Chapter 1 : Basic Concepts

Example1_1,pg 481

In [1]:
# unknown resistance(refer fig. 1.4(a))

import math
#VAriable declaration
Ir=10*10**-3             #current drawn by resistor
Vr=100.0                 #voltage across resistor
Rv=40*10**3              #voltmeter resistance

#Calcualtions
Ru=(Vr/Ir)*(1/(1-(Vr/(Ir*Rv)))) 

#Result
print("output resistance:")
print("Ru = %d ohm"%Ru)

output resistance:
Ru = 13333 ohm

Example1_2,pg 481

In [4]:
# unknown resistance(refer fig. 1.4(b))

import math
#Variable declaration
Ir=10*10**-3                   #current drawn by resistor
Vr=100.0                       #voltage across resistor
Rv=40*10**3                    #voltmeter resistance
Ra=1.0                         #ammeter resistance

#Calculations
Ru=(Rv/Ir)-Ra

#Result
print("output resistance:")
print("Ru = %.2f ohm"%Ru)
# Answer in the book is in k-ohm

output resistance:
Ru=3999999.00 ohm

Example1_3,pg 481

In [8]:
# find ammeter reading

import math
#Variable declaration
Rv=40*10**3                        #voltmeter resistance
Ra=1.0                             #ammeter resistance
Vr=40.0                            #voltmeter reading
Ru=10*10**3                        #unknown resistance

#Calculations
Ir=(Vr*(Rv+Ru))/(Ru*Rv)
Ir1=(Vr/(Ru+Ra))

#Result
print("ammeter reading case1:")
print("Ir = %d mA"%(Ir*10**3))
print("\nammeter reading case2:")
print("Ir1 = %.d mA"%(Ir1*10**3))

ammeter reading case1:
Ir = 5 mA

ammeter reading case2:
Ir1 = 3 mA

Example1_4,pg 482

In [7]:
# unknown resistance

import math
#Variable declaration
Vs=3.0                       #supply voltage
Vu=2.75                      #voltmeter reading
Rp=10*10**3                  #parallel resistance

#Calculations
Ru=Rp*((Vs/Vu)-1)

#Result
print("unknown resistance:")
print("Ru = %.2f ohm"%Ru)
#Answer in the book is not matching

unknown resistance:
Ru=909.09 ohm

Example1_5,pg 482

In [9]:
# Find input vlotage

#with input voltage exceding 2Vd,diodes conduct and the voltage divider circuit with diodes can allow only a Vi given by Vi=2Vd

#Result
print("input voltage to amplifier:")
print("Vi = 2*Vd")

input voltage to amplifier:
Vi = 2*Vd

Example1_6,pg 482

In [11]:
# find shunt resistance

import math
#Variable declaration
Rm=1000.0                      #meter resistance
Is=900*10**-6                   #shunt current
Vm=100*10**-3                  #drop across meter

#Result
Rs=Vm/Is
It=1*10**-3
#Is=It*(Rm/(Rs+Rm))
Rs=(Rm*(It-Is))/Is

#Result
print("shunt resistance:")
print("Rs = %.1f ohm"%Rs)

shunt resistance:
Rs = 111.1 ohm

Example1_7,pg 483

In [12]:
# find series resistor

import math
#Variable declaration
If=100*10**-6                 #full scale current
Rm=1000.0                     #meter resistance
Vf=10.0                       #full scale voltage

#Calculations
Rs=(Vf/If)-Rm

#Result
print("series resistance:")
print("Rs=%.0f ohm"%Rs)

series resistance:
Rs=99000 ohm

Example1_8,pg 483

In [13]:
# sensitivity

import math
#Variable declaration
If=100*10**-6       # Current

#Calculations
S=1/If

#Result
print("sensitivity:")
print("S = %.2f ohm/volt"%S)

sensitivity:
S = 10000.00 ohm/volt

Example1_9,pg 483

In [16]:
# error in measurment

import math
# Variable declaration

#assume that the voltmeter full scale reading is 12V which gives its resistance as 1.2*10^6 ohm 
#which is in parallel with 10*10^6 ohm making as equivalent of Rq given as
R=1.2*10**6                    #voltmeter resistance
R1=10*10**6                    #voltage divider resistance
Vin=12.0                       #input voltage to divider network
Rs=4*10**6                     # series resistance


#Calculations
Rq=(R*R1)/(R+R1)
Vq=(Rq*Vin)/(Rq+Rs)            #voltage across equivalent combination
Va=(R1*Vin)/(R1+Rs)            #actual volatge
er=(Vq-Va)/Va                  #error

#Result
print("error in measurement:")
print("\ner = %.3f i.e %.1f%%"%(er,er*100))

error in measurement:

er = -0.704 i.e -70.4%