-Megohm Resistor Veri-
l-3. Differences Between the Models fication. . . 35
6108 and 610BR. ....... 1 4-10. Calibration of Ohms Ranges. 35
l-4. Specifications. ....... 2 4-11. Meter Zero Calibration. . 3j
l-5. Applications. ........ 3 4-12. Accuracy Check. . . . . . 35
l-6. Accessories ......... 4 4-13. Drift Check . 36
l-7. Equipment Shipped ...... 4
5. ACCESSORIES . . . . . . 43
2. OPERATION ............. 5
5-l. Model 6101A Shielded Test
2-1. Front Panel Controls and Lead. . . . . . . . . 43
Terminals .......... 5 5-2. Model 61018 Gripping Probe. 43
2-2. Rear Panel Controls and 5-3. Model 6102A Voltage Divider
Terminals .......... 6 Probe . . . . . . . . . 43
2-3. Input Connections ...... 6 5-4.. Model 6103A Voltage Divider
2~4. Preliminary Procedures. ... 8 Probe . . . . . . . . . 43
2-5. Voltage Measurements ...... 9 5-5. Model 6104 Test Shield. . . 44
2-6. Current Measurements. .... 10 5-6. Model 6105 Resistivity
2-7. Resistance Measurements ... 13 Adapter . . . . . , . . . 44
2-8. Charge Measurements ..... 15 5-7. Models 2501 and 2503 Static
2-9. Recorder Outputs. ...... 15 Detector Heads. . . . . . . . 45
Z-10. Unity-Gain Output ...... 17 5-8. Model 6106 Electrometer
Z-11. current source. ....... 17 Connection Kit. . . . . . . . 46
2-12. Static Charge Measurements. . 17 5-9. Model 6107 pH Electrode
Z-13. Capacitance Measurements. .. 18 Adapter . . . . . . . . . . . 4i
2-14. Application Notes ...... 19 5-10. Model 370 Recorder. . . . . . 48
3. CIRCUIT DESCRIPTION ........ 21 6. REPLACEABLE PARTS . . . . . . . 51
3-l. General ........... 21 6-l. Replaceable Parts List. . . . 51
3-2. Voltmeter Operation ..... 21 6-2. How to Order Parts. . . . . . 51
3-3. Voltmeter circuit ...... 22 Models 6108, 610BR Replaceable
3-4. Ammeter Operation ...... 24 Parts List. . . . . . . . 52
3-5. Ohmmeter Operation. ..... 24 Model 6108 Schematic Diagram
3-6. Coulombmeter Operation. ... 25 177953. . . , . . . . . . . 59
3-7. Power Supply. ........ 26 Green Repair and
Calibration Forms . . 61
4. UAINTENANCE ............ 29
* Change Notice Last Page
4-l. General ........... 29
4-2. Parts Replacement ...... 29
4-3. Troubleshooting ....... 29
4-4. Procedures to Guide Trouble- * Yellow Change Notice sheet is included
shooting. .......... 30 only for instrument modifications affect-
4-5. 234-Volt Ooerarion. ..... 32 ing the Instruction Xanual.
O268R 1
GENERAL DESCRIPTION MODELS 6lOB, 610BR ELECTROMETERS
FIG
FIGURE 2. Keithley Instruments Model 610BR Electrometer. Model
610BR is the rack version of the Model 6108.
i
ii 1064R
MODELS 6108, 610BR ELECTROMFPERS GENERAL DESCRIPTION
SECTION1. GENERAL
DESCRIPTION
l-l. GENERAL.
a. The Keithley Model 610B Electrometer is a versatile instrument which
measures wide ranges of dc voltages, currente, resistances and charges. It
is a highly improved form of conventional dc vecuum tube voltmeters that
ueee an electrometer tube input to provide greeter than lo14 ohm Fnput re-
sistance. T'he Model 6lOB has all the capabilities of conventional VTVMe,
but it ten also make many more measurements without loading circuits.
b. The Electrometer has 11 voltage ranges from 0.001 volt full scale to
100 volts, 28 ~urm-ie: ranges from Lo-14 ampere full scale to 0.3 ampere,
25 linear resistance ranges from 100 ohms full scale to 1014 ohms, and 15
couLomb ranges from LO-12 coulomb full scale to LO-5 coulomb.
c. The Model 6LOB input stage uses a matched pair of electrometer tubes.
The output stage uses a vacuum tube; othewiee.solid-state devices are
used for all amplifier stages and the power supply. This increases re-
liability end stability and aLlows greater regulation of the power supply.
l-2. FEATURES.
a. Voltmeter accuracy is Cl% of full scale, exclusive of noise and drift.
b. Zero drift of the Model 6108 is 200 microvolts per hour maxirmun averaged
over any 24-hour period after warm-up. During the 2-hour warm-up, zero drift
is no more then 2 millivolts after the first hour.
c. Two amplifier outputs are available. A switch on the rear panel allows
either 23 volts or 21 milliampere for full-scale meter deflection. The current
output is variable 25% with 1.4-kilohm recorders. The unity-gain amplifier
output is equal to the input voltage within 50 ppm or 100 microvolts, exclusive
of zero drift.
d. Current measurements can be made by one of two methods, the normal method
in which the current is determined by measuring the voltage drop across a re-
sistor shunting the input, or the fast method in which negative feedback is
appliedthrough the shunt resistor. The latter method reduces ehe input drop
end greatly increases the response speed on the low-current ranges.
1-3. DIFFERENCES BETWEEN THE MODELS 610B AND 610BR.
a. The Model 610BR is the rack version of the cabinet configuration,
Model 610B. The circuits, specifications, electrical parts end operating
procedures for the two models are the same. Besides the outside dimensions,
the main difference between them is the Model 6LOBR's COARSE ZERO Control
is on the front panel, not on the rear panel.
b. The instructions in the Manual are for both models, although only the
Model 610B is mentioned. Any differences are identified for the correct model.
t064R 1
GENERAL DESCRIPTION ?,ODELS 6108, 610BR ELECTROMTERS
1-4. SPECIFICATIONS.
AS A VOLTMETER:
RANGE: ,001 volt full scale to 100 volts in eteven Lx and 3x ranges.
ACCURACY: ?L% of full scale on all ranges exctusive of noise and drift.
ZERO DRIFT: After L-hour warm-up no more than 2 millivolts in the second hour, and in any
subsequent 24-hour period, the average drift wilt not exceed 200 microvolts per hour.
HETER NOISE: +tO microvotes with input shorted.
INPUT IMPEDANCE: Greater than Lot4 ohms shunted by 22 picofarads on the VOLTS position of
the Range Switch. Input resistance may be selected in decade steps from LO to LOLL ohms
with the Range Switch.
AS AN AMMETER:
RANGE: 10-14 ampere full scale to 0.3 ampere in twenty-eight Lx and 3x ranges.
AccuRAcY: ?2% of full scale on 0.3 to 10-11 ampere ranges using smattest available Ilulti-
ptiee Switch setting; 14% of full scale on 3 x tOeL2 to tOdL4 ampere ranges.
METER NOISE: Less than i3 x lO-L5 ampere.
GRID CURRENT: Less than 2 x lO-L4 ampere
AS AN OHMMETER:
RANGE: 100 ohms full scale co 1014 ohms on twenty-five Linear Lx and 3x ranges.
`KcIJRAcY: ?3% of full scale on 100 to log ohm ran es using highest available Multiplier
Switch setting; ?5% of full scale on 3 x LO9 to to K4 ohm ranges.
AS A COULOMBMETER:
RANGE: LO-L2 coulomb full scale to tom5 coulomb Ln fifteen lx and 3x ranges.
ACCURACY: ?5% of full scale on all ranges. Drift due to grid current does not exceed
2 x 10eL4 coulomb per second.
AS AN AMPLIFIER:
INPUT IHPEDANCE: Greater than tot4 ohms shunted by 22 picofarads on the VOLTS position
of the Range Switch. Input resistance may be selected in decade steps from LO to LOLL
ohms with the Range Switch,
OLTPUTS: Unity-gain output and either voltage or current recorder output.
Unity-Gain Output: At dc, output is equal to input within 50 ppm or 100 microvolts.
exclusive of zero drift, for output currents of LOO microamperes or Less. up to one
milliampere may be drawn for input vottages OE LO votes or Less.
.* * .
t066R .
MODELS 6108, 610BR ELECTROMETERS GEXERAL 3ESCRI?TIO"
Voltage Recorder Output: +3 volts for full-scale input. Internal resistance is 3 kil-
ohms. Output polarity is opposite input polarity.
Gain: 0.03, 0.1, etc., to 3000
Frequency Response (Within 3 db): dc to 300 cps at a gain of 3000, rising to 25 kc
at a gain of 30, decreasing to 2.5 kc at a gain of 0.03.
Noise: 3% rms of full scale at a gain of 3000, decreasing to 1% at gains below 100.
Current Recorder Output: tl milliampere for full-scale input, variable T5% with LLiOO-
ohm recorders.
GENERAL:
POLARITY: METER Switch selects left zero (positive or negative) or center-zero scales
Output polarity is not reversed.
LINE STABILITY: A 10% change in line voltage will ca"se less than a LO-microvolt merer
defLection on aLL ranges.
CONNECTORS
: Input: uhf type; ground binding post.
output: Voltage or current, AmphenoL 80-PCZF; Unity-gain, binding posts
POWER: 105-125 or 210-250 volts (switch selected): 50 to 1000 cps; IO Watts
DIMENSIONS, WEIGHT: Model 6108: 10-l/2 inches high x 6-S/8 inches wide x 10 inches dee?;
net weight, 12 pounds. Model 610BR: 5-l/4 inches high x 19 inches wide x 10 inches deep;
net weight, 12 pounds.
ACCESSORIES SUPPLIED: Mating input and output plugs; 3:2 power line adapter; binding plug.
l-5. APPLICATIONS.
a. Voltmeter applications include directly measuring potentials of vacuum tube plates
and grids, pH electrodes, piezo-electric crystals, capacitors and electrochemical cells,
and the gate potentials of field effect transistors. With the Model 2501 or 2503 Static
Detector Probe, the Model 610B can measure electrostatic voltages.
b. As a picoammeter, the Electrometer can measure mass spectrograph currents. It can
be used with photo multiplier tubes, flame and beta ray and lithium ion-drift detectors.
Other uses are in gas chromatograph work, nuclear studies, plasma physic studies and
vacuum studies. Also, it can be used as a current null detector with an accurate current
reference source.
c. As an ohmeter, its uses include measuring diode characteristics, insulation resis-
tance, and resistor voitage coefficients. With the Model 6105 Resistivity Adapter and a
power supply, the Node1 610B can measure volume and surface resistivities.
d. In addition to measuring charge directly, other coulombmeter uses are measuring charge
current over a period and obtaining integral curves of time-varying currents. The Model
6108 can measure the total energy output from a pulsed laser on its coulomb ranges when
used with a calibrated photo tube or photo diode. It also can be used as a charge ampli-
fier to measure pieza-electric crystal outputs.
1066R 3
GENERAL DESCRIPTION MODELS 61OB, 610B~ ELECTROMETERS
1-6. ACCESSORIES.
a. Three accessory probes, fully described in Section 5, facilitate measurements end
extend the Electrometer's voltage range to 30 kilovolts.
b. Model 6104 Test Shield is suitable for resistance measurements with either 2 or 3-
terminal guarded connections, as well as voltage and current tests.
c. Model 6105 Resistivity Adapter ts a guarded test fixture for measuring volume and
surface resistivitirs of materials when used with the Model 6108 and the Keithley Node1
240A High Voltage Supply.
d. Models 2501 and 2503 Static Detector Probes are capacitive voltage dividers with a
10,OOO:l ratio, when used with the probe 3/B inch from the charged surface.
e. Model 6106 Electrometer Connection Kit contains a group of the mwt useful leads
and adapters for electrometer measurements.
f. Model 6107 pH Electrode Adapter has a 2-Eoot cable and coaxial caxxector and accepts
a Beckman and Coleman (B-C) or a Leeds and Northrup (L &N) connector. The Adapter allows
accurate and convenient pH potential measurements with the Model 6lOB.
g. Model 370 Recorder is uniquely compatible with the Model 610B es well es other
Keithley microvoltmeters, electrometers and picoarmneters. The recorder is a high quality
economical instrument that maximizes the performance of the Model 6108 and many other
Keithley instruments, even in the most critical applications.
l-7. EQUIPMENT SHIPPED. The Model 6108 Electrometer is factory-calibrated and is ship-
ped with all components in place. The shipping cartnn contains the Instruction Manual and
mating plugs for the input and output receptacles. The Model 610BR is shipped with the
rgles and screws for rack mounting packed separately within the shipping carton.
FIGURE 3. Model 610ER Front Panel Controls and Terminals. Circuit designations refer to
Replaceable Parts List and the schematic diagram.
I 0667R
MODELS 610B, 610BR ELECTROMETERS OPERATION
SECTION2. OPERATION
2-1. FRONT PANEL CONTROLS AND TERMINALS (See Figures 3 and 4)
a. Range Switch. The Range Switch selects the measuring mode and the
range. It is divided fnto a VOLTS position, 11 AMPERES ranges, eight OHMS
ranges and four COULOMBS ranges. The range used is indicated by an X above
the dial skirt.
b. Multiplier Switch. The Multiplier Switch determines the voltage sen-
sitivity of the dc amplifier and sets the full-scale voltage range when the
Range Switch is set to VOLTS. The Multiplier Switch may also be used to
multiply the AMPERES (3x maxinolm setting above LO-3), OHMS and COULOMBS
ranges on the Range Switch.
c. METER Switch. The Switch has five positions: POWER OFF shuts off
the instrument. OFF disconnects only the meter during recorder operation.
The + and - positions determine the polarity of the meter. CENTER ZERO
sets the instrument for center zero operation (lower meter scale).
d. ZERO Controls. Two ZERO Controls are on the front panel: a MEDIUM
Switch (outer knob) and a lo-turn FINE potentiometer (center knob). These
allow precise meter zeroing.
Circuit designations refer to Replaceable Parts List and the
schematic diagram.
0764R
OPERATION MODELS 6108, 610BR ELECTROMETERS
e. ZERO CHECK Button. Depressing the Button effectively removes all input
signal from the instrument by shunting the input and amplifier through 10
megohms. This allows meter zeroing on any range. The Button is locked in
the zero check position when the line is horizontal.
f. FEEDBACK Switch. The FAST and NORMAL positions of the Switch determine
the feedback connections within ehe instrument. Voltage measurements are
made only in NORMAL. With the Switch et FAST, current measurements are made
with lower input voltage drops and faster response speeds. The FAST position
is also used to make guarded resistance measurements, for couLomb measurements,
and to increase response speed.
!z. INPUT Receptacle. The INPUT Receptacle fs a Teflon-insulated uhf-type
connector. A dust cap is provided. The ground post is below the recep-
tacle.
2-2. RFAR PANEL CONTROLS AND TERMINALS (See Figure 5).
a. COARSE ZERO Switch (On front panel of Model 610BR). The COARSE ZERO
Stitch has 11 positions to extend the zeroing capability of the front panel
ZERC Controls.
b. Output Switch. The Switch fs a two-position slide switch for the output.
In the 1 MA position, the instrument will drive l-milliampere recorders. In
the 3 V position, the output is 3 voles for full-scale meter deflection.
Source resistance is 3 kllohms.
c. 1 MA CAL Control. The Control varies the output from 0.95 to 1.05 milli-
ampere for 14CO-ohm recorders , so the recorder scale will correspond with the
Electrometer panel meter.
d. OUTPUT Receptacle. A 2-terminal microphone-type receptacle provides
3 volts or 1 milliampere for full-scale meter deflection. Pin no. 2 is at
case ground potential if the FEEDBACK Switch is at NORMAL.
e. Xl OUTPUT and GUARD Terminals. The potential between the Xl OUTPUT
Terminal and the CUARD Terminal (case ground for the FEEDBACK Switch in NORMAL)
Fs eaual to the input voltage with 0.005% linearity or LOO microvolts. when
the FEEDBACK Switch is at FAST, the Xl OUTPUT Terminal is et case ground end
rhe,GUARD Terminal is floating.
f. FUSE. For 105-125 volt operation, use a l/4 ampere, 3 AG Slow Blow
fuse. For 210-250 volt operation, use a L/8 ampere, 3 AC Slow Blow fuse.
g. 117-234 Switch. The screwdriver-operated,slide switch sets the Model
610B for 117 or 234-volt ac power lines.
h. Power Cord. The 3-wire power cord with the NEMA approved 3-prong plug
provides a ground connection for the cabinet. An adapter for operation from
2- tenninal outlets is provided.
2-3. INPUT CONNECTIONS.
a. The accessories described in Section 5 are designed to increase the
6 1064R _
MODELS 610B, 6108R ELECTROMETERS OPERATION
PJ.wJtu 3. PlOceL OIVH liear Y*"eL m*troLs an* TerminaLs. CLl32U
designations refer to Replaceable Parts List and the schematic
diagram.
accuracy and convenience of input connections. Use them to gain the maximm
capability of the Model 6LOB.
NOTE
Using the accessories and coaxial cables is the best
way to make input connections.
b. Carefully shield the input connection and the source being measured,
since power Line Erequencies are well within the pass band of the Electrometer
Unless the shielding is thorough, any alteration in the electrostatic field
near the Input circuitry will cause definite meter disturbances.
c. Use high resistance, Low-Loss materials - such as Teflon (reconrmended),
polyethylene or polystryene - for insulation. The insulation leakage resis-
tance of test fixtures and Leads should be several orders magnitude higher
than the internal resistance of the source. If it is not, leakage Losses
will cause Lowered readings. Coaxial cables used should be a Low-noise type
which employ a graphite or other conductive coating between the dielectric
and the surrounding shield braid. Amphenol-Borg Electronics Corporation,
Hicrodot , Inc. , and Simplex Wire and Cable Company make satisfactory types.
1064R
OPERATION MODELS 6108, 610BR ELECTROMETERS
Using the Model 6LOLA Probe is a simple way to insure.good input connections.
NOTE
Clean and dry connections and cables are very important
to maintain the value of all insulation materials.
d. Any change in the capacitance of the measuring circuit to ground will
cause extraneous disturbances. Make the measuring setup as rigid as possible,
and tie down connecting cables to prevent their movement. If a continuous
vibration is present, it may appear at the output as a sinusoidal signal and
other precautions may be necessary t" isolate the instrument and the connecting
cable from the vibration.
e. For Low impedance measurements, unshielded Leads and a binding post
adapter may be used. However, keep the leads short.
f. When measuring currents LO-l4 ampere or less with the FEEDBACK switch
at FAST, some insulators - such as Teflon - may produce random signals which
show up as erratic meter deflections. Insulation used in the Model 6108 is
carefully selected to minimize these signals.
.s. Connect the M"deL 610B to the circuit only when a reading is being made.
I" some cases, the grid current can charge the external test circuitry when
it is connected to the Electrometer input. One example is measuring a
capacitor's Leakage resistance by observing the decay of its terminal voltage.
If the Leakage currant is less than the grid current, there is no decay of
the terminal voltage when the electrometer is Left connected across the
capacitor's terminals. Instead, there is a build-up which seems to indicate
that the capacitor dielectric has a negative resistance.
NOTE
Techniques and applications are thoroughly discussed
in thebrochure, Electrometer Measurements, by Joseph
F. Keithley. It is available by writing to Keithley
I"stnlae"ts, 1