ISW 8000
4 DIGIT (8000 COUNTS)
DIGITAL WATTMETER
User Manual
INSTRUMENTS ET SYSTEMES
ZI des Radars, 12 rue Diderot
F-91350 GRIGNY FRANCE
tel. : 33 (0)1 69 02 31 56
Fax. : 33 (0)1 69 02 08 93
www.instruments-systemes.fr
01/03
ISW 8000
Specifications
(+18°C to +28°C)
Voltage
True RMS measurement
Ranges :
50.00 V 150.0 V 500.0 V
Resolution :
10 mV, 100 mV, 100 mV
Accuracy :
20 Hz-3 kHz : ±(0.4% + 5 digits)
DC:
±(0.6% + 5 digits)
Input impedance :
1 M // 100 pF
Bandwidth (-3dB) :
typ. 100kHz
Crest Factor :
max. 2 at full scale
Protection :
750 V peak
Current
True RMS measurement
Ranges :
160.0 mA 1.600 A 16.00 A
Resolution :
0.1 mA, 1 mA, 10 mA
Accuracy :
20 Hz-3 kHz : ±(0.4% + 5 digits)
DC :
±(0.6% + 5 digits)
Bandwidth (-3dB) :
typ. 100kHz
Crest Factor :
4 max. at full scale
Protection :
16 A fuse
Power
Ranges :
Resolution :
Accuracy :
Reactive Power
Ranges :
Resolution :
Accuracy :
8.000W 24.00W 80.00W 240.0W 800.0W
2400W 8000W
1 mW, 10 mW, 100 mW, 1W
±(0.5%+ 10 digits) from 20 Hz to 3 kHz
± (0.5% + 10 digits) in DC
8.00VAr 24.0VAr 80.0VAr 240VAr
800VAr 2400VAr 8000VAr
1 mVAr, 10 mVAr, 100 mVAr, 1 VAr
± (2 %+ 10 digits)
3
ISW 8000
Power Factor
Display of PF (0 to +1.00)
Resolution :
± 0.01
Accuracy :
± (2%+2 digits) (U and I sine wave and > 1/10 of
range)
Safety:
IEC 1010-1 Cat III 600 V
Power Supply:
Temperature
of Utilisation:
230 V ± 10% , 50-60 Hz, max. 7 W
Dimensions:
240 x 240 x 75 mm (L x W x H)
10-40 °C RH < 80 %
Weight:
about 1,3 kg
General:
4 Digits 25mm high LED Display plus sign
Rugged PVC Case with Handle
Buzzer indicates Overload
4
ISW 8000
Safety
INSTRUMENTS et SYSTEMES certifies that this instrument has left the
factory in perfect working order, both in operation and safety.
This instrument has been designed and manufactured with great care to bring
the user the best possible safety to the user. If the instrument no longer
functions properly or is damaged, it must be immediately disconnected from the
ac supply voltage, from the measured circuit voltages and returned for repair.
Opening, maintenance, repair and calibration must be carried out by qualified
and approved personnel.
Warranty
Provided it is used under the recommended conditions, this instrument is
guaranteed for a two year period against manufacturing defects and component
failure. This warranty applies to material and workmanship. The instrument
must be shipped back to an agreed repair centre. It will be repaired or replaced
without charge. Warranty repairs are made at the discretion of IES.
Maintenance
Your wattmeter does not need any specific maintenance. Whenever cleaning is
necessary, use a soft material. Avoid water or liquids that may penetrate inside.
Operation
Carefully unpack the instrument and make sure that it was not damaged during
transportation. Insert the power cord on the rear of the instrument and connect
to the ac supply. Switch power on by means of the power switch located on the
rear panel.
5
ISW 8000
6
ISW 8000
Symbols used
Indicates the possibility of a dangerous voltage
Refer to the user manual
Changing a fuse
Before you change a fuse, disconnect the instrument from
all possible dangerous voltages!
The defective fuse must be replaced using a fuse of the same type and value.
Two different types of fuses are used:
 100 mA time delay fuse on the ac power input circuit (T 100 mA)
 16 A semi time delay fuse in the ammeter circuit (16 A M)
Selectable Option
At start up, the instrument displays the software version and then selects the W
function (power measurement).
Buzzer
The buzzer indicates overrange conditions or manipulation errors. It can be
switched ON or OFF (toggle) in the following way:
Switch OFF the instrument. Hold the VAr key in and switch ON.
Release the VAr key when the W function is reached. The new state of
the buzzer is kept in memory until you decide to change it.
7
ISW 8000
About Electricity
RMS
VALUE
The RMS (Root Mean Square) value of a signal refers
directly to the power. The RMS value of a current which
circulates in a resistance equals the value of the DC current
which would produce the same heat in the resistance (same power). For this
reason, voltage and current measurements are carried out with RMS circuits.
The crest factor characterises the shape of a signal. It is the
ratio of the peak value to the RMS value (1.414 for a sine
wave). The electronic circuits that compute the RMS value
are generally sensitive to crest factor. The accuracy of measurements is
guaranteed only for moderate crest factors. The max. value of the crest factor is
given at full scale. Note that for smaller deviations, the crest factor may be
significantly higher.
CREST
FACTOR
In AC circuits, the power is not expressed as the product of
the voltage across the load by the current. If voltage and
current are sinusoidal, then the power is easily calculated
when the phase shift between them is known. Calculation of power parameters
becomes complex with non-sinusoidal waveshapes.
The ISW 8000A Wattmeter measures the average value of the instantaneous
power and remains accurate whatever the shape of the signal, provided it stays
inside the specification limits (frequency and crest factor).
POWER
When reactive elements are inserted in the generator/load circuit, the current
and voltage are phase shifted with respect to each other.
8
ISW 8000
For :
- a sine wave voltage of RMS value V
- a sine wave current of RMS value I
- a phase shift  between voltage and current
we can write the following relations:
Apparent Power (Volt Amperes)
Active Power (Watts)
Reactive Power (Volt Amperes Reactive)
VA = V x I
W = V x I cos 
VAr = V x I sin 
At some moments, voltage and current have the same polarity, at others the
signs are unlike. This indicates that some power is either expended in the load,
some is returned to the source. When the load is a pure reactance (perfect
inductor or capacitor) the power is only reactive and entirely returned to the
source.
The ISW 8000A Wattmeter measures all kinds of power and displays active or
reactive power. For sine waves it can also show the cosine of the phase angle.
9
ISW 8000
Input Terminals
The ISW 8000A Wattmeter uses four input terminals:
 a red plug and a blue plug ( SOURCE) which must be connected to the
voltage source.
 a red plug and a black plug (LOAD) which must be connected to the load.
Caution ! : the two red plugs are connected together inside the
instrument. The black plug is connected to the blue plug through
a low resistance path consisting of the resistive shunt and the
protective fuse.
No voltage should be applied between the two red plugs and
between the black and the blue plugs!
Function selection
Press the appropriate key to select the measuring function. At start up the
default measurement function is W (power measurement).
The available functions are:
W:
VAr :
PF :
V:
A:
effective power
reactive power
phase shift between voltage and current (cosine)
True RMS voltage (DC + AC). If pure DC is applied, the DC
indicator is lit and the polarity displayed.
True RMS current (DC + AC). If pure DC is applied, the DC0
indicator is lit and the polarity displayed.
Measuring Ranges
Whatever the selected function, voltage and current default to autoranging – e.g.
the ranges are automatically switched.
There are three ranges for voltage and three ranges for current:
50.00 V, 150.0 V & 500.0 V for the voltage
160.0 mA, 1.6000 A & 16.00 A for the current
The selected ranges are indicated by LED’s on the right of the display.
10
ISW 8000
To measure voltages
To measure voltages, select the V function. The voltage to be measured is
applied between the red plug and the black plug (LOAD). The range is
automatically selected.
If the voltage is pure DC, the DC indicator lights on and the indication of the
polarity is activated. A voltage is positive with respect to the black plug is a
positive voltage is present on the red plug. No sign is shown for a positive
voltage. A negative voltage is indicated by the - sign.
To measure currents
The internal circuits are protected by a fuse. If the fuse is blown, it must be
replaced with the same type. The fuse is located on the front panel. Make sure
that no voltages are applied to the front panel inputs before removing the fuse.
The current to be measured is applied between the blue plug (SOURCE) and
the black plug (LOAD). The range is automatically selected.
11
ISW 8000
If the current is pure DC, the DC indicator lights and the indication of the
polarity is activated. A current is positive if it flows from the black plug to the
blue plug (this is the polarity of a current delivered by a positive source
connected to the red source plug, to a load connected to the LOAD terminals).
No sign is shown for positive current. A negative current is indicated by the sign.
To measure power (1 Phase)
12
ISW 8000
The ISW 8000A Wattmeter can display true power (expressed in
W) or reactive power (expressed in VAr).True power may be
measured in DC or AC (inside the bandwidth limits). But reactive
power makes sense only AC.
True power measurement is selected by means of the W key, reactive power by
means of the VAr key. The displays shows the power received (or delivered) by
the load. It may be slightly smaller (or greater) than the power dissipated by the
source because of the small power lost in the voltage divider and the current
shunt.
True power
The true power is generally positive if the generator delivers power to the load.
But some loads (batteries, motors) have a strong back e.m.f. and send power
back to the source. The wattmeter senses the circulation of the energy in the
circuit. If the source delivers energy to the load, the power is considered as
positive. If the load sends energy to the source, the value is negative.
Reactive power
The reactive power is due to the phase shift between voltage and current. When
voltage and current are in phase, there is no reactive power. When voltage and
current are ±90° phase shifted, there is no active power.
Two Wattmeter Method (Balanced 3 Phase)
The power is easily measured on 3 Phase Network when no neutral wire is used
by means of the Two Wattmeter Method. This method is also useable on
Balanced Networks with a neutral wire.
Generally a single wattmeter is used with a switch. Two successive
measurements are accomplished. The total power is the sum of the two results.
13
ISW 8000
To measure power factor.
The source and the load are connected as for power measurements. If either
voltage or current is too low, the display shows moving signs " -- ".
The power factor is defined as the ratio:
PF = True Power / Apparent Power
The active power is measured by the instrument. The apparent power is
calculated as the V x I product (voltage x current=).
When both voltage and current are sine waves, the power factor represents the
phase shift between voltage and current :
PF = cos 
14