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Sanwa U-50D, Operator'S Manual, Page: 4 / 37

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Sanwa U-50D Operator'S Manual Download Page 4

GENERAL  DESCRIPTION

1 

Introduction.

The 

U-50

d

 

is  a  pocket-size,  high  performance  circuit 

tester  equipped  with  a  meter  movement  of  35  micro­
amperes  in  sensitivity.

The  high  internal  resistance  of the  DC  range  accurately 
measures  voltage  of  high  impedance  circuits.

The  acrylic  front  cover  admits  full  light  on  the scale  dial 
with  a  mirror  to  obtain  accurate  reading.

The  meter  movement  is  doubly  protected  from  damage. 
The  protection  circuit  electrically  safeguards  the  move­

ment  against  accidental  overcurrent,  and,  mechanically, 

the  moving  element  is  supported  by  spring-backed  jewel 
bearings  to  absorb  shock.

Use  of  the  battery  sheaths  eliminates  reading  error 
regardless  of  the  battery  armour,  magnetic  or  non­
magnetic.

Measurement  ranges  of  DC  voltage  and  current  can  be 

extended  by  the  use  of  accessories  available  separately.

2

Summary of Contents for U-50D

Page 1: ...f i1 ...

Page 2: ......

Page 3: ...eter Movement Protection 5 6 Other Precautions 7 OPERATION 1 DC Voltage Measurements 8 2 AC Voltage Measurements 11 3 Internal Resistance of the Voltage Range 14 4 DC Current Measurements 16 5 Resistance Measurements 19 6 Volume Level Measurements 23 7 Capacity and High Resistance Measurements 28 SUPPLEMENTARY DATA 1 Schematic Diagram 31 2 Arrangement of Parts Rear View 32 3 List of Main Parts 33 ...

Page 4: ...scale dial with a mirror to obtain accurate reading The meter movement is doubly protected from damage The protection circuit electrically safeguards the move ment against accidental overcurrent and mechanically the moving element is supported by spring backed jewel bearings to absorb shock Use of the battery sheaths eliminates reading error regardless of the battery armour magnetic or non magneti...

Page 5: ...x 100 Rx IK Midscale son soon 5kn 50kn Minimum in ion loon lkn Maximum 5kn 50kn 500kn 5Mn Volume level 20 62dB Capacity Megohm 0 0001 0 2 iF use external power l 500M n 1 b Internal Batteries Two 1 5V dry cells UM 3 or equivalent c Allowance DC voltage AC voltage DC current Resistance d Size Weight Within 3 f s d Within 4 f s d 62 for 2 5V Within 3Cg f s d Within 3 o of scale length 131x89x43 mm 4...

Page 6: ...surements as a rule the red lead is inserted in the jack marked and the black lead in the jack marked The jack marked 0 1 V 50 A is for the red lead connection for measurements on the DC 0 1 volt and 50 microampere ranges Before the test leads are connected to the circuit to be measured confirm the position of the selector switch If a voltage is checked when the switch is set at a resistance or cu...

Page 7: ...t reading Look at the scale right over where the pointer falls exact ly over its image in the mirror 5 Meter Movement Protection The meter movement of the U 50o is completely pro tected against voltages below 1000 volts which might be accidentally impressed on any measurement range only by having some resistor or the rectifier burnt out The following table shows the resistors subject to getting bu...

Page 8: ...a R7 DC 0 5mA 841H 84 2a 5 41ka Rll R12 R19 DC 5mA 84 2a R12 DC 50mA 7 5a R13 DC 250mA i 87a R14 AC 2 5V 14 5 10 lka R9 AC 10V ooka R8 AC 50V 320ka R6 CAUTION When a resistor is burnt out through misapplication and if the connection mistake be left as it is some other resistor as well as the protection circuit or the meter movement itself would suffer damage 6 ...

Page 9: ... internal components could be damaged b Avoid allowing the meter to receive severe shock or vibration Do not leave it where there is high temperature or moisture or strong magnetic field c Do not rub the acrylic surface or clean it with cleaning material anti electrification coating will come off to cause erroneous reading 7 ...

Page 10: ... of radio TV receivers and amplifiers Their circuits generally have minus potential grounded though pnp transistor circuits their plus potential For measurements go through the following procedure a Zero Correction Before making a measurement confirm the pointer to be exactly on zero of the scale left If it is off the position adjust it by the 8 ...

Page 11: ...eading the switch can be reset to a lower range for a more accurate reading Fig 1 2 For accurate measurements use a range which will allow the pointer to fall within the right hand half of the scale corrector screw at the base of the scale dial Fig 1 1 Measurement of Proper range to be used 250 1000 volts 1000V 50 250 volts 250V 5 50 volts 50V 0 5 5 volts 5V 0 1 0 5 volts 0 5V 0 0 1 volts 0 IV ...

Page 12: ... When measuring the black lead may be fixed to the chassis and voltage is checked by applying the red lead to the check point Fig 1 3 4 With pnp transistor circuits the plus potential of the battery is earthed and the connections of the test leads are reversed Wrong connections deflect the pointer to the left Just reverse the connections if this occurs d Scale Reading Use the black scale just belo...

Page 13: ...ed for checking the mains secondary voltages of a power transformer etc Audio frequency voltages of 30 5000Hz can be meas ured without trouble but error might occur for higher frequencies The pointer will vibrate for frequencies lower than 30Hz making it impossible to read The meter is calibrated for sinusoidal AC RMS so error will also occur for non sinusoidal voltages 11 ...

Page 14: ...imate voltage present always start with the highest range After the first reading the switch can be reset to a lower range for a more accurate reading Fig 2 2 a Zero Correction See 1 a Fig 2 5 I Fig 2 i To obtain an accurate reading use a range which will allow the pointer to fall within the right hand half of the scale ...

Page 15: ...cted to the meter are applied across the voltage to be checked Since alternating current is being measured the readings are correct to which side of the voltage the test leads are con nected Fig 2 3 4 d Scale Reading Use the red scale third from the top marked AC 10V UP for all AC voltage measure ments except for the 2 5 volt range for which the black scale below marked AC 2 5 V is used Fig 2 5 13...

Page 16: ... erroneous reading Current consumption is inversely proportional to the internal resistance of the meter the bigger the resistance the less the current consumption As a rule the internal resistance of a voltmeter is ex pressed by resistance per volt using the symbol of Q V Therefore the internal resistance of a certain voltage range is known by the voltage value multiplied by the Q V of the meter ...

Page 17: ...here is greater voltage drop and the meter reads lower than the true value the con nection of the meter upsets the circuit to be checked Error can be minimized by the use of a meter of high internal resistance but unless it is infinite some error is inevitable even if a vacuum tube voltmeter be used for checking such a circuit The internal resistance of a meter little affects the check ing of the ...

Page 18: ...of the five current ranges prescribed When in doubt as to the approximate current present always start with the highest range The switch can be reset to a lower range for a more accurate reading Fig 3 2 To obtain an accurate reading use a range which will allow the pointer to fall within the right hand half of the scale lti ...

Page 19: ...Before taking a measurement the circuit to be checked is opened and the meter is connected in series with the load by way of the test leads the red lead to plus and the black lead to minus potential Fig 4 3 4 d Scale Reading Use the black scale just below the mirror marked OCV mA for all DC current meas urements It is used in common with DC voltage measurements 17 ...

Page 20: ...1 0 5mA 0 50 0 01 5mA 0 50 0 1 50mA 0 50 1 250mA 0 250 1 Note For measurement of a low resistance circuit the internal resistance of the current range used is connected in series with it resulting in current decrease to cause erroneous reading 18 ...

Page 21: ...1 a Fig 4 1 b Range Selection The selector switch can be rotated to any one of the four Q positions Fig 4 2 For an accurate measurement use a range which will allow the pointer to fall near the middle of the ohm scale Refer to the following table 19 ...

Page 22: ...e exactly over zero by turning the zero ohm adjuster 012 ADJ Fig 4 4 5 Do not force it beyond its stop position Zero ohm adjustment is to avoid error caused by the wearing out of the internal batteries or change of their load current The pointer must be adjusted every time the range is moved over and from time to time when resistances are checked If zero adjustment is impossible when the adjuster ...

Page 23: ...e read the figures directly For the RxlO RxlOO and Rx lK ranges read the figures multiplied by 10 100 and 1000 respectively Note 1 Replacement of the batteries Put the meter face down on a soft cloth and loosen the bolt on the back to remove the case To take out the batteries the fixing bolts on the minus sides are loosened After the batteries are replaced do not tighten the bolts too much or the ...

Page 24: ...asuring terminals are reversed for resistance ranges the plus terminal being in minus and the minus terminal in plus potential It must be remembered when semiconductor circuits are checked CAUTION 1 Do not check resistance while power is on Be sure the electric charge of con densers is discharged 2 While checking keep off the fingers from the metal parts of the test leads part of the current runs ...

Page 25: ...ock DC component This is called AF audio frequency output measurement for which any AC voltage range can be used reading the scale for AC voltage measure ments On the other hand what matters to amplifiers and trans mission circuits is their input output power ratio which is gain amplification or loss attenuation of the circuit Comparative reading by voltage current or power would annoy one with th...

Page 26: ...en 0 001 watt is dissi pated across a 600 ohm line while voltage E is related to decibel as follows L E Px Z j i 0 bOT OiKi 0 77 15 Z u Zo Line impedance Therefore zero reference level is established at approxi mately 0 775 volt Though a meter does not read power level directly if the line impedance is uniform it can be known by the voltage because voltage and power are proportionately related If ...

Page 27: ... given on page 26 The power level can be compared by the decibel values thus obtained The AC voltage ranges of the U 50d measure decibel by reading the dB scales provided in pair on the bottom of the scale dial a Range Selection Any AC voltage range may be used for decibel measurement b Test Lead Connections See GENERAL INST RUCTIONS Before taking a decibel measurement a condenser of 0 1 2 microfa...

Page 28: ...volt range For the 50 250 and 1000 volt ranges l4 dB 28 dB and 40 dB is added respectively to the reading of each range d Impedance Matching by a Graph Decibel output power is obtained from output voltage measured by reading the graph given below Load Impedance kn ir a a 5 2 26 ...

Page 29: ...e decibel value to be taken for comparison Example 2 Providing the primary of an output transformer of 5k ohm impedance is checked on AC 50 volt range and the meter reads 20 2dB on the scale for AC 10 volt reading it is 20 2 14 34 2 dB for the 50 volt reading Now 5 of the Load Impedance k Q is followed down and then to the left at the intersecting point with the oblique line to obtain 9 2 on the D...

Page 30: ...ments a Zero Correction See 1 a b Range Selection Use a suitable range referring to the following table c Connections For the connections of the meter external power and the unit to be checked see the illustrations of next page M easurem ent of R ange m easured E xtern al power M eter ran ge C ap acity C ap acity H igh resistan ce 0 001 0 2 xF 0 0001 0 006 m F 1 500MX1 AC 10 volts AC 10V AC 250 vo...

Page 31: ...ated to full scale by means of a vol tage regulator for AC or potentiometer for DC The test leads are then applied across the unit to be checked and the reading of the meter is noted d Scale Reading For capacity use the pair of scales marked C A F either for AC 10 or 250 volt range For high resistance read the red scale marked Mf directly setting the selector switch to the DC 250 volt range 29 ...

Page 32: ...Note The static capacity of electrolytic condensers can not be checked 30 ...

Page 33: ...SUPPLEMENTARY DATA 1 Schematic Diagram A CV CIKO VJ o 0V ZOKO V E Cm A 0 2 5 10 5 0 2 5 0 1000 0 5 5 50 250 1000 0 5 5 5 0 2 5 0 RXI RX10 RX100 RXiK SW 31 ...

Page 34: ...Arrangement of Parts Rear View 32 ...

Page 35: ...7 ohm w irew ound DC 250mA shunt R15 R esistor 47 3k ohm film 4W R x lK series R16 R esistor 5 56k ohm film W RX100 p arallel R17 R esistor 505 ohm film W RXlO p arallel R 18 R esistor 49 ohm Gfilm 4W R x l p arallel R19 R esistor 5 41k ohm film 4W v ariab le resisto r series R20 R esistor 22 2k ohm film W AC vo ltage a u x ilia r y R21 R esistor 160d l 42k ohm film W m eter movem ent series R22 R...

Page 36: ...For exclusive use of the U 50i SA 25A to extend the DC current range to 1 5 and 25 amperes 2 High Voltage Probe 25kV rating for 20k QfV to 8W measure high DC voltage 3 Carrying Case Type PL 8 4 Clip Adapter Extension lead with an aligator TL 12 clip ...

Page 37: ...T CO LTD SANWAMETfR TOKYO Kakuta Bldg 1 MO Yushima Bunkyo ku ...

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