Racal Instruments 9915 User manual

9915
UHF Frequency Meter
Service Manual
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G0RSQ
29th June 2015
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U.H.f
Frequency Meter 9915
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CONTENTS
Page
SECTION 1TECHNICAL SPECiFiCATION
AND
SUPPLEMENTARY DATA
SECTION 2DESCRIPTION OPERATION
AND MAINTENANCE
CHAPTER 1GENERAL DESCRIPTION 1-1
CHAPTER 2 OPERA TING INSTRUCTIONS
OperaH
ng Instructions
2-1
Carrying Handle
2-3
Description of Controls 2-4
Indicators 2-5
Rear Panel Items 2-6
CHAPTER 3PRINCIPLES OF OPERATION
The CDI Chip
3-1
Basi cCounter Diagram
3-1
General Circuit Functions 3-2
Dynamic Display System
3-2
Mul tiplex Readout 3-3
Decimal Point 3-4
Control Codes 3-4
Resistor Arrays 3-4
CHAPTER 4TECHN ICAL DESCRIPTION
Introducti on
4-1
'A' Channel Input
4-1
Signal Path
4-1
'A IChannel Overload Protection 4-2
P. I. N. Diode Attenuator
4-2
Counter Enable Circuit
4-3
Automatic Gain Control 4-3
'B' Channel Input 4-3
Signal Input 4-3
'B 'Channel Amplifier
4-4
Input Selection 4-4
Channel Switching 4-4
24V Generator
4...:4
Input Signal Steering 4-4
Ancillary Steering Functions 4-6
One-Second Gate
4-6
Segment Check 4-6
9915 Vol. 2Contents (1)
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CHAPTER 5
9915 Vol. 2
Hold/Reset
Burst Mode
Summary
Burst Circuit
Function of Q21 and Q22
Data Output and Display System
Data Output Format
Multiplex Readout and Display
Decimal Point Selection
Overflow Indi cator LP1
Gate/Charging Indicator LP3
Power Supply
AC Supply
+5V Switching
Standby Indi cator
+5 and -5V Stabilization
Battery Economy Operation
Battery Charging
Charge Indicator
Battery Powered Operation
Battery Low Indi cator
Over-Discharge Protection
Frequency Standard
Standard
Osci "ator 19-0834
Frequency Doubler
1 MHz Reference Output
External Standard Input
LF Multiplier Assembly (Option)
MAINTENANCE
List of Test Equipment
Removal of Covers
Transformer Voltage Selection
Fuses
Power Lead
Power Supply Check
Performance Tests and Cal ibration
Segment, Decimal Point and Self Check
Sensitivity Check: Input 'B
I
Sensitivity Check: Input 'A'
AGC Output Check
Overload Indicator Check
Standby (Battery Economy) Check
Battery Charging Checks
Frequency Standard Ca I ibrati on
Dismantling
Removal
of Display PCB
Removal of Main PCB
4-6
4-6
4-6
4-7
4-8
4-8
4-8
4-8
4-8
4-9
4-9
4-10
4-10
4-10
4-10
4-11
4-11
4-12
4-13
4-13
4-14
4-14
4-14
4-14
4-15
4-15
4-15
4-15
5-1
5-2
5-2
5-4
5-4
5-4
5-5
5-5
5-6
5-8
5-9
5-9
5-10
5-10
5-12
5-13
5-13
5-13
Contents (2)
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Fig. No.
Page
Replacement of Main PCB 5-14
Fitting Optional Frequency Standard Unit 5-15
Fi tti ng Battery Pock (Opti on) 5-16
Fitting LF Frequency Multiplier
Assembly (Option) 5-17
IN TEXT ILLUSTRATIONS
Page
Al
3.1
3.2
3.3
3.4
4.1
4.2
4.3
4.4
5. 1
Table No.
1
2
3
4
5
6
7
8
9915
Vol. 2
Data Sequence Diagram
Basic Frequency Meter
Mul tiplex Display System
D.
1. L. Resi stor Array
Control Sequence Diagram
Theoretical P. I. N. Diode Attenuator
-5V Stabilizer
Battery Charging Circuit
Battery Power System
Mains Voltage Selection
LIST OF TABLES
Title
Data Output Connector
Time Base Selection Code
Signal Gating Paths
Test Equipment Required
Segment Check
Self Check Readout
'B' Input
Sensitivity Check
'A' Input Sensitivity Check
Tech. Spec. (8)
3-1
3-3
3-4
3-5
4-3
4-11
4-12
4-13
5-3
Page
Tech. Spec. (6)
T ech. Spec. (7)
4-5
5-1
5-5
5-6
5-7
5-8
Contents (3)
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SECTION 3
PARTS LISTS, COMPONENT LAYOUTS AN D CIRCUIT DIAGRAMS
Component Layout: Display Assembly
Parts List 1: Display Assembly'
Circuit and Layout: Oscillator PCB Assembly
Parts List 2: Oscillator PCB Assembly
Parts List 3: Chassis, Front and Rear
Panel Assemblies
Fig. 1
Fig. 2
SECTION 4
9915 Vol. 2
Parts List 40 and 4b: Main PCB Assembly
Component Layout: Main PCB Assembly Fig. 3
Circuit: 'A' Input Amplifier Fig. 4
Circuit: Main PCB and Display Assemblies Fig. 5
Parts List 5: LF Multiplier Assembly
Circuit and Layout: LF Multiplier Assembly (Option) Fig. 6
APPEND'CES AND CHANGE INFORMATION
APPENDIX 1: 0 PTION 01
SERIAL- TO- PARALLEL IN TERFACE UN IT
Contents (4)
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DISPlA Y
Format:
Latch:
Display Time:
Reset:
Check
Gate/Charging
Indi eator:
Overflow /Standby
Indicator:
Eight digit in-line LED 7 segment numerical display
pI
us overflow i nd: cator. Deci ma I pei nt posi ti oned
automati eally.
Previous measurement is displayed during period
required
to complete new measurement. Display is
updated automati col Iy at end of each measurement.
Approximately equal
to gate time plus 1 ms.
A biased Check/Operate/Reset Swi tch resets the
reodi ng to zero when pressed to Reset cnd re leased.
With Check/Operate/Reset Switch in Check position
display reads:-
Channel A - Al Idigi ts set to 8 to check all segments.
Channel B - Counter reads 1 MHz to check operation.
LE Dill um i noted when gate is open or batteri es are
being charged.
LED ill umi nates on overflow or when standby is
selected,
Battery Low Indi cator:
Overload Indi cator:
INPUT 'A'
Frequency Range:
Sensitivity:
Signal Range:
Input Impedance:
9915Vol. 2
LED indicates when botteries require recharging.
LED indicates when 'A' channel input exceeds about
5V r.m,s.
40 MHz to 520 MHz.
Better than 10 mV.
10 mV to
5V r.m.s. with automatic gain control.
500 nominal.
Tech. Spec. (1)
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IN PUT 'A' (Cont'd.)
Overload Protection:
P re$ca ling:
AGe:
Frequency Range:
Sens iti vi ty:
Input Impedance:
Maximum Input Levels:
(Damage Overload
Levels)
FREQUi:NCY MEASUREMENT
Range:
Accuracy:
Gate Times:
Resolution:
Burst Mode:
LF Multiplier Facility:
9915 Vol. 2
Up to 35V r. m. s. maximum by p. j . n. diode anenuotor
and reed relay.
Input frequencies are prescaled by a factor of ten.
50 dB minimum range. AGe output is available at
two pins on rear panel.
10 Hz to 60 MHz.
Better than 10 m V. Ad justable by front ponel control.
1
MD in parallel with 25 pF.
250V r.m.s. up to 10 kHz.
50V r. m. s. up to 100 kHz.
lOV r. m, s. above 100 kHz.
400V d.e.
Channel 'A' 4{) MHz to 520 MHz (prescaled by 10).
Channel 'B' 10 Hz to 60 MHz (direct).
±1 count ± frequency standord accuracy.
o.01 s, O. 1s, 1. Os I1 Os .
Channel 'A': 1kHz, 100 Hz, 10 Hz, 1Hz.
Channel '13': 100 Hz, la Hz, 1 Hz, O. 1Hz.
In the Burst Mode the gate remains closed until
tri ggered by i ncomi ng signal. After measurement
the display is held until manually reset.
The minimum signal duratIon is 30 ms plus gate time.
See Option 09.
T ech. Spec. (2)
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FREQUENCY STANDARD
Frequency:
Ageing Rate;
Temperature Stabi Ii ty:
AI ternative Standards:
STANDARD FREQUENCY
OUTPUT
Frequency
Level:
Waveform:
EXT ER NAL 5T AND ARD I NP LIT
Frequency
Minimum Level:
Maximum Ll~vel:
I:nput Impedance:
DATA OUTPUTS
Display:
POWER REQUIREMENTS.
Supply:
Vo I toge Ranges (a. c .) :
5 MHz.
±1 part in 10
6
per month .
±8 parts in 1 O~ over temperature range 00C to +55
0C.
±3 parts in 10 over temperature range +20
0C
to +40
0C.
See Options 04A and O,~,B.
1 MHz.
Standard TTL output.
Approximatel y rectongul ar.
1MHz.
500 mV r. m.S •
1 av r. m. s. 400 Vd. c .
Approximately 2000(0.c. coupled).
Serial BeD output is provided at stondard TTL logic
levels giving 8 digits and decimal points. Static
timebose and overflow output with timing controls
ore provided. Refer to Table 1 on page Tech Spec.
(6) .
94V to 265\/ r. m.s. I 45 to 450 Hz a.c. or optiona I
battery pack.
Eight ranges selected by transformer connection and
link:-
Consumption;
9915 Vol. 2.
94V to l06V
106V to 119V
118V to 132V
188V to 212V
19VA opproximal·ely.
200V to 225V
212V to 239V
223V to 251V
235V to 265V
Tech.Spec. (3).
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ENVIRONMENTAL AND SAFETY SPECIFICATIONS
Operating Temperature:
Storage Temperature:
Humidity:
Mechanical:
Safety:
MECHANICAL
0° C to +5fC (0° C to +40° C wi th Option 07)
.,
-40°C to'+70oC (OoC to +60
oC
with Option 07)
°
95% r. h. at +40 C
In accordance with IEC 68.
Meets I EC 348 (BS 4743).
Dimensions: Height
110 mm
Width "
284 mm
Depth
268 mm
Weight:
Accessories Supplied:
Approximately 2.7 kg excluding Battery Pack.
Battery Pack 1.5kg.
Operators t-.Aonual, Spare Fuses and Supply Vo Itage
Label.
OPTION Cl SERIAL TO PARALLEL INTERfACE
Data and Control
Information
8decades of dota in 4 line BeD weighted
1248, 3 I ine decimal point position, print
command, print hold, reset, overflow and time-
bose information. All logic levels t. t.1 .
compatible.
OPTION 04A FREQUENCY STANDARD 9442
Frequency:
Ageing Rote:
Warm-Up Time:
Tempera ture StabiIi ty:
9915. Vol.2.
5MHz.
±:3 parts in 10
9
/day after 3mon ths conti nuous operation.
Better than ±2 part in l0
7
wi th in 6 minutes.
Be tter than :1:3 parts in 10
9
per °C over the range
-lOoC to +4SoC.
Tech. Spec. (4)
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OPTION 04B FREQUENCY STANDARD 9421
Frequency:
Ageing Rate:
Warm-Up Time:
Temperature Stab iIity:
5MHz.
±S parts in 10 lO/dey after 3months continuous
operation.
Better than ±1 part in 10
7within
20 minutes.
Be tter the n ±6 parts in 10
10
per °eover the range
-1 DOe to +45°(.
OPTION 07 BATTERY POWER PACK
Mechanical:
Selection:
Battery Life:
Battery Condi ti on:
Charge Time:
Standby F~ci Iity:
Battery Pack is mouMed on 0 metal tray inside the
instrument and connected via 0 polarised 4 pin
connector.
By means of 3posi tion Mai ns/Charge/Battery swi tch
on I'ear panel.
4 hours minimum continuous ot +200 c: 15 hours
minimum on stondby at +20
0C.
Indicated by 'Battery Low' lamp on front panel.
o
14 hours at +20 C.
With power switch in standby position only the
j nterna I st~ ndord is operati ono I. Press; ng the
Reset Switch activates the counter for opproximately
1 minute after which it reverts to the standby
condiHon.
OPTION 09 LF FREQUENCY MULTIPLIER
Function:
Frequency Range:
Mul tipli cation:
Gate Time:
Resolution:
9915 Vol. 2
To increase measurement resolution at low frequencies
on 'B' input channel.
10 Hz to 5kHz.
x 100
Fixedatls.
0.01 Hz.
Tech. Spec. (5)
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DATA OUTPUT CONNECTIONS
A1 Data
and Command information is available via a28-way edge connector
accessibIe
by remov i n9 acover on the 'rear pone I. The foci Ii ti es and pi n
connections are listed In Table 1below. The logic for the time base code is given in Table 2
on the next page.
TABLE 1
Data Output Connector
Pin
Facility
Pin Foci Ii ty
1
.. 5V ( nominal)
A
OV
•
2
+5V ( nominal)
BOverflow (Static
Indi cation)
3
Key Way C
Key Way
--
44 (BeD)
D1
(BCD)
5
8" (BeD)
E 2" (BeD)
6
External Hold Input
F
10 kHz sync.
•
7
External Reset Input H
Main Gate
8Not
Used
JNot
Used
9n
Held at K
;} Time Bose
10
Logic '1'
Ly
Information
11 M
-; (See Table 2)
-
12 Ro
N
Not Used
13 Hold/Reset
P Not Used
14
PrescaJe
R Not Used
NOTES: 1.
2.
9915 Vol. 2
External Hald Input If, when used with external circuitry, it is required
to extend the cycle time, the external hold, (logic '0', pin 6) must be
applied during the gate time or up ~o 100 IJs after gate closure. To
ini ti ate anew cycle of measurement, the external hold must go 'high' for
not less j'han 200 1-1$.
External Reset Input External reset is achieved by the application of
logic '0' to pin 7 of the connector for a period of not less than 100 nS
J
on returning to 11' level this will reset the display to 'all zeros' and
initiate a new measurement cycle.
Tech. Spec. (6)
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TIME BASE LOGIC CODES
A2 Table 2 gi yes the logic leve Is at the Data Output edge connector. The
inverse IeveIs are appl i ed to the CD I Chi (: :nthe ipstrument.
TABLE 2
Time Base Selection C0-:
1
.,
Code Gate Time
---
(seconds)
xyz
01,.01
101 0.1
0011
1,0
10
Fu neti on Logic Output
The 9915 is 0si nglefuneti on instrumentJtherefore the obe lines ore heId
at '1' level.
9915 Vol. 2Tech. Spec. (7)
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DATA FORMAT PRINCIPLES
FUNCTION AND TIME BASE CODES
A3. The functi on and ti me base requi rements ore appl i ed jnternall y to the CD J
Chip on asix-line code. The inverse'states of this code are fed out to the rear
Data Output connector. As the 9915 is asingle function instrument the a, b, c'functionl
lines are held permanently at logi c 111. The time base information code is given in Table 2.
DA TA OUTPUT FORMAT
A4. The b.c.d. output data is available at the 28-way edge connector in abit
parallel byte serial
form. The data is sequenced by a 10 kHz synchronising
signal. The data presentation is delayed 0.5!Js from the negative edge of the synchronising
signal.
An additional synchronising pulse (Ro) determines the first state (lOo digit).
Accessories are available
to give data output in parallel form (for printers etc.) or IEC/
ASCII bus compatible formaL
AS. Fig. Al (not drawn to scale) shows the timing sequence for the ten states. The
data on each state is as follows:-
\0 K H. SYNC.
IPIN Fl
Rc IPIN 12)
OutPUT STATfS
QATA ourpUTS
States
1 to 8
9
10
I
I lOCus
I
I
:11
:_IL;
I0-5
~ 51
I1
I I
I I
I
100 I10' I IQ 2
Facility
Digit (display) information. 7
Overflow for 10
3,
10
4,
10
6
and 10 digits on pins
D, E, 4 and 5respeci tively.
Decimal point position in kHz units, plus
overflow information for 10
5
di gi t ~ela ti ve to
directl ygated i npu t} via pin 5.
II
II,
II
u:
II
II
(I
II
II
II
')
I678SI
la
II
10)
10L
I10')
rob
ID 7I
OI(,IT DATA
I.~---------"vr------_---J ~~
OVER OVERFLOW
FLOW AND d_p.
9915 Vol. 2
Data Sequence Diagram
Fig A,1
T ech. Spec. (8)
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INTRODUCTION
1 .1 The 9915 is an eight digi t frequency meter with a measurement capabi 11 ty of
over 520 MHz and con ta ini ng anumber of advanced operational fee tures.
The instrument operates from a.c. mains supplies and contains abattery charging facility.
An intemally-fi tted battery pack is available 0$ an option.
1 .2 Four go te times of .01/ O. 1/ 1 and 10 seconds are provided. The swi tch
posi tions are marked wi th ~he frequency uni ts of the dispaI y. A GATE
lamp illuminates when measurement is in progress. An OVERFLOW lamp illuminates
if the' A' Channel display is over-filled (the reading would exceed 'all nines'). The
display and all indicator la(llps are LED's (light-emitting diodes) with provision for
lsegment check' on the display.
INPUTS
1.3 Two input channels ore provided: Input IB' is a directly gated, high impedance
channel for frequencies up to 60 MHz and with manual sensitivity control.
Input 'AI is 0 500channel covering the range 40 MHz to 520 MHz, prescaled by ten and
with a .g.c., automatic overload protection and overload indicator. The front panel
symbol advises the user to consult the handbook for further details.
SPECIAL FEATURES
Large Seal e Integration
1A The heart of the instrument is an integrated circuit element which performs
all the measuring functions of an 8-digit 60 MHz counter.
1Burst' Measurement
1.5 This facility is provided for measurements on signals which occur ::1 short
bursts at irregular intervals. The minimum burst duration is 30 ms plus
gate time.
Battery Economy (Stondby) Foci Ii ty
1 .6 \Alhen the optional battery pack is fitted and continuous reodout is not
required, a significant increase in battery operating time can be obtained
by swi tching to 5T ANDBY. The instrument is then 'off' except for the internal
frequency standard. If the RESET but ton is depressed the ins trumen t will opera ~e norma 1I y
for approximately one minute, ail"er which it reverts to the standby conditions. This
operation may be repeated as required.
9915 Vol. 2
1-1
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LF Multiplier (Option)
1 .7 An optional 1 LF
'
facility is suitable for measurements of low frequencies such os
audio tones. By means of afrequency multip')ication technique the resolution
below 5 kHz is improved by a factor of 100 with ameasurement time of one second. The
Burst facility is not operative in LF mode.
AGC Output
1 ,8 The lA' Channel amplifier has automatic gain control .his a.9. c. voltage is
brought out to two pins on the rear pane! (AGe 0/P) for use as apeak indication,
in} for examp1e} transmi tter tunjng .
Segment
Check
1.9 By selecting INPUT lA' and CHECK} the reodout will display loll 81 s1,thus
checking that the segments in the display LED's are functioning correctly.
FREQUENCY STANDARD
1,10 Adiscrete component 5 MHz oscillator is fitted in the basic versions of the
instrument, but
at customer1s option a high stability fast-worm-up oscillator unit
from the Racal range may be fitted. This optional unit should be serviced only by Race I
Instruments or authorized agent. An aperture in the rear panel provides access for calibration
of the oscillator. Early deliveries of the 9915 are fitted with the optionol oscillator 9442.
An external frequency standard can be connected via a rear panel BNC socket. A 1 MHz
reference} derived from the standard in use, is available via an adjacent BNC socket. When
external standard is connected the instrument automatically changes to external standard
operation.
AC (tJlAINS) SUPPLY
1 .11 The instrument operates from a. c. suppl ies between 94 and 265 volts, 45 to
450 Hz. Atapping on the internal mains transformer must be correctly set
according to the user's supply voltage. Alabel fixed to the rear panel should indicate the
se lected range. Spare Iabels ore suppl ied wi th the instrument for vol toge ranges other than
223 to 251V.
BATTERY POWER SUPPLY (OPTION)
1.12 The instrument can operate either from normal a.c. mains supplies, or from an
internal battery pack containing re-chargeable nickel cadmium cells. The
batteries allow 4hours continuous operation from the full charged condition. A 3-position
rear paneIswitch selects mai ns or battery power, or full rate charging of the batteri es from
the
internal charging circuit. When on battery operation 0 warning light indicates when
battery voltage is low . To fu IIycharge adischarged battery requi res 14 hours. A vci d
overcharging
as it wi II progressiveIyredu ce battery charge coped ty. Wh en the instrument
is operating from a.c. mains supply the batteries rece've a trickle charge which can continue
indefinitely without detriment to the batteries.
ACCESSORIES
1 .13 The following accessories are available:-
(1) A rigid carrying case for portable use (Part No. 15-0450)
(2) A19 inch rack mounting kit. (Part No. 11-1126)
1-2
9915 Vol. 2
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POWER SUPPLY
2. 1 AC Supply: Before operati ng a new ins trume nt I or at a new Ioeati on I check
that the mains voltage selection is correct (see rear panel label). Set the rear
panel switch to MAINS.
Battery Supply: Set the rear panel swi tch to BATTERY, Set the POWER swi tch
to ON and veri fy that the BATTERY LOW i ndi cator is not ill umi noted.
FREQUENCY MEASUREMENT (NORIVIAL)
2.2 (1) Set the controlsas foil ows: -
(0) CHECK/OPERAlE/RESET switch to OPERA lE.
(b) NORMAVBURST switch to NORMAL.
(c) INPUT switch to channel IA
Ior IB' as
required.
(d) SENSITIVITY control fully clockwise.
(2) Connect the external signal to the appropriate input socket IAI or IB
I•
The damage overload input levels are:-
Input 'A I
35V r. m. s. (overload
protection above 5V
r.m.s. )
Input I
B'
250V r.m.s. up to 10 kHz
50V r. m. s. up to 100 kHz
lOV
r.m.s. above 100 kHz
9915 Vol. 2
(3)
(4)
(5)
Check that the GATE lamp is illuminated.
When using Channel lA' observe the OVERLOAD indicator.
Illumination indicates that the input signal h::Js exceeded 5V r.m.s.,
that input protection has come into operation and the input impedance
will have risen above 500.
When using Channel IBI adjust the SENSITIVITY control anti-clockwise
to obtain stable counting. The maximum sensitivity is 10 mV. At low
frequeneies
th is control is usefuIfor fi Iteri ng out h .f. interference and
noise.
2-1
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(6) Set the GATE TIME switch to fill the display, or as required. Read the
display in the units indicated by the switch position. If required, use
the overflow procedure (see next paragraph).
Overflow Procedure
2.3 Enhanced resolution at higher frequencies can be obtained by "overspi"ing"
one or more of the left-hand digits. First, select a short gate time and record
the most significant digjts displayed. Then select a longer gate time to display the less
significant digits to ~he required resolution. The OVERFLOW indicator will illuminate to
show that one or more di gi ts ore bei ng overspi r led at the Ianger gate time.
FREQUENCY MEASUREMENT (BURST)
2.4 NOTES 1: The minimum burst duration is 30ms plus gate time.
2: The user may, if desired, use the BURST mode to obtain asingle
shot reading from 0 normal continuous input signal.
(1) Set the NORMAL/BURST switch to BURST, the SENSITIVITY control to
the 10 mV setting. Select required Input channel and operate.
(2) Briefly press the CHECK/OPERA lE/RESET swi tch to RESET. The display
(except
the d.p.) will go blank. When a signal burst is received it will
be measured and the display held until the RESET switch is operated again.
BATTERY ECONOMY OPERATION
2.5 (1) Prepare the instrument for battery power suppl y (para. 2. 1) and norma I
measuremen t (para. 2.2).
(2) Set the POWER switch to STANDBY and briefly press the CHECK/
OPERA TE/RESET to RESET. The instrument wi" operate for approximately
one minute and then revert to standby. To repeat the operation press
RESET when reguired.
STANDBY OPERATION
2.6 The operation described in sub-section 2.5 (2) can be used with mains powered
instruments. It may be noted that when switching from POWER ON 10
STANDBY the display generally rem"'lins on for about a minute before settling into the
I di sp Iay off' stondby conditi on.
9915 Vol. 2
2-2
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