Sanwa PC20TK, Инструкция по сборке и эксплуатации

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12
[3] Basic Knowledge of Digital Multimeter
3-1 Analog vs. digital
Quantities are roughly classified into analog quantities and digital ones. Analog quantities represent
quantities having continuous intensity, such as time, length, weight, electric voltage and current.
Digital quantities mean quantities having discontinuous intensity, such as 1, 2 and 3 counted for
things. Visually, the former is liken to a slide, while the latter is liken to a flight of stairs. Digital
display seems to be rough at a perceptional level, but the use of the present advanced electronic
and digital technologies allows for measuring quantities at high accuracy because digital signals
have an advantage in that noises, if included, can be easily eliminated to minimize the deterioration
of signals.
3-2 Analog multitester (AMT) vs. digital multimeter (DMM)
With an analog multitester, you can accurately measure voltage or other up to a level of only 1/100
(3 digits) of the full-scale value. In addition, the reading differs depending upon individual users. In
contrast, a digital multimeter displays the measured value in numerals, allowing the user to
correctly read the displayed value to the full digits. Unlike an analog multitester, a digital multimeter
does not require the user to make a troublesome conversion of the reading (e.g., by multiplying it
by 10 or 1/10), but allows the user to simply use the reading as it is with the corresponding unit. A
digital multimeter provides other useful capabilities such as holding data, displaying the negative
sign, and warning an input overflow. When popular models are compared between analog
multitesters and digital multimeters, there are no differences in size and price. The following table
compares the rough specifications of popular models between analog multitesters and digital
multimeters.
Fig. 3-1
Analog multitester
Digital multimeter
Digital multimeter Analog multitester
Construction of
readout
Electronic construction
using an A/D conversion
LSI, an LCD, etc.
(a numeric value is
displayed on the readout) Mechanical construction
using a magnet, a moving
coil, etc.
(the pointer indicates a
reading on the scale).
Main
measurements
DCV, ACV, DCA, ACA,
Ω
,
,
DCV, ACV, DCA,
Ω
, dB,
hEF, BT, ( )
Mode selection
and other
operations
The auto mode is
selectable. The decimal
point, a unit, and a polarity
can be displayed.
In general, operations are
manually performed. The
decimal point, a unit, a
polarity and others are
determined by the user
when he reads what the
pointer indicates.
Reading error
Accuracy
In principle, there is no
reading error.
High
A reading error occurs from
parallax and personal
differences.
Slightly low
Input resistance
in the voltage
mode High
(about 10 M
Ω
regardless of
the range selected)
Varies depending on the
range selected
(2 k-10 M
Ω
)