HP 54753A, 54754A User Manual
User’s Guide
Publication number 54753-97010
Second edition, January 1999
For Safety information, Warranties, and Regulatory information, see pages
behind the index
© Copyright Hewlett-Packard Company 1999
All Rights Reserved
HP 54753A and HP 54754A TDR
Plug-in Modules
HP 54753A and HP 54754A Plug-in Modules
The HP 54753A and 54754A TDR plug-in modules provide you with TDR
and TDT measurement features. In addition to the TDR and TDT
measurement features, the TDR plug-ins provide two accurate
oscilloscope measurement channels with user selectable bandwidths of
12.4 or 18 GHz. The lower bandwidth mode provides excellent
oscilloscope noise performance for accurate measurement of small
signals. The high bandwidth mode provides high-fidelity display and
measurement of very high-speed waveforms.
The HP 54753A TDR plug-in module provides:
• Automatic and manual single-ended TDR and TDT measurement
capability
• Automatic and manual waveform, histogram, FFT, waveform math,
eye pattern measurements, statistical measurements, and limit
testing capabilities.
• User selectable 12.4 or 18 GHz bandwidth (Channel 1).
• User selectable 12.4 or 20 GHz bandwidth (Channel 2).
• 2.5 GHz bandwidth trigger channel.
• 3.5 mm (m) connectors.
The HP 54754A TDR plug-in module provides:
• Automatic and manual single-ended and differential TDR and TDT
measurement capability.
• Automatic and manual waveform, histogram, FFT, waveform math,
eye pattern measurements, statistical measurements, and limit
testing capabilities.
• User selectable 12.4 or 18 GHz bandwidth.
• 2.5 GHz bandwidth trigger channel.
• 3.5 mm (m) connectors.
ii
Accessories Supplied
The following accessories are supplied with the TDR plug-in modules:
One 50 ohm SMA (m) terminator, HP part number 1250-2153
Two SMA shorts (m), HP part number 0960-0055
TDR Demo Board, HP part number 54754-66503
One User’s Guide
One Programmer’s Guide
One Service Guide
Accessories Available
The following accessories are available for use with the TDR plug-in
modules.
Options
Option 0B1 Additional set of user documentation
Option 001 HP 83480A mainframe operating system upgrade
Option 002 HP 54750A mainframe operating system upgrade
Option 003 Delete demo board
HP 54755A TDR option for HP 83480A mainframe operating system upgrade
Optional Accessories
HP 10086A ECL terminator
HP 54006A 6 GHz divider probe
HP 54007A accessory kit
HP 54008A 22 ns delay line
HP 54118A 500 MHz to 18 GHz trigger
HP 54701A 2.5 GHz Active Probe with Option 001
Connection Devices
SMA (f-f) adapter, HP part number 1250-1158
APC 3.5 (f-f) adapter, HP part number 1250-1749
iii
In This Book
This book is the operating manual for the HP 54753A and HP 54754A TDR plugin modules, and contains 13 chapters.
General Information Chapter 1 contains overview information, menu
and front panel key information, trigger information, and calibration
information. Chapter 2 contains important information on the care of the
TDR plug-in connectors.
TDR Front Panel and Menu Keys Chapter 3, 4, 5 and 6 describe the
front panel keys and all the menu keys.
Task Oriented Examples Chapter 7 contains example single-ended
TDR measurements using a demo board included with each TDR plug-in
module. Chapter 8 contains example differential TDR measurements.
TDR Theory Chapters 9, 10, and 11 contain in-depth theory of TDR
transmission lines and how to use TDR in designing systems.
Specifications and Characteristics Chapter 12 contains the
specifications and characteristic for the TDR plug-in modules.
Problems and Error Messages Chapter 13 contains troubleshooting
information and error messages.
iv
Contents
1 The Instrument at a Glance
Menu and Key Conventions 1-3
The HP 54753A, 54754A TDR Plug-In Modules 1-4
Plug-in Module Purpose 1-4
Front Panel of the Plug-in Module 1-4
Getting the Best Performance 1-5
Installing a Plug-in Module 1-6
Trigger 1-6
2 Care and Handling of Precision Connectors
3.5 mm Connector Care 2-3
Connector Wear 2-3
Operator Skill 2-3
Device Specifications 2-3
Accuracy Considerations 2-6
Visual Inspection 2-8
Mechanical Inspection 2-8
Connecting the Devices 2-16
3 Setup Channel Menu
Displaying the Setup Channel menu 3-4
Display 3-4
Scale 3-4
Offset 3-5
Bandwidth. . . 3-6
Alternate scale. . . 3-6
Calibrate . . . 3-8
Calibration Overview 3-12
Factory Mainframe Calibration 3-13
User Calibrations 3-16
4 HP 54753A TDR/TDT Setup Menu
Displaying the TDR/TDT Setup Menu 4-4
Stimulus 4-4
TDT 1 dest 4-4
Contents-1
Contents
TDR 1 dest 4-5
Normalize response . . . 4-5
TDR rate automatic . . . (250 kHz) 4-8
Preset TDR/TDT 4-8
5 HP 54754A TDR/TDT Setup Menu
Displaying the TDR/TDT Setup Menu 5-7
Stimulus 5-7
TDT 1 dest 5-8
Normalize response . . . 5-8
TDR rate automatic . . . (250 kHz) 5-11
Preset TDR/TDT 5-12
TDT 2 dest 5-13
Normalize response . . . 5-13
TDR rate automatic . . . (250 kHz) 5-16
Preset TDR/TDT 5-17
TDT 1 dest 5-18
TDT 2 dest 5-18
Normalize 1 response . . .
Normalize 2 response . . . 5-19
TDR rate automatic . . . (250 kHz) 5-21
Preset TDR/TDT 5-22
TDR/TDT 5-23
TDR response 1 5-23
TDR response 2 5-24
TDT response 1 5-25
TDT response 2 5-25
Establish ref plane 5-26
TDR rate automatic . . . (250 kHz) 5-27
Preset TDR/TDT 5-28
TDT 1 dest 5-30
TDR 1 dest 5-30
Normalize response . . . 5-31
TDR rate automatic . . . (250 kHz) 5-34
Preset TDR/TDT 5-34
6 Measure and Other TDR Specific Menus
TDR/TDT Measure Menu 6-4
Contents-2
Marker Menu 6-9
Reference 6-9
Marker units . . . 6-9
Response Menu Items 6-10
7 Single-ended TDR Measurements
Single-ended TDR Features 7-3
Establishing the Reference Plane and Normalizing 7-8
Measuring Transmission Line Impedance 7-19
Measuring Transmission Line Percent Reflection 7-25
Measuring Excess L/C 7-32
Measuring the Distance to a Discontinuity 7-37
8 Differential TDR Measurements
Differential TDR Features 8-3
Measuring Differential and Common Mode Impedance 8-5
Making Differential TDT Measurements 8-15
Contents
9 TDR Fundamentals
Propagation on a Transmission Line 9-4
Step Reflection Testing 9-6
Instrument Configuration 9-20
10 Improving Time Domain Network Measurements
Sources of Measurement Error 10-3
Removing Measurement Errors 10-6
11 Transmission Line Theory Applied to Digital Systems
Transmission Line Design 11-2
Signal Propagation Delay for Microstrip and Strip Lines with Distributed or Lumped
Loads 11-15
Microstrip Transmission Line Techniques Evaluated Using TDR Measurements 1121
References 11-38
Contents-3
Contents
12 Specifications and Characteristics
Specifications 12-3
Vertical Specifications 12-4
Environmental Specifications 12-5
Power Requirements 12-6
Weight 12-6
Characteristics 12-6
Trigger Input Characteristics 12-6
Product Regulations 12-7
13 In Case of Difficulty
If You Have Problems 13-3
If the Mainframe Does Not Operate 13-3
If the Plug-in Does Not Operate 13-4
Error Messages 13-5
Contents-4
1
The Instrument at a Glance
The Operating the Instrument
What you’ll find in this chapter
This chapter describes:
• the key conventions used in this manual
not
• the front panel, rear panel and keys that do
Understanding the information in this chapter will help you successfully operate
the instrument.
display menus on the screen
CAUTION
The input circuits can be damaged by electrostatic discharge (ESD). Therefore,
avoid applying static discharges to the front-panel input connectors. Before
connecting any coaxial cable to the connectors, momentarily short the center
and outer conductors of the cable together. Avoid touching the front-panel
input connectors without first touching the frame of the instrument. Be sure
the instrument is properly earth-grounded to prevent buildup of static charge.
1-2
The Instrument at a Glance
Menu and Key Conventions
Menu and Key Conventions
The keys labeled Trigger, Disk, and Run are all examples of front-panel keys.
Pressing some front-panel keys accesses menus of functions that are displayed
along the right side of the display screen. These menus are called softkey
menus.
Softkey menus list functions other than those accessed directly by the frontpanel keys. To activate a function on the softkey menu, press the unlabeled key
immediately next to the annotation on the screen. The unlabeled keys next to
the annotation on the display are called softkeys.
Additional functions are listed in blue type above and below some of the frontpanel keys. These functions are called shifted functions. To activate a shifted
function, press the blue front-panel Shift key and the front-panel key next to
the desired function.
Throughout this manual front-panel keys are indicated by bold lettering of the
key label, for example, Time base. Softkeys are indicated by italic lettering of
the key label, for example,
panel key pressed and which menu is selected. Shifted functions are indicated
by the front-panel Shift key followed by the shaded shifted function, for example
the Local function (above the Stop/Single front-panel key) will be shown as Shift,
Local.
A softkey with On and Off in its label can be used to turn the softkey’s function
on or off. To turn the function on, press the softkey so On is highlighted. To
turn the function off, press the softkey so Off is highlighted. An On or Off softkey
function will be indicated throughout this manual as:
A softkey such as
this case you could choose Triggered by pressing the softkey until Triggered is
highlighted, or choose Freerun by pressing the softkey until Freerun is
highlighted. Softkey choices will be indicated throughout this manual as:
Triggered Freerun
When some softkeys, such as
calibration will be made. Some softkeys, such as
numeric value. To enter or change the value, use the general purpose knob
located below the front-panel Measure section.
Sweep Triggered Freerun
Triggered.
Scale
. The softkeys displayed depend on the front-
Tes t
On.
offers you a choice of functions. In
Calibrate Probe
, are pressed the first time, a
Offset
require the entry of a
Sweep
1-3
The Instrument at a Glance
The HP 54753A, 54754A TDR Plug-In Modules
The HP 54753A, 54754A TDR Plug-In Modules
The TDR plug-in modules are two of several plug-in modules available for the
HP 83480A and HP 54750A mainframes.
Plug-in Module Purpose
The purpose of the plug-in module is to provide measurement channels,
including sampling, for the mainframe. The plug-in module scales the input
signal, sets the bandwidth of the system, and allows the offset to be adjusted so
the signal can be viewed. The output of the plug-in module is an analog signal
that is applied to the ADCs on the acquisition boards inside the mainframe. The
plug-in module also provides a trigger signal input to the time base/trigger board
inside the mainframe.
Front Panel of the Plug-in Module
The plug-in module takes up two, of the four, mainframe slots. The front panel
of the plug-in module has two channel inputs and an external trigger input. The
front panel also has two probe power connectors for HP 54700-series probes,
an auxiliary power connector for general purpose use, and a key for each
channel that displays the softkey menu. The softkey menu allows you to access
the channel setup features of the plug-in module for the selected input.
The front-power Probe Power connector allows automatic channel scaling and
probe calibration with HP 54700 series probes. The front-panel Aux Power
connector provides only power to HP 54700 series probes for use as a trigger
input. Probe calibration and scaling are not required for a trigger input.
1-4
Figure 1-1
The Instrument at a Glance
Getting the Best Performance
Front panel of the plug-in module.
Getting the Best Performance
To ensure you obtain the specified accuracy, you must perform a plug-in module
vertical calibration. The calibration must also be performed when you move a
plug-in module from one slot to another or to a different mainframe. Refer to
"Performing a Plug-in Module Vertical Calibration" in Chapter 3 for information
on performing a plug-in module vertical calibration.
1-5
The Instrument at a Glance
Installing a Plug-in Module
Installing a Plug-in Module
You do not need to turn off the mainframe to install or remove a plug-in module.
The plug-in module can be installed in slots 1 and 2 or 3 and 4 on the HP 83480A,
54750A mainframe. The plug-in module will not function if it is installed in slots
2 and 3.
To make sure the instrument meets all of the published specifications, there
must be a good ground connection from the plug-in module to the mainframe.
The RF connectors on the rear of the plug-in module are spring loaded, so fingertighten the knurled screw on the front panel of the plug-in module to make sure
the plug-in is securely seated in the mainframe.
CAUTION
CAUTION
CAUTION
Do not use extender cables to operate the plug-in module outside of the
mainframe. The plug-in module and/or mainframe can be damaged by
improper grounding when using extender cables.
Trigger
The external trigger level range for this plug-in module is ±1 V. The trigger
source selection follows the slots the plug-in module is installed in. For example,
if the plug-in module is installed in slots 1 and 2, then the trigger source is listed
as trigger 2. If it is installed in slots 3 and 4, then the trigger source is listed as
trigger 4. Because the external trigger capability of this module is restricted to
signals of 2.5 GHz or less, use of the HP 54753A and HP 54754A modules with
Option 100, extended trigger, is not recommended.
The maximum safe input voltage is ±2 V + peak ac (+16 dBm). Therefore, to
!
avoid damaging the trigger input circuitry, do not apply any voltage outside
this range.
The input circuits can be damaged by electrostatic discharge (ESD).
Therefore, avoid app lying static discharges to the front-panel i nput connectors.
Before connecting any coaxial cable to the connectors, momentarily short the
center and outer conductors of the cable together. Avoid touching the frontpanel input connectors without first touching the frame of the instrument. Be
sure the instrument is properly earth-grounded to prevent buildup of static
charge.
1-6
2
Care and Handling of Precision Connectors
The Care and Handling of Precision
Connectors
What you’ll find in this chapter
This chapter describes:
• 3.5 mm connector care
• connector wear
• device specifications
• accuracy considerations
• visual inspection
• mechanical inspection
• connecting devices
Understanding the information in this chapter will help you successfully operate
the instrument.
CAUTION
The input circuits can be damaged by electrostatic discharge (ESD). Therefore,
avoid applying static discharges to the front-panel input connectors. Before
connecting any coaxial cable to the connectors, momentarily short the center
and outer conductors of the cable together. Avoid touching the front-panel
input connectors without first touching the frame of the instrument. Be sure
the instrument is properly earth-grounded to prevent buildup of static charge.
2-2
Care and Handling of Precision Connectors
3.5 mm Connector Care
3.5 mm Connector Care
This chapter shows you how to take care of 3.5 mm connectors so that you can
maintain high levels of accuracy, repeatability, and system performance. Taking
appropriate care of your connectors will also extend their service life. Most of
the information can also be applied to 2.4 mm connectors. For additional
information on 2.4 mm connectors, refer to operating note "2.4 mm Adapters
and Calibration Accessories" HP part number 11900-90903.
Connector Wear
Connector wear will eventually degrade performance. The calibration devices,
which are typically used only a few times each day, should have a very long life.
However, because the connectors often undergo many connections a day, they
wear rapidly. Therefore, it is essential that all connectors on the HP 54753A or
HP 54754A TDR plug-in modules be inspected regularly, both visually (with a
magnifying glass) and mechanically (with a connector gage), and replaced as
necessary. Procedures for visual and mechanical inspection are given in the
next section of this manual. It is easier and cheaper to replace a worn adapter
than a worn channel connector.
Operator Skill
Operator skill in making good connections is essential. The mechanical
tolerances of the precision 3.5 mm connectors used in the HP 54007A kit are
two or three times better than the tolerances in regular 3.5 mm connectors.
Slight errors in operator technique that would go unnoticed with regular
connectors often appear with precision connectors in the calibration kit.
Incorrect operator technique can often result in lack of repeatability. Carefully
study and practice the connection procedures that are explained later in this
manual until your calibration measurements are consistently repeatable.
Device Specifications
Electrical specifications depend upon several mechanical conditions. A 3.5 mm
connector is a precision connector dedicated to very specific tolerances. SMA
connectors are not precision mechanical devices. They are not designed for
repeated connections and disconnections and are very susceptible to
2-3
Care and Handling of Precision Connectors
Device Specifications
mechanical wear. They are often found, upon assembly, to be out of
specification. This makes them potentially destructive to any precision 3.5 mm
connectors to which they might be mated.
Use extreme caution when mating SMA connectors with 3.5 mm precision
connectors. Prevent accidental damage due to worn or out-of-specification
SMA connectors. Such connectors can destroy a precision 3.5 mm connector,
even on the first connection.
Hewlett-Packard recommends that you keep three points clearly in mind when
you mate SMA and precision 3.5 mm connectors: SMA inspection, alignment,
and mechanical mismatch.
SMA Inspection
Before mating an SMA connector (even a new one) with a precision 3.5 mm
connector, carefully inspect the SMA connector, both visually and mechanically
with a precision connector gauge designed to measure SMA connectors. A male
SMA connector pin that is too long can smash or break the delicate fingers on
the precision 3.5 mm female connector. Gauging SMA connectors is the most
important step you can take to prevent damaging your equipment.
Alignment
Be careful when aligning the connectors. Push the two connectors together
with the male contact pin precisely concentric with the female. Do not
overtighten or rotate either center conductor. Turn only the outer nut of the
male connector and use a torque wrench (5 lb.in., 60 N-cm) for the final
connection. Note that this torque is less than that when mating precision 3.5
mm connectors with each other. A torque wrench suitable for SMA connectors
preset to 5 lb.in. is available (HP part number 8710-1582, CD 0).
The TDR plug-in modules come with adaptors already installed to prevent
damage to the channel connectors. Then, if accidental damage does occur, the
adapter is all that needs to be replaced. It is easier and cheaper to replace a
damaged adapter than a channel connector. SMA connectors can then be mated
with precision 3.5 mm connectors without difficulty or fear of expensive and
time-consuming repairs.
Mechanical Mismatch
Significant structural and dimensional differences exist between these two
types of connectors. Precision 3.5 mm connectors, also known as APC-3.5
connectors, are air-dielectric devices. Only air exists between the center and
outer conductors. The male or female center conductor is supported by a plastic
"bead" within the connector. In SMA connectors, a plastic dielectric supports
2-4
Figure 2-1
Care and Handling of Precision Connectors
Device Specifications
the entire length of the center conductor. In addition, the diameter of both the
center and outer conductors of an SMA connectors differ from that of a precision
3.5 mm connector.
If these precautions and recommendations are followed, SMA connectors can
be mated with 3.5 mm precision connectors without fear of expensive and time
consuming repairs.
SMA and a Precision 3.5 mm Connectors
When an SMA connector is mated with a precision 3.5 mm connector, the
connection exhibits a continuity mismatch (SWR), typically about 1.10 at 20
GHz. This mismatch is less than when precision 3.5 mm connectors are mated.
Keep this fact in mind when making measurements on SMA and precision 3.5
mm coupled junctions.
2-5
Figure 2-2
Care and Handling of Precision Connectors
Accuracy Considerations
Typical SWR of SMA and Precision 3.5 mm Connectors
Accuracy Considerations
Accuracy requires that 3.5 mm precision connectors be used. However, SMA
connectors can be used if special care is taken when mating the two, and all
connectors are undamaged and clean. Before each use, the mechanical
dimensions of all connectors must be checked with a connector gauge to make
sure that the center conductors are positioned correctly. All connections must
be made for consistent and repeatable mechanical (and therefore electrical)
contact between the connector mating surfaces.
Carefully study and practice all procedures in this chapter until you can
successfully perform them repeatedly. Accuracy and repeatability are critical
for good high frequency measurements. Note that the device connection
procedures differ in several important ways from traditional procedures used
in the industry. Hewlett-Packard procedures have been developed through
careful experimentation.
2-6
Care and Handling of Precision Connectors
Accuracy Considerations
Handling Precision 3.5 mm Connectors
• Precision 3.5 mm connectors must be handled carefully if accurate
calibrations and measurements are to be obtained.
• Store the devices in the foam-lined storage case when not in use.
• Avoid bumping or scratching any part of the mating surfaces.
• Be careful to align the center connectors.
• Check the alignment carefully before tightening the connector nuts.
• Use a torque wrench for all final connections in order to avoid
overtightening.
• Support the devices being used in order to avoid vertical or lateral force on
any connectors. This precaution is critical when using the airline, 6 cm "L",
or cables.
When Disconnecting Devices:
• Do not rock or bend any connections.
• Pull the connector straight out without unscrewing or twisting.
• Before storage, screw the connector nut all the way out to help protect the
surfaces, and use the plastic caps provided. These plastic caps can be taken
off easily by unscrewing, rather than pulling.
CAUTION Do not use a damaged or defective connector. It will damage any good
connector to which it is attached. Throw the connector away or have it
repaired.
A connector is bad if it fails either the visual or mechanical examinations or
when an experienced operator cannot make repeatable connections. The time
and expense involved in replacing channel connectors warrants considerable
caution when any connector might be less than perfect.
If any doubts exist about a connector, call your Hewlett-Packard representative.
Hewlett-Packard field offices offer limited professional advice and have access
to the factory for information.
2-7
Care and Handling of Precision Connectors
Visual Inspection
Visual Inspection
Always begin a calibration with a careful visual inspection of the connectors,
including the test set connectors to make sure they are and undamaged.
CAUTION
Make sure that you and your equipment are grounded before touching any
center conductor so you won't cause static electricity and create a potential
for electrostatic discharge. When using or cleaning connectors, be aware that
you are touching exposed center connectors that are connected directly to the
internal circuits of the oscilloscope. Touching the center conductor, especially
with a wiping or brushing motion, can cause an electrostatic discharge (ESD)
and severely damage these sensitive circuits.
Use an illuminated, 4-power magnifying glass for visual inspection.
1
Before you begin, make sure you and any equipment you are using are
grounded to prevent electrostatic discharge.
2
Examine the connectors first for obvious problems, such as deformed
threads, contamination, or corrosion.
3
Next concentrate on the mating surfaces of each connector. Look for
scratches, rounded shoulders, misalignment, or any other signs of wear
or damage.
4
Make sure that the surfaces are clean, free of dust and solvent residues.
Dirt or damage visible with a 4-power magnifying glass can cause
degraded electrical performance and possible connector damage. All
connectors should be repaired or discarded immediately.
Mechanical Inspection
Mechanical inspection of the connectors is the next step. This inspection
consists of using the appropriate male or female precision 3.5 mm connector
gauge to check the mechanical dimensions of all connectors, including those on
the test set. The purpose of doing this is to make sure that perfect mating will
occur between the connector surfaces. Perfect mating assures a good electrical
match and is very important mechanically to avoid damaging the connectors
themselves, especially on the oscilloscope.
2-8
Care and Handling of Precision Connectors
Mechanical Inspection
Center Conductor
The critical dimension to be measured is the recession of the center conductor.
This dimension is shown as MP and FP in Figure 2-3 and Figure 2-4. No
protrusion of the center conductor's shoulder is allowable on any connector.
The maximum allowable recession of the center conductor shoulder is 0.003 in.
(0.08 mm) on all connectors, except those on the channel connectors.
On the channel connectors, not only is no protrusion allowable, the shoulder of
the center conductor must be recessed at least 0.0002 in. (0.005 mm). The
maximum allowable recession of the center conductor shoulder on the channel
connectors is 0.0021 in. (0.056 mm).
2-9
Figure 2-3
Care and Handling of Precision Connectors
Mechanical Inspection
D = inside diameter of the outer conductor
d = diameter of male/female center connector
A = outside diameter of outer conductor at the mating plane
r = corner relief for male connector
B = protrusion of the male contact pin tip beyond the outer conductor mating plane
C = recession of the outer conductor mating plane behind outer face of connector
MP = recession of male contact pin shoulder behind outer conductor mating plane
Male Connectors Female Connectors
inches millimeters inches millimeters
D = 0.1378 ± 0.0005 3.500 ± 0.013 D = 0.1378 ± 0.0005 3.500 ± 0.013
d = 0.0598 ± 0.0003 1.519 ± 0.008 d = 0.0598 ± 0.0003 1.519 ± 0.008
A = 0.1803 + 0.000
- 0.002
r = 0.003 0.08 r = 0.003 0.08
B = 0.085 +0.005
- 0.015
C = 0.120 ± 0.015 3.05 ± 0.38 C = 0.176 ± 0.002 1.93 ± 0.05
Mp = 0.00 + 0.003
- 0.000
dm = 0.037 + 0.000
- 0.001
Mechanical Dimensions of Connector Faces
4.580 + 0.00
- 0.05
2.16 + 0.13
- 0.38
0.000 + 0.08
- 0.00
0.94 + 0.00
- 0.03
A = 0.1807 + 0.002
- 0.000
N/A
Fp = 0.000 + 0.003
- 0.00
N/A
4.590 + 0.05
- 0.00
0.000 + 0.08
- 0.00
2-10
Figure 2-4
Care and Handling of Precision Connectors
Mechanical Inspection
Mechanical Dimensions of the Short Circuit
Outer Conductor
If any contact protrudes beyond the outer conductor mating plane, the contact
is out of tolerance and must be replaced. If the center conductor is not recessed
at least 0.0002 in. (0.005 mm), it is out of tolerance and must be replaced. In
both cases the out-of-tolerance connector will permanently damage any
connector attached to it. Destructive electrical interference will also result due
to buckling of the female contact fingers. This is often noticeable as a power
hole several dB deep occurring at about 22 GHz.
If any contact is recessed too far behind the outer conductor mating plane
(0.0021 in. 0.056 mm, except in test sets), poor electrical contact will result,
causing high electrical reflections. Careful gauging of all connectors will help
prevent this condition.
Before using the connector gauge to measure the connectors, visually inspect
the end of the gauge and the calibration block in the same way that you
inspected the connectors. Dirty or damaged gauge facings can cause dirty or
damaged connectors. Two connector gauges are available from HewlettPackard, one for each connector type, male and female. Refer to Figure 2-5.
The part number for one gauge is HP 11752D. This gauge has a 3.5 mm
connector (male and female). Or, you can use the 85052-60043 gauge with 3.5
mm female connector with an 85052-60042 3.5 mm male gauge.
Figure 2-5 to Figure 2-8 show how to use the connector gauges. Zero the gauge
with the calibration block. Refer to Figure 2-5. It is recommended that you
zero both gauges first, then measure each of the terminations and/or adapters
that will be used. Then, as the last step, measure the channel connectors.
Figure 2-7 and Figure 2-8 show how to measure precision 3.5 mm connectors.
Note that a plus (+) reading on the gauge indicates recession of the center
conductor and a minus (-) reading indicates protrusion. Since no protrusion of
either connector is allowable, readings for connectors within the allowable
2-11
Figure 2-5
Care and Handling of Precision Connectors
Mechanical Inspection
range will be on the plus (+) scale of the gauge. Also note that the allowable
tolerance range for the test set connectors is different from the range for other
connectors. Both ranges are shown in Figure 2-7 and Figure 2-8. Before
measuring test set connectors, be sure that the power to the test set is off and
that you and your equipment are grounded to prevent electrostatic discharge.
Precision 3.5 mm Connector Gauges
2-12
Figure 2-6
Care and Handling of Precision Connectors
Mechanical Inspection
Zeroing Precision 3.5 mm Connector Gauge
2-13
Figure 2-7
Care and Handling of Precision Connectors
Mechanical Inspection
Measuring Precision 3.5 mm Male Connectors
2-14
Figure 2-8
Care and Handling of Precision Connectors
Mechanical Inspection
Measuring Precision 3.5 mm Female Connectors
2-15
Care and Handling of Precision Connectors
Connecting the Devices
Connecting the Devices
Figure 2-9 and Figure 2-10 illustrate the Hewlett-Packard recommended
procedures for making connections with the calibration devices. Notice that
these recommended procedures differ from traditional procedures used in the
microwave industry, especially the counter-rotation technique and procedure
for connecting the airline.
The counter-rotation technique, recommended here, involves a slight rotation
of the termination or adapter just before the final tightening of the connector
nut. This eliminates the very small air wedge between the outer conductors
that frequently occurs when the body is held stationary during tightening, as it
is in the traditional procedure. The HP 54753A or HP 54754A plug-in modules
will detect the reflections caused by such small wedges.
The counter-rotation technique does not harm the connectors. The gold plating
on the outer conductor surface will become burnished in time. This is normal,
and as long as the surface remains smooth, the connector is still good. After
much use the gold plating may eventually wear through and expose the
beryllium-copper substratum. This too is normal, and if it is smooth the
connector is still good, although the beryllium-copper surface may oxidize if the
connector is used infrequently.
If the burnished surface is rough, scratched, rippled, or has other irregularities,
too much tightening force is being used. If the roughness is severe, the
connector is ruined and should not be used.
CAUTION
Damage can result if SMA connectors are overtightened to precision 3.5 mm
connectors. Use a torque wrench designed for SMA connectors, set to a 5 in
lb (60 N/cm). A torque wrench suitable for SMA connectors is available, HP
part number 8710-1582.
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