SRS Labs SR625 Manual de usuario

MODEL SR625

RUBIDIUM TIMEBASE

/PRESCALER

1290-D Reamwood Avenue

Sunnyvale, CA 94089 U.S.A.

Phone: (408) 744-9040, Fax: (408) 744-9049

email: infor@thinkSRS.com • www.thinkSRS.com

Revision 2.1 (07/2001)

Safety and Preparation for Use

This instrument may be damaged if

operated with the LINE VOLTAGE

SELECTOR set for the wrong ac line

voltage or if the wrong fuse is installed.

LINE VOLTAGE SELECTION

The SR625 operates from a 100V, 120V,

220V, or 240V nominal ac power source

having a line frequency of 50 or 60 Hz.

Before connecting the power cord to a power

source, verify that the LINE VOLTAGE

SELECTOR card, located in the rear panel

fuse holder, is set so that the correct ac input

voltage value is visible.

Conversion to other AC input voltages

requires a change in the fuse holder voltage

card position and fuse value. Disconnect the

power cord, open the fuse holder cover door

and rotate the fuse-pull lever to remove the

fuse. Remove the small printed circuit

board and select the operating voltage by

orienting the board so that the desired

voltage is visible when it is pushed firmly

back into its slot. Rotate the fuse-pull lever

back into its normal position and insert the

correct fuse into the fuse holder.

LINE FUSE

Verify that the correct line fuse is installed

before connecting the line cord. For

100V/120V, use a 1 Amp slow blow fuse

and for 220V/240V, use a 1/2 Amp slow

blow fuse.

LINE CORD

The SR625 has a detachable, three-wire

power cord for connection to the power

source and to a protective ground. The

exposed metal parts of the instrument are

connected to the outlet ground to protect

against electrical shock. Always use an

outlet which has a properly connected

protective ground.

WARNING: Dangerous voltages, capable of causing death, are present in this instrument.

Use extreme caution whenever the instrument covers are removed.

SPECIFICATIONS:

2.0 GHz Prescaler

Input

Impedance 50 Ω

Maximum Input level +23dBm

Frequency Range 50 MHz - 2.0 GHz

Sensitivity See Figure below

Output

Expected Load 50 Ω

Frequency 1/10 of the input frequency

Waveform square wave, 700 mV pk-pk, +500 mV DC

-40.00

-30.00

-20.00

-10.00

0.000

10.00

20.00

Input amplitude (dBm)

1000 1200 1400 1600 1800

Input frequency (MHz)

Prescaler Sensitivity (Typical)

Maximum amplitude

Minimum amplitude

2000

Rubidium Timebase (see Operation Manual of Rb Oscillator)

Frequency 10 MHz

Accuracy at Shipment ± 5 E-11

One Day Stability 4E -11/day

Long Term Drift ≤5E -11/month, ≤5E -10/yr

Short Term Stability 1 Second (Allan Variance): 1 E -10

10 Second (Allan Variance): 3.16 E -11

100 Second (Allan Variance): 1 E -11

Warm-up time 10 minutes to meet short term stability

INTRODUCTION

The SR625 Rubidium Timebase and

Prescaler is designed to extend the frequency

measurement range of the SR620 Time

Interval Counter to 2.0 GHz and to provide

an extremely stable timebase. The prescaler

is a divide by 10 circuit with variable

sensitivity adjustment for

measuring signals up to 2.0 GHz. The

timebase is an atomic-resonance (Rubidium)

standard that provides a stable 10 MHz

signal once locked. The 10 MHz output

from the Rb timebase can be used to

increase the resolution and accuracy of the

of the SR620 time interval counter.

Figure 1 – SR625 Front Panel

FRONT PANEL FEATURES

POWER indicator is lit when the SR625 is

powered from line voltage.

LOCK indicator is lit when the 10 MHz

oscillator is locked to the Rubidium atomic

resonance (Note: this light may turn on

momentarily after power is turned on.)

RF INPUT BNC accepts signals from

50 MHz to 2.0 GHz (see Figure 3 for

sensitivity curve.) The input impedance is

50 Ω. The maximum allowable input level is

+23dBm (3.15 Vrms into 50 Ω). The shield

of the prescaler input is connected to

earth ground.

PRESCALE OUTPUT BNC provides an

output signal that is one-tenth (÷10) the

frequency of the input signal. When

terminated into a 50 Ωload the output is a

700 mV pk-pk square wave with a 500 mV

DC offset. This output is connected to the

input of the SR620 to measure frequencies

from 50 MHz to 2.0 GHz. The SR620 input

(channel A or B) should be DC coupled, 50

Ωimpedance, and the trigger level set to

autolevel. The shield of this output is

connected to earth ground.

PRESCALE ADJUST knob adjusts the

amplitude necessary to trigger the prescaler.

The threshold is closest to the zero crossing

voltage (i.e. the prescaler is most sensitive)

when the knob is pointing straight up.

Turning the knob changes the threshold and

makes the prescaler less susceptible to false

triggers due to noise.

REAR PANEL FEATURES

Figure 2 – SR625 Rear Panel

POWER ENTRY MODULE contains the

fuse and line voltage selector of the

prescaler/timebase. Use a 1 amp slow blow

fuse for 100/120 volt operation, and a 1/2

amp fuse for 220/240 volt operation. To set

the line voltage selector for the correct line

voltage, first remove the fuse. Then, remove

the line voltage selector card and rotate the

card so that the correct line voltage is

displayed when the card is reinserted.

Replace the fuse.

10 MHz OUTPUT should be connected to

the 10 MHz timebase input on the back

panel of the SR620 with a standard BNC

cable. The Rb oscillator can be also be

independently used as a high stability source

through this output. The timebase will

operate independently of the SR620 as long

as power to the module is applied. The

output is a 1 V pk-pk 10 MHz sine wave (50

Ωimpedance). The shield of this output is

connected to earth ground.

CONFIGURING SR620

The SR620's default timebase is its own

internal source. To use the Rb timebase the

configuration of the SR620 must be changed.

To change the settings of the SR620 press

the SEL button in the CONFIG area of the

front panel (right hand side) until the "CAL"

menu flashes. Now press the SET button in

the CONFIG area until "CLOCK SOURCE"

is displayed. Press either the up or down

arrow key in the SCOPE and CHART area

to toggle the clock source from "INT"ernal

to "REAR" panel. The 10 MHz Rb output

from the prescaler/timebase must be

connected to the rear connector of the

SR620. Pressing the SET key again should

show that the clock frequency is 10 MHz. If

it is not use the arrow keys in the SCOPE

and CHART section to toggle the value to

10 MHz. To exit the configuration menus

press any other key outside the configuration

area of the keyboard. The unit is ready for

operation once the locked light on the front

of the SR625 module is lit.

CIRCUIT DESCRIPTION

Prescaler-

The combination of R18,R19 and R20 attenuate the input signal to provide input protection for

the circuit. U9 amplifies the input signal. U5 frequency divides the signal by two. P1 adjusts the

threshold at which the differential clock of U5 will trigger. Components U4, U7 and U8 are

configured to act as a synchronous divide by five counter. Transistor Q1 drives the output signal.

R10 provides reverse termination of 50Ω.

PARTS LIST

REF. SRS part# VALUE DESCRIPTION

C 1 5-00170-509 6800U Capacitor, Electrolytic, 50V, 20%, Rad

C 2 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad

C 3 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad

C 4 5-00100-517 2.2U Capacitor, Tantalum, 35V, 20%, Rad

C 5 5-00030-520 2200U Capacitor, Electrolytic, 16V, 20%, Rad

C 6 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 7 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 8 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 9 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 10 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 11 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 12 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 13 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 14 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 15 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 16 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 17 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 18 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 19 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 20 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 21 5-00298-568 .01U Cap, Ceramic 50V SMT (1206) +/-10% X7R

C 22 5-00219-529 .01U Cap, Monolythic Ceramic, 50V, 20%, Z5U

D 1 3-00001-301 1N4001 Diode

D 2 3-00001-301 1N4001 Diode

D 3 3-00001-301 1N4001 Diode

D 4 3-00001-301 1N4001 Diode

D 5 3-00001-301 1N4001 Diode

D 6 3-00001-301 1N4001 Diode

D 7 3-00001-301 1N4001 Diode

D 8 3-00001-301 1N4001 Diode

D 9 3-00424-307 GREEN LED, T-3/4

D 10 3-00424-307 GREEN LED, T-3/4

D 11 3-00203-301 1N5711 Diode

P 1 4-00445-447 SR620-48 Pot, Single Control

PC1 7-00577-701 SR625 SIDECAR Printed Circuit Board

REF. SRS part# VALUE DESCRIPTION

Q 1 3-00570-360 MMBR536L Integrated Circuit (Surface Mount Pkg)

R 1 4-01464-461 240 Thick Film, 5%, 200 ppm, Chip Resistor

R 2 4-01479-461 1.0K Thick Film, 5%, 200 ppm, Chip Resistor

R 3 4-01459-461 150 Thick Film, 5%, 200 ppm, Chip Resistor

R 4 4-01475-461 680 Thick Film, 5%, 200 ppm, Chip Resistor

R 5 4-01464-461 240 Thick Film, 5%, 200 ppm, Chip Resistor

R 6 4-01457-461 120 Thick Film, 5%, 200 ppm, Chip Resistor

R 7 4-01457-461 120 Thick Film, 5%, 200 ppm, Chip Resistor

R 8 4-01457-461 120 Thick Film, 5%, 200 ppm, Chip Resistor

R 9 4-00833-406 24 Resistor, Thick Film, (SMT1206) 5% 1/8W

R 10 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 11 4-00031-401 100 Resistor, Carbon Film, 1/4W, 5%

R 12 4-00169-407 249 Resistor, Metal Film, 1/8W, 1%, 50PPM

R 13 4-00169-407 249 Resistor, Metal Film, 1/8W, 1%, 50PPM

R 14 4-00169-407 249 Resistor, Metal Film, 1/8W, 1%, 50PPM

R 15 4-00187-407 4.53K Resistor, Metal Film, 1/8W, 1%, 50PPM

R 16 4-00241-407 787 Resistor, Metal Film, 1/8W, 1%, 50PPM

R 17 4-00187-407 4.53K Resistor, Metal Film, 1/8W, 1%, 50PPM

R 18 4-01459-461 150 Thick Film, 5%, 200 ppm, Chip Resistor

R 19 4-01459-461 150 Thick Film, 5%, 200 ppm, Chip Resistor

R 20 4-01444-461 36 Thick Film, 5%, 200 ppm, Chip Resistor

R 21 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 22 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 23 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 24 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 25 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 26 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 27 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 28 4-01448-461 51 Thick Film, 5%, 200 ppm, Chip Resistor

R 29 4-00021-401 1.0K Resistor, Carbon Film, 1/4W, 5%

R 30 4-00062-401 270 Resistor, Carbon Film, 1/4W, 5%

R 31 4-00062-401 270 Resistor, Carbon Film, 1/4W, 5%

R 32 4-00021-401 1.0K Resistor, Carbon Film, 1/4W, 5%

R 33 4-01464-461 240 Thick Film, 5%, 200 ppm, Chip Resistor

R 34 4-01455-461 100 Thick Film, 5%, 200 ppm, Chip Resistor

R 35 4-00851-407 340 Resistor, Metal Film, 1/8W, 1%, 50PPM

R 36 4-00021-401 1.0K Resistor, Carbon Film, 1/4W, 5%

RX0 4-00056-401 22 Resistor, Carbon Film, 1/4W, 5%

RX2 5-00313-552 1P Capacitor, Chip (SMT1206), 50V, 5%, NPO

U 2 3-00384-329 LM350T Voltage Reg., TO-220 (TAB) Package

U 3 3-00149-329 LM317T Voltage Reg., TO-220 (TAB) Package

U 4 3-00568-360 MC10EL35D Integrated Circuit (Surface Mount Pkg)

U 5 3-00573-360 MC10EL32D Integrated Circuit (Surface Mount Pkg)

U 6 3-00149-329 LM317T Voltage Reg., TO-220 (TAB) Package

U 7 3-00568-360 MC10EL35D Integrated Circuit (Surface Mount Pkg)

U 8 3-00568-360 MC10EL35D Integrated Circuit (Surface Mount Pkg)

U 9 3-00569-360 MAR6SM Integrated Circuit (Surface Mount Pkg)

X 0 1-00321-165 10 PIN SOLDER Connector, D-Sub, Female

REF. SRS part# VALUE DESCRIPTION

X 0 1-00322-100 COAX INSERT Connector, Misc.

Z 0 0-00000-000 UNDECIDED PART Hardware, Misc.

Z 0 0-00014-002 6J4 Power_Entry Hardware

Z 0 0-00025-005 3/8" Lugs

Z 0 0-00042-010 4-40 HEX Nut, Hex

Z 0 0-00089-033 4" Tie

Z 0 0-00100-040 1/4X1/16 Washer, Flat

Z 0 0-00109-050 1-1/2" #18 Wire #18 UL1007 Stripped 3/8x3/8 No Tin

Z 0 0-00128-053 4" #24 Wire #24 UL1007 Strip 1/4x1/4 Tin

Z 0 0-00129-053 5" #24 Wire #24 UL1007 Strip 1/4x1/4 Tin

Z 0 0-00150-026 4-40X1/4PF Screw, Black, All Types

Z 0 0-00153-057 GROMMET2 Grommet

Z 0 0-00208-020 4-40X3/8PF Screw, Flathead Phillips

Z 0 0-00209-021 4-40X3/8PP Screw, Panhead Phillips

Z 0 0-00211-020 4-40X5/8PF Screw, Flathead Phillips

Z 0 0-00212-021 6-32X2PP Screw, Panhead Phillips

Z 0 0-00228-052 17" #22 GREEN Wire #22 UL1007

Z 0 0-00231-043 #4 SHOULDER Washer, nylon

Z 0 0-00241-021 4-40X3/16PP Screw, Panhead Phillips

Z 0 0-00243-003 TO-220 Insulators

Z 0 0-00251-004 SR620-49 Knobs

Z 0 0-00256-043 #6 SHOULDER Washer, nylon

Z 0 0-00263-052 3" #22 Wire #22 UL1007

Z 0 0-00264-052 9-1/2" #22 RD Wire #22 UL1007

Z 0 0-00266-052 8-1/2" #22 BLK Wire #22 UL1007

Z 0 0-00306-026 4-40X3/16PP Screw, Black, All Types

Z 0 0-00317-000 40MM 24V Hardware, Misc.

Z 0 0-00418-000 CLIP, CABLE Hardware, Misc.

Z 0 0-00419-056 RG178B/U Cable, Coax & Misc.

Z 0 0-00421-032 SOLDR SLV RG178 Termination

Z 0 0-00440-052 2-1/2" #22 RED Wire #22 UL1007

Z 0 0-00493-021 10-32X1/2"PP Screw, Panhead Phillips

Z 0 0-00523-048 5-5/8" #18 Wire, #18 UL1015 Strip 3/8 x 3/8 No Tin

Z 0 0-00854-031 PEM 4-40 Standoff

Z 0 1-00003-120 BNC Connector, BNC

Z 0 1-00218-120 227699-2 Connector, BNC

Z 0 1-00220-170 3" BNC Cable Assembly, Multiconductor

Z 0 1-00227-172 Y JUNCTION Line Cord

Z 0 1-00228-172 USA 3' Line Cord

Z 0 4-00541-435 130V/1200A Varistor, Zinc Oxide Nonlinear Resistor

Z 0 6-00004-611 1A 3AG Fuse

Z 0 6-00167-610 SR625 Transformer

Z 0 7-00571-709 SR625 Lexan Overlay

Z 0 7-00572-720 SR625 Fabricated Part

Z 0 7-00573-720 SR625 Fabricated Part

Z 0 7-00574-720 SR625 Fabricated Part

Z 0 7-00576-720 SR625 Fabricated Part

Z 0 7-00581-721 SR625-6 Machined Part

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