Keithley 415 Service manual

Instruction Manual

Model 415

Micro-Microammeter

Keithley Instruments, Inc.

Instrument Division

Cleveland, Ohio, U.S.A.

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.

To exercise this warranty, contact your Keithley
field engineering representative. You will be

given assistance and shipping instructions.

REPAIRS AND RECALIBRATION

Keithley Instruments and its internat.ional dis-

tributors maintain complete repair facilities.
To insure prompt repair or recalibration service,

please contact your Keithley field representative

before returning the instrument.

Estimates for repairs, normal recalibrations, and
calibrations traceable to the National Bureau of
Standards are available upon request.

INSTRUCTION MANUAL

MODEL 415

MICRO-MICROAMMETER

CONTENTS

SECTION
INTRODUCTION
SPWZIFICATIONS

REXlgeS

Accuracy

Zero Drift
Grid Current

output

Rise

Time

Current Suppress~ion

Zero Check
Tube Complement
Power

Accessories Supplied

Accessories Available
Dimensions

OPERATION

Operating Controls

Inout and Outpyt Connections
PrelimJ.nary Set Up
Makinp Measurements

Speed o.f Response

I
II

CIRCUIT DESCRIPTION

Circuit Block Diagram
Speed of Response

Detailed Circuj.t Description

MAINTENANCE AND CALIBRATION

General

Calibration

Trouble Shooting Procedure

Voltare Resistance Diagram
Circuit Schematic
Replaceable Parts List

415

ICE= mm, nio.

IV

v

cLEvEm, OHIO

SkCTION I - INTRODUCTION

The Model h15 Micro-microammeter incorporates advanced
high-speed circuitry developed by Keithley Instruments for rocket
and satellite experimentation -- where measurements of Lyman­Alpha night slow, cosmic radiation, and upper air density re­quire fast response,

The I~15 also provides zero suppression up to 100 full scales,

permitting full scale display of one per rant variatiors of a

signal, or suppression of a steady background signal.

Excelling other Keithley LOO Series Micro-microammeters in

speed of response, the Model hl5 is ideal for current measure-

ments in ion chambers, ionization pages, and photo-multipliers.

Other applications include uses with flame and Beta-ray

ionization detectors and in gas ChromatoKranhy, mass spectrometry.

Speed of respp? se of less than 600 milliseconds to 90% of

final value at lo-

capacity is less than 50 picofarads (uuf). Critical damping of

the circuit, with any input capacity, is maintained on all ranges

through one infrequent adjustment. There is no possibili.ty of

oscillation or poor transient response on any ranpe.

ampere is possible where external circui~t

-8

Accuracy is 22% of full scale o 10m3

ranses; -+3$ of full scale on 3 x 10

ranples.

Other features i
approximately 1 x 10
2% per day and a one volt output at one milliampere; a 1%

mirror scale pane:1 meter.

lude capability of detecting current of

-YE

ampere; zero stability of better than

-9

throuph 10

througQ210

ampere

ampere

415

-1

I

SECTION II -

SPECIFICATIONS

RANGES: lo-=, 3 x 10-12, lo-, 3 x lo-=,

etc. to 10e3 ampere

full scale.

ACCURACY: Z 2% of full scale 10e3 ttiu lOWE ampere ranges;+ 3% of

full scale 3 x 10-9 thru lo-l2 ampere ranges.

Z!SO DRIFT: After 30-minute warmup, less than 2% of full scale per

2L hours on all ranges.

GRID CT:r'WNT: Less than 5 x 10-lL ampere.
~!ITPIIT:

One volt for ful! scalp

3~i.

up to 5 ma. Noise less than

20 m'llivolts.

RISE TIME: Typical value &ven in seconds to 90% of final value.

Range Gin-50 uuf

amps f.s.
10-12

3 x 10-12

10-11
3&o-ll

seconds

.600
.200 .300 1.0
,060
.020

Cin=150 uuf

seconds

.800 2.5
.080 .250

,030 .lOO

Cin=1500 uuf

seconds

.006 ,010 .030
3 x 10-10
10-9

3 x 10'9

,002

.OOl

.OOl

.003 .OlO
.OOl .003

.OOl .OOl

and above
CURRENT SUPPRFSSION:

Up to 100 full scales; maximum buckout 10-5
ampere.

One setting of bucking current serves
five adjacent ranges within above limits. FINE
adjustment allows precise control up to 100 times

suppression.

ZERO CHECK:
TUBE COMPLEMENT:
POAER:

Allows zeroing without disturbing the circuit.

2-5886, 2-6CB6, l-6Ch6, l-12BLA; 2-12AX7, l-OG3.

loo-130 v, 60 cps, 50 watts; 50 cps and 230 v units on

special order.

ACCESSORIES SUPPLIED1 Mating connectors for input, output; six

foot power cord.

ACCESSORIES AVAILABLE:

Mating 6032 End Frames, mounting hardware,

rubber feet. Model L102 Input Assembly,
2-5886 electrometer tubes in a plug-in
can (replacement spare).

CABINET:

19" x 59 high x 10" deep. Net wei&ht 21 lbs.

415

II - 1

SECTION III - OPERATION

A. OPERATING CONTROLS

-

The controls are discussed in order from left to right on the
front panel.

ZERO CHECK: Depressins this control effectively re-

(1)

moves all current from the amplifier input and allows
the meter to be set to zero with the ZERO ADJUST con-

trol. After the button is depressed it may be locked
in position by turning the button one quarter turn as
indicated by the panel marking.

AMPERES FULL SCALE:

(2)

The full scale meter sensitivity
is selected by this control. The use of zero suppres­sion does not change the sensitivity.

CURRENT SUPPRESSI

(3)

(a) MULTIPLIER and AMPEHES: The combination of these

two dials set the amount of zero suppression. On
the OFF position of the AMPERES dial, the suppres-

sion circuit is disconnected.

(b) FINE8 The FINE control extrapolates between posi-

tions of the MULTIPLIER switch. For example when
the MULTIPLIER control is on aero, the FINE con­trol has a ranpe of 0 to 1. If the control is on
1, the range of the FINE control is

from

so forth.

METER: The METER switch allows the choice of plus or

(Ii)

minus current polarity;

using the meter for indica­tion; or switching it off. In the METER OFF position,
the switch still permits choice of plus or minus cur­rent polarity.

ON: This switch turns on power. The instrument is

(5)

ready to operate in about 60 seconds.

1 to 2 and

B.

415

ZERO ADJlJSTz This control is used with the ZERO CHECK

(6)

button depressed to adjust the micro-microammeter zero.

INPUT AND OUTPUT CONNECTIONS

(1) Input Connections:

­The input connections and the

current generator being measured must be carefully

shielded since power line frequencies are well within
the pass band of the amplifier on most ranges. Also,

unless the electrostatic shielding is thorough, any

alteration in electrostatic field in the neighborhood

will cause marked output disturbances. The insulation

III - 1

used in brinping the signal into the amplifier must
be either polyethylene, polystryene, teflan or similar
hish resistance, low-loss material. Any Coaxial cables
used must be of the low-noise type.

This type of cable
employs a graphite coating between the dielectric and
the surrounding shield braid. Satisfactory types are

made

by Amphenol, Microdot and Simplex. The use of
low-noise cable is mandatory due to the wide frequen­cy response of the instrument.

The Model hl5 is,
therefore, markedly more sensitive to external dis­turbances than other Keithley Electrometers. Any

chance in the capacitance of the measuring circuit

to ground will, cause extraneous disturbances. It is,

therefore, recommended that the measuring set-up be
made as rigid as possible and any connecting cables
be tied down to prevent their movement. If continuous
vibration is present, itmay appear on the output as

a sinusoidal sJFna1 and some precautions may be nec-

essary to isolate the instrument and connectinS cable

from this vibration.

C.

(2) Output Connections:

The output of the instrument is

one volt for full scale meter deflection. up to 5 ma.

may be drawn from the output.

The output is intended
primarily for driving oscilloscopes and pen recorders.
It may be divided down to drive 10 and 50 millivolt
recorders by placing: a suitable network across the

output.

1 ma.

In general it will not satisfactorily drive

Ester-line-Angus and Texas Instruments recorders
directly since the output voltage is too low for full
scale deflection or for providing the proper coil
dampin!?.

PRELIMINARY SET-UP

(1) Connect current source to input terminals per directions

in paragraph Bl above.

(2) Depress and lock ZERO CHECK button.
(3) Set CURRENT SUPPRESS controls as follows:

(a) MULTIPLIER: Set to zero.
I”{ $W’BES: Set to OFF.

Turn to most counter-clockwise position.

(Z, METEA:

Turn to +position.

(b) Turn on power.

After about 30 seconds meter should

indicate on scale.

(5) Set meter to zero with ZERO ADJUST.

III - 2