# Chapter 13: Shielding And Grounding¶

## Example13_1,pg 405¶

In [1]:
# find diagnostic ratio

import math
#Variable declaration
t1=0.1*10**-6             #time span for voltage
t2=1*10**-6               #time span for current

#voltage switching
V1=0.5                    #level-1
V2=5.0                    #level-2

#current switching
I1=0                      #level-1
I2=10*10**-3              #level-2

#Calculations
DR=(((V2-V1)/t1)/((I2-I1)/t2))

#Result
print("dissipation ratio:")
print("DR = %.f ohm\n"%DR)
print("DR is quite large indicating noise interference by capacitive coupling.")

dissipation ratio:
DR = 4500 ohm

DR is quite large indicating noise interference by capacitive coupling.


## Example13_2,pg 509¶

In [4]:
# find diagnostic ratio

import math
#variable declaration
t1=1*10**-6                #time span for voltage
t2=1*10**-6                #time span for current

#voltage switching
V1=0.5                     #level-1
V2=1.0                     #level-2

#current switching
I1=1*10**-3                #level-1
I2=10*10**-3               #level-2

#Calculations
DR=(((V2-V1)/t1)/((I2-I1)/t2))

#Result
print("pseudoimpedance:")
print("DR = %.f ohm\n"%(math.floor(DR)))
print("DR is not quite large indicating noise interference by inductive coupling.")

pseudoimpedance:
DR = 55 ohm

DR is not quite large indicating noise interference by inductive coupling.


## Example13_3,pg 510¶

In [8]:
# find ground loop current

import math
#Variable declaration
Vi=12.0                    #input DC voltage
Vo=3.182                   #output voltage
Rg=130*10**3               #grounding resistance
R2=1*10**3                 #output resistance
R1=6.8*10**3               #divider chain

#Calculations
Ig=(Vo-((2*R2*Vi)/(R1+R2)))/Rg

#Result
print("grounding loop current:")
print("Ig = %.1f micro-A"%(Ig*10**6))

grounding loop current:
Ig = 0.8 micro-A