Leader Electronics Corp. LMV-181A Manuale utente

ILEADER ELECTRONICS CORP.

f2-6-33 TSUNASHIMA-HIGASHI, KOHOKU-KU. YOKOHAMA. JAPAN

PHONE:(045)541-2123

FAX:(045)544-1280 TELEX:J47780 JPLEADER

LEADER INSTRUMENTS CORP.

380 OSER AVENUE. HAUPPAUGE. N. Y. 11788 U.S. A.

PHONE:(516)231-6900

TELEX:510-227-9669 LEADER HAUP

FAX: 516-231-5295

90091 K®[5] Printed in Japan. LEADER ELECTRONICS CORP.

CONTENTS

1. General ^

2. Features ^

3. Specifications f

4. System diagram ^

5. Panel functions 4

6. Preliminary notes ^

7. Operation ^

8. Functional description 11*

9. Maintenance

10. Schematic diagram

Note: This instruction manual applies to both 181 Aand 181B,

and the information in brackets []refers to the 181 B.

1. General

These instruments are millivoltmeters and voltmeters with mean

value indicating devices that offer effective value calibration, and

are used for measuring sine wave alternating current voltages of

100/xV to 300V [150V to 500V] in the 5Hz to IMHz frequency

range. These instruments are highly sensitive and precise. New

circuitry insures wide range readings with excellent linearity

characteristics. The use of output terminals enables applic-

ation of these units as wide-band high gain amplifiers or pre-a-

mplifiers on other electronic apparatus.

2. Features

1. Wide band-width of 5Hz to IMHz.

2. High accuracy; ±2%.

3. Highly precise, reliable and stable voltmeters of new circuit

design.

4. Wide-use voltmeters with two decibel scales (OdB =IV, OdB =

0.775V) in addition to the effective voltage scales.

5. The output is calibrated at IVrms full scale, so that these

instruments can be used as low-noise high-gain pre-amplifiers

on wave form monitors.

3. Specifications

Voltmeter

Measuring voltage range 100/iV to 300V

[150mV to 500V]

Measuring range Measuring range 12 ranges

1, 3, 10, 30, 100, 300 mV

1, 3, 10, 30, 100, 300V

"l.5, 5, 15, 50, 150, 500mV

1.5,5,15,50,150,500V

Decibel range 12 ranges

-60, -50, -40, -30, -20, -lOdB

0, +10, +20, +30, +40, +50dB

(0 dB= IV, 0dB =0.775 V)

Measuring accuracy ±2% of full scale

(at 1kHz or 400 Hz)

Frequency characterisitcs 5Hz to 1MHz ±10%

10 Hz to 500 kHz ±5%

20 Hz to 100 kHz ±2%

(1 kHz as base)

Input resistance 10 M^2

Input capacitance Under 50 pF

(ImV to 300mV [1.5mV to 500mV])

Under 35 pF

(IV to 300V [1.5V to 500mV])

Maximum input voltage AC peak +DC =600V

Noise Within 2% of full scale by shorting input

Amplifier

Output voltage

Frequency characteristics

Output impedance

Distortion factor

Operating temperature range

IV no load

when l.OV [5.0V] is indicated

at full scale of each range

lOHz to 500kHz -3 dB (1 kHz

as base)

60012±20%

Within 1% at full scale (1 kHz)

0to 40°C

Operating humidity range Less than 85%

Power Supply lOOV ±10% 50/60 Hz

(can be changed to 120V, 220V,

240V by switching over the in-

terior trans-tap)

2.5 VA

Size and weight 132(W)X150(H)X250(D)mm, 2

kg. (exclusive of buttons, rub-

ber legs and handle)

Accessories Terminal adaptor for plug type 1

Connection cable (pair-plug to clip) 1

Spare fuse 1

Instruction manual 1

4. System diagram

INPUT

attenuator input _impedance conversion __ attenuator

60dB "protective

circuit and 10 dB amplifier 10 dB step

RANGE switch ^

5. Panel functions

Explanations of the front and rear panel controls are shown

below.

(T) Meter Faces

Voltage and dB scales are calibrated as shown in Figure 3.

1) Model 181A 2) Model 181B

Fig 3

2) Mechanical zero adjustment screw

Turn power switch (9) to off. Set the voltage calibration to 0by

adjusting the mechanical zero adjustment screw with an

insulated screwdriver.

(3) Pilot lamp

When power switch (9) is pushed up to turn power on, the lamp

should light.

0“INPUT” (metallic terminal)

This is the ground terminal when measuring voltage.

(D INPUT (plug, U.H.F. type)

This is the connector for applying voltage to be measured. Type

Mand type UHF connectors and twin-type banana plugs can be

used because 0and 0are 19mm apart. Individual banana

plugs may also be used with 0and ®separately.

0RANGE button

This button is used for selecting full scale value. At each stop

position, the voltage values of the full scale are indicated in

black, and the absolute levels of 0dB calibration are shown in

dB.

©“OUTPUT” (black terminal)

When this instrument is used as an amplifier, this output

terminal is ground.

©“OUTPUT” (red terminal)

This is the “Hot” output terminal when this instrument is used

as an amplifier. When the meter indicates full scale at each stop

position of the range switch ©,1Vrms of voltage can be

obtained.

“1” calibration in the case of 181

“5” calibration in the case of 181B

©“POWER” switch

Power goes on if the switch is pushed up to “ON”.

®FUSE

Protects instrument against overload and short circuits. Fuse is

removable by counter-clockwise rotation.

(Jj) Power supply cord

Connects unit to power source.

@Cord winder

Provides convenient power cord storage.

6. Preliminary notes

6-1 The line voltage used for this instrument should be ±10% of

the rated value.

6-2 Mechanical zero adjustment of the indicator

If the pointer of the scale is not at 0when power is off, set

to 0by adjusting the mechanical zero adjustscrew with an

insulated screwdriver.

6-3 Excessive input voltage

The maximum input voltage of this instrument is AC peak +

DC =600V. Do not apply avoltage greater than this value, if

alarger input is applied to the input terminals, circuit parts

may be damaged or destroyed.

6-4 Input waveform

This instrument gives indications according to the mean value

of the input waveform, and the calibration is done in

effective values of sine waves. Therefore, distortion of the

input voltage waveform may result in incorrect readings.

5Induction noise

When the measured voltage is very small, or when the

impedance of the source of the measured voltage is relatively

high, an incorrect indication may result due to the induction

of external noises, if this occurs, use shielded cables to

reduce or eliminate noise pick-up.

7. Operation .j..

1Preparation

1. Before connecting this instrument to the power source,

check to see that the pointer of the scale is at 0. If it is off

0, set it to 0by adjusting the zero adjustment screw.

2. Connect the power plug to the power source of the correct

voltage.

3. Set the range switch to 300V [500V] in advance.

4. When the power switch is turned to ON, the pilot lamp

should light.

The pointer will vibrate irregularly for about five seconds

after power goes on, but it does not indicate amalfunction.

5The instrument will stabilize in about five seconds after

power is applied.

7-2 Measurement of AC Voltage

1. The meter will indicate presence of voltages when a

connection is made to the “INPUT” terminal and the

voltage to be measured is applied.

2. if the reading is less than 30% of full scale, turn the

“RANGE” button counterclockwise, and reduce the volt-

age range gradually. Read the indicated value when the

pointer is more than 30% of the full scale and less than full

scale.

3. There are two maximum voltage calibrations, “1” and ‘3

[“1.5” and “5”], on the scale. Tables 1and 2show the

positions of “RANGE” buttons vs. the calibration of the

voltages used.

LMV- 181A

Table 1

LMV-181B

RANGE Scale Multiplier Vper DIV

500 V0-5 100 10 V

150 V0-1.5 100 5V

50 V0-5 10 1V

15 V0-1.5 10 0.5 V

5V0-5 10.1 V

1. 5V 0-1.5 10.05V

500 mV 0-5 100 10 mV

150 mV 0-1.5 100 5mV

50 mV 0-5 10 1mV

15 mV 0-1. 510 0.5 mV

5mV 0-5 .10. 1mV

1. 5mV 0-1.5 10.0 5mV

Table 2

7-3 How to use Decibel Range

The indicator has the following two red dB calibrations:

0dB =0.775 V(1 mW 600^2 dBm)

0dB =1VdBV

Table 3shows each dB range vs dBm and dBV.

Range LMV--181A LMV--181B

setting dBm dBV dBm dBV

+50

+40

+30

+20

+10

+30to+52

+20to+42

+10to+32

0to+ 22

-lOto+12

—20to+ 2

+30to+50

+20to+40

+10to+30

Oto+20

-lOto+10

—20to+ 0

+30to+56

+20to+46

+10to+36

Oto+26

-lOto+16

-20to+ 6

+30to+54

+20to+44

+10to+34

Oto+24

-lOto+14

-20to+ 4

-10

-20

-30

-40

-50

-60

-30to- 8

-40to-18

—50to— 28

—60to— 38

—70to— 48

-80to-58

-30to- 10

-40to- 20

—50 to— 30

—60 to— 40

-70to- 50

—80 to— 60

—30 to— 4

—40 to— 14

-50to- 24

-60to- 34

-70to-44

-80to- 54

—30 to— 6

-40to-16

—50 to— 26

—60 to— 36

-70to- 46

-80to- 56

Table 3

Decibel values can be read by adding range dB values to

indicated values of the pointer.

Example 1

Scale +1dB

Range +20 dB

Level +21 dBm

Example 2

Scale -4dBV

Range —30 dB

Level -34 dBV

7-4 Use of “OUTPUT” terminal

When the indicator show “1” [“5”] at full scale, the

“OUTPUT” terminal can obtain an output of IVrms no

matter where the RANGE switch is positioned. An oscillo-

scope can be used as amonitor of measured signal wave-

forms, or as apre-amplifier by connection to the “OUTPUT”

terminal. Table 4shows the degrees of amplification when

the instrument is used as apre-amplifier.

Notes: The following troubles will occur if alow load

impedance is connected to the terminal.

Resistance Output voltage is lowered. Low frequency

characteristics deteriorate.

Capacitance As load capacitance increases, high fre-

quency characteristics deteriorate.

Range setting (dB; -60 -50 -40 -30 -20 -10 010 20 30 40 50

Degree of amplification(dB) 60 50 40 30 20 10 0-10 -20 -30 -40 -50

Table 4

7-5 Measurement of alternating current

When AC voltage is V, alternating current is Iand resistance

is R, there is arelationship as follows:

1=V/R

Current can be determined out by measuring the voltages at

both ends of the resistance based on the above relationship.

Fig 4

Note: The “INPUT” terminal of this instrument is grounded

at one end.

8. Functional description

LMV-181A and LMV-181B are similar as far as functions are

concerned. They consist of a60 dB attenuator, input protective

circuit, impedance conversion circuit, 10 dB step attenuator,

meter pre-amplifier, meter amplifier, meter circuit, monitor

amplifier and stabilization power circuit.

1. 60 dB attenuator

Controls input voltage so that the impedance conversion

circuit will work normally. The attenuation quantity is 0dB in

the 1mV —300 mV [1.5 mV —500 mVJ range, and 60 dB in

higher ranges.

2. Input protective circuit

It consists of Qi and Q2, and protects FET Q3 from

excessively large input voltages.

3. Impedance conversion circuit +10 dB amplifier

It consists of Q3 (FET) and Q4 converts high input impedance

into low impedance, and has an amplification factor of +10

dB.

4. 10 dB step attenuator

In conjunction with the 60 dB attenuator, it selects proper

values to be measured.

5. Meter pre-amplifier

It consists of Qs and Q7 ,and amplifies small signals into large

signals.

6. Meter amplifier and meter circuit

Consists of Q9, Qio, Qii, D2, D3 and meter. The rectifier

circuits of D2 and D3 and the meter are in the feedback circuit

of the amplifier, so, the indications of the meter are in

proportion to the input voltage.

7. Monitor amplifier

1Vrms output is obtained at the “OUTPUT” terminal when

the meter indicates full scale after asignal is taken out of a

part of the meter preamplifier and amplified.

8.Stabilization power circuit

This circuit consists of D4 ,D5 ,and D7 rectifier circuits

and Dg, Qi 2and Q13 stabilization circuits. With Dg Zener

diode as the reference voltage, it supplies +18V stabilized

voltage to the impedance conversion circuit, meter pre-

amplifier, meter amplifier and monitor amplifier.

9. Maintenance

9-1 Changing fuses

Afuse can be removed by turning the fuse holder on the rear

side in the direction of the arrow. Use 0.1 Afuses. After fuses

are changed, be sure to investigate the cause. Take appropriate

steps before power is turned back on.

11 12

9-4 Adjustment and correction

If specifications are not met after repairs are made, make

adjustments or corrections as follows:

Adjustment of stabilization power

Connect aDC voltmeter to the +18V line of the printed

circuit, and adjust VR4 (VcclSV ADJ) of Figure 7to get

+18V.

when viewed from above

2. Procedure for correcting indicated values

1) Connect avoltmeter calibrator to the INPUT.

2) Set the voltmeter range at 10 mV.

3) Set the output voltage of the calibrator to 10 mV, and

adjust VR2 (10 mV 400 Hz AJD) of Figure 7to full scale.

4) Next, set the voltmeter range at 10 V.

5) Set the output voltage of the calibrator to lOV, and adjust

so that it will be full scale at VRl (lOV 400Hz ADJ) of

Figure 7.

6) Next, set the voltmeter range at IV.

7) Change the signal source from the calibrator to an oscillator

of good frequency characteristics. Set the frequency of the

oscillator to 500Hz, and set the output voltage so that the

instructed value is IV full scale.

8) Next, change the signal frequency from 500 Hz to 50 kHz,

and adjust VCl (50kHz ADJ) of Figure 7so that the

frequency characteristics is flat, if this adjustment does not

work, repeat the correction procedure from the beginning.

3. Adjustment of output voltage terminals

After the above adjustment is finished, set the voltmeter

range at IV. Next, apply a1kHz signals to attain full scale,

and adjust VR3 (OUT IV ADJ) of Figure 7so that the

output terminal voltage is 1Vrms.

Note: In the case of the 181B, adjust each set voltage by

amultiplier of 1.5. For instance, 10 mV should be

changed to 15 mV.

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