# Chapter 7 : Display Devices and recorders¶

## Example 7.1 Page No : 349¶

In :
# Variables
N  =  4.;

# Calculations and Results
R = 1./10**N;
print "Resolution of the meter = ", R
VR = 1;
R1 = VR*R;
print "Resolution of the meter for voltage range 1V = ", R1
VR1 = 10;
R2 = VR1*R;
print "Resolution of the meter for voltage range 10V = ", R2

Resolution of the meter =  0.0001
Resolution of the meter for voltage range 1V =  0.0001
Resolution of the meter for voltage range 10V =  0.001


## Example 7.2 Page No : 351¶

In :
# Variables
N  =  3.;

# Calculations and Results
R = 1./10**N;
print "Resolution of the meter = ", R
print "12.98 will be layed as 12.980 on 10V scale"
VR = 1.;
R1 = VR*R;
print "Resolution of the meter for voltage range 1V = ", R1
print "0.6973 will be layed as 0.6973 on 1V scale"
VR1 = 10;
R2 = VR1*R;
print "Resolution of the meter for voltage range 10V = ", R2
print "0.6973 will be layed as 00.697 on 10V scale"

Resolution of the meter =  0.001
12.98 will be layed as 12.980 on 10V scale
Resolution of the meter for voltage range 1V =  0.001
0.6973 will be layed as 0.6973 on 1V scale
Resolution of the meter for voltage range 10V =  0.01
0.6973 will be layed as 00.697 on 10V scale


## Example 7.3 Page No : 353¶

In :
# Variables
R = 5.;

# Calculations and Results
V = 0.005*R;
print "0.5 percent of the reading", V
TPE = V+0.01;
print "Total possible error (V) = ", TPE
R1 = 0.10;
V1 = 0.005*R1;
TPE1 = V1+0.01;
print "Total possible error (V) = ", TPE1
PE = (TPE1/0.1)*100;
print "Percentage error = ", PE

0.5 percent of the reading 0.025
Total possible error (V) =  0.035
Total possible error (V) =  0.0105
Percentage error =  10.5


## Example 7.4 Page No : 355¶

In :
# Variables
N = 034;
t = 10.*10**-3;

# Calculations
f = N/t;

# Results
print "frequency(Hz) = ", f

frequency(Hz) =  2800.0


## Example 7.5 Page No : 357¶

In :
# Variables
R = 5*10**6;

# Calculations and Results
V = 0.00005*R;
print "0.005 percent of the reading(micro sec) = ", V
LSD = 1;
ME = V+1;
print "Maximum error (micro sec) = ", ME
R = 500;
V = 0.00005*R;
print "0.005 percent of the reading(sec) = ", V
LSD = 1;
ME = V+1;
print "Maximum error (sec) = ", ME

0.005 percent of the reading(micro sec) =  250.0
Maximum error (micro sec) =  251.0
0.005 percent of the reading(sec) =  0.025
Maximum error (sec) =  1.025


## Example 7.6 Page No : 359¶

In :
import math

# Variables
D = 8.*10**-3;

# Calculations and Results
A = D**2;
print "A = ", A
J = 8*10**-3;
K = 16*10**-3;
B = 4*J*K;
print "B = ", B
print "since A<B so the instrument is underdanped",
th = (100*math.pi)/180;
i = 10*10**-3;
F = 0.2*10**-6;
G = (K*th+F)/i;
l = 65*10**-3;
d = 25*10**-3;
N = G/(B*l*d);
print "number of turns = ", N
i = F/G;
print "current required to overcome friction (A)", i

 A =  6.4e-05
B =  0.000512
since A<B so the instrument is underdanped number of turns =  3356426.44614
current required to overcome friction (A) 7.16192114565e-08


## Example 7.7 Page No : 361¶

In :
# Variables
Lam = 2.5*6.25;
f = 50000;

# Calculations
S = Lam*10**-6*f;

# Results
print "speed(m/s) = ", S

speed(m/s) =  0.78125


## Example 7.8 Page No : 363¶

In :
# Calculations
ND = 12000/1.5;

# Results
print "Number density (numbers/mm)", ND

Number density (numbers/mm) 8000.0


## Example 7.9 Page No : 365¶

In :
# Variables
Y1 = 1.25;
Y2 = 2.5;

# Calculations
PA = math.asin(Y1/Y2);

# Results
print "phase angle (degree)", PA
print "possible angle are 30 degree and 330 degree",

phase angle (degree) 0.523598775598
possible angle are 30 degree and 330 degree


## Example 7.10 Page No : 367¶

In :
import math

# Calculations and Results
print "if spot generating pattern moves in the clockwise direction"
Y1 = 0;
Y2 = 5;
PA = math.asin(Y1/Y2);
print "phase angle (degree)", PA
Y1 = 2.5;
Y2 = 5;
PA = math.asin(Y1/Y2);
print "phase angle (degree)", PA
Y1 = 3.5;
Y2 = 5;
PA = math.asin(Y1/Y2);
print "phase angle (degree)", PA
Y1 = 2.5;
Y2 = 5;
PA = 180-(math.asin(Y1/Y2));
print "phase angle (degree)", PA

if spot generating pattern moves in the clockwise direction
phase angle (degree) 0.0
phase angle (degree) 0.523598775598
phase angle (degree) 0.775397496611
phase angle (degree) 179.476401224