SIGVIEW supports real-time data acquisition from the following device types:
· Windows compatible sound cards (up to 16-bit resolution, up to 2 channels, old-style
· DirectSound compatible sound cards ( maximal supported sound card resolution, typically
24-bit for professional sound cards, typically all available channels)
· ASIO sound card drivers (by Steinberg) for low-latency and high fidelity sound card
· Data acquisition simulation by reading data from specially prepared signal file
SIGVIEW offers a generic user interface and settings for data acquisition from all supported
devices. Device-specific settings (if any) are available through additional dialogs (by clicking on
"Default-specific settings" button). To understand the settings available in these custom dialogs,
please consult user manual for your specific data acquisition device.
To start data acquisition, choose Data acquisition/Open data acquisition menu option or
toolbar button. A dialog appears which allows you to choose data acquisition device and to
change the data acquisition settings:
Device type: Device type to be used. It corresponds to the above list of device classes
supported by SIGVIEW. If you have no devices of specific type installed in your system,
you will not see the corresponding entry in this combo-box.
Device: Actual device to perform data acquisition. Only available devices from the selected
device type will be shown in the combo-box.
Device-specific settings button: Some devices allow special settings to be made, for
example hardware triggering, input range, gain, etc. By pressing this button, a new
device type specific dialog will open allowing you to change device specific settings. For
more information about these settings, please consult your hardware manual for the data
acquisition device. If there are no specific settings for currently chosen devices, this
button will be disabled.
Calibration file: see calibration topic for details. Alternatively, some professional DAQ
devices offer “Automatic calibration” option. This means that SIGVIEW will
try to obtain data
in physical units (usually Volts) from the DAQ device.
Channels: You can choose one of the following:
· a number of channels to use for the acquisition (first [1...NumberOfChannels]
channels of the device)
· or the exact list of channels to use for the data acquisition (for example "1,4,7").
By pressing the "List" button, an edit box will appear instead
of the combo-box for the
selection of the channels number. In the edit box, you will be able to enter a comma-separated list of channel indexes (for example "1,4,7") which should be used for the data
acquisition. Please note that not all devices support this exact channel selection.
By pressing the "Count" button, you will switch back to the
channel count selection mode.
Sample rate (samples/sec) : this is the sampling rate for one
channel. The maximum value
is determined by your DAQ device capabilities. The combo box will show some standard
types supported by most cards. If you want to use some other custom sampling rate, press
“Custom” button and enter the sample rate manually. Please note that some sound cards will
simply report that they support any sample rate even if they don’t
support it in hardware.
Those will simply try to simulate it on a driver level. If you want to avoid it, please consult the
card's manual to determine which sample rates are really supported. Most devices do not
allow arbitrary sample rate settings. SIGVIEW will try to find the next possible sample rate
settings applicable to your device and apply it automatically. You will see the actual sampling
rate in the status bar of the data acquisition window after you close this dialog.
Block length (samples): SIGVIEW retrieves signal from your
DAQ device in blocks of a
constant length. After one block is retrieved, it is displayed in the DAQ window and processed
with any attached analysis functions. This option enables you to define the block size, i.e.
how much samples will be retrieved from device and shown in a window during acquisition.
Recording length: This option enables you to define the overall
length of the data
acquisition. Following options are available:
· Absolute recording length (seconds): After the defined recording length in seconds
has been reached, acquisition will sto. During acquisition, you will always see the last
"Block length" samples in your acquisition window but you will see all samples after
zooming-out. Please note that SIGVIEW stores all data in physical memory (RAM).
Therefore, saving more then several minutes of data by using this method is not
recommended. You can use Logging data to file feature
for that purpose.
· One block: Only one block of data (as defined by "Block length") will be retrieved.
· Continuous monitoring: If you want only to monitor the signal without any saving, use
this option. Data acquisition will run until explicitly stopped. You will always see only the
last "Block length" samples in your data acquisition window. No other samples will be
Decimation ratio: To reduce the amount data which has to be processed
you can use decimation feature, i.e. convert multiple samples from the DAQ device to one
sample in SIGVIEW. You can define a decimation ratio by determining how many samples
from the DAQ device will be converted to one sample in SIGVIEW. If you choose decimation
ratio greater then 1, SIGVIEW will calculate the actual sample rate and show it as a read-only
information under this field. For example, if the sample rate on Sound card is 44100Hz, and a
decimation ratio is 100, then the actual sample rate in SIGVIEW will be 441Hz.
Trigger recordings in windows with external trigger: Check this option if you want that
start of this recording (manual or triggered) also starts all other recordings which are waiting
on "external trigger" (see below for more details about that "external trigger" type).
Start recording after trigger: If you check this option, recording
will not start immediately
after pressing START button – SIGVIEW will wait for a specific
trigger (i.e. signal level) value
in the signal and then start recording automatically. Trigger behavior and the definition of
trigger value is determined by using the following options:
Trigger on channel: Determines which of the data acquisition
channels will SIGVIEW
monitor for a trigger value. It is possible to receive data on one channel and use the other
one only for triggering.
Threshold (% full scale): This option determines which signal
level is exactly regarded
as a trigger value in the signal. Each sample with the amplitude higher than the threshold,
by default 50%, from the maximum possible signal amplitude will be regarded as a
trigger. For example, if your trigger is very strong signal impulse, you can set threshold to
Trigger type: This option enables you to choose the type of trigger.
Following types are
· Signal level: If signal level is above Threshold (in % of the full scale), start
· Absolute signal level: If absolute signal level is above Threshold (in % of the full
scale), start acquisition
· Rising edge: If absolute signal level is above Threshold (in % of the full scale), and
the signal is rising, start acquisition
· Falling edge: If absolute signal level is above Threshold (in % of the full scale), and
the signal is falling, start acquisition
· External trigger: If external trigger type has been set, this recording will start after
another window with "Trigger recordings in windows with external trigger" option
starts its recording. Please note that the start of this recording and trigger recording
will not be perfectly synchronized as if using hardware-based triggering. You can
expect to see time difference of up to 1 block length between recordings.
Start recording X samples before/after the trigger: This option
determines on which
position, relative to the trigger appearance, will SIGVIEW start recording. The position is
defined in number of samples. Negative value will cause SIGVIEW to start recording
before the trigger and positive value after the trigger. Maximal number of samples you
can set for pre-trigger option is equal to "Block length" setting (see above).
Re-Arm trigger trigger after each recording: After data acquisition
is started after
trigger and required signal length has been recorded, data acquisition would normally
stop. By turning this option on, you can instruct SIGVIEW to automatically open a new
data acquisition window after the triggered data acquisition has been finished. New data
acquisition window will use exactly the same settings as the previous one, i.e. will wait on
trigger, record, and then start new data acquisition window. This way, you can let SIGVIEW automatically record multiple triggered signal events. Each recording will be
stored in a separate window. To limit numbers of new windows which can be created
during this operation, you can set "Max Re-Arm Count" option. Please note that trigger
Re-Arm options make sense only if you define some specific recording length. If you use
the value of zero (monitoring only), trigger will never be re-armed because recording will
Reuse the same window after Re-Arming : This option works similar
as above "Re-Arm trigger trigger after each recording" option, but does not create a new window
after each Re-Arming. Instead, each new acquisition is started in the same window,
deleting all previously recorded samples. This can be used only in combination with the
setting Block length = "One block". If you attach an Averager window to your acquisition
window, you will be able to perform Time synchronous averaging. To limit numbers of
retrieved data blocks, you can set "Max Re-Arm Count" option.
For further information about the triggering, please see the How-To:
Starting/stopping data acquisition
After you set all these data acquisition parameters and press OK button, one or more signal
windows will appear (depending on number of channels). Now you can press button on
toolbar or choose Data acquisition/Start menu option to start data acquisition. If you choose
"Continuous monitoring" as block length, you can stop it by pressing button on the toolbar or
choosing Data acquisition/Stop menu option. Otherwise, data acquisition will stop automatically
after the desired acquisition length is reached. While data acquisition is running, you can work
with the signal window as you would with any window containing static signal: for example, you
can perform FFT of a running signal, track its changes as 3D graphics, and as a result, you will
have a real 3D spectrum analyzer.
After the data acquisition has finished, the signals in data acquisition signal windows are zoomed-in to show only the last recorded block. You will have to choose Zoom-out option to see the whole
You can also use Control Window to start or stop multiple data acquisitions at once (context-menu option).
Resetting Data acquisition
After you have performed data acquisition and recorded some signal, you will not be able to start
data acquisition in the same window again because it already contains recorded data.
If you would like to repeat the acquisition in the same window (for example, because the result of
the first one was not satisfactory), you can reset the acquisition window by using "Data
acquisition/Reset acquisition window" from the main menu. This function will bring acquisition
window in its initial state enabling you to re-run data acquisition.
Using "File" driver
If you choose ‘File’
driver type you will be able to simulate data acquisition by reading data from
file in 16-bit signed binary format (You can store any data in that format by using Binary file export
feature). After clicking on “Device specific options” button you will be able to choose the file
name. SIGVIEW will try too keep the desired sample rate if there is enough data in the file.