Krohn-Hite 6500A Operating instructions

3SHz TO 5MHz
DIGITAL
PHASEMETER
MODEL
6500A
SERIAL
NO.
OPERATING
AND
MAINTENANCE
MANUAL
U/US
INSU
KROHN-HITE
CORPORATION
AVON
INDUSTRIAL
PARK/BODWELL
STREET/AVON,
MASS.
02322
USA
PRINTED IN USA — APRIL 1983

Contents
ig a SESS SS EE EES EE EES
CONTENTS
Section Page
1
GENERAL
DESCRIPTION
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OPERATION
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3 INCOMING INSPECTION AND CHECKOUT ....c.+ccececce8 12
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CIRCUIT
DESCRIPTION
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CALIBRATION
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ILLUSTRATIONS
Figure Page
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3
Phase
Error
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Typical
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Operating
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8 Incorrect Amplifier Detector... ... ce eee ee cee eee cae e es 17
9 Switched Filter and Hot Carrier Limiter ..,.........00e04. 17
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14
Differential
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Power
Supplies
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Test
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17 Phase vs, Amplitude, Input A, Test Set-up ........00008 2. 29
18
Phase
vs.
Amplitude,
Input
B,
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Set-up
..........
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29
19 Attenuator Impedance Adjustment Test Set-up.......502e000- 31
TABLE
Table Page
2
Optional
BCD
Output
Pin
Connections
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10
APPENDIX Inside
Schematic, Component Diagrams, Parts List ,....... Back Cover

Model 6500 Phasemeter
Or? te wR
Figure 1. Model 6500 Phasemeter
ii

Section 1 - General Description
SECTION 1
GENERAL DESCRIPTION
4.1 INTRODUCTION
The Krohn-Hite Model 6500 Phasemeter measures the phase angle between two
waveforms of coincident frequency, over a range of 3 Hz to 5 MHz, and provides a
typical accuracy of 0,02°, with 0.01° resolution, A 5 digit planar gas discharge
display provides direct readout of the phase angle from 000. 00° to 360,00°,. The
6500 accepts input voltages from 0.01 volts RMS to 120 volts RMS, The fluctuations
or inconsistencies normally encountered in phase angle readings near zero and 360°
(sometimes referred to as ambiguity) are eliminated by a unique network in the 6500
that permits reading s as small as 0.01° to be observed, without the need of chang-
ing ranges or 180° shifting. In addition, the circuitry of the 6500 significantly
reduces the effects of distortion and noise on phase accuracy, An analog output on
the rear panel provides a DC voltage equal to -10 mv/degree phase, for use with an
external meter or recorder, An optional BCD output is also available, A read/hold
switch also provides continuous display of the phase angle reading, or holding of the
reading for an indefinite period,
An optional rack-mounting kit (Part No, RK-319) is available from Krohn-Hite, for
installing the Model 6500 in a standard 19'' rack-spacing.
The phasemeter is carefully inspected, aged, and adjusted before shipment, and
should be ready for operation when it is unpacked, If it appears to have been
damaged in shipment, make a claim with the carrier, and notify Krohn-Hite
immediately,
1.2 SPECIFICATIONS
Frequency Range
3 Hz to 5 MHz
Accuracy
(For typical performance, refer to Figure 4)
Sinewave:
+0.1°+1
digit
from 20Hz
to
50kHz,
rising
to
+0.7°
at
100kHz;
+0.2°
at
10Hz;
for
any
amplitude
within
the
selected
voltage
range.
Above
100kHz,
+0.
7°
per
100kHz,
with
equal
amplitude
and
the
same
voltage
range
on
each
input.
Squarewave:
+0.1°+1
digit
from
10Hz
to
20Hz,
rising
to
+0.7°
at
100kHz;
for
any
amp-
litude
within
the
selected
voltage
range.
Above
100kHz,
+0.7°
per
100kHz,
with
equal
amplitude
and
the
same
voltage
range
on each
input.

Model 6500 Phasemeter
Input Signal Amplitude
0,01 volts RMS to 120 volts RMS in three ranges: 0. 1-1,2, 1-12 and 10-120, For
higher input voltages, the use of matched attenuator probes, such as Tektronix types
P6006, P6007, P6013A, P6049A, or P6060 is recommended,
(For input levels between 0,01 volts and 0, | volts RMS, the 0, 1-1,2 volt range is
used; refer to Figure 4 for typical performance),
Input Waveforms
Sine, triangle, square and positive pulse waveforms,
(The phasemeter is triggered on the negative-going transition of the input waveform
in both sine and square wave positions of the WAVEFORM switch, )
Input Impedance
1 Megohm in parallel with 50 pf.
Maximum DC Component
+200 volts (for higher voltages, the use of matched, attenuator probes, such as
Tektronix types P6006, P6007, P6013A, P6049A, or P6060 is recommended),
Response
Time constant: Less than 500 msec,
Settling Time: To within specified accuracy, within one to eight seconds, dependent
upon input signal amplitude.
Display
0,55 inch, 7-segment, planar gas discharge
Display Range
Continuous, 000, 00° to 360, 00°
Resolution
0,01°
Repeatability
Better than +1 digit
Drift
None
VS TIME (30 days without CAL reset):
Sine Wave: +0, 025° from 20 Hz to 100 kHz; +0, 1° at 10 Hz; +0, 35° per 100 kHz
above 100 kHz,
Square Wave: +0, 025° from 10 Hz to 5 kHz; £0, 05° to 100 kHz; +0, 35° per 100 kHz
above 100 kHz,

Section 1 - General Description
Analog Output: £0, 1 mv (20, 01°)
VS TEMPERATURE (without CAL reset):
+0,01°/°C, 10 Hz to 100 kHz; 40. 05°/°C to 1 MHz; +0.05°/°C per MHz about
1 MHz,
Ambient Temperature Range
0°C to 45°C
Analog Output
(For use with an external meter or recorder): 0 to -3,6 volts DC, -10 mv DC/
degree phase, impedance 250 ohms,
BCD Output (Optional)
Provides 18 lines of phase angle equivalent BCD output, plus polarity, data ready,
read/hold and read rate control lines, Compatible with DTL, TTL logic.
Programming connector AMP type 200277-2 rear panel mounted; mating connector
(AMP type 200276-2), is provided,
Panel Controls and Adjustments
Front Panel: 3 decade push-button RMS VOLTS RANGE control (each channel), plus
push-button READ/HOLD, WAVEFORM, POWER, 0° CAL and 360° CAL,
Rear Panel: 115/230V LINE, CHASSIS/F LOATING,
Terminals
Front Panel: BNC for A input, B input,
Rear Panel: BNC for A input, B input, analog output, AMP type 200277-2 for BCD
output (optional),
Power Requirements
105-125 volts, or 210-250 volts, single phase, 50-60 Hz, 40 watts,
Dimensions and Weights
Model 6500: 16-1/2" wide, 3-1/2" high, 16" deep, 15 1lbs/6, 8 Kgs net, 18 lbs/8 Kgs
shipping,
Optional Rack Mounting Kit
Part No. RK-319, permits installation of the 6500 into a standard 19" rack spacing,

Model 6500 Phasemeter
71.3 FACTORS AFFECTING PHASEMETER ACCURACY
1.3.1
Inconsistencies
in
Meter
Readings
Near
0°
and
360°
A
problem
affecting
a
phasemeter's
accuracy
is
the
inability
of
the
phasemeter
cir-
cuit
to
detect
relatively
small
phase
angles,
resulting
in
meter
fluctuations
or
incon~
sistencies
in
readings.
The
6500
overcomes
this
inconsistency
(or
ambiguity
as
it
is
sometime
referred
to)
by
using
a
specially
designed
network
that
permits
meas-
urements
as
small
as
0,019
to
be
made
without
meter
fluctuations
or
repeatability
errors,
and
eliminates
the
need
for
multiple
meter
ranges,
or
shifting
of
the
meter
scale,
1.3.2 Distortion Present on the input Signal
If
there
is
distortion
present
on
one
of
the
signals,
a
phase
error
may
be
introduced,
depending
on
the
relationship
between
the
fundamental
and
its
harmonics,
If
the
amplitudes
of
all
odd
or
even
harmonics
add
up
to
zero
at
the
negative
zero
crossing
of
the
fundamental,
then
the
harmonics
will
produce
no
phase
error,
If
the
resultant
of
the
amplitudes
is
not
zero,
however,
it
will
cause
a
shift
in
the
zero
crossing
of
the
input
waveform,
(Worst
case
would
occur
when
the
maximum
of
the
harmonic
coincides
with
the
negative
zero
crossing
of
the
fundamental.)
The
effect
of
an
even
harmonic
will
not
only
shift
the
zero
crossing
of
the
waveform,
but
also
alter
the
symmetry
of
the
comparator
or
detector
output,
If
a
symmetry
control
loop
is
added
to
the
phasemeter
circuit,
the
effect
of
the
even
harmonic
on
accuracy
can
be
mini-
mized,
The
6500 uses
the
type
of
symmetry
loop
mentioned
above,
The
effect
of
an
odd
order
harmonic,
however,
is
not
as
easily
corrected,
An
odd
order
harmonic
simply
shifts
the
phase
of
the
output
of
the
comparator
or
detector
loop.
Since
the
symmetry
is
not
affected
there
is
no
way
to
detect
any
phase
error,
Figure
2
shows
the
maximum
phase
error
introduced
versus
the
percentage
of
har-
monic
distortion
present
on
each input
channel,
6°
°
2
r
CHANNELS AOR B
ALL ODD HARMONICS
~ 4
rf
uy
xc
oO
WwW
Qa Ze 4
a
oO
a
e&
ld o
w COASINE A
4'™ HARMONIC
a
ONIG
yt
= is
CHANNEL a7 |
ALL EVEN HARMONICS
‘
! 2 3 4 5 6 7 8 9 10
PERCENT DISTORTION
Figure 2, Maximum Phase Error vs % Harmonic Distortion
(Worst case would occur when the maximum of the harmonic
coincides with the negative zero crossing of the fundamental, )

Section 1 - General Description
SLE EN a EE EE TTD
1.3.3. Noise Present on the Input Signals
Another problem affecting phase accuracy is random noise. If there is a sufficient
noise level on either input (or both), false triggering will occur and a phase error
is introduced, The 6500 uses special circuits plus filtering to minimize the effects
of noise on the phase accuracy. Typically, any broadband noise present on both
inputs 40 db down from the input signals will produce only a 0.05° error, Figure 3
gives a typical curve for phase error versus input frequency, for a signal to noise
ratio of 10:1 on both inputs.
1.3.4 Typical Performance
The typical performance of the Model 6500 is illustrated in Figure 4,
3°
PHASE ERROR (DEGREES)
lOHZ IOOHZ IKHE 1OKHE 1OOK Hz
INPUT FREQUENCY
Figure 3. Phase Error vs, Random Noise
res nee =
50
20
10
= 5.0
iH
g
8 2.0-—-—+--—
8
RB («No
g
=
8 08
8 INPUT 80% OF
RMS VOLTS RANGE
¥ ooh
= x
Oty
\
‘.
0.05
0.02 0.1¥ —120¥ INPUT.
0.0}
3 10 1oo IK 10K 100K a 5M
FREQUENCY (Hz)
Figure 4, Typical Performance

Model 6500 Phasemeter
OOOVOKMOOYONC
POWER SWITCH
WAVEFORM SWITCHES
RMS VOLTS RANGE SWITCHES
READ/HOLD SWITCHES
O° CAL SWITCH
0° CAL SCREWDRIVER ADJUST
360° CAL SWITCH
» 360° CAL SCREWDRIVER ADJUST
DIGITAL PANEL METER
SET RANGE INDICATORS
OQ@GOOOQOOOO)
CHANNEL A INPUT (BNC)
CHANNEL B. INPUT (BNC)
CHANNEL B REAR INPUT (BNC)
ANALOG DC OUTPUT
GROUND SWITCH (CHASSIS/FLOATING)
CHANNEL A REAR INPUT (BNC)
FUSE
LINE SWITCH
POWER RECEPTACLE
BCD OUTPUT (OPTIONAL;
AMP TYPE 200277 -2)
Figure 5, Operating Controls, Displays and Connectors

Section 2 - Operation
SECTION 2
OPERATION
2.1 POWER REQUIREMENTS
The
Model
6500
Phasemeter
may
be
used
with
either
a
105
-
125
volt,
50
-
400
Hz
line
or
a
210-250
volt
50
-
400
Hz
line.
The
line
voltage
can
be
selected
by
opera-
tion
of
the
LINE
switch
on
the
rear
panel.
When
the
line
voltage
is
115
volts,
a
0.5
ampere
fuse
is
required;
when
the
line
voltage
is
220
volts,
a
0.25
ampere
fuse
should
be
used.
2.2
OPERATING
CONTROLS,
DISPLAYS
AND
CONNECTORS
(See
figure
5)
2.2.1 Front Panel Controls
POWER:
On-off
pushbutton
switch.
WAVEFORM:
Two-position
push
button
switch
selects
sine
wave
or
Square
wave
mode
of
operation.
When
sine
or
triangle
waveforms
are
used
as
input
signals,
the
WAVEFORM
switch
should
be
set
for
\U;
when
square
waves
or
positive
pulses
are
used,
the
WAVEFORM
switch
is
set
to
the
"1,
mode.
RMS
VOLTS
RANGE:
Three
position
push
button
switch
(each
channel)
for
selecting
input
voltage
ranges
from
0.01
volts
RMS
to
120
volts
RMS,
For
input
levels
between
0,01
volts
and
0,
1
volts
RMS,
the
0,
1-1,
2
volt
range
is
used,
(Refer
to
Figure
4,
Page
5
for
typical
performance.)
The
voltage
ranges
are
0,
1-1,2,
1-12
and
10-120,
The
voltage
range
may
be
extended
using
Tektronix
matched
probes,
(Types
P6006,
P6007,
P6013A,
P6049A,
or
P6060,
)
READ/HOLD: Two - position push button switch. In the READ mode, the phase
angle being measured is continuously displayed on the readout. In the HOLD
mode, the last reading is held for an indefinite period.
0° CAL: Push-button hold-release switch for checking 0° calibration. A front
panel screwdriver control is also provided for adjustment of zero scale.
360° CAL: Push-button hold-release switch for checking 360° (full scale) calibra-
tion, A front panel screwdriver control is also provided for adjustment of full scale.
2.2.2 Rear Panel Controls
LINE: Two-position slide switch for selecting 115 or 230 volt operation,
CHASSIS/FLOATING: Two-position slide switch for selecting chassis or floating
ground, In the FLOATING mode, signal ground is isolated from chassis ground,

Model 6500 Phasemeter
EIS a a TEC DTG TOT TTT OI TOT ETE TE TE ITE TTS
2.2.3 Displays
5
digit
planar
gas
discharge
displays
the
phase
angle
being
measured,
in
degrees,
from
000,
00°
to
360,
00°,
SET
RANGE:
Front
panel
LED
indicator,
(one
for
each
channel)
illuminates
when
the
input
voltage
for
that
particular
channel
is
either
above
or
below
the
selected
range.
2.2.4 Connectors
Front
panel:
BNC
connector
for
each
channel
input.
Rear
panel:
BNC
connector
for
each
channel
input.
ANALOG
OUTPUT,
BNC,
equal
to
-10
mv/degree
phase,
for
use
with
external
meter
or
recorder,
BCD
OUTPUT
(optional),
AMP
type
200277-2
connector,
Power
Receptacle
for
line
cord,
2.3 OPERATION
To operate the 6500 phasemeter proceed as follows:
1,
Make
appropriate
power
connections
(see
Section
2.
1).
2,
Push
the
POWER
switch
to
the
ON
(recessed)
position,
and
allow
the
unit
to
warm
up
for
at
least
30
minutes
to
achieve
rated
accuracy.
3.
Set
the
READ/HOLD
switch
to
the
READ
position.
4.
Push
the
0°
CAL
button.
Adjust
the
0°
screwdriver
control
(if
necessary)
so
that
the
meter
reads
000.
00°,
5.
Push
the
360°
CAL
button,
Adjust
the
360°
screwdriver
control
(if
necessary)
so
that
the
meter
reads
360.
00°,
After
the
unit
has
been
allowed
to
warm
up,
connect
the
reference
signal
to
the
A
input
and
the
signal
to
be
measured
to
the
B
input.
(It
is
recommended
that
matched,
equal
length,
coaxial
input
cables
be
used,
asa
difference
in
length
or
cable
capacitance
may
affect
the
phasemeter
accuracy,
particularly
at
high
frequencies.
As
an
example,
consider
two
cables
that
are
the
same
type
(approximately
30
pf/foot)
but
of
different
length.
A
difference
of
one
foot
between
the
two
cables
will
create
an
error
at
100
KHz
of
about
0.
06°.)
After
connecting
the
cables
to
the
two
input
channels,
set
the
WAVEFORM
switch
to
the
desired
mode.
Inthe
\,
mode,
the
phasemeter
will
measure
phase
angles
between
sine
waves,
a
sine
and
triangle
wave,
or
triangular
waves.
in
the
Ly
mode,
square
waves,
a
square
wave
and
positive
pulse,
or
positive
pulses
should
be
used,
If
a
sine
wave
is
used
in
the
a
mode
or
vice-versa,
an
error
of
several
degrees
can
be
expected,
,
After
selecting
the
proper
WAVEFORM
mode,
set
the
VOLTS
RMS
RANGE
buttons
to
a
position
where
the
LED
indicator
is
extinguished.
This
will
indicate
that
the
input
signal
level
is
within
the
proper
range.
The
6500
will
now
display
the
phase
angle,
in
degrees,
between
the
two
input
signals.
Refer
to
Section
1
for
the
appropriate
accuracy
specifications.
For
phase
angle
readings
passing
through
360,
00°,
the
meter
reading
will
remain
at
the
360,
00°
end
until
the
reading:is
approximately
364.
00°.
At
this
point
the
meter
reading
will
shift
itself
360°
to
its
corresponding
low
end,
or
004.
00°.

Section 2 - Operation
mmm
TT
Conversely,
if
the
meter
reading
passes
through
000.
00°,
the
meter
reading
will
remain
at
the
low
end
until
about
-004.
00°,
where
it
will
then
shift
itself
360°
to
a
new
reading
of
356.00.
This
feature
allows
readings
to
be
taken
at
or
near
0°
or
360°
without
meter
fluctuations.
It
is
also
possible
to
shift
the
phase
reading
as
follows
(applicable
to
sine
wave
position
of
WAVEFORM
switch,
only):
If
the
meter
is
reading
near
0°,
anda
reading
near
360°
is
de
sired,
simply
depress
the
360°
CAL
button
for
about
3
seconds,
then
release.
If
the
meter
reading
is
near
360°,
anda
reading
near
0°
is
desired,
simply
depress
the
0°
CAL
button
for
about
3
seconds,
and
then
release,
When
the
input
voltage
level
exceeds
120
volts
RMS,
or
the
DC
component
of
the
signal
exceeds
+200
volts,
the
input
range
of
the
6500
can
be
extended
with
Tektronix
or
similar
type
matched
probes.
(Tektronix
types
P6006,
P6007,
P6013A,
P6049A
or
P6060,
or
equivalent).
The
probe
should
match
an
input
resistance
of
1
megohm
and
should
be
adjustable
to
match
an
input
capacitance
up
to
50
pf.
The
broadbanding
screw
should
be
adjusted
for
0°
(or
360°)
reading
with
a
signal
directly
on
one
of
the
phasemeter
inputs
and
the
probe
(on
the
other
phase
meter
input)
connected
to
the
same
signal.
Reverse
the
procedure
for
a
probe
on
the
other
phase
meter
input,
For
optimum
accuracy,
the
probe(s)
should
be
adjusted
at
each
frequency
used
before
making
phase
measurements.
For
less
stringent
accuracy
requirements,
the
probe(s)
need
not
be
adjusted
carefully.
If
a
10
Megohm
probe
(or
10
Megohm
source
impedance)
is
used
on
one
channel
only,
below
200
Hz,
or
a
1
Megohm
source
impedance
below
20
Hz
on
one
channel
only,
an
appreciable
error
is
introduced,
because
of
the
phasemeter
input
coupling
capacitors.
(10
Megohms
will
produce
approximately
0.
8°
at
10
Hz).
This
error
can
be
cancelled
by
adding
an
equivalent
source
impedance
in
series
with
the
input
to
the
other
channel
at
these
low
frequencies,
(If
left
in
at
higher
frequencies,
it
must
be
accurately
broadbanded
with
a
shunt
capacitance)
2.4 BCD OUTPUT (OPTIONAL)
A
digital
programming
connector
(AMP
type
200277-2),
is
mounted
on
the
rear
panel,
and
provides
an
equivalent
BCD
output
of
the
front-panel
display,
plus
four
additional
data
control
lines.
A
total
of
22
programming
lines
plus
3
lines
of
the
programming
ground
return
are
provided,
A
total
of 18
lines
are
used
to
provide
the
BCD
equivalent
output
of
the
5
digit,
front
panel
display.
Each
digit,
with
the
exception
of
the
100!s
digit,
is
represented
by
four
output
lines,
and
is
binary-coded
in
a
1-2-4-8
format,
The
100!s
digit
is
rep-
resented
by
two
lines,
coded
in
a
1-2
format,
The
four
additional
data
control
lines
provide
the
following
functions:
1,
POLARITY
(OUTPUT):
The
output
logic
level
of
this
line
remains
ina
"High"
state
when
the
displayed
phase
angle
is
positive;
output
level
will
convert
to
a
"Low"
state
if
the
phase
angle
display
goes
negative,
(Con't on Page 11)
8

Model 6500 Phasemeter
Table 1.
OPTIONAL BCD OUTPUT PIN CONNECTIONS
(Using AMP type 200277-2 Connector)
Pin Letter Function Description
A 000,01
000, 02
000, 04
000, 08
DIG, GND.
000, 10
tT ye baw
000, 20
a
000, 40
000, 80
DIG, GND.
001, 00 Phase Angle BCD
OUTPUTS
002, 00
004, 00
008, 00
DIG. GND,
010, 00
020, 00
040, 00
080, 00
100, 00
4 %e ¢s GHuwy zee sz
200, 00
N
Polarity (Output) ''High" for pos, angle
"Low" for neg, angle
a Conversion Complete "High! for data ready
(Output) ''Low' for conversion
b Transfer Inhibit "Low" for data read
(Input) "High" or open for data hold
c Read Rate (Input) "High" for 4 cts/sec
L "Low" for 20 cts/sec
10

Section 2 - Operation
2, CONVERSION COMPLETE (OUTPUT): The output logic level of this line will
remain ''Low' during the Digital Panel Meter’ s measurement or conversion
cycle; the output will convert to a ''High" state when conversion of data is com-
pleted,
3. TRANSFER INHIBIT (INPUT): This input is used in conjunction with the front
panel READ/HOLD switch, and provides remote control of the READ/HOLD
function, When the front panel READ/HOLD switch is in the READ mode, the
TRANSFER INHIBIT control line is inoperative; when the switch is in the HOLD
mode, a ''Low'! level applied to the TRANSFER INHIBIT input line will allow
both the front panel display and the BCD outputs to be continuously updated by
new data. A ''High" level applied to the TRANSFER INHIBIT line will hold or
maintain the last data displayed, plus the equivalent data on the BCD outputs.
4. READ RATE (INPUT): This input is provided for selection of the DPM's read/
rate, A'!High' level applied to the READ/RATE input will effect a DPM read/
rate of 4 counts/second; a ''Low'! level will convert the read/rate to 20 counts/
second,
The logic levels for all OUTPUT lines are as follows:
OV = Low = 0,5V; L.. = 10mA
sink
2,4V = High = 5,5V; R = 6K Ohm
source
The logic levels for all INPUT lines are as follows:
OV = Low = 0. 8V; 1... = 1l,6mA
sink
2,0V = High= 5,0V; I = 0, lmA
source
A mating connector for the AMP type 200277-2 (Part No. AMP type 200276-2) is
provided,
il

Model 6500 Phasemeter
SECTION 3
INCOMING INSPECTION AND CHECKOUT
3.1 INTRODUCTION
The following procedure is used to verify that the phasemeter is operating within
specifications, both for incoming inspection and for routine servicing. Tests
should be made with all covers in place, and the procedure given below should be
followed in sequence,
SPECIAL NOTE
As an alternate to the following procedure, a Primary Phase Angle
Standard such as the Dytronics Model 311/RT-1/717S may be used
for accuracy measurements between 30 Hz and 10 KHz. A second
alternative is the use of a Computing Counter System such as the
Hewlett Packard Model 5360A when used with a suitable phase shifting
circuit),
3.2 EQUIPMENT REQUIRED
(a) 10 Hz to 100 KHz low distortion* oscillator, with output adjustable from
0, 1 volts RMS to 10 volts RMS, Krohn-Hite Model 4000A or equivalent.
(b) 10 Hz to 10 MHz sine wave oscillator, with two outputs, 180° apart, and
output voltage adjustable from zero to 1,5 volts RMS, Hewlett Packard Model 654A
or equivalent,
(c) Variable phase generator, capable of providing two sine wave and/or square
wave outputs, with adjustable phase angle from 0° to 360° Hewlett Packard Model
203A or equivalent,
(ad) 10 Hz to 5 MHz square wave signal source, with two outputs, not in phase,
and output voltage at least 1 volt peak to peak. (If a signal source with two outputs
is not available, a single source may be used with a suitable balanced transformer
such as the North Hills Electronics Model 50-201RA, to produce two outputs ap-
proximately 180° apart. )
{e) 50 ohm terminators, (2 required), Tektronix type 011-0055-00 or equal,
(For use with above transformer only).
{f) Calibrated DPM, zero to -3.6 volts DC, with 0, 1 millivolt resolution,
Newport Model 2000AS or equal.
(g) Matched set of coaxial cables (BNC) for connections to inputs. (Same
length and impedance).
* Less than 0.01% from 10 Hz to 20 KHz, rising to 0. 1% at 100 KHz.
12

Section 3 - Incoming Inspection and Checkout
3.3 PROCEDURE
After allowing the instrument to warm up for at least 30 minutes, set the controls
to the following positions:
WAVEFORM N
RMS VOLTS RANGE (input A) 0.1-1.2
RMS VOLTS RANGE (input B) 0.1-1.2
READ/HOLD READ
GROUND SWITCH CHASSIS
3.3.1 Meter Calibration
Press the 0° CAL button. Adjust the screwdriver control on the front panel until
the meter reads 000.00°. Press the 360° CAL button. Adjust the screwdriver
control on the front panel until the meter reads 360. 00°.
3.3.2 100 Hz Sine Wave Check
Connect the output of the low distortion oscillator to both inputs of the phasemeter,
using the set of matched cables, Set the oscillator frequency to 100 Hz, output
amplitude to 0. 1 volts RMS, Depress the 0° CAL button momentarily, then release;
meter should read 000. 00° +0.05°. Depress the 360° CAL button, then release;
meter should read 360,009 +0.05°. Repeat procedure at 20 Hz, 1 KHz and 10 KHz,
3.3.3 10 Hz Sine Wave Check
Repeat procedure of 3.3.2 at 10 Hz; meter tolerance is +0. 2°,
3.3.4 100 KHz Sine Wave Check
Repeat procedure of 3,3,2 at 100 KHz; meter tolerance is +0. 2;
3.3.5 High Frequency Sine Wave Check
Connect the outputs of the 10 MHz oscillator to the phasemeter inputs, using the
matched cables, Set the oscillator frequency to 200 KHz.and both output voltages
to 0,1 volts RMS, Observe the phase reading.
Reverse the two inputs, Observe the phase reading. The Total™ of both readings
should equal 360, 00° +2. 8° at 200 KHz. Repeat this procedure at 500KHz, 1 MHz,
2MHz and 5 MHz. Tolerance of the total reading is +7° at 500 KHz, +14° at 1 MHz,
28° at 2 MHz and +70° at 5MHz. Disconnect the oscillator.
3.3.6 100 Hz Square Wave Check
Set the phasemeter WAVEFORM switch to™, . Connect the outputs of the square
wave Signal source to the phasemeter inputs. (If a signal source with two outputs
is not available, proceed as follows: Connect a single square wave source to the
input of a suitable balancing transformer, as described in 3.2.c. The output im-
pedance (Z) of the signal source should approximately equal the input Z of the
transformer. Some transformers require a load on their outputs equal to their
output Z. Check manufacturer! s specifications), Set the signal source output
voltage for 1 voit peak to peak at the phasemeter inputs. Observe the phase read-
ing. Reverse the inputs and observe the reading. The Total* of both readings
* If both readings are in error by E degrees, the total will be off by (2xE) degrees.
Therefore the tolerance of the total is twice the specified accuracy. (See Section 1, 2)
13

Model 6500 Phasemeter
SLES ENE TSG LE IEEE TESTIS DL LEY ELLE LIS GISELE, SITY TT ITT TT ESE TT TR SS TTT
should equal 360° £0.1°. Repeat this procedure at 10 Hz, 1 KHz and 5 KHz, Total
of the two readings should be 360° +0. 1°
3.3.7 20 KHz Square Wave Check
Repeat the procedure of 3. 3.6 at 20 KHz; total of the two readings should be
360° +0, 2°.
3.3.8 High Frequency Square Wave Check
Repeat the procedure of 3.3.6 at 200 KHz, 500 KHz, 1 MHz, 2 MHz, and 5 MHz.
Tolerance of the total reading from 360° should be +2. 8° at 200 KHz, +7° at
500 KHz, +14° at 1 MHz, +28° at 2 MHz and +70° at 5 MHz. Disconnect square
wave source (and transformer if applicable).
3.3.9 Analog Output Check
Set the phasemeter WAVEFORM switch to “WV . Connect the sine wave outputs
of the variable phase generator to the phasemeter inputs. Set the generator
frequency to 1 KHz, output voltage to 1 volt RMS, Connect the DVM to the analog
output, Check to see that the analog output is approximately-10 mv /degree for
any phase angle between 0° and 360°,
3.3.10 Read/Hold Control Check
Set the output angle of the variable phase generator to some angle between 0° and
360°, Press the front panel HOLD button. Remove the phasemeter inputs. The
last meter reading should remain stored until the READ button is pressed,
NOTE
The analog output voltage will still vary with a change
in the input phase angle, even though the meter display
is in the HOLD mode.
3.3.11 Optional BCD Output Check
The operation of the phasemeter's optional BCD output can be checked by connecting
the variable phase generator to the phasemeter inputs, and measuring the logic
levels on the respective pins for the meter readings listed in Table 1, Page 10, It
may be nece ssary to use a large angle to measure the BCD outputs of phase angles
less than 1,0°, for example, 200,01, 200.02, etc. Be sure to connect the common
or ground lead of the DVM to the BCD output Digital Ground (pins E, L or §),
To check the ''Conversion Complete" output (pin a), the logic level should remain
“high! when, the meter reading is stable, To check the ''low'" condition, depress
either the 0° CAL or 360° CAL button; the level at pin a should go "low" while the
meter reading is converting,
To check the 'Transfer Inhibit" input, place the READ/HOLD switch in the HOLD
mode,
Vary
the
phase
angle
of
the
generator,
The
meter
reading
should
not
change.
Connect
a
jumper
from
pin
b
to
pin
E,
LorS
and
vary
the
phase
angle
of
the generator; the reading should vary as the phase angle is varied,
i4

Section 4 - Circuit Description
SE
TS
SECTION 4
CIRCUIT DESCRIPTION
4.1 SYSTEM OPERATION
SYMMETRY a
CONTROL
—
7
an =f 1
wNeuT,
400
rex.
|
2)
GE}
F—farremuaron
tnrur
swircren
RR
|
‘uvear
ANP
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|
ame
ve mld # cRs20 CRSZI
} | one —
Jcouranaron| —t
a
ampLiTuDE
|
>
rue
OFF
active
,
7A)
verecton
f-———-——
2
~
FLOP
ane
Fuser
-
FOr CARERS
140)
—
~——_
inpur
ce00
rex
nye
{
wer
6S
1}
[ATTENUATOR
Input
nee.
oT
ee
paca
+
7
'
os
a
Deas
ma
he
WOT
CARRIERS
eee
®
ANALOG
OC
=
]
4
©
output
srmeTaY
contra.
oo
-
ee
|
.00F
ike
%
Figure 6, Simplified Block Diagram
A
simplified
block
diagram
of
the
phasemeter
circuit
is
shown
in
Figure
6,
A
reference
signal
is
applied
to
the
A
input
and
the
signal
to
be
measured
is
applied
to
the
B
input.
Each
input
signal
goes
through
a
coupling
capacitor,
an
attenuator,
a
high
impedance
(FET)
amplifier
for
isolation
and
a
switched
filter
that
reduces
any
high
frequency
signals
or
noise.
Each
signal
is
then
fed
to
a
high
speed
com-
parator.
The
comparator
detects
the
point
where
the
input
signal
crosses
the
zero
axis,
and
produces
a
square
wave.
The
output
of
each
comparator
is
then
used
to
trigger
a
bi-stable
flip
flop.
The
output
of
the
flip
flop
is'a
square
wave,
with
a
duty
cycle
that
is
proportional
to
the
time
between
the
two
trigger
inputs.
The
DC
average
of
the
accurately
clamped
flip-flop
output
is
displayed
by
a
digital
meter,
and
corresponds
to
the
phase
angle,
in
degrees,
between
the
two
input
Signals,
15

Model 6500 Phasemeter
4.2 ATTENUATOR AND FET INPUT AMPLIFIER (see figure 6)
To
WAVEFORM
+Ev SWITCH
eiiaeediatientintantiantiaadtantientietion Aycrazo
c400 |
To
(o——— SWITCHED
Saat FILTER
i
J
i # ag
INCORRECT
| cRa21 WN + > AMPLITUDE
| DETECTOR
cra23
iv
$401 = | -8v
Figure 7. Attenuator and Fet Input Amplifier
{NOTE: since both channels are similar up to their comparator outputs, we shall
limit part of the circuit description to channel A. )
The input signal first goes through an AC coupling capacitor, C400, that is matched
with C200 for equal low frequency phase shift. The signal is then fed to an attenua-
tor that provides a constant input impedance on all three ranges. Capacitors C401
through C411 are used for broadbanding and to keep the impedance the same on all
three ranges at high frequencies, Diodes CR420 and CR421 on the attenuator
output prevent damage of the FET amplifier by excessive input signal levels,
The FET amplifier is a high impedance non-inverting amplifier with gain, and
consists of an input stage Q420, a balanced differential stage Q421 and Q423, a driver
Stage Q424, and an emitter follower Q425. The amplifier provides both isolation
and gain between the attenuator and the switched filter (section 4,4.) A degenera-
tive path from the amplifier output through CR422, CR423 and R443 limits the
amplifier gain and output swing.
4.3 INCORRECT AMPLITUDE DETECTOR (see figure 8)
The incorrect amplitude detector monitors the output of the Fet amplifier. When
the input signal voltage falls within the attenuator voltage range selected, the
positive DC voltage developed on C464 opens diodes CR 464 and CR465, so that
the current in R475 turns Q461 on, turning off Q460, and turning off the LED Set
Range Indicator. When the input signal exceeds the upper limit of the attenuator
range, the negative DC voltage developed across C463 is sufficient to turn on
CR466, turning off Q461 and turning on the LED. When the input signal falls below
the selected range Q461 is shut off by the current from the -8v supply through
R478, CR464 and CR465. Diode CR465 is in series with CR464 for temperature
compensation,
16

Section 4 - Circuit Description
+8V
+8V +8V
(i Sex: ance
Pres INDICATOR
R467 CR462 CR466
+t- I 9460
c463 cR465
ee
FROM FET
(PUT AMP OUTPUT >?
C464
CR464
ss
tO
<—
—8Vv
R470 CR463
R476
Figure 8. Incorrect Amplitude Detector
4.4 SWITCHED FILTER AND HOT CARRIER LIMITER (see figure 9)
R52i R522 R
FROM OUTPUT : pee TO
OF FET AMPLIFIER EINEAR
csai
e522
R520
cRS2i
2520 R647
9540
FROM OUTPUT
a 841 OF 1540
540
R544 c5al C595,
jomss =
OF —
(CHANNEL 8) my
Figure
9,
Switched
Filter
and
Hot
Carrier
Limiter
The
switched
filter
is
a
low
pass
filter
that
is
used
to
reduce
excessive
high
fre-
quency
noise
at
input
frequencies
below
200
Hz.
The
control
signal
is
taken
from
the
output
of
IC540.
At
low
frequencies,
the
control
signal
charges
C541,
turning
on
Q541
and
Q540.
This
drives
the
base
of
Q520
plus,
providing
a
path
to
ground
for
C521
and
C522.
17