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GVT-427B User Manual
GVT-427B User Manual
Contents Page
Safety Terms and Symbols……………………….
Introduction……………………………………….
Preliminary Notes…………………………………
Panel Description………………………………….
Operation Method………………….……………..
Specifications……………………………………
…
Maintenance……………………………………….
Cleaning……………………………………….16
Troubleshooting……………………………….16
Interchangeable Parts…………………………….
1
4
5
6
10
13
16
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SAFETY TERMS AND SYMBOLS
These terms may appear in this manual or on the product:
WARNING. Warning statements identify condition or
practices that could result in injury or loss of life.
CAUTION. Caution statements identify conditions or
practices that could result in damage to this product or
other property.
The following symbols may appear in this manual or on the
product:
DANGER High Voltage
ATTENTION refer to Manual
Protective Conductor Terminal
(Ground) Earth Terminal
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GVT-427B User Manual
GVT-427B User Manual
FOR UNITED KINGDOM ONLY
NOTE: This lead/appliance must only be wired by
competent persons
WARNING: THIS APPLIANCE MUST BE EARTHED
IMPORTANT: The wires in this lead are coloured in
accordance with the following code:
Green/ Yellow: Earth
Blue: Neutral
Brown: Live (Phase)
As the colours of the wires in main leads may not correspond
with the colours marking identified in your plug/appliance,
proceed as follows:
The wire which is coloured Green & Yellow must be connected
to the Earth terminal marked with the letter E or by the earth
symbol
or coloured Green or Green & Yellow.
of 0.75mm² should be protected by a 3A or 5A fuse. Larger
conductors would normally require 13A types, depending on
the connection method used.
Any moulded mains connector that requires removal /replacement must be destroyed by removal of any fuse & fuse carrier
and disposed of immediately, as a plug with bared wires is
hazardous if a engaged in live socket. Any re-wiring must be
carried out in accordance with the information detailed on this
label.
The wire which is coloured Blue must be connected to the
terminal which is marked with the letter N or coloured Blue or
Black.
The wire which is coloured Brown must be connected to the
terminal marked with the letter L or P or coloured Brown or
Red.
If in doubt, consult the instructions provided with the equipment
or contact the supplier.
This cable/appliance should be protected by a suitably rated
and approved HBC mains fuse : refer to the rating information
on the equipment and/or user instructions for details. As a
guide, cable
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GVT-427B User Manual
GVT-427B User Manual
Introduction
GVT-427B is versatile AC voltmeter which is able to measure AC
voltage from ranges of 10 Hz to 1 MHz with full scale ranges from
300 µV to 100 V. The dB scale measures 1V as 0dB and ranges from
-90 dB to +41 dB. The 600 Ω (1mW) dBm scale ranges from -90 dBm
to +43 dBm.
The scales on the meter are graduated up to 1.1 (for +1dB) and these
extended scales are especially useful when measuring the
characteristics of audio amplifiers. In addition, both instruments can
give AC voltage output of approximately 0.1V in full scale from the
output terminals, and the measurements can therefore be monitored.
GVT-427B is a two channels voltmeter with isolated output for each
channel which enables it to be used as a two channels preamplifier.
Preliminary Notes
1. Chassis grounding terminal:
Make sure the chassis ground terminal is connected to the earth
before inserting the power plug into the main supply.
2. Maximum input voltage:
The voltmeter may be damaged if any input voltage exceeding
the specified voltage is applied to it. The specified voltage is
determined by adding the peak value of the input signal and the
superimposed DC voltage: 300 V for the 300 µV ranges, and
500 V for the 3 V to 100 V ranges.
3. Connection leads:
When the measured signal level is low (i.e. 300 µV) or the
measured signal source impedance is high, the input line is
susceptible to external noise. To resist the noise, shielded wires
or a coaxial cable should be used depending on the noise
frequency.
4. Full scales:
GVT millivoltmeter adopts a special extended scale which has a
reading range larger than the conventional full scale.
Conventional Extended
0 to 1.0 0 to 1.12
0 to 3.1 (3.2) 0 to 3.5
-20 to 0 dB -20 to +1 dB
-20 to +2 dBm -20 to +3.2 dBm
Note that the term “full scale” considers ‘1.0’ on the 0 - 1.12
scales as the rated value. The red ▼ mark is setting at ‘1.0’ on
the outermost scale.
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GVT-427B User Manual
GVT-427B User Manual
Panel Description
(1) Meter
Provide easy readings for both voltage and dB scales. For
GVT-427B, the black pointer is CH 1 and the red one is CH 2.
(2), (3) ZERO adjustment
Mechanical ZERO adjustment for the pointer. For GVT-427B,
the black-mark screw (2) is to adjust CH 1 pointer whereas the
red-mark screw (3) is to adjust CH 2.
(4), (5) CH 1 and CH 2 Range selector switch
10 dB step attenuator to select a desired voltage range for an
easy readout. When the mode switch (10) of GVT-427B is
DISENGAGED, CH 1 and CH 2 range can be selected
independently. However, when the mode switch is
DISENGAGED, the CH 2 range will change according to the
selected CH 1 irrespective of the CH 2 selector switch (5)
position.
(6), (7) CH 1 and CH 2 input connector respectively
The terminal where the measured signal is applied.
The maximum voltage of DC isolation is ±30 V (peak value)
(8), (9) CH 1 and CH 2 Output connector
respectively
Provide output signals when the meter is used as a preampl ifier.
When the range selector switch is setting at 100 mV, the output
voltage will be approximately equal to the input voltage.
However, when the range selector switch is setting to the next
higher or lower voltage range, the amplification factor is
decreased or increased by 10 dB respectively.
The maximum voltage of DC isolation is ±12 V (peak value)
(10) Mode switch
If this button is setting as DISENGAGED, the CH 1 and CH 2
range selector switches could select their related own ranges.
If the mode switch has been pressed, the CH 1 range selector
switch could select both CH 1 and CH 2 voltage ranges
simultaneously, and the CH 2 range selector switch would be
ineffective.
(11) Grounding selector switch
If this switch is setting to the upper position, the CH 1 and CH 2
Input Command Lines are isolated from each other, and they
are floated relative to chassis ground through a resistance of
100 kΩ. If the switch is setting the down position, both lines
could be connected directly to the chassis.
The maximum voltage of DC isolation is ±30 V (peak value)
(12) Power Indicator
(13) Power Switch
(14) Appliance AC Inlet
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Operation Method
A. Voltage measurement
1. Turn off the power.
2. Check the ZERO setting of the pointers. If there is offset,
you could use a screwdriver to adjust the zero adjustment
screw at the center of the meter front cover.
3. Plug the AC plug into the AC line.
4. Set the RANGE to 100 V and turn on the power.
5. Connect leads to the INPUT terminal and the load is
under testing.
6. Alter the RANGE selector switch until the pointer is at a
position which located at ≧1/3 of the scale, therefore, the
reading can be taken easily.
B. Use of decibel ranges
There are two dB scales provided on the dial which have been
calibrated as
0 dB = 1 V
0 dBm = 0.775 V (1 mW into 600Ω)
1. dB:
Decibel is originally the ratio of power as explained above.
However, the logarithm of the ratio of other values (ratio of
voltage or current) can also been called “decibel”.
For example, If the input voltage of an amplifier is 10 mV and
its output voltage is 10 V, the degree of amplification could be
10 V / 10 mV = 1000 times. This is also expressed in dB as
follows:
Degree of amplification = 20 log 10 V / 10 mV = 60 dB
2. dBm
“dBm” is the abbreviation of dB (mW). This decibel value
expressed the power ratio with respect to 1 mW. Normally,
“dBm” implies the condition where the power exists in an
impedance of 600 Ω.
Therefore, “0 dBm” can be signified as the following:
0 dBm = 1 mW or 0.775 V or 1.291 mA
3. The power or voltage levels are determined by adding up
the scale readings and the selected RANGE settings.
Example:
Scale RANGE Level
“Bel” is a logarithmic unit which expresses the ratio of two
powers. One “decibel” (abbreviated dB) is one-tenth of a Bel.
The dB is defined as follows:
dB = 10 log P
2
/ P
1
If the impedance is at the place where P1 and P2 are equal to
each other, the ratio of power could be expressed as follows:
dB = 20 log E
/ E1 = 20 log I2 / I
2
1
10
(-1 dB) + (+20 dB) = +19 dB
(+2 dBm) + (+10 dBm) = +12 dBm
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4. The dB and dBm scales of the indicating meter are as
stated the following:
Range setting dB dBm
+40
+30
+20
+10
0
-10
-20
-30
-40
-50
-60
-70
+20
+10
-10
-20
-30
-40
-50
-60
-70
-80
-90
to
+ 41
to
+31
0
to
+21
to
+11
to
+ 1
to
- 9
to
-19
to
-29
to
-39
to
-49
to
-59
to
-69
+20
+10
-10
-20
-30
-40
-50
-60
-70
-80
-90
to
+43
to
+33
0
to
+23
to
+13
to
+ 3
to
- 7
to
-17
to
-27
to
-37
to
-47
to
-57
to
-67
Specifications
This section contains a table of GVT-427B characteristics.
Table 1: Specifications
Model
Specification
Channels
*Indicating Meter
(105mm in scale length)
Scale Values V
2-Pointers (Black and Red)
value of sinusoidal wave,
rms
dB value with 1 V as 0 dBm
dBm value with 1 mW
Range Select Mode Independent / tracking control mode for each
Voltage
Measurement
12 ranges: 300 µV, 1, 3, 10, 30, 100, 300 mV,
1, 3, 10, 30 and 100 V of full scale
GVT-427B
Two
channel range
12
Decibel Range 12 range: -70 to +40 dB in increments of 10
dB
Decibel Scale -20 to +1 dB ( 0 dB = 1 V ),
-20 to +3 dBm (0 dBm = 1 mW [ 600 Ω])
Voltage Accuracy
Within ±3% of full scale at 1 kHz
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GVT-427B User Manual
Table 1: Specifications (Cont.)
Frequency Response
(Reference : 1 kHz)
300uV range:
From 20 Hz to 200 kHz, ≦ ±3%
From 10 Hz to 500kHz, ≦ ±10%
Other ranges:
From 20 Hz to 200 kHz, ≦ ±3%
From 10 Hz to 1 MHz, ≦ ±10%
Distortion Factor
Input Impedance
Input Capacitance
Input Maximum
Voltage
≦2 % of full scale at 1 kHz
Approximately 1 MΩ
≦50 pF
300 V (at 300 µV~ 1 V ranges)
500 V (at 3 V ~ 100 V ranges)
(DC + AC peak)
**DC isolation
0.1 Ω /100 kΩ ±10% (selectable)
Resistance
Maximum Voltage of
±30 V (peak value) (at 100 kΩ isolation)
**DC isolation
AC Power
115/230 Vac, 50/60 Hz
Requirement
Table 1: Specifications (Cont.)
AC Power
Consumption
Fuse Replacement
for 115 Vac selected
Fuse Replacement
for 230 Vac selected
8.5VA or 5.0 Watts, Maximum
T type, 0.3 A, 250Vac
T type, 0.2 A, 250Vac
Indoor user,
Altitude up to 2000M
Operation
Environment
Installation Category II
Pollution Degree 2
Operating Temperature :
0
C to +400C, < 80% relative humidity
+0
Dimensions 130 (W) x 210 (H) x 295 (D) mm
Weight Approximately 2.84kg
AC Output Voltage
AC Frequency
Response
Stability against Line
Voltage Fluctuation
0.1 V
±10% for each range of 1 kHz
rms
(at full scale without load)
10 Hz to 1 MHz, ≦ ±3%
(reference: 1 kHz, without load)
Indication change with respect to line voltage
fluctuation of ±10% : is within ±0.5% of full
scale.
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*: Dual scales in different colors.
**: Between the input common and chassis.
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GVT-427B User Manual
Maintenance
This section includes the basic maintenance information for
GVT-427B.
Cleaning
To clear GVT-427B, use soft cloth dampened in a solution of mild
detergent and water. Do not spray cleaner directly onto the
instrument, since it may leak into the cabinet and cause damage.
Do not use chemicals containing benzine, benzene, xylene, acetone,
toluene, or similar solvents.
Do not use abrasive cleaners on any portion of this equipment.
Troubleshooting
Troubleshooting the GVT-427B is limited to checking the input
power fuse. If you have other operational difficulties with your
GVT-427B, contact your Good-Will representative for assistance.
WARNING. To avoid electrical shock, the power cord
protective grounding conductor must be connected to
ground.
Interchangeable Parts
Interchangeable parts can be ordered from your authorized Goodwill
dealer directly.
Accessories
The items are shipped with the GVT-427B as following:
Table 2: Accessories
Accessory Good Will Part Number
Test Leads GTL-101 x 2
(for GVT-427B)
User Manual
1100-TL101U0
82VT-427B0MC
WARNING. To continued fire protection. Replace fuse
with the specified type and rating, and disconnect the
power cord before replacing fuse.
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