Page 27
6/23/04 DI-50B51 320 Series (NZ306)
Texmate, Inc. Tel. (760) 598-9899
•
www.texmate.com
Logarithmic Bargraph Scaling
Logarithmic scales are used in a wide variety of measurements.
Probably the most well known logarithmic scale is the Richter
scale for measuring earthquakes. Other log scales used include
sound level (dB), radio frequency signals, power levels (dBm),
and numerous radiation signals.
In all logarithmic scales a reference level is required that is the
level at 0 dB. For example, in an RF measurement 0 dBm is at
a reference of 1 mW.
The scale is calculated from:
If the meter is scaled so that:
1 mW = 100 counts and 1 W = 100,000 counts
Then the reference for 0 dBm would be set to 100
counts:
10 log
10
counts (input)
reference
10 log
10
(input)
100
= 0 dBm
Decade
(Counts)
–
20
–
10
0
10
20
30
40
1
10
100
1000
10,000
100,000
1,000,000
Now every 10 dBm represents a decade, the bargraph can be
scaled to a different amount of bars per decade (as set in the
3rd digit).
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Bargraph Display Format
After the bargraph colors have been
set and the bargraph scaled, the dis-
play format can be set. This is nor-
mally the final setting. The 2nd digit
selects the format of the bargraph
display. There are four display format
settings available:
•
Setpoints on Bar
. Selecting [X0X]
means that the setpoints are dis-
played on the bar as lit segments in
the current display color. When the
bargraph lights up on or beyond a
setpoint, the setpoint segment goes
out.
100
80
60
40
20
0
SP4
SP5
SP6
SP3
SP2
SP1
SP
Segments
Go Out
Lit SP
Segments
Lit Segments
Showing
Signal
Example of Setpoints on Bargraph
Reference
. This is the number of counts displayed for a 0 dB
reference. Range: 1 to 99999 counts.
Bar Nominal
. See Bar Nominal description under heading:
Linear Bargraph Scaling.
Selecting
3
in the 1st digit and
3, 4, 5, 6, or 7
in the 3rd digit
enters the Set Up Scaling for Logarithmic Bargraph sub-menu:
•
Selecting
3
in the 3rd digit sets the log to 10 Bar/Decade.
•
Selecting
4
in the 3rd digit sets the log to 20 Bar/Decade.
•
Selecting
5
in the 3rd digit sets the log to 25 Bar/Decade.
100 dBm
80 dBm
60 dBm
40 dBm
20 dBm
0 dBm
10 Bars/Decade
90 dBm
70 dBm
50 dBm
30 dBm
10 dBm
40 dBm
20 dBm
0 dBm
20 Bars/Decade
50 dBm
30 dBm
10 dBm
40 dBm
0 dBm
25 Bars/Decade
30 dBm
20 dBm
10 dBm
0 dBm
33 Bars/Decade
30 dBm
20 dBm
10 dBm
0 dBm
50 Bars/Decade
20 dBm
10 dBm
100
1000
10,000
100,000
1,000,000
100
1000
10,000
100,000
1,000,000
100
1000
10,000
100,000
1,000,000
100
1000
10,000
100,000
100
1000
10,000
Example of Bars per Decade
•
Peak and Valley on Bar
. Selecting
[X1X] means that peak and valley
are displayed as lit segments and
are updated as they change. The
setpoints are not displayed.
•
Min/Max
with
Setpoints
.
Selecting [X4X] means that the
segments of the bar remain lit
over the minimum and maximum
signal variations. The setpoints are
displayed as lit segments.
This is a useful mode for seeing
process variations at a glance.
Note:
When moving from another dis-
play format to the Min/Max with
Setpoints mode, the peak and
valley settings must be set to the
current settings by entering the
Peak View mode or Valley View
mode and pressing the UP and
DOWN buttons at the same time.
PEAK
Input Signal
Displayed using
Bargraph Center
Zero Mode
VALLEY
Example: Peak and Valley on Bargraph
MAX
All segments
between MAX
and MIN
remain lit
except any
SPs in that
area
SP4
SP5
SP6
SP3
SP2
SP1
MIN
Example: MIN and MAX on Bargraph
When moving from Min/Max
with Setpoints mode to another
display format, the bar nominal
[bAr_n] setting must be reset to
its original settings in Code 10
[3XX].
•
Bar Only
. Selecting [X7X] means
that only the bargraph display signal
is displayed on the bar. Setpoints
and peak and valley are not dis-
played.
•
Selecting
6
in the 3rd digit sets the log to 33 Bar/Decade.
•
Selecting
7
in the 3rd digit sets the log to 50 Bar/Decade.
Example Procedure
. The example procedure on Page 34
shows how to scale the bargraph using example logarithmic
settings.
