Tektronix 605 Instruction Manual
INSTRUCTION MANUAL
MODEL 605
NEGATIVE CAPACITANCE
ELECTROMETER
WARRANTY
We warrant each of our products to be free
from defects in material and workmanship. Our
obligation under this warranty is to repair or
replace any instrument or part thereof (except
tubes and batteries) which, within a year after
shipment, proves defective upon examination.
We will pay domestic surface freight costs.
To exercise this warranty, call your local
field representative or the Cleveland factory,
DDD 216-248-0400. You will be given assist-
ance and shipping instructions.
REPAIRS AND RECALIBRATION
Keithley Instruments maintains a complete repair service and standards laboratory in Cleveland, and has an authorized field repair facility
in Los Angeles.
0 1967
To insure prompt repair or recalibration serv-
ice, please contact your local field representa-
tive or the plant directly before returning the
instrument.
Estimates for repairs, normal recalibrations,
and calibrations traceable to the National Bureau of Standards are available upon request.
KEITHLEY INSTRUMENTS. INC.
MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER
TABLE OF CONTENTS
TABLE OF CONTENTS
Section
MODEL 605 SPECIFICATIONS . . . . . .
1. GENERAL DESCRIPTION. . . . . . .
l-l. General. . . , . . . .
l-2. Features . . . . . . . .
2.
OPERATION. . . . . . . . . . .
2-l. Input Head . . . . . . ,
2-2. Power Module . . . . . .
2-3. Operating Procedure. . .
2-4~. Line Frequency Noise and
Minimum Response Speed .
2-5. Capacitance Tuning . .
2-6. Microelectrode Resistance
Measurement. . . . . . .
2-7.
3. CTRCUIT DESCKIPTION. . . . . . . . 9
3-l. General. . . . . . . . . . 9
3-2. Input Head , . . . . . 9
3-3. Power Module . . . . . .lO
Drift, Grid Current and
Ringing. . . . . . . . .
Page
.ii
.l
.l
.l
.3
.3
.3
.3
.5
. 6
.7
. 7
Section
4. MAINTENANCE. . . . . . . . . . . . 11
4.-l.
4,-2. Parts Replacement. , . . . . 11
4,-3.
4,-4.. Troubleshooting. . . , . . . 13
4.-s.
4,-b.
5. ACCESSORIES. . . . . . . . , . . . 19
5-l. Model 6051 Mounting
5-2. Model 6052 Integrator. . . . 19
5-3. Model 6053 Cable . . . . . . 19
6. REPLACEABLE PARTS. . . . . . . . . 21
6-1.
6-2.
General. . . . . . . . . , . 11
Spec'ial Maintenance
Precautions. . . . . . . . . 11
Procedures to Guide
Troubleshooting. . . . . . . 14,
Calibration. . . . . . . . . 14,
Bracket. . . . . . . . . . . 19
Replaceable Parts List . . . 21
How to Order Parts . . . . . 21
Model 605 Replaceable
Parts List . . . . . . . . . 22
Schematic Diagram
20387~ . . . . . . . . . . . 27
Green Repair and
Calibration Forms . . . . . . 29
Page
0168~
gr Change Notice
9~ Yellow Change Notice sheet is included
only for instrument modifications
affecting the Instruction Manual.
Last Page
GENERAL DESCRIPTION
MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER
TABLE 1. Model 605
INPUT RESISTANCE: Greater than
INPUT CAPACITANCE NEUTRALIZATION: Up to 100 picofarads.
GRID CURRENT: Less than 10-L3 ampere without compensation.
RESPONSE AND NOlSE CHARACTERISTICS:
source Max. Rise Time,
Resistor, Min. f.ldb
megohms kilocycles
”
li
22 15 20
GAIN: 2 +5%.
VOLTAGE SUPPRESSION: Zero may be offset with IO-turn zero
control approximately flOO millivolts with respect to the input.
DRIFT: Less than 1 millivolt per hour after l-hour warmup;
DYNAMIC RANGE: iI volt at input.
MAXIMUM INPUT OVERLOAD: 3~100 volts.*’
OUTPUT RESISTANCE: Less than 1000 ohms.
CALIBRATION: Ramp required, may be Senerated by a triangle
CONNECTORS: Input, Output and Calibrate: BNC. Indifferent
BATTERIES: Five TR286, one E12. 200 hours battery life.
DIMENSIONS, WEIGHT:
ACCESSORIES SUPPLIED:
~.~,__
-*Ma” reclwre *eVeral minutes to recover 10 soecified drift.
less than 1 millivolt per “C;
less than lo-l4 ampere per day;
18s.~ than 10.” ampere per “C.
wave (ramp) generator. An oscilloscope square wave calibrator
output may be used when integrated by Keithley Model 6052.
Electrode: Spring-loaded clip.
Input Head: 1%” high x 3%” wide x 2%” deep;
net weiSht. 9 ounces (3.foot power cable attached).
Power Module: 2” high x IO” wide x 5%” deep;
“et weight. 3 pounds.
Model 6051 Mounting Bracket: Permits head to be supported by
ring stand and rod clamp.
BNC to Binding Post adapter, mating input co”“ector.
*Noise measured between 10 cp* and ml KC with Amplifier tuned for
rated rise t,me.
nnn
,~”
20
(63%) (lo-90%)
Specifications.
W
ohms.
microseconds Max. Input Noise,”
1 26
15
26 3;;
27 450
microvolts rms
FIGUW 1.
ii
Kci~thley Model 605 Negative Capacitance Elect:rometer.
0267
MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER
GENERAL DESCRIP'TION
SECTION 1.
l-l.
1-2.
introducing extraneous power line noise.
meter which compensates for resting potentials and other dc offsets up to 100 millivolts;
a control on the input head for preliminary capacitance adjustment; and a fine capacitance
adjustment on the power module.
zero potentiometer allows adjustment without disturbing the experiment.
GENERAL.
a. What is a negative capacitance electrometer?
When a signal from a high impedance source is amplified, the capacitance of the
1.
amplifier input and the connecting cable greatly degrades the signal rise time.
example,
a 4,00-microsecond rise time.
A negative capacitance electrometer is useful for improving the rise time of signals
2.
from high impedance sources. This is accomplished by applying in-phase feedback from
the output of a fixed gain amplifier to the input through a properly chosen capacitor.
Reducing the effective capacitance in the example to 1 picofarad, possible with the
Model 605, improves rise time to 20 microseconds.
FEATURES.
Battery operation allows the Model 605 to operate inside shielded areas without
a.
"Only three operating controls and a power switch are used:
b.
The Keithley Model 605 is a negative capacitance electrometer
with only ZO-picofarad shunt capacitance, a signal from a ZO-megohm source has
The remote location of the fine capacitance control and
GENERAL DESCRIPTION
For
a lo-turn zero potentio-
10!i4
current minimizes the possibility of polarizing the cell under study.
lof5
and short circuit noise less than 35 microvolts rms. The rise time of less than 20 micro-
seconds with a 22-megohm source permits faithful reproduction of pulse.
testing and optimum neutralization adjustment without disturbing the test preparation.
The Model 605 has grid current less than lo-l3 ampere and current drift less than
ampere per day or per % without requiring a compensating adjustment. The low grid
1n addition to low grid current,
ohms,
e. The power module has an input for a ramp calibrating s~ignal, allowing microelectrode
shunt capacitance adjustable to less than 1 picofarad with a 22 megohm source,
the Model 605 offers input resistance greater than
04,67R
OPERATION
MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER
TABLE 2.
The table briefly describes each control and terminal,
Input Head Controls and Terminals.
and indicates the paragraph which
contains instructions on the use of the control or terminal.
:ontrol or Terminal
:ord
Input Receptacle
Connects the Input Head to the Power Module
Bnc connector for signal input from microelectrode
Functional Description Par.
2-3
2-3, 2
and indifferent electrode
Spring Lock Terminal
Ground post for easy connection of indifferent
2-3
electrode
:apacitance Adjust
:ontro1
For preliminary adjustments for neutralizing
strav caDacitances on the inout circuitrv
TABLE 3.
Power Module Controls and Connectors.
2-3, 2
The table briefly describes each control and connector, and indicates the paragraph which
contains instructions on the use of the control or connector.
3ntrol or connector Functional Description
3WER Switch
ERO Control
Turns the power supply on and off 2-3
Zeroes the output voltage.
Also compensates for
resting potentials and other dc offsets.
INE CAP ADJ Control
Used for neutralizing small changes of input capa-
citance
ROBE Receptacle
Nine terminal mating connector for the Cord from
the Input Head
UTPUT Receptacle
AL Receptacle
Bnc connector for output signal
Bnc connector to receive ramp calibration signal,
allowing microelectrode testing and optimum capacitance neutralization adjustment
Par.
2-3
2-3 2-t
2-3
2-3
2-3
0767R
MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER
OPERATION
SECTION 2.
2-l.
amplifier,
mental system.
the supplied mounting bracket.
caused by salt solutions,
solutions.
2-2. POWER MODULE.
teries to operate the amplifier. Battery power allows the Model 605 to operate inside
shielded areas without introducing extraneous power line noise.
2-3. OPERATING PROCEDURE.
from the Input Head to the PROBE Receptacle on the Power Module.
Cord in place by rotating the outer jacket clockwise.
amplifier, potentiometric recorder, or some other suitable monitoring device. The OUTPUT
Receptacle is a bnc connector.
INPUT HEAD.
enabling the Model 605 to be placed conveniently anywhere in a crowded experi-
Connect the Input Head to the Power Module by connecting the nine-lead,shielded Cord
a.
Connect the OUTPUT Receptacle on the Power Module to the input of an oscilloscope,
b.
The Input Head is a small nine-ounce remote head that contains the
The Head may be easily mounted in a standard rod and clamp system, using
The Input Head is chrome plated to minimize corrosion
and its tight fitting cover protects the amplifier from spilled
The Power Module contains the operating controls and six mercury bat-
OPERATION
Lock the plug on the
c. Apply a triangular wave to the CAL Receptacle on the Power Module.
Apply this signal with either a triangular wave generator, or, as shown in Figure 3,
1.
with an oscilloscope square-wave calibrator output integrated by the Keithley Model 6052
Integrator. Turn the generator signal to off.
The CAL Receptacle is an input for a ramp calibrating signal, allowing microelectrode
2.
testing and optimum neutralization adjustment without disturbing the test preparation.
(See paragraphs 2-5 and Z-6).
Spring Lock
Terminal (5102)
Receptacle
(X01)
Control (C101)
The triangular signal is applied at the CAL Receptacle.
OUTPUT
Receptacle
(5106)
CAL
Receptacle
PROBE
Receptacle
(5103)
FINE CAP ADJ
Control (R131)
POWER Switch
(5101)
FIGURE 2.
Parts List and schematic diagram.
0367R
Model 605 Controls and Terminals. Circuit designations refer to Replaceable
3
OPERATION MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER
This signal is differentiated by the RC combination of a 5 picofarad capacitor in the
Input Head, C103,
the indifferent electrode through the bath.
the input of the amplifier.
and the resistance of the microelectrode connected from the Input to
Thus, a current square wave is applied to
Since, however,
neither electrode has yet been connected,
an appropriate resistor, approximately 22 megohms, can be connected across the Input
to simulate the source resistance of a microelectrode.
Mount the Input Head with a standard rod and clamp system using the supplied mount-
d.
ing bracket or just place the Head on the bench top.
Connect the Input Receptacle on the Input Head to the microelectrode or the calomel
e.
cell.
mating bnc connector.
Shielded or unshielded cable may be used. For shielded connections, use the
For unshielded connections, insert a bare wire into the center ter-
minal of the Input Receptacle or use the banana jack adapter.
Connect the indifferent electrode to the bath or dish. The indifferent electrode
f.
may be connected either to the shield of the mating bnc connector or to the Auxiliary
Spring Lock Terminal.
Short the tip of the microelectrode to the indifferent electrode by dipping the end
g.
of the microelectrode into the salt bath.
FIGURE 3.
The Power Module on the Model 605 has an Input for a Ramp Calibrating Signal,
Allowing Microelectrode Testing and Optimum Neutralization Adjustment Without Disturbing
any Test Preparation. The ramp signal may be obtained from a ramp generator, or, as
shown above, from an oscilloscope square-wave calibrator output integrated by the accessory Keithley Model 6052 Integrator.
4,
0767R
m
MODEL 605 NEGATIVE CAPACITANCE ELECTROMETER OPERATION
h. Turn POWER Switch on the Power Module to "on".
supply on and off.
Zero the oscilloscope and observe the output of the Model 605 on the oscilloscope.
1.
Zero the output 01 the Model 605 with the ZERO Control on the Power Module. Besides
i.
zeroing the output,
The Supply is on when the red dot is visible through the switch knob.
the ZERO Control also compensates for resting potentials and other dc
The POWEK Switch turns the power
offsets within a span of approximately 100 millivolts.
NOTE
There is no output overload protection on the Model 605.‘ A brief output short
circuit will not damage the Model 605,
but will cause excessive drain on the
batteries.
k. Apply a triangular signal with the signal generator to the CAL Receptacle on the
Power Module and note the output on the oscilloscope.
Compensate for stray capacitance
on the input by adjusting the Capacitance Adjust Control on the Input Head and the FINE
CAP ADJ Control on the Power Module.
The Capacitance Adjust Control on the Input Head,
which is a 55-turn stable glass piston trinnner, because of its fine resolution and wide
range,
is for preliminary adjustments. The FINE CAP ADJ Control is used for neutralizing
small changes of input capacitance, and, since it is on the Power Module, can be used
without disturbing the Input Head or the microelectrode.
Start with the FINE CAP ADJ Control at MAX (completely clockwise) and the
1.
CapBcitance Adjust Control on the Input Head in the completely counter-clockwise
position.
Turn the Capacitance Adjust Control on the Input Head until the square wave rise
2.
time on the oscilloscope decreases. When maximum tolerable overshoot is reached, the
input capacitance is nulled.
If fine
3.
Turn off the triangular signal to the CAL Receptacle. Do not disconnect the cable
1.
between the signal generator and the CAL Receptacle.
capacitance
adjustment is also necessary, use the FINE CAP ADJ Control.
If the cable is disconnected, the
input capacitances will change and the Model 605 will no longer be tuned.
m. Insert the microelectrode into the cell and observe the resting potential, pulses
and the response to external stimulae.
The microelectrode resistance can be checked
periodically by applying a triangular signal with the signal generator and observing the
magnitude of the output square wave (see paragraph 2-6).
NOTE
The Model 605 has a voltage gain of 2.
Therefore, be sure to divide the output
signal by a factor of 2 when using an oscilloscope, recorder, etc.
Z-4,. LINE FREQUENCY NOISE AND MINIMUM RESPONSE SPEED.
problem in many measurement setups.
There are several ways in which this noise can be
Line frequency noise may be a
eliminated or minimized.
a. Using shielded cable at the Input Receptacle on the Input Head of the Model 605 re-
duces the noise pickup. However,
mum obtainable rise time because of the distributed
use of a shielded cable at the input increases the mini-
capacitance
of the cable.
0767~
5
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