SRS Labs SR625 Manual

SRS Labs SR625 is an advanced Rubidium Timebase and Prescaler designed to extend the frequency measurement range of compatible devices, like the SR620 Time Interval Counter, up to 2.0 GHz and provide an extremely stable timebase. With a 10 MHz output, the SR625 can enhance the resolution and accuracy of time interval measurements. Its prescaler features adjustable sensitivity, allowing accurate measurements of signals from 50 MHz to 2.0 GHz.

PDF

Dokument

Annons

MODEL SR625

RUBIDIUM TIMEBASE

PRESCALER

1290-D Reamwood Avenue

Sunnyvale, CA 94089 U.S.A.

Phone: (408) 744-9040, Fax: (408) 744-9049 email: [email protected] • www.thinkSRS.com

Revision 2.1 (07/2001)

Safety and Preparation for Use

WARNING

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

Use extreme caution whenever the instrument covers are removed.

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.

SPECIFICATIONS:

2.0 GHz Prescaler

Input

Impedance

Maximum Input level

Frequency Range

Sensitivity

Output

Expected Load

Frequency

Waveform

50 Ω

+23dBm

50 MHz - 2.0 GHz

See Figure below

50 Ω

1/10 of the input frequency square wave, 700 mV pk-pk, +500 mV DC

20.00

Prescaler Sensitivity (Typical)

10.00

0.000

-10.00

-20.00

Maximum amplitude

-30.00

-40.00

1000

Minimum amplitude

1200 1400 1600

Input frequency (MHz)

1800 2000

Rubidium Timebase

Frequency

Accuracy at Shipment

One Day Stability

Long Term Drift

Short Term Stability

Warm-up time

(see Operation Manual of Rb Oscillator)

10 MHz

± 5 E-11

4E -11/day

≤ 5E -11/month, ≤ 5E -10/yr

1 Second (Allan Variance): 1 E -10

10 Second (Allan Variance): 3.16 E -11

100 Second (Allan Variance): 1 E -11

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.

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

Figure 1 – SR625 Front Panel frequency of the input signal. When terminated into a 50 Ω load 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

Ω impedance, 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

Ω impedance). 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 50 Ω .

PARTS LIST

C 4

C 5

C 6

C 7

REF.

C 1

SRS part# VALUE

5-00170-509 6800U

C 2

C 3

5-00100-517

2.2U

5-00100-517

5-00030-520

5-00298-568

2.2U

2200U

.01U

C 8

C 9

5-00298-568 .01U

C 10 5-00298-568 .01U

C 11 5-00298-568 .01U

C 12 5-00298-568 .01U

C 13 5-00298-568 .01U

C 14 5-00298-568 .01U

C 15 5-00298-568 .01U

D 6

D 7

D 8

D 9

D 2

D 3

D 4

D 5

C 16 5-00298-568 .01U

C 17 5-00298-568 .01U

C 18 5-00298-568 .01U

C 19 5-00298-568 .01U

C 20 5-00298-568 .01U

C 21 5-00298-568 .01U

C 22 5-00219-529 .01U

D 1 3-00001-301 1N4001

3-00001-301

3-00424-307

1N4001

GREEN

D 10 3-00424-307 GREEN

D 11 3-00203-301 1N5711

P 1 4-00445-447 SR620-48

PC1 7-00577-701 SR625 SIDECAR

DESCRIPTION

Capacitor, Electrolytic, 50V, 20%, Rad

Capacitor, Tantalum, 35V, 20%, Rad

Capacitor, Electrolytic, 16V, 20%, Rad

Cap, Ceramic 50V SMT (1206) +/-10% X7R

Cap, Monolythic Ceramic, 50V, 20%, Z5U

Diode

LED, T-3/4

Diode

Pot, Single Control

Printed Circuit Board

REF.

SRS part#

Q 1 3-00570-360

VALUE

MMBR536L

R 1 4-01464-461 240

R 2

R 3

R 4

R 5

4-01479-461

4-01459-461

4-01475-461

4-01464-461

1.0K

150

680

240

R 6

R 7

R 8

R 9

4-01457-461 120

4-00833-406 24

R 10 4-01448-461 51

R 11 4-00031-401 100

R 12 4-00169-407 249

R 13 4-00169-407 249

R 14 4-00169-407 249

R 15 4-00187-407 4.53K

R 16 4-00241-407 787

R 17 4-00187-407 4.53K

R 18 4-01459-461 150

R 19 4-01459-461 150

R 20 4-01444-461 36

R 21 4-01448-461 51

R 22 4-01448-461 51

R 23 4-01448-461 51

R 24 4-01448-461 51

R 25 4-01448-461 51

R 26 4-01448-461 51

R 27 4-01448-461 51

R 28 4-01448-461 51

R 29 4-00021-401 1.0K

R 30 4-00062-401 270

R 31 4-00062-401 270

R 32 4-00021-401 1.0K

R 33 4-01464-461 240

R 34 4-01455-461 100

R 35 4-00851-407 340

R 36 4-00021-401 1.0K

RX0 4-00056-401 22

U 5

U 6

U 7

U 8

RX2 5-00313-552 1P

U 2 3-00384-329 LM350T

U 3

U 4

3-00149-329

3-00568-360

LM317T

MC10EL35D

U 9

X 0

3-00573-360

3-00149-329

3-00568-360

3-00569-360

1-00321-165

MC10EL32D

LM317T

MC10EL35D

MAR6SM

10 PIN SOLDER

DESCRIPTION

Integrated Circuit (Surface Mount Pkg)

Thick Film, 5%, 200 ppm, Chip Resistor

Resistor, Thick Film, (SMT1206) 5% 1/8W

Thick Film, 5%, 200 ppm, Chip Resistor

Resistor, Carbon Film, 1/4W, 5%

Resistor, Metal Film, 1/8W, 1%, 50PPM

Thick Film, 5%, 200 ppm, Chip Resistor

Resistor, Carbon Film, 1/4W, 5%

Thick Film, 5%, 200 ppm, Chip Resistor

Resistor, Metal Film, 1/8W, 1%, 50PPM

Resistor, Carbon Film, 1/4W, 5%

Capacitor, Chip (SMT1206), 50V, 5%, NPO

Voltage Reg., TO-220 (TAB) Package

Integrated Circuit (Surface Mount Pkg)

Voltage Reg., TO-220 (TAB) Package

Integrated Circuit (Surface Mount Pkg)

Connector, D-Sub, Female

Z 0

REF.

SRS part#

X 0 1-00322-100

VALUE

COAX INSERT

Z 0

DESCRIPTION

Connector, Misc.

0-00000-000 UNDECIDED PART Hardware, Misc.

Z 0

0-00014-002

0-00025-005

0-00042-010

0-00089-033

6J4

3/8"

4-40 HEX

Power_Entry Hardware

Lugs

Nut, Hex

Tie

0-00100-040

0-00109-050

0-00128-053

0-00129-053

0-00150-026

0-00153-057

0-00208-020

0-00209-021

1/4X1/16

1-1/2" #18

4" #24

5" #24

4-40X1/4PF

GROMMET2

4-40X3/8PF

4-40X3/8PP

Washer, Flat

Wire #18 UL1007 Stripped 3/8x3/8 No Tin

Wire #24 UL1007 Strip 1/4x1/4 Tin

Screw, Black, All Types

Grommet

Screw, Flathead Phillips

Screw, Panhead Phillips

0-00211-020

0-00212-021

0-00228-052

0-00231-043

0-00241-021

0-00243-003

0-00251-004

0-00256-043

0-00263-052

0-00264-052

0-00266-052

0-00306-026

0-00317-000

0-00418-000

0-00419-056

0-00421-032

4-40X5/8PF

6-32X2PP

17" #22 GREEN

#4 SHOULDER

4-40X3/16PP

TO-220

SR620-49

#6 SHOULDER

3" #22

9-1/2" #22 RD

8-1/2" #22 BLK

4-40X3/16PP

40MM 24V

CLIP, CABLE

RG178B/U

SOLDR SLV RG178

Screw, Flathead Phillips

Screw, Panhead Phillips

Wire #22 UL1007

Washer, nylon

Screw, Panhead Phillips

Insulators

Knobs

Washer, nylon

Wire #22 UL1007

Screw, Black, All Types

Hardware, Misc.

Cable, Coax & Misc.

Termination

0-00440-052 2-1/2" #22 RED

0-00493-021 10-32X1/2"PP

0-00523-048 5-5/8" #18

0-00854-031 PEM 4-40

1-00003-120 BNC

1-00218-120 227699-2

1-00220-170 3" BNC

1-00227-172 Y JUNCTION

1-00228-172 USA 3'

4-00541-435 130V/1200A

6-00004-611 1A 3AG

6-00167-610 SR625

7-00571-709 SR625

7-00572-720 SR625

7-00573-720 SR625

7-00574-720 SR625

7-00576-720 SR625

7-00581-721 SR625-6

Wire #22 UL1007

Screw, Panhead Phillips

Wire, #18 UL1015 Strip 3/8 x 3/8 No Tin

Standoff

Connector, BNC

Cable Assembly, Multiconductor

Line Cord

Varistor, Zinc Oxide Nonlinear Resistor

Fuse

Transformer

Lexan Overlay

Fabricated Part

Machined Part

Hej! Jag är en AI-chattbot som är särskilt tränad för att hjälpa dig med SRS Labs SR625 Manual. Jag har noggrant granskat dokumentet och kan hjälpa dig att hitta den exakta information du behöver eller förklara innehållet på ett tydligt och enkelt sätt. Oavsett om du letar efter vägledning om specifika funktioner, felsökningssteg eller allmän användning, tveka inte att ställa dina frågor. Ju mer detaljer du ger om dina bekymmer eller behov, desto mer exakt och effektivt kan jag hjälpa dig!