Saadat DENA 1210 User Manual page 29

Chapter 2: System settings
Warning
• The use of 25, 35, and 75 Hz Low Pass filters may reduce the amplitude of the heart
signal and omit some useful signal details.
• If you turn on the local power noise cancellation filter, in proportion to the selected
frequency, its third harmonic will also be removed. In other words, if the local power
frequency is 50 Hz, in addition to the 50 Hz frequency, the 150 Hz frequency is also
removed. If the power frequency of the local city is 60 Hz, in addition to the
frequency of 60 Hz, the frequency of 180 Hz is also removed. The reason for this is
to make the heart signal clearer and smoother.
• If the EMG filter is turned on, only 75 or 150 Hz options for the low-pass filter are
available. Because if the EMG and the 25 or 35 Hz low-pass filters are on at the same
time, significant changes will be observed in the signal amplitude.
• The EMG filter is a time-varying nonlinear adaptive filter designed solely for
application to ECG signals. Due to the non-linear nature of this filter, the user should
turn on and use it after receiving sufficient training from qualified people. In some
cases, the above filter may reduce the amplitude of P and T waves and the QRS
complex.
Note
• After setting EMG: On, first wait a few seconds, then start recording.
• Refer to the Troubleshooting and Error messages chapter to eliminate ECG signal
noise.
• If the drift filter is inactive and the signals have offset, the signals may not be at the
same level with the corresponding labels and the paper space may not be partitioned
correctly.
• For Low Pass Filters, the -3dB cut-off frequencies are at 150 ± 20 Hz, 75 ± 5 Hz, 35
± 2 Hz and 25 ± 2 Hz, respectively.
• For Drift filter, -3dB cut-off frequency is at 0.6 ±0.1 Hz. If the drift filter is switched
off, the cut-off frequency will be about 0.05Hz.
• It should be noted that the Drift filter can affect the analysis of the ST segment.
• Failure to display the signal and reaching the final line above or below the display
range can mean that the signal is saturated.
• For EMG filter, -3dB cut-off frequency increases to about 55Hz in areas where the
signal slope is high and decreases to about 10Hz when the signal slope is low.
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