Saturday, 16 March 2013
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
Saturday, 16 March 2013 0
Digital Voltmeters (DVMs)
are a special case of A/Ds.
DVMs are general purpose instruments commonly used to measure
voltages in labs and in the field. DVMs display the measured voltage
using LCDs or LEDs to display the result in a floating point format.They
are instruments of choice for voltage measurements in all kinds of
situations.
They display measurements of
both AC and DC voltages as discrete numerals.
Analog measuring instrument
is current instrument where as digital measuring instrument is a voltage
measuring instrument
Types of DVMs
1)Ramp type
2)Dual slope
3)Successive approximate
type
DVM = A/D converter +
digital read out
Resolution of DVM
It is small incremental change in input which
can be detected. It depends on number of digits
Resolution = 1 / 10N N = number of full digits
Sensitivity
The minimum input voltage
level that can be sensed and displayed by DVM
Sensitivity = resolution *
range
Number os sesitivities of
DVM = number of ranges
Features of DVM
1)They offer superior
resolution of order of 1: 106
2) improved accuracy = +
0.005%
3) parallax errors are
eliminated
4) more portable
5) They offer very high
input resistance in the range of mega ohms.So loading errors are minimized
6) The output is available
in digital form. So further processing is made possible
Friday, 15 March 2013
In Millman's Theorem, the
entire circuit can be drawn as a parallel network of branches, each branch
containing a resistor in series with battery combination.
Rules
Friday, 15 March 2013 0
Thursday, 14 March 2013
RECIPROCITY THEOREM
The theorem states that
The current I in any branch of a network, due to a single voltage source E anywhere else in the network, will equal the current through the branch in which the source was originally located if the source is placed in the branch in which the current I was originally measured.
The reciprocity theorem is
applicable only to single-source networks.It is, therefore, not a theorem
employed in the analysis of multisource networks
In other words, the location of the voltage source
and the resulting current may be interchanged without a change in current. The
theorem requires that the polarity of the voltage source have the same
correspondence with the direction of the branch current in each position.
Thursday, 14 March 2013 0
Monday, 11 March 2013
Maximum power transfer theorem
A load will receive maximum power from a linear bilateral dc
network when its total resistive value is exactly equal to the Thévenin resistance
of the network as “seen” by the load.
Different cases in Maximum power transfer theorem
1) source resistance and variable load
I = VS / ( RS + RL )
Power ( p) = I2 RL = VS2
RL / (RS + RL)2
For maximum power differentiate power with load resistance
and equate it with zero
Monday, 11 March 2013 2
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