Simpson 390-2 User manual

Model 390-2
Volt-Amp-Wattmeter
INSTRUCTION MANUAL

2
About this Manual
Tothebestofourknowledgeandatthetimewritten,theinformationcontainedinthis
documentistechnically correct and the proceduresaccurateand adequate to oper-
atethis instrumentincompliance with itsoriginal advertised specifications.
Notes and Safety Information
ThisOperator’sManualcontainswarning headings which alerttheuser to checkfor
hazardous conditions.These appear throughout this manual where applicable and
aredefinedbelow.Toensurethesafetyofoperatingperformanceofthisinstrument,
theseinstructions mustbeadhered to.
Warning, refertoaccompanyingdocuments.
Caution, risk of electric shock.
Technical Assistance
SIMPSON ELECTRIC COMPANY offers assistance Monday through Friday
7:30 am to 5:00 pm CentralTime contact Technical Support or Customer Service
at [phone].
Internet: http://www.simpsonelectric.com
Warranty and Returns
SIMPSONELECTRICCOMPANYwarrantseachinstrumentandotherarticlesmanu-
facturedbyitto be free from defectsinmaterialand workmanship under normal use
and service, its obligation under this warranty being limited to making good at its
factory or other article of equipment which shall within one (1) year after delivery of
such instrument or other article of equipment to the original purchaser be returned
intact to it, or to one of its authorized service centers, with transportation charges
prepaid, and which its examination shall disclose to its satisfaction to have been
thusdefective;thiswarrantybeingexpresslyinlieuofallotherwarrantiesexpressed
or implied and of all other obligations or liabilities on its part, and SIMPSON ELEC-
TRICCOMPANY neither assumes nor authorizesany other persons to assumefor
it any other liability in connection with the sales of its products.
This warranty shall not apply to any instrument or other article of equipment which
shall have been repaired or altered outside the SIMPSON ELECTRIC COMPANY
factory or authorized service centers, nor which has been subject to misuse, negli-
genceoraccident,incorrect wiring by others, orinstallationorusenot in accord with
instructions furnished bythe manufacturer.
This manual represents your meter as manufactured at the time of publication. It
assumes standard software. Special versions of software may be fitted, in which
caseyou will be providedwith additional details.
Theapparatushasbeendesigned andtestedin accordancewithEN61010-1,“Safety
RequirmentsforElectricalEquipmentforMeasurement,Controland Laboratory Use.”
This operationg guide contains information and warnings that must be followed by
theuser to ensure safeoperation and to maintaintheapparatus in asafecondition.
We reserve the right to make changes and improvements to the product without
obligation to incorporate these changes and improvements into units previously
shipped.
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3
This Instrument is designed to prevent accidental shock to the operator when
properly used. However, no engineering design can render safe an instrument
which is used carelessly. Therefore, this manual must be read carefully and
completely before making any measurements. Failure to follow directions can
result in serious or fatal accident.
SHOCK HAZARD: As defined in American National Standard, C39.5,
Safety
Requirements for Electrical & Electronic Measuring & Controlling Instrumenta-
tion , a shock hazard shall be considered to exist at any part involving a potential
in excess of 30 volts RMS (sine wave) or 42.4 volts DC or peak and where a
leakage current from that part to ground exceeds 0.5 milliampere, when mea-
sured with an appropriate measuring instrument defined in Section 11.6.1 of
ANSI C39.5.
NOTE: The proper measuring instrument for the measurement of leakage cur-
rentconsists essentially of anetwork of a1500 ohm non-inductive resistorshunted
by a 0.15 microfarad capacitor connected between the terminals of the measur-
inginstrument. The leakage current is that portion of thecurrent that flowsthrough
the resistor. The Simpson Model 229-Series 2 AC Leakage CurrentTester meets
the ANSI C39.5 requirements for the measurement of AC leakage current and
can be used for this purpose. To measure DC Leakage current, connect a 1500
ohm non-inductive resistor in series with a Simpson 0-500 DC microammeter
and use this as the measuring instrument.

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Contents
1. INTRODUCTION ............................................................................... 5
1.1 General................................................................................................5
1.2 Description ..........................................................................................5
1.3 Technical Data.....................................................................................5
2. INSTALLATION .................................................................................. 6
2.1 Unpacking ...........................................................................................6
2.2 Power Source Requirements ..............................................................6
2.3 Installation ...........................................................................................6
3. CONTROLS,CONNECTORS&INDICATOR...................................... 6
3.1 Description ..........................................................................................6
4. OPERATION...................................................................................... 8
4.1 Safety Precautions ..............................................................................8
4.2 Zero Setting Of Meters.........................................................................8
4.3 Input Lead Connections ......................................................................9
4.4 DC Voltage Measurements 0-150V, 0-300V .......................................9
4.5 AC Voltage Measurements, 0-150V, 0-300V.......................................9
4.6 AC Current Measurements, 0-3A, 0-15A ............................................9
4.7 AC Watts 0-300, 0-1500, Using Break-In Plug (Line Voltage 0-150) 11
4.8 AC Watts 0-600, 0-3000, Using Break-In Plug (Line Voltage 0-300) 12
4.9 Determining Power Factor .................................................................12
4.10 Use Of Wattmeter With Two & Three Phase Circuits .........................13
4.11 Troubleshooting.................................................................................13
5. THEORY OFOPERATION .............................................................. 14
5.1 AC And DC Voltmeter Circuit.............................................................14
5.2 AC Ammeter Circuit ...........................................................................14
5.3 AC Wattmeter Circuit .........................................................................15
5.4 Schematic Diagram ...........................................................................15
5.5 Break-In Plug.....................................................................................15
6. MAINTENANCE .............................................................................. 16
6.1 Warranty ............................................................................................16
6.2 Shipping ............................................................................................16
6.3 Care...................................................................................................16
7. ORDERINGINFORMATION ANDSCHEMATIC DIAGRAM ............. 16

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1. INTRODUCTION
1.1 General
TheSimpson Model 390-2Volt-Amp-Wattmeter(hereafter referredto as theModel
390-2 or as the Instrument), has an AC voltmeter, DC voltmeter, AC ammeter and
AC wattmeter all in one compact, convenient instrument.
1.2 Description
This versatile Instrument is extremely rugged and of the highest quality construc-
tion. The full size three-inch meter is of the dynamometer type with a moving coil
armature operating within two field coils. The readings are clearly marked on two
arcs of the scale, one for volts and amperes and one for watts. An unusual and
practical feature is the uniform wattmeter scale of equal divisions which permits
more accurate readings.
A special break-in plug and lead assembly simplifies making connections to
cord-connected devices. The Instrument can also be used with special test leads
when the break-in plug is not used. The panel designations make the connec-
tions for the various ranges apparent. All markings are screened on the panel
with epoxy white enamel for maximum legibility. The ammeter connectors are
identified with a red dot and the voltmeter connectors are identified with a white
dot.
Approximately 2% should be added to the readings. The accuracy of the Model
390-2 is 5% or better of full scale reading. The errors due to phase angle and
frequency are so small that they can be disregarded within the normal frequency
range of 50 to 144 Hz. Approximately 2% should be added to the readings
obtained with 25 Hz current. The current loss in the Model 390-2 is very low and
has no appreciable effect on the readings.
1.3 Technical Data
1. DCVOLTS:
Ranges: 0-150 and 0-300 volts
Resistance: Approximately 50 ohms/volt
Accuracy: 5% of full scale
2. ACVOLTS:
Ranges: 0-150 and 0-300 volts
Resistance: Approximately 50 ohms/volt
Accuracy: 5% of full scale
3. AMPERES (AC only):
Ranges: 0-3 and 0-15 amperes
Voltage Drop: Approximately 0.5 volts
Accuracy: 5% of full scale
4. WATTS (AC only):
Ranges:
(150 VAC): 0-300 and 0-1500 watts
(300 VAC): 0-600 and 0-3000 watts
Phase Error: Negligible at 60 Hz, 2% at 25 Hz
Accuracy: 5% of full scale

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5. FREQUENCY: 50-133 Hz, no correction required
RESPONSE: 25 Hz, add 2% to reading
6. METER SIZE: 3 inches
7. DIMENSIONS:
Height: 5-7/8" (149mm)
Width: 3" (76mm)
Depth: 3-1/2" (64mm)
8. WEIGHT: 2-1/2 lbs. (1.13Kg)
2. INSTALLATION
2.1 Unpacking
Examine the shipping carton for signs of damage before unpacking. If shipping
carton is in good condition, unpack and inspect the Instrument for damage in-
curred during shipment. If damaged, notify the carrier and supplier, and do not
use the Instrument. If the Instrument appears to be in good condition, read
Operator’s Manual in its entirety. Become familiar with the Instrument as in-
structed in the manual; then check the electrical performance.
Save the shipping carton and packing materials for future storing or shipping of
the Instrument.
2.2 Power Source Requirements
No supply source is required. The Instrument is energized by the circuit being
measured.
2.3 Installation
The Instrument can be set horizontally or vertically; however, horizontal position
will assure maximum accuracy.
3. CONTROLS, CONNECTORS & INDICATOR
All operating controls, connectors and indicator are shown in Figure 3-1. Be-
come familiar with each before operating the Instrument for the first time.
3.1 Description
Description of the controls, connectors and indicators are listed in Table 3-1.The
numbers in Figure 3-1 correspond with the numbered items listed in Table 3-1.
Table 3-1. Controls, Connectors and Indicator
1. 15 Amp Jack (red dot): Load side of current coil for 15 Amp range. Also
common for 1500-3000 watt range wattmeter
connection.
2. 3 Amp Jack (red dot): Load side of current coil for 3 amp range. Also
common for 300-600 watt range wattmeter con-
nection.

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3. ±Current Jack
(black dot): Source side of current coil.
4. AMPS Pushbutton: When depressed, provides an AC current indica-
tion in amperes on the meter if a load is con-
nected.
5. WATTS Pushbutton: When depressed, provides an AC power con-
sumption indication in watts on the meter if a
load is connected.
6. ±Voltage Jack
(black dot): Voltage coil connection to one side of power line.
7. 150 VOLTS Jack
(white dot): Voltage coil connection for 150 volt range. Also
common for 300-1500 watt range wattmeter con-
nection.
8. 300 VOLTS Jack
(white dot): Voltage coil connection for 300 volt range. Also
common for 600-3000 watt range wattmeter con-
nection.
9. Zero Adjust: Mechanically sets the meter pointer to zero with
the Instrument disconnected.
10. Meter: Provides readings on two scale arcs, one for volts
and amperes, and one for watts.
11. Break-In Cable
Assembly: Facilitates connections to cord-connected de-
vices. See paragraph 4.3 for special test lead set
with alligator clips.
Figure 3-1. Controls, Connectors and Indicator
10
9
8
7
1
2
3
6
54
11

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4. OPERATION
All power line circuits contain voltages constituting a shock hazard that can be
lethal (refer to Shock Hazard definition on page 3 of manual). This Instrument
was designed to prevent accidental shock to the operator. However, exceeding
its capabilities, or using it carelessly, can be dangerous. Review the Safety
Precautions listed below. Make sure you understand them and observe them
when using this Instrument.
This section of the manual contains all the information related to operation of the
Instrument.
4.1 Safety Precautions
1. The Model 390-2 is intended for use by personnel who are qualified to
recognize shock hazards and trained in the safety precautions needed to
avoid possible injury. Refer to the “SHOCK HAZARD” definition on page 3 of
this manual.
2. Do not work alone when measuring where a shock hazard might exist. Notify
someone that you are making, or intend to make, such measurements.
3. Locate all voltage sources and accessible current paths before making cir-
cuit connections. Be sure the equipment being tested is properly grounded
(if that is its normal mode of operation), and that its fuse(s) are of the correct
type and rating. Make certain the test leads are connected to the proper input
jacks before applying power.
4. Make sure work area, as well as hands and shoes, are dry.
5. Avoid making tests and measurements under humid, damp, or other envi-
ronmental conditions that could affect the dielectric withstanding voltage of
the test equipment.
6. Do not touch “live circuits” or any object that could provide a current path to
the common side of the circuit under test or power line ground.
7. Use a 3-wire power line outlet that is correctly wired in accordance with the
latest National Electrical Code. If you are not certain that the power outlet
meets these requirements, use a 3-wire to 2-wire adapter plug, and ground
the wire from the adapter to a known good earth ground.
8. When using the special test lead set without the break-in plug, shut off the
power to the circuit before making clip connections.
9. When testing a 240-VAC line-operated device, make up a 120-240 VAC
adapter set as shown in Figure 4-4 on page 13. Be sure the outlet used is
correctly wired as discussed in number seven above.
4.2 Zero Setting Of Meters
1. Before you use your Instrument, be sure that the pointer is on zero when
there is no power applied. A zero adjust screw is located directly below the
meter scale (see Figure 3-1 on page 7).
2. Use a screwdriver to rotate the screw either clockwise or counterclockwise
until the knife-edge pointer rests over the zero indication at the left hand side
of the scale.
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4.3 Input Lead Connections
Always make the connections to the Model 390-2 in accordance with the direc-
tions given in the following paragraphs before making connections to the power
source.
When testing line-operated devices, always use the Break-In Cable Assembly
supplied with the Instrument (see Figure 4-1 on page 7). Make up a cable adapter
set for use on 240 VAC line-operated devices (see Figure 4-3 on page 12).
If unable to use the Break-In Cable Assembly, use the special test lead set. For
line voltages up to 150 volts, connect the ±V and the 150V jacks across the line
and the ±A and the 3A or 15A jacks in series with the load for 300 and 1500 watt
ranges respectively. The leads are color coded to match the colored dots of the
respective jacks (see Figure 4-2). For line voltages between 150 and 300 volts,
connect the ±V and the 300V jacks across the line, and the ±A and the 3A or 15A
jacks in series with the load for the 600 and 3000 watt ranges respectively.
4.4 DC Voltage Measurements 0-150V, 0-300V
The voltmeter may be used to measure DC voltages, but NOT DC current or
power. For measuring DC voltages, follow the same procedure as for AC voltage
measurement, as discussed in the following paragraph 4.5.
4.5 AC Voltage Measurements, 0-150V, 0-300V
1. Connect the leads from the Break-in Plug Assembly according to color as
shown in Figure 4-1. Connect the white lead to the jack marked 150V when
testing 120 volt devices, or to the jack marked 300 V when testing 240 volt
devices.
2. Insert the Break-In Plug into the outlet of the AC line to be measured. See
paragraph 4.3 for 240 volt line measurement, or use of special test leads.
3. Read the voltage on the top arc of the meter scale, using the figures 0-150 for
the 150V range and 0-300 for the 300V range. The first heavy line above
zero represents 25 on the 0-150 range and 50 on the 0-300 range. When the
object under test is plugged into the Break-In Plug, the voltmeter will indicate
if there is a voltage drop in the line. The voltmeter can also be used to
indicate voltage drop between no load and full load operation.
4.6 AC Current Measurements, 0-3A, 0-15A
NOTE: DC current will damage the Instrument transformer.
1. Connect the leads from the Break-In plug according to color as shown in
Figure 4-1 on page 10. To use the 3A range, connect the red lead to the
terminal marked “3A”. Use the 0-300 scale and drop two zeros (divide by
100).
2. When the 15A range is to be used, connect the red lead to the terminal
marked “15A” (use the 0-150 scale and divide by 10).
When the appropriate value of current is unknown, always use the higher range
first as a protection to the meter.

10
Figure 4.1 Break-In Plug Connections, 150V, 3A and 300W Ranges
3. Insert the Break-In Plug into 120V power outlet (in the AC line), or follow
procedures as given in paragraph 4.3 for 240V power.
4. Plug the device to be checked into the Break-In Plug as shown in Figure 4-1.
5. Press the AMPS pushbutton.
NOTE: Failure to fully depress the AMPS pushbutton may result in an erroneous
reading.
6. Read the current value on the top arc of the scale. For the 3A range, use the
figures 0-300, and drop two zeros (divide by 100). Use the black digits to
indicate the decimal fraction. Repeat the procedure using the figures 0-150
for the 15A range (divide by 10). The first heavy line above zero represents
0.5A on the 3A range, and 2.5A on the 15A range.
7. Special test leads can be substituted for the Break-In Plug when necessary
(paragraph 4.3). Open (break) the circuit to be measured and connect the
free ends of the test leads across the open circuit.
8. Press the AMPS pushbutton to read the current.
9. Restore the circuit continuity when test is complete.
10. To check the load on the entire line, remove the fuse from the fuse box, or
place the circuit breaker in the OFF position (depending upon the equipment
used).
15A
BREAK-IN
PLUG
WHITE
GN
±
BLACK
RED
LOAD
0-3A
0-15A
V
3A
A
VOLTS
NORMAL
PRESS
FOR
MODEL 390 2
300W
3000W
150V
300V
1500W
600W
0-300V
0-150V
BLACK
CABLE
LINE
±
N
±
±
V
O
L
T
S
-
A
M
P
E
R
E
S
W
A
T
T
S
50
75
100
125
150
100
150
200
250
300
1000
500
200
100
2000
1000
400
200
3000
1500
600
300
0

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Figure 4.2 Model 390-2 and Special Test Lead Set Application
11. Connect the Model 390-2 as an ammeter in series with the line and the load
using the Special Test Lead Set, or as a wattmeter (see Figure 4-2).
12. To extend the current range of the Model 390-2 use a current transformer. A
current transformer with a ratio of 10 to 1, when used with the 3 ampere
range, will permit a reading of 30 amperes. Multiply the readings on the 3A
range by 10. Current transformers with other ratios may be used in the same
way if the scale readings are multiplied by the ratio of the transformer.
4.7 ACWatts 0-300, 0-1500, Using Break-In Plug
(LineVoltage 0-150)
1. Connect the leads from the Break-In Plug according to their color as shown
in Figure 4-1.
NOTE: When the red lead is connected to the 3A terminal and the white lead is
connected to the 150V terminal as shown, the connecting line on the panel
between the 150V and 3A terminals indicates that the 300 watt range is being
used. When the red lead is connected to the 15A terminal, the range is 1500
watts, as indicated by the line on the panel between the 150V and 15A terminals.
2. Insert the Break-In Plug into an AC outlet.
3. Plug the device to be checked into the Break-In Plug as shown in Figure 4-1.
4. Press the WATTS pushbutton all the way down.
15A
6V
3A
6A
VOLTS
NORMAL
PRESS
FOR
MODEL 390 2
300W
3000W
150V
300V
1500W
600W
V
O
L
T
S
-
A
M
P
E
R
E
S
W
A
T
T
S
50
75
100
125
150
100
150
200
250
300
1000
500
200
100
2000
1000
400
200
3000
1500
600
300
0
LOAD
SOURCE

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5. Read watts directly on the lower arc of the scale. Use the figures correspond-
ing to the range being used.
6. In cases where the momentary load exceeds the limits of the 1500 W range,
such as the starting current of a motor, the white lead from the Break-In Plug
may be connected to the 300V terminal and the 3000W range used.
4.8 ACWatts 0-600, 0-3000, Using Break-In Plug
(LineVoltage 0-300)
1. An adapter is required to connect from 120V to 240V line (see paragraph
4.3). The Break-In Plug will not connect directly into a 240V line. Therefore,
it is necessary to construct an adapter plug. Refer to Figure 4-3 for adapter
make-up and test connections.
Figure 4-3. Break-In Cable Assembly and Cable Adapter Set
2. Connect the white lead from the Break-In Plug (see Figure 4-1) to the 300V
meter terminal. Connect the black leads to the ±V and ±A terminals.
3. Connect the red lead from the Break-In Plug to the 3A terminal. The line on
the panel between the 300V and 3A terminals indicates that the 600 watt
range is being used. When the red wire is connected to the 15A terminal the
range is 3000 watts as indicated by the line on the panel connecting the
300V and 15A terminals.
4. Insert the Break-In Plug into the 240V adapter socket and the adapter plug
into a 240 VAC source.
5. Plug the appliance to be checked into the female adapter and the male end
of the adapter into the Break-In Plug.
6. Press the WATTS pushbutton all the way down.
4.9 Determining Power Factor
1. In an AC circuit containing only resistance, such as a toaster, the power will
be approximately equal to the product of the volts and amperes. However,
when the circuit contains reactance, such as a motor, the power will be less
than the product of the volts and amperes because of the power factor.
2. The power factor of a circuit can be determined with the Model 390-2 in the
following manner. Take the voltage, current and power readings of the circuit
under test. Since unity power factor results when the power is equal to the
PLUG INTO 240 VAC OUTLET
120 VAC FEMALE
CONNECTOR
BREAK-IN PLUG
120 VAC MALE
PLUG
240 VAC FEMALE
CONNECTOR
PLUG IN APPLIANCE HERE
240 VAC MALE
PLUG

13
product of the volts and amperes, the power factor of the circuit under test is
the ratio of the power reading on the meter to the product of the volts and
amperes. For example, if the line voltage is 120, current 2.5 amperes, and
power indicated by the meter is 225 watts, the power factor is equal to
100 x 225 = 75%
120 x 2.5
4.10 Use OfWattmeterWithTwo &Three Phase Circuits
Figure 4-4 shows the connections for measuring power in a single phase, two or
three phase, three-wire circuit using two Model 390-2 wattmeters. If a reading is
obtained on both meters, the true power is the sum of the two readings. If the
pointer of one meter deflects to the left of zero, it means that the power factor is
less than 50%, and the connection to the voltage terminals for that meter should
be reversed. The reading then obtained should be subtracted from the reading of
the other meter. If the power factor is exactly 50%, one meter will indicate zero. If
only one Model 390-2 is available, connect it successively in the two positions as
shown in Figure 4-4.
Figure 4-4. Connections for Measurement in Single,
Two and Three Phase AC Three-Wire Circuits
4.11 Troubleshooting
You will find many uses for the Model 390-2 in checking the three simple tests
which diagnose most cases of electrical trouble: line voltage, current drain and
power consumption, . High current drain and high power consumption generally
indicate shorted turns in a motor, too heavy a load or shorted sections in ele-
ments of heaters, irons, etc. This also might be indicated by an excessive drop in
line voltage when the device is connected to a power outlet. A drop in line
voltage may also indicate inadequate or overloaded supply lines. No current
would indicate an open cord, switch or circuit in the device being checked. These
15A
V
3A
A
VOLTS
NORMAL
PRESS
FOR
MODEL 390 2
300W
3000W
150V
300V
1500W
600W
±
±
V
O
L
T
S
-
A
M
P
E
R
E
S
W
A
T
T
S
50
75
100
125
150
100
150
200
250
300
1000
500
200
100
2000
1000
400
200
3000
1500
600
300
0
15A
V
3A
A
VOLTS
NORMAL
PRESS
FOR
MODEL 390 2
300W
3000W
150V
300V
1500W
600W
±
±
V
O
L
T
S
-
A
M
P
E
R
E
S
W
A
T
T
S
50
75
100
125
150
100
150
200
250
300
1000
500
200
100
2000
1000
400
200
3000
1500
600
300
0
3-PHASE
SOURCE LOAD
NEUTRAL,
IF 1 OR 2 PHASE
L
L
L
1
2
3

14
same indications apply to refrigerators, oil burners, washing machines, ventilat-
ing fans, air conditioning systems, air compressors, water pumps, vacuum clean-
ers, heaters, irons, toasters, waffle irons, food mixers, lighting circuits, heat lamps,
radios, televisions and all devices which use a motor or transistorized circuitry.
The wattmeter section may also be used as an indicator for problems with solid-
state radios, stereo sets or television receivers. A high wattage drain would
indicate a shorted transistor or improper bias, while a low wattage drain would
indicate an open transistor or circuit. Many manufacturers include possible clues
pointing to faulty circuits with certain wattage readings.
5. THEORY OF OPERATION
5.1 AC And DC Voltmeter Circuit
Figure 5-1 shows the circuit used when making voltage tests.The multiplier resis-
tors for the 150V and 300V ranges are wound to match each meter.The WATTS
and AMPS pushbuttons are in the normal (out) position and the contacts of these
switches complete the circuit.
Figure 5-1. Simplified Voltmeter Circuit
5.2 AC Ammeter Circuit
Figure 5-2 shows the ammeter circuit used when the AMPS pushbutton is de-
pressed.This connects the meter to transformerT1.When all turns of the primary
winding are connected, the 3 ampere range is provided.The center tap provides
the 15 ampere range. Resistor R6 is used for calibration.
Figure 5-2. Simplified AC Ammeter Circuit
300V
R1 R2 R3 R4
R5
150V
S1
S2 +V
FIELDS
ARMATURE
–
–
S1 DEPRESSED
ARMATURE
FIELDS
R6
3A
15A
+A T1

15
5.3 ACWattmeter Circuit
Figure 5-3 shows the circuit used when the WATTS pushbutton is depressed and
the Break-In Plug is connected for the 300 watt range. In this position the arma-
ture of the meter is connected across the line through a series resistor and the
field coils of the meter are connected across the current transformer T1.
F igure 5-3. Simplified Wattmeter Circuit, 300 Watt Range
5.4 Schematic Diagram
The simplified circuits shown in Figure 5-1, 5-2 and 5-3 together with the AMPS
andWATTS pushbuttons,are combined in thecomplete schematic diagramshown
in Figure 7-1.
5.5 Break-In Plug
The special Break-In Plug supplied permits connections across the line for volt-
age measurements and in series with the load for current measurements.These
connections are clearly shown in Figure 4-1. Figure 5-4 shows the cable connec-
tions within the plug.
Figure 5-4. Cross Section of Break-In Plug, Showing Cable Connections
–
–
BREAK-IN PLUG
AC LINE
BLACK
RED
LOAD
+A 15A 3A
T1
R6
FIELDS
ARMATURE
R5
+V
150V
R1 R2
300V
WHITE
BLACK
BLACK LEAD RED LEAD
3 RDWIRE GROUND
RED LEAD
BLACK LEADS
WHITE LEAD (NEUTRAL)

16
6. MAINTENANCE
This Instrument contains internal voltages that constitute a SHOCK HAZARD
when connected to an AC line. Review the SHOCK HAZARD definition on page
3. Repairs should be performed only by qualified personnel, preferably a Simpson
Authorized Service Center.
The model 390-2 is constructed with high quality components. By providing rea-
sonable care, and following the instructions in this manual you can expect a long
useful service life from this Instrument.
6.1 Warranty
The Simpson Electric Company Warranty policy is printed on the inside cover of
this manual. Read it carefully before requesting a warranty repair.
NOTE: For all assistance contact your nearest Authorized Service Center. If you
wish to contact the factory directly, give full details of the problem and date of
purchase. Service data or shipping instructions will be sent to you promptly. If an
estimate of charges for non-warranty or other service work is required, a maxi-
mum charge estimate will be quoted. This charge will not be exceeded without
your prior approval.
6.2 Shipping
Pack the Instrument carefully and ship it prepaid to the proper destination. Insure
the shipment.
6.3 Care
The Model 390-2 has a rugged exterior, but its mechanism is delicate. Keep it
clean, free from continuous, severe vibration and avoid dropping it.
7. ORDERING INFORMATION AND
SCHEMATIC DIAGRAM
SimpsonAuthorizedService Centers have beenestablished throughout the United
States and Canada. To obtain repair or recalibration for any items of Simpson
equipment, contact the nearest Authorized Service Center and make arrange-
ments with them for the service you require.
Table 7.1 Instrument and List of Items Furnished
Quantity Description Part No.
1 Model 390-2 12481
1 Break-In Cord Assembly 10-863226
1 Operator’s Manual 5-118348
!

17
Table 7.2 Replacement Parts List
Reference
Number Description Part No.
T1 Transformer 1-112996
S1 Switch Assembly (Amps) 0-008818
S2 Switch Assembly (Watts) 0-008817
R3 Resistor 10-675575
R1,R2,R5 Resistor, Spool 10-675328
R4 Resistor, Bobbin 10-805200
Phenolic Case 3-360107
Meter Cover Assembly 10-560179
Lower Cover 3-230372
Banana Plug 5-131969
Pushbutton 3-310214
Break-In Cord Assembly 10-863226
Figure 7-1. Model 390-2, Schematic Diagram
–
R1—1 SPOOL
R2—1 SPOOL
R3—1 RESISTOR
R4—1 BOBBIN
R5—1 SPOOL
R6—1 SHUNT RESISTOR
+A
15A
3A
T1
R6
FIELDS
ARMATURE
+V
–
150V
300V R1 R2
R5
R4
R3
S2 WATTS
PRESS
S1 AMPS
PRESS

18
SIMPSON ELECTRIC COMPANY 853 Dundee Avenue
Elgin,IL 60120-3090 [phone] FAX [phone]
Printed in U.S.A. Part No. 05-118348 Edition 6, 2/03
Visit us on the web at: www.simpsonelectric.com