Chapter 8: Differential, Instrumentation and Bridge amplifiers

Example 8.1 Page No 218

In [1]:
#Given
m = 100.0              #Differential Gain
E1 = 10*10**-3
E2 = 10*10**-3         #input voltages
E3 = 0*10**-3 
E4 = -20*10**-3        #input voltages

#Calculation
Vout1 = (m*E1)-(m*E2)    
Vout2 = (m*E1)-(m*E3)
Vout3 = (m*E1)-(m*E4)

#Result
print" Output Voltages are   ", Vout1,"V, ",Vout2,"V ,",Vout3,"V"

 Output Voltages are    0.0 V,  1.0 V , 3.0 V

Example 8.2 Page no. 220

In [5]:
#Given
V=5      #V
d=2       #mV
E1=V+d*10**-3
E2=V-d*10**-3

#Calculation
Eds=E1-E2
Ecm=(E1+E2)/2.0

#Result
print"Input signal voltage is",Eds*1000,"mV"
print"Common mode voltage is",Ecm,"V"

Input signal voltage is 4.0 mV
Common mode voltage is 5.0 V

Example 8.2 Page No 225

In [2]:
#Given
a = 2/9.0       #Differential Gain
E1 = 10*10**-3
E2 = 5*10**-3   #Input Voltages 

#Calculation
Vout = (E1 - E2)*(1+(2/a))

#Result
print" output voltage = ", Vout*1000,"mV"

 output voltage =  50.0 mV

Example 8.3 Page No 227

In [6]:
#Given
R = 25*10**3 
aR = 50.0 

#Calculation
a = aR / R 
Gain = 1 + (2/a) 

#Result
print"Voltage Gain = " , Gain 

Voltage Gain =  1001.0

Example 8.4 Page No 227

In [1]:
#Given
import numpy
a=numpy.inf

#Calculation
Gain = 1+(2/a)  

#Result
print" Voltage Gain =  ", Gain

 Voltage Gain =   1.0

Example 8.5 Page No 227

In [9]:
#Given
m = 1001.0     #Gain
E1 = 5.001
E2 = 5.002
E3 = 5.001 
E4 = 5.000  
E5 = -1.001 
E6 = -1.002 

#Calculation
Vout1 = m*(E1-E2)
Vout2 = m*(E3-E4) 
Vout3 = m*(E5-E6)

#result
print" Output Voltages are   ", Vout1,"V ",Vout2,"V ",Vout3,"V"

 Output Voltages are    -1.001 V  1.001 V  1.001 V

Example 8.6 Page No 231

In [10]:
#Given
Vout = 5.0    #Output Voltage

#Calculation
Vce = Vout  

#Result
print" Vce=",Vce,"V"

 Vce= 5.0 V

Example 8.7 Page No 231

In [11]:
#Given
Vre = 1.2  
Re = 1*10**3 
Vce = 5
Vcc = 15         #Voltages in the circuit

#Calculation
Ie = Vre / Re 
Vcol = Vce + Vre 
Vrl = Vcc - Vcol 

#Result
print" Collector Voltage =  ", Vcol,"V"
print" Voltage across Rl  =", Vrl,"V"

 Collector Voltage =   6.2 V
 Voltage across Rl  = 8.8 V

Example 8.8 Page No 232

In [6]:
#Given
Rs = 1*10**3
E1 = 100*10**-3 
E2 = 0  
Rl = 5*10**3 
Gain = 10 

#Calculation
Il = 10*((E1-E2)/Rs)
Vr = Il * Rs 
Vref = Il * Rl 
V9 = Vref + Gain*(E1 - E2)

#Result
print" Current across Load Resistor = ", Il*1000 ,"mA"
print" Voltage across R  =  ", Vr,"V"
print" Reference Voltage  =  ", Vref,"V" 
print" Voltage at terminal 9 =", V9,"V"  

 Current across Load Resistor =  1.0 mA
 Voltage across R  =   1.0 V
 Reference Voltage  =   5.0 V
 Voltage at terminal 9 = 6.0 V

Example 8.9 Page No 234

In [9]:
#Given
GF = 2.0     #Gage factor
DR = 0.001 
R = 120.0 

#calculation
L = DR /(R*GF)  

#result
print" Change in length is ",round(L*10**6,1),"microinches per inch"

 Change in length is  4.2 microinches per inch

Example 8.10 Page No 236

In [10]:
#Given
E = 1.0  
DR = 0.001 
R = 120.0    #Resistance in Ohm

#Calculation
Vout = (E*DR)/(4*R) 

#Result
print" Output of the Bridge = ", round(Vout*10**6,1),"micro voltage"

 Output of the Bridge =  2.1 micro voltage

Example 8.11 Page No 241

In [12]:
#Given
Vout = 100*10**-3 
E = 5.0
R = 120.0 
Gain = 1000.0 
E1 = 30 *10**6 
Gf = 2.0          #Gage factor

#calculation
Vbridge = Vout / Gain 
DL = 20*10**-6 
DR = (R * Vbridge)/E 
Rratio = DR / R   #Change in Resistance
Strain = DL / Gf  #Change in Length 
Stress = E1 * Strain  

#Result
print " Change in Resistance =  ", DR*1000 ,"mohm"
print " Ratio of Resistance =  ", Rratio,"micro ohm/ohm"
print " Strain value =  ", Strain ,"micro inch/inch"
print " Stress value = ", Stress ,"psi"

 Change in Resistance =   2.4 mohm
 Ratio of Resistance =   2e-05 micro ohm/ohm
 Strain value =   1e-05 micro inch/inch
 Stress value =  300.0 psi

Example 8.12 Page No 245

In [2]:
#Given
T1=25    #C Temprature
T2=50
Tref=25   #C Reference temprature
Rref=10000
Rtrans=3603    #ohm, at 50 C


#Calculation
dR=Rtrans-Rref
R1=10     #Kohm say
E=1    #V trial choice
I=E/(R1+Rref/1000.0)
Vo=-I*dR

#result
print"The value of dR for each temprature is",dR,"ohm"
print"The current is",I,"mA"
print"Vo for each value of R",Vo,"mV"
#NOTE: In the book the value of Vo is calculated wrong

The value of dR for each temprature is -6397 ohm
The current is 0.05 mA
Vo for each value of R 319.85 mV