Guralp Systems CMG-DM24S12AMS User Manual
CMG-DM24S12AMS
Acquisition and Monitoring System
Operator’s guide
Part MAN-D24-0002
Designed and manufactured by
Güralp Systems Limited
3 Midas House, Calleva Park
Aldermaston RG7 8EA
England
Proprietary Notice: The information in this manual is
proprietary to Güralp Systems Limited and may not be
copied or distributed outside the approved recipient's
organisation without the approval of Güralp Systems
Limited. Güralp Systems Limited shall not be liable for
technical or editorial errors or omissions made herein,
nor for incidental or consequential damages resulting
from the furnishing, performance, or usage of this
material.
Issue Date Comments
A 2003-01-26 First issue
B 2004-03-19 Rewrite
CMG-DM24S12AMS Operator's guide
Contents
Contents..................................................................................................................2
1 Introduction........................................................................................................ 3
2 Quick start........................................................................................................... 9
3 Using Scream!................................................................................................... 13
System ID.................................................................................................... 15
Output control............................................................................................16
Triggering................................................................................................... 20
Mux Channels............................................................................................ 29
Ports............................................................................................................. 30
System..........................................................................................................32
Triggering................................................................................................... 33
Calibration.................................................................................................. 34
Data Flow.................................................................................................... 35
Recording.................................................................................................... 36
Files.............................................................................................................. 38
The UFF file format....................................................................................40
My Client.....................................................................................................43
My Server....................................................................................................44
4 Inside the DM24S12AMS................................................................................ 52
Power...........................................................................................................53
GPS...............................................................................................................53
USB to RS232 converter............................................................................ 54
5 Using CMG-5U sensors................................................................................... 58
Unpacking and packing............................................................................60
Initial testing...............................................................................................60
Installing the sensor...................................................................................61
Centring the 5U..........................................................................................63
Electrical connections................................................................................ 64
Absolute calibration...................................................................................65
Relative calibration.................................................................................... 65
Using a DM24 series digitiser for calibration.........................................67
Appendix A: Connectors and cables................................................................ 71
Data ports....................................................................................................71
Power ports.................................................................................................73
PC ports.......................................................................................................74
Appendix B: Specifications................................................................................ 78
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CMG-DM24S12AMS Operator's guide
1 Introduction
The Güralp CMG-DM24S12AMS 12-channel acquisition and monitoring
system is a self-contained seismic data collection station specially
configured to operate 12 single-component CMG-5U strong motion
accelerometers. It combines all the features of the CMG-DM24 3 or 6channel digitiser with an integrated laptop PC for viewing and
transmitting the recorded data.
The housing of the digitiser is made from high impact copolymer
polypropylene with mil-spec connectors fitted on to metal plates. There
is also a small internal pocket for storing cables or documentation. The
unit features a roller trolley design for ease of transportation.
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CMG-DM24S12AMS Operator's guide
The integrated laptop PC is supplied with Güralp Systems’ Scream!
software pre-installed. Using the PC, you can process incoming data and
transfer it to any compatible storage device over a telephone line
(modem) or network connection.
Care must be taken when handling the integrated PC, which is a
standard laptop model. In particular, you should not force the screen lid
closed. Closing the lid would cause the PC to enter hibernation mode,
and halt all data collection. Instead, you should rest the lid on the rubber
stops fitted to the PC's keyboard, so that the PC remains active and the
digitiser functions as expected. There is sufficient room within the
DM24S12AMS unit to allow you to leave the PC in this state and still
close the outer case completely.
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CMG-DM24S12AMS Operator's guide
Note: Because the integrated PC requires ventilation, the DM24S12AMS
is not completely waterproof. The water level must not be allowed to
reach the ventilation grilles on the sides, front and rear of the box at any
time.
A typical setup for a DM24S12AMS acquisition and monitoring system
is shown below.
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CMG-DM24S12AMS Operator's guide
Here, the twelve CMG-5U uniaxial sensors can be distributed
throughout a building to capture its response to ground motion, while a
digital CMG-5TD unit is embedded in the ground nearby to capture the
ground motion itself. Data from all thirteen instruments is fed into the
DM24S12AMS, where it can be stored and processed on-site or
alternatively sent across a local network or the Internet. If required, up
to five further digital instruments can be connected to the
DM24S12AMS (not shown).
The DM24S12AMS unit’s 12 analogue input connections are each
identical to the output connection of the Güralp CMG-5U. These
connections also serve as the sensors’ 12V power supply. If required,
other types of sensor may also be wired to a DM24S12AMS module.
Using compatible connections, you can control all the sensors through
the module, either using its integrated PC or from a remote location on
your network. The digitiser can also provide common calibration and
GPS timing signals to all the sensors.
All DM24 digitiser units are fitted with high-impedance, low-noise,
differential input pre-amplifier modules.
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CMG-DM24S12AMS Operator's guide
In addition to the main 24-bit analogue inputs, the digitiser module
features an additional 16 slow rate 16-bit resolution analogue inputs.
The inputs to the slow rate channels are through the connector marked
AUXILIARY INPUTS. These inputs are all single-ended and use a fixed
sample rate of 4 samples/s.
The DIGITAL A − F connectors are provided for use with Güralp
Systems digital output seismometers (such as the CMG-3TD) or
accelerometers (CMG-5TD). Like the analogue inputs, the DIGITAL A −
F connectors can supply power to the digital sensors. Alternatively, if
required, the DIGITAL A − F can be used as serial interfaces (e.g. to
remote installations connected by modem.)
The DM24S12AMS unit can be powered either from 110 – 250V AC
mains power, or from a 12 V DC power source. In addition, a
BATTERY/UPS connector is provided, for attaching to a rechargeable
battery or UPS. If power is provided through one of the other sockets,
the battery will be recharged at 14 V. There is also an external USB port,
and a standard parallel port within the casing.
For more details on the internal design of the DM24S12AMS, see
Chapter 4, “Inside the DM24S12AMS”.
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CMG-DM24S12AMS Operator's guide
1.1 Feature overview
• A built-in Digital Signal Processor (Motorola 56002) provides
simultaneous multiple sample rate data streams at user selectable
rates. Up to 4 streams of data for each component are available at
sample rates from 1 to 200 samples/s.
• A precision microprocessor-controlled time base synchronizes
Analogue to Digital Converters, and DSP and time-stamps data
blocks.
• Time synchronization to external GPS or serial time code.
• A control microprocessor (Hitachi H8) formats and buffers data
in an on-board 512k RAM ring buffer.
• Efficient data storage and transmission using the Güralp
Compressed Format.
• Serial data output (RS232) at user selectable baud rates—options
of RS422, DPSK or fibre-optic.
• Built-in microprocessor system configuration and sensor control,
including locking and unlocking, centring and calibration.
• Low system power consumption, less than 3W (excluding the
integrated PC)
• Flash EEPROM for program code and filter coefficients.
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2 Quick start
1. If you are using a GPS timing signal to synchronize your
instruments, first connect a GPS receiver to the digitiser's GPS
socket.
2. Power up the system. The DM24S12AMS module can take power
from the mains, or from any ~12 V DC supply such as a battery or
UPS. If a rechargeable battery is connected to the BATTERY/UPS
socket, and enough external power is provided, the battery will
be recharged as required.
3. Open the lid of the unit, and power up the built-in laptop PC,
which is configured to automatically run the latest version of
Güralp's Scream! software. After a short while, Scream!'s main
window will open:
4. Scream! will then connect to the digitiser. The DM24S12AMS
houses two separate 6-channel digitiser modules, which work on
CH 1-6 and CH 7-12 respectively. After a short wait, the two
modules should appear under Local in the left hand pane, each
on its own Com port.
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CMG-DM24S12AMS Operator's guide
5. Whilst Local is selected in the left-hand pane, the list on the right
details all the data streams coming from any instrument directly
attached to the DM24S12AMS. Clicking on Network will display
all data coming from networked instruments or other Scream!
servers, if there are any. Clicking on the entry for a particular
digitiser picks out streams coming from that digitiser; likewise,
clicking on a Comxx entry will display only streams attached to a
particular Com port.
6. The columns in the table provide useful information about each
stream.
Stream ID: A unique name for the data stream, being a
combination of six letters A – Z and numbers 0 – 9. Streams
ending in “00” carry status information about the internal
digitiser, whilst other streams contain data coming from
connected instruments. The slow-rate environmental channels
(Mux channels) generally have Stream IDs ending in “Mx” where
x is a hexadecimal digit (0 – 9 or A – F), whilst other Stream IDs
are used for seismic data from attached instruments.
Rec.: Whether the data stream is currently being recorded to the
hard disk.
Format: The format of the data the stream is producing; one of 8,
16 or 32 bit.
SPS: The sampling rate of the data stream, in samples per second.
Status streams ending in “00” do not constantly output data and
have an SPS of 0. By default, the stream list is sorted in order of
sample rate, with the status streams at the bottom.
End time: The time the data stream last sent data to Scream!. The
time is taken from the digitiser's internal clock, which can be set
from signals coming from an attached GPS receiver (see “GPS” in
Section 4.1).
Date: The date the data stream last sent data to Scream!.
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RIC: The ‘Reverse Integrating Constant’. In effect this is the value
of the last sample received. This is most useful for reading mass
positions or other environmental streams.
7. You can now connect a Güralp CMG-5U sensor to one of the CH
1 – 12 connectors on the side of the unit. See Section 5.2,
“Installing CMG-5U sensors” for more details.
8. Double-click on one of the streams to open a WaveView window
for viewing the data.
9. You can add further streams to the WaveView window by
selecting them from the streams list and dragging the selection
into the WaveView window.
10.You can open new WaveView windows by making a selection of
streams from the list and double-clicking on that selection.
11.To see the status information coming from each digitiser, rightclick on the status stream (ending in “00”), and select View from
the pop-up menu. A Status window will open containing all the
text that has been received since power-up.
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CMG-DM24S12AMS Operator's guide
The first blocks will give the boot message from the digitiser,
including its software revision and the data streams selected for
downloading and triggering. Later blocks give information on
visible GPS satellites, the location of the GPS antenna and time
synchronization status. Also displayed are the baud rates
currently used for each channel and for the data link.
The following chapters describe a selection of the features available in
the Scream! 4 software provided with the DM24S12AMS. For full
information on what you can do with Scream! please consult its own
user guide or the extensive online help.
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CMG-DM24S12AMS Operator's guide
3 Using Scream!
3.1 Configuring digitisers
The DM24S12AMS unit contains two built-in 6-channel DM24 digitiser
modules, one running the ports CH 1 – 6, and the other using ports CH
7 – 12. These may be configured from within Scream!, together with any
external Güralp digital instruments attached to the DM24S12AMS's
DIGITAL A – F connectors.
Scream! 4 distinguishes between configuration and control of digitisers.
The most important difference is that a digitiser may be controlled
through Scream! whilst in the process of acquiring data, whereas
configuring a digitiser requires that it be rebooted (with consequent loss
of data.)
To change the configuration of any attached digitiser, including the two
6-channel digitisers installed within the DM24S12AMS unit, right-click
on the digitiser's entry in the list to the left of Scream!'s main window
(not the Local or Comxx icons) and click Configure.... Scream! will then
contact the digitiser and retrieve its current configuration, a process
which will take a few seconds, after which the Configuration setup
window will be displayed. Once you are happy with any changes you
have made in the Configuration Setup window, click UPLOAD to send
them to the digitiser and reboot. This will take a short while.
To control a digitiser whilst it is running, either right-click on the
digitiser's entry in the list and click Control..., or double-click the entry.
In either case Scream! will contact the digitiser to retrieve control
information and display the Control window. The options you can
control immediately are:
• The type of sensor you are using
• GPS power cycling options
• The short-term and long-term average values for triggering (but
not which streams perform the trigger, or which are output by it)
(see also “Triggering” in Section 3.1)
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CMG-DM24S12AMS Operator's guide
• The length of pre-trigger and post-trigger periods (see also
“Triggering” in Section 3.1)
• Calibration signal options
• Mass control functions
Some of these options can also be altered in the Configuration setup
window. For more information on the Control window, see Section 3.2,
“Controlling digitisers”.
If you need a more powerful interface to the digitiser modules, you can
also issue commands to it directly using Scream!'s terminal mode. A
terminal window is opened by right-clicking on the digitiser's entry in
the list and selecting Terminal.... The digitiser will stop collecting data
while you have a terminal window open. For more details on the
DM24's terminal mode commands, please see its technical
documentation (available from Güralp Systems.)
The remaining sections of this chapter describe in detail the
configuration options available for the DM24S12AMS's in-built
digitisers. Many of these options will also be available for other Güralp
digitisers or digital sensors connected to the unit's DIGITAL A – F ports.
For the most accurate information, you should consult the Operator's
Guide for the digitiser or sensor you connect.
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System ID
The System ID pane gives information about the digitiser and its internal
software, and allows you to change GPS timing parameters.
System Identifier and Serial Number: The digitiser type is identified by
its system identifier and serial number. Every data and status block
generated by the digitiser includes these two fields at the beginning, so
that the block’s origin can be identified. On delivery from the factory,
the system identifier and the serial number are set to the GSL works
order number and the digitiser’s serial number, but you can set either
value to any combination of up to 6 letters A-Z and numbers, such as an
abbreviation of your institution’s name, etc.
Sensor Type: If the sensor attached to the digitiser is a Güralp velocity
sensor, useful seismometer functions (such as sensor locking, centring,
and calibration) may be controlled through the digitiser. The type of
sensor programmed with this option determines which functions will be
available through the Scream! digitiser configuration set-up interface or
through interactive commands. The in-built digitisers are already
programmed to the proper sensor type for Güralp CMG-5U uniaxial
sensors.
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CMG-DM24S12AMS Operator's guide
GPS Type: The digitiser needs to be able to time-stamp accurately all
data that passes through it. It can set its clock either by receiving time
signals from the GPS satellite network using an attached Garmin GPS
unit, or by taking time information from a central site (stream sync
mode). In stream sync mode, the digitiser expects to receive GCF packets
from the central timing source (which may have its own GPS unit, or
take signals from one of the radio time standards).
Enable GPS power cycling: If you are using a GPS unit to receive time
signals, but do not experience significant drift in the system's clock (for
example, in a stable-temperature environment), you can save power by
selecting Enable GPS power cycling. With this option in use, the GPS
time is only checked at intervals of a specified number of hours.
Disabling this option keeps the GPS unit running constantly; if you have
ample power, this will give the most accurate results. You can choose
any whole number of hours for the interval.
Output control
The Output control tab allows you to configure which data streams are
sent to Scream! from each digitiser.
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Güralp instruments output data sampled at 2000 Hz, which is then
filtered and reduced to a lower rate (decimated) using an on-board digital
signal processing unit, or DSP. The DSP has four filtering-decimation
stages, which run one after the other. The output of each stage is called a
tap. The first filter stage, tap 0, is pre-set to reduce the data by a factor of
10 to 200 samples/second.
Each of the three remaining taps may be configured for a different
decimation factor by choosing values from the drop-down menus on the
left. Decimation factors of 2, 4, 5, 8, and 10 are available. The numbers
visible in the drop-down menu of each tap are the data rates that each of
the possible decimation factors will provide, given the settings of the
taps above it. Only integer (Hz) data rates are allowed: thus, for
example, if one tap emits data at 25 Hz, the only possible further
decimation factor is 5.
To the right of each decimation factor menu is a grid of check-boxes.
These boxes mark which streams of data to record at each sample rate.
The screenshot above shows a possible configuration for a triaxial
instrument (similar to a CMG-5TD connected to one of the ports
DIGITAL A – F).
If you want to change the names used for the channels, click in the white
box containing a Z in the above picture, and type a letter or number. It
will name the channels with a sequence of letters or numbers beginning
with the one you choose (e.g. A, B, C; 2, 3, 4; 9, A, B), unless you type Z
in which case they will revert to Z, N, and E.
Each combination of channel and tap has two check-boxes. The upper
check-box of each pair activates continuous output, whilst the lower
activates triggered output. In the example above, the digitiser will output
data continuously for all three channels at Tap 2, but never for any other
taps. If you do not need all the streams to output at all rates, you should
leave boxes unchecked to save communications capacity. You cannot
check both continuous and triggered output for the same channel and
tap.
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CMG-DM24S12AMS Operator's guide
Triggered output causes the digitiser to output data only when a
particular set of trigger criteria are met. This is shown diagrammatically
as data passing through a switch. In the example above, we might want
the more detailed data from Tap 0 to be recorded only when an event
registers at some other tap. To do this, the lower check-boxes of Tap 0
should be ticked:
With this configuration uploaded, Tap 2 will continue to produce output
at all times, but Tap 0 will also emit data whenever the trigger criteria
are met. The Triggering button is now shown in red to remind you that
the trigger is active.
Every checked box in this window will give rise to a data stream coming
from the digitiser, which will be displayed in Scream!'s main window
when Scream! first receives some data from it. Every stream is identified
by a 6-character code, where the first four characters identify the
digitiser, and the last two characters identify the individual stream.
Using the example above, there are three data streams, Z, N and E,
which each output data at 20 samples/s (continuously) and 200
samples/s (occasionally). The streams appear in Scream!'s main window
like this:
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In this example:
• DA79 is the serial ID of the digitiser.
• Z0, N0, E0 correspond to input channels Z, N, and E, output
through Tap 0.
• Z4, N4, E4 correspond to input channels Z, N, and E, output
through Tap 2. A six-channel digitiser connected to two triaxial
instruments will use Z0, N0, E0, Z1, N1, E1 for tap 0; Z2, N2, E2,
Z3, N3, E3 for tap 1; Z4, N4, E4, Z5, N5, E5 for tap 2; and Z6, N6,
E6, Z7, N7, E7 for tap 3. The digitiser in the example has only one
triaxial instrument connected to it, so Z/N/E1, 3, 5 and 7 are
unused.
You can change these designations if you wish: see the Scream!
manual or online help for more details.
• 00 is the digitiser status stream (notice: no sample rate),
• M8, M9, MA are slow-rate Mux channels reporting the sensor
mass positions for the Z, N, and E components (“Mux Channels”
in Section 3.1).
• ME is another Mux channel, here used for reporting the
temperature.
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CMG-DM24S12AMS Operator's guide
Triggering
In its standard configuration, the digitiser modules inside the
DM24S12AMS output continuous data at a sample rate you specify. In
addition to this, the digitiser can run a triggering algorithm on the data
it acquires. This allows you to record data continuously at a relatively
low sample rate, but record at a much higher sample rate during short
periods when the trigger is active. The parameters controlling the
triggering algorithm, and controlling the data output once the system is
triggered, are all selectable by the user, permitting maximum flexibility
of operation and the most efficient use of available storage space.
The digitiser modules inside the DM24S12AMS can be set up for
triggered output, that is, to output certain data streams only when a
particular trigger criterion is met. The trigger criterion can be tested with
data from the same or some other stream. For example, you could use a
later tap (with a lower sample rate) as a trigger for output from an
earlier, more detailed tap. Scream! 4 also allows each digitiser to receive
triggers from other digitisers.
To create a new stream with a trigger, open Scream!'s Digitiser
configuration window for the relevant digitiser, and click on the Output
control tab. In the Output control pane, a tap which gives rise to a
triggered stream has a tick in the lower row of its grid of check-boxes.
You cannot configure the trigger criteria until you have selected at least
one stream to be affected by the trigger.
Once you have decided which streams should be output when the
trigger is activated, you will be able to click on the Triggering button to
describe the trigger condition. Alternatively, click on the Triggering tab
at the top of the window. Either action will open the Triggering pane:
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CMG-DM24S12AMS Operator's guide
There are two triggering algorithms which Güralp digitisers can use.
However, not all models can use both methods. Scream! will find out
from the digitiser whether its on-board software supports each method.
STA/LTA
The STA/LTA algorithm applies a simple short-term average – long-term
average calculation to the triggering stream. It works by identifying
sections of an incoming data stream when the signal amplitude
increases. The purpose of taking a short term average, rather than
triggering on signal amplitude directly, is to make it less likely that
spurious spikes will trigger the device. Averaging also introduces an
element of frequency selectivity into the triggering process.
You can select which tap is tested for the trigger from the Data source
drop-down menu. The tap does not have to output data to Scream! for
you to be able to use it here.
Any or all of the channels available at that tap may be used to determine
a trigger. You can select which channels are considered by checking the
boxes in the Channel column of the table. If any of the checked channels
passes the trigger condition, the trigger will activate, and will not
detrigger until all of the checked channels have fallen below their
respective ratio values.
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CMG-DM24S12AMS Operator's guide
The STA and LTA columns allow you to set the intervals over which the
two averages are calculated, in seconds. Typically, the time interval for
the short term average should be about as long as the signals you want
to trigger on, while the long term average should be taken over a much
longer interval. Both the STA and LTA values are recalculated
continually, even during a trigger.
The Ratio column determines by what factor the STA and LTA must
differ for the trigger to be passed. Finding the ratio most suited to your
needs is best done by experiment. Too high a value will result in events
being missed, while too low a value will result in spurious non-seismic
noise triggering the system. Like the averages, their ratio is continuously
recalculated for all components. Note that none of the boxes are allowed
to be empty, and so you will need to enter the new value before
removing the old one. Alternatively, you can use the up and down
cursor keys to change the values.
For example, setting the STA to 1 second, the LTA to 10 seconds and the
Ratio to 4 would give rise to the following trigger behaviour:
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CMG-DM24S12AMS Operator's guide
Usually, the values of the STA and LTA periods, and of the Ratio, will
be the same for all checked channels. For convenience, Scream! will
automatically fill in other values to match ones you enter. If you want to
use different values for some channels, you should uncheck Common
values before altering them.
Once you have enabled the STA/LTA triggering method on a particular
channel, you can use the Control window to change the values of the
STA and LTA periods, together with the Ratio, without restarting the
digitiser (see Section 3.2, “Controlling digitisers”.)
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CMG-DM24S12AMS Operator's guide
Since it is not generally advisable to trigger from broadband data, the
digitiser provides a set of standard bandpass filters to apply to the data
streams before they are tested for the trigger condition. This filtering
serves to maximise sensitivity within a the frequency band of interest,
and filter out noise outside this band. You can select which bandpass
filter to use from the Bandpass filter drop-down menu. The corner
frequencies of the pass band of the filter are determined by the Nyquist
frequency, which is given by the sampling rate of the triggering data.
The three filter options have pass bands between 10 % and 90 %,
between 20 % and 90 % and between 50% and 90% of the data’s Nyquist
frequency, respectively.
The possible filter configurations are shown in the following table:
Tap #
Rate
(samples/s)
Bandwidth 1
(Hz)
Bandwidth 2
(Hz)
Bandwidth 5
(Hz)
0 200 10 – 90 20 – 90 50 – 90
1 100 5 – 45 10 – 45 25 – 45
50 2.5 – 22.5 5 – 22.5 12.5 – 22.5
40 2 – 18 4 – 18 10 – 18
25 1.25 – 11.25 2.5 – 11.25 6.25 – 11.25
20 1 – 9 2 – 9 5 – 9
2 50 2.5 – 22.5 5 – 22.5 12.5 – 22.5
25 1.25 – 11.25 2.5 – 11.25 6.25 – 11.25
20 1 – 9 2 – 9 5 – 9
10 0.5 – 4.5 1 – 4.5 2.5 – 4.5
8 0.4 – 3.6 0.8 – 3.6 2 – 3.6
5 0.25 – 2.25 0.5 – 2.25 1.25 – 2.25
4 0.2 – 1.8 0.4 – 1.8 1 – 1.8
2 0.1 – 0.9 0.2 – 0.9 0.5 – 0.9
3 25 1.25 – 11.25 12.5 – 11.25 6.25 – 11.25
10 0.5 – 4.5 1 – 4.5 2.5 – 4.5
5 0.25 – 2.25 0.5 – 2.25 1.25 – 2.25
4 0.2 – 1.8 0.4 – 1.8 1 – 1.8
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