,-.
“v’EW&;
~.~/~~~~~ ,A)
VOLTMETER
(Including Option 001)
Operating and Service Manual
SERIAL NUMBERS
This manual provides complete information for instruments with serial-number prefmes:
2812U and above
For additional important information about s&l
numbers, refer to “INSTRUMENTS COVERED BY
THIS MANUAL” in Section 1.
NOTE
Use this manual only with instruments that have a
“u” in their serial-number prefm.
‘First Edition
Copyright @HEWLETT+PACKARD LIMITED
SOUTH GUEENSFERRY, WEST LOTHIAN, SCOTLAND EH30 9TG
HEWLETT
PACKARD
COPYRIGHT AND DISCLAIMER NOTICE
Copyright - Agilent Technologies, Inc. Reproduced with the permission of Agilent
Technologies Inc. Agilent Technologies, Inc. makes no warranty of any kind with regard
to this material including, but not limited to, the implied warranties of merchantability
and fitness for a particular purpose. Agilent Technologies, Inc. is not liable for errors
contained herein or for incidental or consequential damages in connection with the
furnishing, performance, or use of this material or data.
3-1 GETTING STARTED
3-2
INTRODUCTION
This section provides complete operating information for the Vector Voltmeter. The items covcred include:
l
detailed descriptions of each front and rear panel key, connector, switch and display
l
general and detailed operating instructions
* information on remote operation
3-3 OPERATOR’S MAINTENANCE
The only maintenance you ES ~II operator should normally perform is replacement of the primary power fuse. Fuses
may
be ordered under
HP
Part Number 2110-0~05 (I+LUA/25Ov) for
lDO/KWac operation OF
under HP Part
Number 2110-0360 (TO,75A/250V) for 220/24OVac operation.
You can perform an automatic calibration sequence by pressing [CAL TEST].
All other maintenance should be referred to qualified service personnel.
Before the Vector
Voltmeter
is switched on, all protective earth
terminals, extension cords, autotransformer and devices
connected to it should be connected to a protective earth
grounded socket. Any interruption of the protective earth
grounding will cause a potential shock hazard that could result
in personal Injury.
For cootinued protection against fin hazard, replan the line
fuse tith only a
250V
fuse of the same rating. Do not ase
repaired fases or short-circuited fuse holders.
CAUTION
Before the
Vector
Voltmeter is switched on, it must be set to the
same line voltage as the power source or damage to the instrument
may result
ATENTION
StaUc Sensitive
Devices
Won’t mp your input probes!
The probes of the HP 85@8A are susceptible to damage from electro-static discharge (ED). Comply with the
following precautions to help avoid damage to your
Anti-static precnutioos
probes.
Never touch the tip of the probe.
Elimiiate ESD on the body by wearing a snug-fittivg ground strap that is connected to earth ground through a IM
ohm resistor.
Eliminate ESD on the work surface by using a grounded anti-static bench mat. Optional floor mats provide an extra
measure of protection especially ia axeas with floor carpet. Never we this product
on
a carpeted work surface
unless the carpet is of a conductive w specifically designed to eliminate ESD.
Do not introduce ESD
into
the Device Under Test (DUT) while using the probes. If an unprotected person touches
a part of the DUT, a static surge could damage the DUT as weA as the probes.
Always refit the protective cover when the probe is not in USC.
Mechanical abuse
The tips of the probes are fragile and can break if the probe is dropped.
Operation
3-5 FRONT PANEL FEA’I’UlZES
Figure 3-1. Front Panel
Introduction
The following four keys operate similarly. One press lights the LED and the measurement result is shown in the
appropriate display window. A second press turns off the LED and the measuremeut result. Any single measurement is available and any combination can be chosen by selecting the required measurement& Note that A, B/A
mag and B, B-A phase combinatioas can be selected using shifted functions (that is, pressing [SHIFT] and the
appropriate key). If a new measurement is selected which use8 the same display as an hating measurement, the
&sting mcawrement will be turned off (for example, se1ecting’Pha.x when B is displayed will turn B off).
A
Measures the amplitude of A. Default is mV on Display 1, changeable to &uV by t&g the [DXSPLAYJ key to
dB. Power can be displayed by pressing the [POWER MEAS] key and selecting either 50 or 75 ohms with the
[SYSTEM IMPDJ key. Units available are uW and dl3m.
B
Operates in the same way as A but the value appears on Display 2, units are controlled by the [DISPLAYJ key.
B/A mag
Measures the B/A ratio. Default is linear units on Diiplay 1, changeable to dB using the MISPLAY] key,
B-A phase
Measures the phase of B with respect to A, in degrees.
,’
.’
Operation
I
A, B/A mag .
Places
the A measurement in Display I. and the B/A mcasuremenr in Display 2.
E,
B-A
phase
Places the B measurement in Display 1 and the B-A phase in Display 2.
DISPLAY
Defines the scale associated tith the display(s), depending on what measurement is displayed. Units selecls the
linear scale and dB sclccts the log scale.
Example 1 - Amplitude of A has a units scale in mV and a dB scale in dbuV.
Example 2 - Power in A has a units SC& in uW and a dB scale in dBm.
REF
Works in A amplitude, B amplitude B/A magnitude and Phase to make measurements relative to 8 set of reference
values. [SAVE REFj stores the current A, B and Phase values, and turns [REFj on. When [REF] is turned on:
displayed phase = measured phase - saved phase and displayed
measured amp. or mag.
amplitude or magnitude =
saved amp. or msg.
REFL MEAS
Uses measurements of B/A ratio and B-A phase to make simple reflection measurements - using an external
device. The [SHORT] and [OPEN] reference impedances we used tith a bridge or directional coupler and [LOAD]
is used when making measurements with a Tee. Note that [LOAD] is selected as a shifted function.
To initialii the measuremeot, connect the external equipment and connect the appropriate reference impedance to
the test port . Press [SAVE REF]. The REF LED is automatically turned on. The A, B and phase values are then
retained and used as a correction for any level and/or phase changes occurring between the A channel (incident)
signal and the B channel (reflected) signal.
To make a corrected measurement, connect the DUT to the test port. It is also possible to make an uncorrected
measurement
When making 2 or l/Z measurements, absolute values can be displayed by choosing the appropriate [SYSTEM
IMPD] of 50 or 75 ohms. If values normalined to 2% are required, choose [NORM].
POWER
Works with A and B amplitude only to convert the measured voltage to an equivalent power using the value selected
by the [SYSTEM IMPD] key,
by turning REF off.
MRAS
I!
FORMAT
The default display cotiguration for magnitude and phase related measurements is magnitude in Display 1 and
phase in Display 2. Au alternative real and imaginary format L available when displaying the follotiing: B/A and
Phase (together), rho and phase angle, 2 and l/Z.
DELAY
Uses the B-A phase to make simple delay measurements. The delay is calculated assuming a 4kHz change between
the two frequencies. The delay is sbovm in Display 1 with Display 2 showing “delv (for delay). The delay can be
zeroed by pressing [SAVE REF].
PRESET
This key forces the instrument into a defmed measurement state, as follows: A is displayed in mV with no other
functions engaged and all raaging is automatic.
LOCAL
Returns the instrument to front panel control unless local lockout has been asserted over the HP-IB.
ADDUESS
Used to show the current HP-IB address of the i&.rument.
It
is changed by using the [STEP] keys. The display
reverts to measurement display when another key is pressed.
MAC RANGE
When
[Mm]
is selected, the display resolution is controllable using the [STEP] keys, which move the position of the
decimal point. When A and B are displayed together, both displays show the same resolution.
DIX ANLG OUT
When this mode is engaged, the raw phase and magnitude detector outputs are fed directly to the rear panel $0 that
external measurements can be made when a CW or swept(‘) source is used. Internal gain ranging is forced into
manual operation with the display showing Xxx mV t%llxale deflection, adjustable by use of the [STEP] keys.
The WCK RANGE] is ako forced into manual mode. The only vatid measurement selection is A or B.
(‘) The HP NLSA will lose lock if the sweep rate exceeds approximately l5MHz/second or if the frequency reaches
a
lock
range boundary.
LOCK RANGE
When [MNL] is selected, the instrument is ,prevented from signal searching outside the current frequency range.
RANGE
Display the
current lock range, the range 011 then be changed by using the [STEP]
keys. The display
reverts to
mea.wement display when another key is pressed.
(,,,
“”
.:‘, I.
.,
&>
B is the fumti& is associated with the A chamcl. WI& the function & engaged,
the LED beside key
flashes to show that a reading is b&g held.
METER SELECT
This key is used to associate the METER with eitbcr Display 1 or Display 2, or to turn it off.
diplaycd in Display 2, a HI or LO
annunciator
lights to show tix meter range.
If phase is being
Qp,eration
3-6 REAR PANEL FEATURES
Figure 3-2. Rear Panel
The Rear Panel Outputs provide dc signals which can be fed to external measur~g equipment. There are tW0
distinct modes of operation for these outputs.
Normal Mode
This mode provides an analog representation of the digital display values, including internal instrument correction
factors. OUTPUT 1 corresponds to DISPLAY 1 and OUTPUT 2 corresponds to DISPLAY2. The update rate is
the same as the display update rate (approximately 3 readings per second). The sensitivity is 1mV per displayed
digit.
A display value of 123.4mV will produce a d.c. output of 1234mV.
A display value of -l35.7 degrees will produce a dc output of -1357mV.
If the MAG RANGE key is used to change the display resolution, the rear panel outputs will change with the
display values.
A typical use of this mode might be to drive a chart recorder or similar logging instrument.
Direct Analog
This mode provides continuous direct output signals from the internal magnitude and phase detectors through
8OOHz low-pass filters. Only limited internal instrument correction factors are applied to the output signals. OUT-
PUT 1 corresponds to either A or B magnitude (in mV) ,wbichever is selected on the front panel. OUTPUT 2
corresponds to B-A phase. The full scale deflection (FSD) chosen on the front panel always produces an output of
1 volt and this defmes the OUTPUT 1 sensitivity.
Output Mode
A display FSD of 1OOOmV will produce an output of !OOOmV for an input of lO@JmV.
A display FSD of 31.6mV will produce an output of 1OGOmV for an input of 31.6mV.
The OUTPUT 2 sensitivity is fiwed at 1mV per 0.1 degrees.
A
A typical use of this mode might be to make narrowband swept measurements on
crystals.
I
Operation
3-7 MAKING MEkSUREMENTS
3-S BASIC MEASUREMENTS
Introduction
There are two types of Input Module that can be used with the HP 8508A Vector Voltmeter mainframe. These
Input Modules are the HP 8508lA High Impedance Input Module and the HP 8So82A 50 ohm Input Module.
The HP 8508lA High Impedance Input Module has a frequency range from 1M)kHz to 1GHz. This Input Module
has high-impedance probes which can be used either alone or with accessories to make in-circuit measurements.
The following accessories iire
(probing accessory), HP 115776A IO:1 Divider (probing accessory).
The HP 850824 50 ohm Input Module has a frequency range from 3CCWIz to 2GHz. This Input Module has 50 ohm
type-N connectors. Using the HP 850824 gives you a higher frequency range than the HP 8508lA for measurements
in a 50 ohm environment.
Getting acquainted with the Vector Voltmeter
available:
HP X157OA Accessory Kit (50 ohm accessories), HP 10216.4
kdafor
To introduce you to the main functions of the HP 8508A, here are a few simple measurements you can try. YOU will
learn to make single channel voltage and power mcawremcats, and measure the vector ratio betweee two voltages.
a. Measurements with probes
For this section, measurements arc made on a printed circuit board buffer amplitier. It is part of a SOMHZ
assembly, and has a gain of approximately 14dB.
Probing at the input of the amplitier (the output of the oscillator) gives a reference signal and probing at the output
of the amplifier will give the amplifier gain. Use the integral source as the stimulus, so the amplifier will be tested
under normal operating conditions.
Jl
J2
SOWCC
I
Figure 3-3, Test Assembly With Measurement Points
Operation
Since the circuit impedance 4 50 ohms, and the measurements are at relatively low frequencies, we can neglect the
loading cffefcus of the probe tips on the circuit response. For more sensitive applications, the HP ll576A 1O:l
Divider or HP 10216A Isolator accessories can be used with the probes to minimize loading effects and mca~uremerit errors,
Mczwwement details
1. Connect both probes at point “Jl” (the amplifier input) in the circuit. Press [PRESET] to return the HP 8508A to
a known starting state.
2. Check that the circuit under test is powered up and that the HP 8XkSA A UNLOCKED indicator is off. Press [B/
A MAG] and [B-A PHASE] to display vector ratio.
3. Select [DISPLAYJ dB to rn~awr~ the amplifier’s gain as a log ratio. Press [SHIFT] then [SAVE REF] to store
the reference and set the ratio displays to magnitude O.OdB and phase 0 degrees.
4. Move the B probe to point “52” (the amplifier output) and measure the gain and phase change. Change the
frequency of the oscilIator over its operating range and check the frequency response variation. In a circuit with
adjustable ga;n, the HP 850% METER display is an aid
to
tuning. (Use of the meter display is covered in the nexf
example.)
Any unmodulated RF signal in the frequency range lCW-Iz to 1GHz can be used as a source for tbesc measure-
ments. This includes a source that is part
of
a larger
device
under test.
This diagram shows all the keys you wilI need to make the measurements.
2.3
r
6 10 5
4.7,Q
8
5 1
Figure 34. Front Panel Keys
In the descriptions throughout this section, keys Ott the instrument are described by writing the
key
name in square
brackets, for example [PRESEY.
Keys that have multiple scIections are described by writing %&ct”, followed by
tht
key
name in square brackets,
then the required function in bold type, for ewmple “SeIeu [REm. MEAS] SWR”. When you press this type of key,
the next valid state will be selected. PKS
th
key the required number of times to light the LED beside the state
requested Some seIc~.ions arc only avaiIable in combination with other keys, so don’t worry if all the selections arc
not available.
3-10
Loading...