<p>Chapter - 4 Questions</p><p>Measuring Instruments</p><p>Chapter 4 : Ohmmeters</p><p>Complete the following :- </p><p>1- The ohmmeter consists of : a ) ...... b ) ...... c ) ...... d ) ...... </p><p>2- In series type ohmmeter , oo corresponds to ...... deflection .</p><p>3- The ohmmeter is divided into ...... types .</p><p>4- In shunt type ohmmeter the 0 [ zero resistance value ] corresponds to...... deflection </p><p>5- The ohmmeter has ...... control resistance connected either in series or shunt with meter .</p><p>6- Th ohm’s scale for the shunt type ohmmeter is …………………………… .</p><p>0cc767e14695328692b2ab030efe0875.doc 1 Switching section Chapter - 4 Questions</p><p>Show True or False : -</p><p>1- The ohmmeter has zero adjust control resistance connected either series or parallel with meter . ( )</p><p>2- The error in ohmmeter measuring due to battery aging . ( )</p><p>3- The accuracy of shunt OHMS ADJUST control is less than the Series OHMS ADJUST control in the series type ohmmeter. ( )</p><p>4- The ohms scale for the shunt type ohmmeter is backwards . ( )</p><p>5- The ohms scale for the series type ohmmeter is backwards . ( )</p><p>6- The zero value for the series type ohmmeter located at the left of the scale .( )</p><p>7- To get good accuracy of resistance measurements select the scale that cause deflection of pointer at upscale. ( )</p><p>0cc767e14695328692b2ab030efe0875.doc 2 Switching section Chapter - 4 Questions</p><p>Choose the correct answer :-</p><p>1 ) The scale of ohmmeter is : a ) linear scale . b ) log scale . c ) non-linear .</p><p>2 ) To get good accuracy for resistance measurement : a ) Select the lower scale . b ) Select the scale that cause deflection of pointer at mid scale position c ) Select the higher scale .</p><p>3 ) To measure resistance : a ) First short circuit the leads and adjust zero . b ) Open circuit and connect the Rx . c ) Select the suitable scale . d ) All the above .</p><p>4 ) When the deflection “ D “ of the series ohmmeter is equal to 62.5 % this means : a ) Rx = 0 b ) Rx = RT c ) Rx = 0.6 RT d ) None of the above.</p><p>0cc767e14695328692b2ab030efe0875.doc 3 Switching section Chapter - 4 Questions</p><p>Solve The following Problems</p><p>1 ) The following series type ohmmeter circuit shown in figure is used to measure the value of RX ( IFS = 50 µA and Rm = 2 K Ω , R1 = 10 K Ω ) Find: a ) The value of R2 required to zero the ohmmeter .</p><p> b ) What the ohmmeter will read ( measure ) if Rx = 15 K Ω ( i.e. Deflection “ D “ )</p><p> c ) Repeat ( a ) and ( b ) if the battery aging down to 1.2 volt . </p><p>0cc767e14695328692b2ab030efe0875.doc 4 Switching section Chapter - 4 Questions</p><p>2 ) a ) Complete the following table which represents the calibration of the series type ohmmeter face scale . </p><p> b ) Draw the face scale of ohmmeter , </p><p> c ) Repeat step ( b ) if RT = 10 K ohm</p><p>D % RX = ( 1 – D / D ) / RT</p><p>0</p><p>10</p><p>15</p><p>20</p><p>30</p><p>50</p><p>75</p><p>100</p><p>0cc767e14695328692b2ab030efe0875.doc 5 Switching section Chapter - 4 Questions</p><p>3 ) a ) Complete the following table which represents the calibration of the shunt type ohmmeter face scale . </p><p> b ) Draw the face scale of ohmmeter , </p><p> c ) Repeat step ( b ) if RP = 10 K ohm</p><p>D % RX = ( D / 1 – D ) / RP</p><p>100</p><p>90</p><p>80</p><p>70</p><p>60</p><p>50</p><p>40</p><p>30</p><p>20</p><p>10</p><p>0</p><p>0cc767e14695328692b2ab030efe0875.doc 6 Switching section Chapter - 4 Questions</p><p>4 ) a) The figure shows a circuit of an Ohmmeter .</p><p>Complete the following:</p><p>1) The circuit is a ………………… - type Ohmmeter.</p><p>2) The adjust control in this circuit is …………….. zero ohm adjust.</p><p>3) The function of R2 is to compensate the battery …………… b) For a new battery V = 1.5 Volt, the value of R2 required to zero the Ohmmeter is = 6 K Ω.</p><p>1) What is the total resistance ( RT ) ?</p><p>2) What the Ohmmeter will read if Rx = 10 K Ω ( Same as “4 “ ,but more simple and less of requirements)</p><p>0cc767e14695328692b2ab030efe0875.doc 7 Switching section Chapter - 4 Questions</p><p>5 ) A 50 μA, 2 K Ω movement is used in the circuit shown in figure.</p><p>Determine:</p><p> a) The value of RZ to zero the Ohmmeter.</p><p> b) The Ohmmeter reading if Rx = 15 K Ω</p><p> c) If the battery ages down to 1.2 V, i - What is the value of RZ required to zero the Ohmmeter ? ii - What will be the indication of the Ohmmeter ?</p><p>0cc767e14695328692b2ab030efe0875.doc 8 Switching section</p>