SC7USB PQA Definition Guide
Average Bar or InterBar Gap
Widths are the average of widths measured across the entire postal
barcode. A low score for the average bar width or interbar gap width grade indicates
that print
conditions either expanded or shrunk the apparent size of the dark portions,
thereby threatening to make the narrow bars or spaces disappear.
- Potential areas of correction include adjusting the print
process, such as ink flow, transfer heat, print speed; adjusting
the original barcode symbol or by making the symbol larger.
Average Height
or Extension Height is a measure of the average height of the bars or the dark
portions in a
symbol.
- Depending on the symbology and print process, this can be
corrected by graphically stretching the symbol for 2D stacked
symbols or may be an indication that the symbol generating
program, in the case of postal barcodes, did not meet the required
specifications.
Bar Sequence is the bar height pattern within a height modulated,
multi-state
postal barcode.
- In a 2-State symbol, a "1" represents a tall or full height
bar and a "0" represents a short or half height bar.
- In a 4-State symbol, "A" represents the ascending bars, "D"
the descending bars, "T" the short bars and "H" the tall bars
that both both ascend and descend.
Codeword is a symbol character value or
intermediate level of coding between source data and the graphical
encodation.
- A data codeword encodes data according to the rules or
scheme of the symbology.
- A check codeword is reserved for error detection and error
corrections purposes.
Codeword Yield
indicates interference between adjacent rows in a 2D barcode. A low Codeword
Yield can indicate print conditions where this interference is
caused by drag, streaking or bleeding of ink from one row to
another.
Data Safety Margin is the ratio of unused error
correction codewords to the recommended number of error correction
codewords. A low Data Safety Margin indicates a symbol that is close
to reading failure and can be bettered by improving printing,
correcting the cause of bad or missing symbol characters or by
raising the Error Correction Level of the barcode.
Edge Accuracy is a measure of the accuracy of
the bars or dark portioned edge positions within the symbol.
- A low Edge
Accuracy indicates print conditions, such as a "print pitch to
X-Dimension" mismatch or general edge irregularities (but not
uniform print growth), which can hard character decoding.
- The first
condition is improved by properly scaling the symbol to the print
pitch and both conditions are improved by making the symbol larger.
The Encoded Message is the alpha, numeric and/or
control characters used to create a message contained within the barcode and
output as part of the decoding process. This information precedes
the calculated PQA output and must be manually compared to the
characters that should be encoded.
Error Correction is a reader or decoder's use of
mathematical processes to reconstruct or replace damaged or missing
symbol characters. Error correction characters are specific symbol
characters that are created automatically from the other symbol data
characters and used for error correction and detection.
- Error Correction Characters are symbol
characters that are reserved for error detection and calculated
automatically from the other symbol characters.
- Error Correction Level is an indication of
the number of characters used in the symbology for the purpose
of error correction. Higher levels of error correction allow for
correcting greater potential symbol damage.
- Error Detection is the use of error
correction characters to detect whether the presence of errors
in the symbol exceeds the error correction capability. Error
detection will keep the symbol from being decoded as erroneous
data.
Mask Pattern, also known as Masking, is a
specific part or characteristic of QR Code where a process is used
to provide a more evenly balanced number of light and dark modules
to reduce the occurrence of arrangements of adjoining modules that
might interfere with efficient processing of a symbol's image.
Module Errors are individual errors within fixed
pattern and data areas. Although often benign, module errors in the
fixed regions of a symbol can signal a fault that, in some
instances, can prevent proper decoding. They can generally be
corrected by using a larger X-dimension and/or cleaning up the print
process to remove stray ink, voids and other inconsistencies of
printing.
Print Growth is a measure of the growth or shrinkage of the bar
widths, elements or modules width and/or height.
- A low print growth grade indicates print conditions that expand or shrink the apparent size of the dark bars or elements, which can cause them to optically
disappear.
- In 2d matrix symbols, if the growth or shrinkage in one direction is larger than the other, this can indicate excessive drag in the direction of label travel.
- Potential areas of correction include adjusting the print process
adjusting the original barcode symbol graphic or pattern or by making the symbol larger.
Row Height is an approximate measure of the average height
of the elements in a row, which indicates growth or shrinkage of the element
widths. In 2D barcodes, row heights of less than the recommended height can
impede barcode readability. This can be corrected by graphically stretching the
barcode.
- Useful Row Height is the measured Row Height times the
codeword yield. A low Useful Row Height
usually indicates print conditions where rows interfere with their adjacent
neighboring rows, created a dead band of wasted scanning in between. Useful
row height scales these interfering rows to the printed row height, giving
more leeway to symbols printed with above the minimum row heights. A poor
grade here is corrected either by stretching the symbol vertically or
correcting the print condition that causes rows to interfere.
Symbology is a standard means of representing data in a
barcode form. Each symbology specification sets out its particular rules of
composition or data architecture.
The X-Dimension is an approximate
measure of the average width of the narrow elements in a 2D stacked barcode
symbol or a single element or module in a 2D matrix symbol and indicates growth
or shrinkage of the element widths.
Aztec Code PQA Results
The Full Report from a typical scan looks like the following (line
numbers have been added in curly brackets):
{1} This is a representative
Aztec Code symbol
{2} >>> PQA from IDAutomation <<<
{3} AZTEC
CODE: 3 layers (Compact) => 23x23 modules
{4} Data Field: 29 data & 22
chks in GF(256), 0 Erasures & 0 Errors
{5} X roughly = 0.021"
{6}
[A] < Core Symbol: 0 errors
{7} [A] < Data Safety Margin = 146%
{8}
[A] < Horizontal Print Growth = +1% of X
{9} [A] < Vertical Print Growth
= +1% of X
{1} is the Encoded Message.
{2} is the Banner heading.
{3} identifies the Symbology (AZTEC CODE) and lists the symbol's size and
format.
{4} lists the numbers of Data and Check Words, as well as the
Error Correction used.
{5} presents an approximate X-dimension.
{6} lists the number of Module Errors in the central Core
Symbol, which consists of the finder bulls-eye, four orientation clusters
at its corners, and the mode message along its perimeter. The grade is
assigned as:
A if there are 0 (zero) errors,
B if there is 1 error,
1 - 10
C if there are 2 errors,
D if there are 3 errors
F if there
are 4 or more errors.
In Screening modes, this parameter is reported as
"Too many Code Symbol Errors (3)" when that is the case.
{7} lists the
Data Safety Margin. In Aztec Code symbols, the recommended number of
error correction words is a minimum that is generally exceeded because
any excess codeword capacity is filled with extra check words. Thus this
parameter often exceeds 100%, but it also can be forced to much higher or
lower levels by user options.
{8} and {9} list the Horizontal & Vertical
Print Growths, respectively. When one direction's growth is substantially
larger than the other, excessive bar dragging in the direction of label
travel is indicated and should be fixed. When both directions have
excessive growth, then either (a) adjustment of the print process or (b)
undercutting of the original bar code symbol graphic is recommended.
Data Matrix PQA Results
The Full Report from a typical scan looks like the following (line
numbers have been added in curly brackets):
{1} This is a representative Data Matrix symbol
{2}
>>> PQA from IDAutomation <<<
{3} DATA MATRIX ECC200: 24
x 24 modules in size
{4} Data Field: 36 data & 24 chks in
1 block(s) of GF(256)
{5} X roughly = 0.025"
{6} [A] <
Fixed Patterns: 0 module errors
{7} [A] < Data Safety
Margin = 100%
{8} [A] < Horizontal Print Growth = +10% of
X
{9} [A] < Vertical Print Growth = +12% of X
{1} is the Encoded Message.
{2} is the Banner heading.
{3} identifies the Symbology (DATA MATRIX) and lists the
symbol's ECC and size.
{4} lists the numbers of Data and Check Words, as well as
the error correction used.
{5} presents an approximate X-dimension.
{6} lists the number of Module Errors in the Fixed
Patterns, which consist of the Finder "L" and Clocking
tracks around the perimeter of the symbol, their adjacent
quiet zones, and any interior alignment patterns in larger
ECC200 symbols.
In Screening modes, this parameter is reported as "Too
many Fixed Pattern Errors (3)" when that is the case.
{7} lists the Data Safety Margin. This parameter is
measured and reported only for ECC200 symbols. These symbols
have a fixed level of error correction. There is no
equivalent parameter for the convolutional error encoding
used in older versions of Data Matrix. This parameter is
just the "Unused Error Correction" and always between 0 and
100%.
{8} and {9} list the Horizontal & Vertical Print Growths,
respectively.
MaxiCode PQA Results
The Full Report from a typical scan looks like the following
(line numbers have been added in curly brackets):
{1} This is a representative Maxicode symbol
{2} >>> PQA from
IDAutomation <<<
{3} MAXICODE: Mode 4
{4} X roughly =
0.043"
{5} [A] < Data Safety Margin = 100%
{6} [A] <
Horizontal Print Growth = +2% of X
{7} [A] < Vertical Print
Growth = -1% of X
{1} is the Encoded Message.
{2} is the Banner heading.
{3} identifies the Symbology (MAXICODE) and lists the symbol's
Mode.
{4} presents an approximate X-dimension.
{5} lists the Data Safety Margin. Because the Error Correction
level for MaxiCode is fixed for each mode, this parameter is just
the "Unused Error Correction," and is always between 0 and 100%.
{6} and {7} list the Horizontal & Vertical Print Growths,
respectively.
PDF417 PQA Results
The Full Report from a typical scan looks like the following (line numbers
have been added in curly brackets):
{1} This is a representative PDF417 symbol
{2} >>> PQA from
IDAutomation <<<
{3} PDF417: 11 rows x 3 cols, 25 data & 8 chks (ECL = 2)
{4} X roughly = 0.014"
{5} [A] < Row Height = 3.1 X
{6} [A] < Useful Row
Height = 2.5 X (82% Row)
{7} [A] < Data Safety Margin = 100% (0 Erasures &
0Errors)1 - 6
{8} [B] < Edge Accuracy = 59%
{9} [C] < Print Growth = -43%
of X
where:
{1} is always the Encoded Message, the usual data output. In this
case "This is a representative PDF417 symbol".
{2} is a standard Banner heading that marks the start of the PQA
portion of the output.
{3} identifies the Symbology, PDF417 (or its derivative
COMPOSITE-C), and lists other characteristics of this symbol: the
height and width of the data field, the numbers of data and check
characters, and the corresponding Error Correction Level.
{4} presents an approximate X-dimension, presuming normal viewing
distance. In the Screening PQA modes, the Symbology Identification
from Line {3} is combined with the approximate X-dimension from Line
{4}.
{5} lists the average Row Height, assigning the grades as:
A if Row Height >= 2.5 X
F otherwise
In Screening modes, this parameter is reported as "Rows are Too
Short (2.2X)" when that is the case.
{6} lists the Useful Row Height, which is the measured Row Height
times the codeword yield (listed in parentheses), the percentage of
symbol characters scanned that actually decode. The grade is
assigned as:
A if Useful Height >= 2.0 X, else
B if Useful
Height >= 1.6 X, else
C if Useful Height >= 1.3 X, else
D if
Useful Height >= 1.0 X, else
F otherwise
In Screening modes, this parameter is reported as "Useful Row
Height is Too Short (1.5X)" when that is the case.
{7} lists the Data Safety Margin, which is the ratio of the
unused error correction words to the recommended (!) number of such
words. Data Safety Margin can exceed 100%, when the ECL is higher
than the minimum recommended, or be limited to 50% or lower, even
with perfect printing, when the ECL is below minimum. The grade is
assigned as:
A if Safety Margin >= 62%, else
B if Safety
Margin >= 50%, else
C if Safety Margin >= 37%, else
D if
Safety Margin >= 25%, else
F otherwise
In Screening modes, this parameter is reported as "Low Data
Safety Margin (44%)" when that is the case.
{8} lists the Edge Accuracy measured in the Start or Stop
patterns. The grade is assigned as:
A if Edge Accuracy >= 62%, else
B if Edge
Accuracy >= 50%, else
C if Edge Accuracy >= 37%, else
D if
Edge Accuracy >= 25%, else
F otherwise
In Screening modes, this parameter is reported as "Poor Edge
Accuracy (59%)" when that is the case.
{9} lists the Print Growth measured in the Start or Stop patterns
(the growth of the dark modules or "bars"). The grade is assigned
as:
A if Print Growth is between +/- 20%, else
B if Print Growth
is between +/- 30%, else
C if Print Growth is between +/- 40%,
else
D if Print Growth is between +/- 50%, else
F otherwise
In Screening modes, this parameter is reported as "Excessive
Print Growth (33%)" or "Excessive Print Shrinkage (-43%)" when those
are the cases. In rare instances where neither a valid Start nor
Stop pattern is measurable, yet the symbol is somehow read, lines
{8} and {9} are replaced by a message to that effect. The message is
either:
"[F] < Start/Stop Decode Fails" in a Full Report or
"Start/Stop Characters are Bad" in a Screening mode.
In Screening modes, it often occurs that none of the parameters
are below the Minimum Acceptable grade. In this case, the final PQA
line becomes: "All Measurements within range".
QR Code PQA Results
The Full Report from a typical scan looks like the
following (line numbers have been added in curly brackets):
{1} This is a representative QR Code symbol
{2} >>> PQA from
IDAutomation <<<
{3} QR CODE: Model 2 Version 3 (29 x
29 modules)
{4} Mask Pattern Reference #3, Error Correction
Level "M"
{5} Data Field: 44 data & 26 checks in 1
block(s) of GF(256)
{6} X roughly = 0.025"
{7} [A] <
Data Safety Margin = 100%
{8} [A] < Horizontal Print Growth =
+20% of X
{9} [A] < Vertical Print Growth = +17% of X
{1}
is the Encoded Message.
{2} is the Banner heading.
{3}
identifies the Symbology (QR CODE) and lists the symbol's model,
version and size.
{4} lists this symbol's Mask
Pattern and Error Correction Level.
{5} lists the numbers of
Data and Check Words and their arrangement into blocks.
{6} presents an approximate X-dimension.
{7} lists the Data Safety
Margin. "M" is the recommended error correction level for QR
Code, so symbols encoded at "H" or "Q" will typically have
safety margins exceeding 100%, while those encoded at "L" are
limited to values below 50%.
{8} and {9} list the
Horizontal & Vertical Print Growths, respectively.
Postnet and Planet Code PQA Results
The Full Report from a typical scan looks like the following
(line numbers have been added in curly brackets):
{1} 51591
{2} >>> PQA from IDAutomation <<<
{3} POSTNET: 32
Bars, nominally from 01.30 to 01.56 in. in Width
{4} Bar
Sequence: 10101000011010101010000011101001
{5} [F] (Hi) < Tall
Bar Heights: 0.155 in.
{6} [F] (Hi) < Short Bar Heights: 0.081
in.
{7} [A] (Ok) < Bar Widths = 0.022 in.
{8} [A] (Ok) <
Inter-Bar Gaps = 0.023 in.
{1} is the Encoded Message.
{2} is the Banner heading.
{3} identifies the Symbology, (POSTNET or PLANET Code), and lists
also the symbol's size and allowed range of measured width.
{4} lists the Bar Sequence, "1" representing a tall bar and "0"
representing a short one.
{5} lists the Average Height of the tall bars, specified to fall
within 0.115 to 0.125 in. The grades are assigned as:
A if within the middle 67% of the specified tolerances, else 1 -
14
B if within the specified tolerances, else
C if within a
range 25% wider(!) than the specified tolerances, else
D if
within a range 50% wider(!) than the specified tolerances, else
F
otherwise
Note: These forgiving grade assignments, employed throughout the
postal symbologies, reflect what are generally tight and unforgiving
print specifications.
In Screening modes, this parameter is reported as ""Tall" Bars
are too Short (or Long) (0.xxx in.)" when that is the case.
{6} lists the Average Height of the short bars, specified to fall
within 0.040 to 0.060 in. In Screening modes, this parameter is
reported as ""Short" Bars are too Short (or Long) (0.xxx in.)" when
that is the case.
{7} lists the Average Width of the bars, specified to fall within
0.015 to 0.025 in. In Screening modes, this parameter is reported as
"Bars are too Narrow (or Wide) (0.xxx in.)" when that is the case.
{8} lists the Average Space Width between bars, specified to fall
within 0.012 to 0.040 in. In Screening modes, this parameter is
reported as "Spaces are too Narrow (or Wide) (0.xxx in.)" when that
is the case.
4-State Codes PQA Results
The Full Report from a typical scan looks like the following
(line numbers have been added in curly brackets):
{1} B15AJ6T
{2} >>> PQA from IDAutomation <<<
{3}
4-STATE(British): 34 Bars, nominally from 38.5 to 42.3 mm. in Width
{4} Bar Sequence: ADHTATDAHDDAADADAADTHTADHHDATHTADH
{5} [A] (Ok)
< "Tall" Bar Extensions: 2.79 mm. from center
{6} [F] (Hi) <
"Short" Bar Extensions: 1.00 mm. from center
{7} [B] (Hi) < Bar
Widths = 0.60 mm.
{8} [A] (Ok) < Inter-Bar Gaps = 0.59 mm.
{1} is the Encoded Message.
{2} is the Banner heading.
{3} identifies the Symbology, 4-STATE (British, or KIX, Canadian,
Japanese, or Australian), and also lists this symbol's size and
allowed range of measured width.
{4} lists the Bar Sequence, "A" representing Ascending bars, "D"
representing Descending bars, "T" representing Tracker (short) bars,
and "H" representing tall bars that both ascend and descend.
{5} lists the Average Extension from the centerline of the tall
ascenders and descenders, as specified in the table below. In
Screening modes, this parameter is reported as ""Tall" Bar
Extensions are too Short (or Long) (0.xxx in.)" when that is the
case.
6} lists the Average Extensions from the centerline of the Short
tracks, as specified in Table 1.
In Screening modes, this
parameter is reported as "Short" Bar Extensions are too Short (or
Long) (0.xxx in.)" when that is the case.
{7} lists the Average Width of the bars, as specified in the
table below.
{8} lists the Average Space Width between bars, as specified in
the table below.
Note: For the Canadian and Australian 4-State
symbologies only, any bar error that has invoked their error
correction triggers an additional PQA parameter line:
"[F] < One or more Bars are in Error!" in a Full Report or
"One or more Bars are in Error!" in a Screening mode.
If there are any questions, please
contact IDAutomation.
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