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INSTRUCTION MANUAL
MODEL 427
CURRENT AMPLIFIER
0 1975, KEITHLEY INSTRUMENTS, INC.
CLEVELAND, OHIO, U.S.A.
DOCUMENTNUMBER29103
CONTENTS MODEL 427
CONTENTS
1. GF,Ng3,&.L DESCRIPT~ON-------------------------------.-------- 1
2. OPERATION-------------------------------------------------- 4
3. APPLICATIONS----------------------------------------------- 9
4. ACCESSORIES------------------------------------------------ 10
5. ClRC"IT DESCRIPTION---------------------------------------- 12
6. REp~Cp`&LE PARTS------------------------------------------ 17
7. CALIBRATION------------------------------------------------ 26
SCNEMATICS---------------------------------------------------- 33
1074
MODEL 427 ILLUSTRATIONS
ILLUSTRATIONS
Figure No. Title Page
1 Front panel. __-___---___-_____-___________________ 1
2 Front pane1 Controls. ________--______-____________ 3
3 Rear Panel Controls. - 3
4 shunt Method Measurement, -----------------__------ 4
5 Effect of Shunt capacitance. ---------------------- 4
6 Compensation for Shunt Capacitance. --------------- 5
6b Extended Frequency Response. ---------------------- 5
7 Fee&a& Method. _--__-_-__________-_______________ 6
8 Input Voltage N&se. -------------___-------------- 6
9 Bandwidrh of Feedback System. --------------------- 7
9b Effect of filter on Noise spectrum. -------------- 7
9, Effect of Input Capacitance on Noise. ------------- 7
10 Frequency Compensafian. ---------_____--_-__------- 7
11 Plot of Noise-Improvement Contours. __- _____ -__-__ 9
12 Block Diagram of a High-Speed Current Amplifier, -- 12
13 Filter circuit. ------_______--_-__-_______________ 13
14 power s"pp~y Regulator. --------------------------- 13
15 current suppression. ------------__---------------- 13
lb COmpOnent Layout - PC-291. ------------------------ 13
17 component Layout - pc-290, -----------------___---- 14
18 component Layout - pc-2?39. ---------_------___-____ 15
19 COmpOnenf Layout - P&292. ---------------__------ 15
20 chassis - Top vie". ------------___--------------- 16
21 Chassis Assembly - Exploded "few. ----------------- 19
22 Bottom CO"er Assembly. -------------------------- 19
23 Measurement of Input Voltage Drop. ---------------- 27
24 Measurement of Rise Time. -------_--_____-___-_____ 28
25 Measurement of Filter Rise Time. ------------------ 29
1074 iii
SPECIFICATIONS MODEL 427
SPECIFICATIONS
RANGE: 10' to 10" volts/ampere in eight decade ranges.
(10-13 ampere resolution to 10." ampere full output).
OUTPUT: *10 volts at up to 3 milliamperes.
OUTPUT RESISTANCE: Less than 10 ohms dc to 30 kHz.
OUTPUT ACCURACY: 12% of reading to the lo9 vattsl
ampere range, +4% of reading on the 1O'O and 10"
volts/ampere ranges exclusive of noise. drift and current
offset.
RISE TIME (10% to 90%): Adjustable in lx and 3.3x steps
from "Fast Rise Time" listed below to 330 rnsec.
NOISE VS. RISE TIME':
I FAST RISE TlML
STABILITY: Current offset doubles per 10