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YOKOGAWA 2768 User Manual Download Page 17

IM 2768-01E

― 12 ―

(c)  When an external power source unit is used, be careful not to burn resistive elements by  

over-current.

 

The allowable electric power of this instrument is 0.2 W (continuous) which dose not  

degrade accuracy of the resistive element.

 

In case a power source unit is used of large capacity, connect a fuse 0.5 A in  

series with the power source.

(d)  The maximum allowable input of the internal galvanometer is 5 V.

 

When a high voltage external power source unit is used,  

first roughly balance the galvanometer with a low voltage, and then increase the voltage.

 

It is essential to complete the measurement as soon as possible.

 

Be sure not set No. 1 dial of Rs to 0, and also not to short the Rx terminals.

Summary of Contents for 2768

Page 1: ...2768 Precision Wheatstone Bridge User s Manual IM 2768 01E IM 2768 01E 4th Edition Oct 2017 YMI ...

Page 2: ...st of worldwide contacts Notice regarding This User s Manual The information covered in this User s manual is subject to change without prior notice Every effort has been made to ensure accuracy in the preparation of this manual Should any errors or omissions come to your attention however please inform YOKOGAWA accordingly YOKOGAWA is by no means liable for any damage resulting from the user s mi...

Page 3: ... to observe the following instructions WARNING Protective Measures If a crack appears in the instrument after it has been accidentally dropped or bumped the safety purpose insulation may be damaged By all means do not use the instrument but ask the manufacture for repair Connection To avoid electric shock be sure to apply protective grounding to the grounding terminal Install a protection fuse as ...

Page 4: ...nt be sure to observe the following instructions CAUTION Batteries Do not use a mixture of different types of batteries or a mixture of old and new batteries If the instrument will not be used for a prolonged period remove the batteries before storage The battery fluid will leak more readily during long term storage resulting in instrument malfunction ...

Page 5: ...MENT 6 4 1 Preliminary Procedure 6 4 2 Measurement 8 5 PRECAUTIONS 9 6 PRINCIPLE 10 7 FOR MORE EFFECTIVE USE OF THE INSTRUMENT 11 7 1 How to Use the Measuring Dial Rs 11 7 2 To Connect External Accessory Equipment Galvanometer and Power Source 11 1 Connection of External Galvanometer 11 2 Connection of External Power Source 11 3 Caution 11 8 CIRCUIT DIAGRAM 13 ...

Page 6: ...it and is provided with a guard terminal and a ground terminal Therefore the precision measurement is accomplished with 2768 2 SPECIFICATIONS 100 mΩ 1 Ω 10 Ω 100 Ω 1 kΩ 10 kΩ 100 kΩ 1 MΩ 10 MΩ 10 µΩ 100 µΩ 1 mΩ 10 mΩ 100 mΩ 1 Ω 10 Ω 100 Ω 1 kΩ 0 5 mΩ 0 02 of setting 0 5 mΩ 0 02 of setting 0 01 of setting 0 01 of setting 0 01 of setting 0 02 of setting 0 02 of setting 0 05 of setting 0 10000 to 1 1...

Page 7: ... C humidity of less than 75 R H Residual resistance Less than 0 02 Ω of setting Measuring Arm Resistance Accuracy 100 mΩ 1 Ω 10 Ω 100 Ω 1 kΩ 10 kΩ 100 kΩ 1 MΩ 10 MΩ 0 02 0 02 0 01 0 005 0 005 0 005 0 01 0 01 0 01 10 Ω 100 kΩ 10 Ω 10 kΩ 100 Ω 10 kΩ 1 kΩ 10 kΩ 1 kΩ 1 kΩ 10 kΩ 1 kΩ 100 kΩ 1 kΩ 100 kΩ 100 Ω 100 kΩ 10 Ω At an ambient temperature of 23 2 C humidity of 75 R H and resistance ratio Ratio A...

Page 8: ...1000 MΩ at 250 VDC User s Manual 1 each Battery 1 set Between the case and the circuits 500 VAC 1 minute Maximum Sensitivity Approximately 10µV div Input Resistance 9 kΩ Max Allowable Input Voltage 5 V peak value Power Source 9 V Dry Cell 006P installed Galvanometer Insulation Resistance Accessories Dielectric Strength Dimensions Approx 310 491 140 mm Weight Approx 9 6 kg Power Source 1 5 V 3 V 6 ...

Page 9: ... is able to change the resistance from 0 1 Ω till 11 111 kΩ in step of 0 1 Ω The resistance value indicated in the windows is connected to the bridge circuit 2 Ratio Arm Range Used to select a multiplying factor depending on the resistance under test 3 Galvanometer Function Switch INT GA Internal galvanometer is connected to the bridge circuit B CHECK Used to check the power source for the interna...

Page 10: ...witch used to switch the power source for the bridge circuit ON and OFF during measurement 7 GA This is a push button type switch used to connect the galvanometer input to the bridge circuit 8 Rx Terminal Used to connect the resistance under test 9 Rs Terminal Used when the measuring dial Rs is employed as a variable resistor 10 EXT GA Terminal Used to connect the external galvanometer 11 EXT BA T...

Page 11: ...stment screw to shift the pointer to the zero on the scale 2 Connection of Resistor under Test Rx Connect the resistor to be measured to Rx terminals A guard 3 terminal measurement is required to measure a resistor higher than 100 kΩ accurately Fig 4 1 and Fig 4 2 Rx Rx Rx ρ1 ρ2 to Rx terminals to Rx terminals Conductor to GUARD terminal to GUARD terminal GUARD Fig 4 1 Rx and GUARD terminal Connec...

Page 12: ... GUARD L L H H Rs Rx ρa ρa ρc ρc ρb RA RA RB RB En Rx ρ4 ρ3 ρ1 ρ1 ρ2 ρ3 ρ4 ρ2 Fig 4 2 Guard Terminal Connection B Guarded Wheatstone Bridge A Leakage Resistance on Wheatstone Bridge Leakage Resistance ρa ρb ρc Leakage Resistance Noise Source ...

Page 13: ...acy 0 001 0 01 0 1 1 10 5 10 4 10 3 10 2 10 1 div R R Rx 3 V 15 V 4 2 Measurement 1 Set the galvanometer to low sensitivity by turning the galvanometer SENSITIVITY adjustment knob Turn the knob counter clockwise 2 Set the measuring dials Rs to 1 9999 3 Observe the direction of the pointer deflection of the galvanometer by depressing momentarily the GA switch after depressing the BA switch If the p...

Page 14: ...d If this order is reversed the galvanometer pointer will misleadingly deflect for the measuring dial operation inductance of the resistor under test when BA switch is depressed 3 The resistance of the lead wires which connect the resistance under test Rx to the Rx terminals is included in the measured value Therefore in measuring the resistance lower than 100 Ω the influence of the lead wire resi...

Page 15: ... A B Ix Rx Is Rs A B Is Ix Rx Rs R R A B R R Rx Rs This instrument is designed so that the multiplying factor is set from 100 mΩ to 10 MΩ by changing the RA RB with the multiplying dial Therefore the unknown resistance Rx is obtained by multiplying the value of the measuring side dial Rs to the multiplying factor which is determined by the multiplying dial GA Is Ix Rx A R B R ig 0 Rs Fig 6 1 Theor...

Page 16: ...galvanometer to EXT GA terminals Set the galvanometer function switch to EXT GA At the same time the guard and the ground must be secured Electronic Galvanometer 2709 is recommended to be used as an external galvanometer Maximum sensitivity 0 2 µA div input resistance 1 kΩ Note Model 2709 has been discontinued 2 Connection of External Power Source When a battery or a DC power source unit is requir...

Page 17: ...se a power source unit is used of large capacity connect a fuse 0 5 A in series with the power source d The maximum allowable input of the internal galvanometer is 5 V When a high voltage external power source unit is used first roughly balance the galvanometer with a low voltage and then increase the voltage It is essential to complete the measurement as soon as possible Be sure not set No 1 dial...

Page 18: ...S 4 S 9 R4 5kΩ R3 2kΩ R2 2kΩ R1 1kΩ R33 330Ω R34 10Ω R32 10Ω S 1 G 2 R8 500Ω R7 200Ω R6 200Ω R5 100Ω S 2 S 7 B 5 006P B 4 B 3 B 2 B 1 R12 50Ω GUARD EXT R11 20Ω R10 20Ω R9 10Ω S 3 GALVA B CHECK INT GA EXT GA GA 006P GUARD GAL B BA B From RANGE RANGE 100 mΩ 1 Ω 10 Ω 100 Ω 1 kΩ 10 kΩ 100 kΩ 1 MΩ 10 MΩ M 5µA AMP SENSITIVITY L L H H M B S 21 M S 11 S 12 EXT POWER SUPPLY BA GUARD L H GUARD BAT BA CASE B...

Page 19: ...Printed in Japan ...

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