Saturday, 16 March 2013

READ OUTS OF DVMs



In 3 / 4 digit numerator indicates maximum value and denominator indicates number of digits


Number of digits
Maximum value
9/10
0,1,2,3………9
9
1/2
0,1
1
3/4
0,1,2,3
3
Note
A full digit has decimal point but ½ , ¾ … doesn’t have decimal point
Example
( 0 – 1 )V 3 digit DVM
SOLUTION

 Resolution  = 1 / 103 =10-3
Sensitivity = resolution * range = 10-3 * 1v =1mv
Roll over
Value
display
0.001v
.001
0.002v
.002
:
:

0.999v
.999 full scale reading

Total valid readings = maximum value / minimum value
                                  = 0.999/0.001
                                  = 999
Total number of readings = valid readings + reset
                                         = 999 + 1
                                         = 1000
Similarly
range
sensitivity
Max value
( 0 – 10 )v
0.01
9.99v
( 0 – 100 )v
0.1
99.9v

3 ¾ digital read out /display
 Examples
A voltage of 0.1234V to be displayed on 100V range of  4 ½  digit DVM
Solution
resolution = 1/ 10N = 1/104 = 10-4

Only full digits have decimal points and ½ digit has no decimal point
( 0 – 1 )V range
sensitivity = 10-4 * 1V =10-4V
0
.1
2
3
4

( 0 - 10)V range
sensitivity = 10-4 * 10V =10-3V
0
0
.1
2
3

( 0 – 100 )V range
sensitivity = 10-4 * 100V =10-2V
0
0
0
.1
2

( 0 – 1000 )V range
sensitivity = 10-4 * 1000V =10-1V
0
0
0
0
.1

2) A voltage of 0.6975V to be displayed on 10V range of  4 ½  digit DVM
    0. 697V
3) A voltage of 12.34V to be displayed on 10V range of  4 ½  digit DVM
    12.340V

1
2
.3
4
0




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