The Input/Output Manager of the software is where you can set the ADC or any type of input. Here you can select or unselect the channels, set their range and change their names based on what you have connected to the corresponding channel.
To work with this module, you first have to choose your input device in the configuration module. EGRET automatically brings the interface of that input module in the I/O Manager.
By default the first 8 channels are marked as open (Enabled). You can enable more channels either in a sequence or selectively. EGRET will display and record from all enabled channels. Even if you turn the signal off in the Display module, EGRET would still record the data from that channel.
By holding down the shift button, you can select a group of channels and by setting one of them, all of them change accordingly.
It is possible to enable a channel without opening the channels preceding it. After you setup this module and change all the settings for channels, you can save this setting to save time and reduce chance of errors next time that you want to use the software with the same configuration. To do so, give a name to your setting in the Save box and click save. This name will appear in the “Saved config files” section. Next time that you open the software, you can load the setup by clicking on the desired saved configuration.
Sampling rate: The sampling frequency or sampling rate, fs, is the average number of samples obtained in one second. This value defines the number of data points used for reduction of a continuous-time signal to a discrete-time signal. For example, if you set the sampling rate to 2000 samples per second, the software will collect 2000 samples from each selected channels of the ADC. As such the maximum sampling rate depends on the ability of the ADC and the number of channels to be recorded from. As an example, MCC 2533 has a maximum sampling rate of 1 MS/s. This means that if you want to record from all its 64 channels, the maximum sampling rate that you can input will be 15,625. Likewise, if you decide to record from 10 channels of this board, you can set the sampling rate to up to 100,000 samples per second. It is important to select an appropriate sampling rate; Following the Nyquist-Shannon sampling theorem, choosing low sampling rates runs the risk of aliasing. While sampling at higher than needed rates does not compromise signal quality, it increases the size of the recorded files. For EMG data, we advise using sampling rates which are 3 to 5 times as much as the bandwidth of the recording Device. A sampling rate of 5000 S/s per channel is usually more than enough for most surface EMG devices.
Ch Enable boxes: Check or uncheck these boxes to select which channels of the ADC you want to record from. If you do not select a given channel here, the software will not record any data from that channel.
Names: The default names of the channels are Ch##. You may change the names to a more meaningful name here. For example, if you are recording from the Soleus Muscle Through Channel #1 of the ADC, you may rename Ch 01 to “Sol”. This name will appear in the rest of the areas of the software (such as Signal Display or Peak Detector), making it much easier for you to quickly realize what signal it is.
Range: These values define and set the input level of the ADCs. it is imperative to choose the correct range for each channel. The correct level depends on the device sending data to the analog board. For example, all analog signals generated by the MA400 are in the range of ± 5 volts so you need to set the analog data collection system to record data or accept input signals at this level. If you select a lower level (i.e. ± 2.5 volts) then the MA400 signals may be
clipped or distorted and will not be measured correctly. If you select too high a level (i.e. ± 10 volts) then the measured signals will be too small and you will loose some
resolution or precision. Please visit “Recommendations for MA-400 configuration” for more information on setting up Motion Lab Systems MA-400 EMG system.
DC offset: Choosing this option causes a removal of any possible DC Bias on the signal. The DC bias, DC component, DC offset, or DC coefficient is the mean amplitude of the waveform. If the mean amplitude is zero, there is no DC bias. A waveform with no DC bias is known as a DC balanced or DC free waveform. It is ordinary that EMG data collection systems apply a small DC signal to the EMG waveform. Removing this DC bias is important for many EMG signal analyses.
Type: define the nature of the signal. While this option does not affect the quality of the recorded signal in any manner, it will significantly help you in other modules of the software. For example, in the Peak Detector module, Reference signals are those which are tagged as TTL signal here. This will avoid populating the list of all signals most of which are irrelevant for being a reference signal.
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