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Single Channel ECG Test System | User Manual
is already built into the waveform (as
downloaded from the Physionet website).
50.102.1
Accuracy of
signal
reproduction
(sensitivity,
non-linearity)
For non-linearity, the standard requires tests
starting with 10% of the display device followed
by 20%, 50% and 100%. However, at 10% the
displayed value is typically only 4mm (peak to
peak) and there may not be sufficient
resolution to accurately perform the test. For
this reason it is recommended to reverse the
order starting at 100% working down to 10%.
Note: this has been corrected in the 2011
edition
Filter settings should have no impact on the
results for the non-linearity test, but may
impact the relationship between set values and
displayed values. For this reason, a wide filter
(diagnostic) is recommended, for which set
values should match displayed values.
The test for sensitivity must be performed with
the 1mVpp 20Hz sine wave, easy to overlook as
the previous test used a triangle wave.
Patient monitors
with a “monitor” filter setting
may have some reduction or variation at 20Hz
due to the filter’s characteristics rather than
any measurement error in the input circuit.
Comparison of results at different frequencies
(e.g. 5Hz) or a
“diagnostic” filter set
ting will
give clause as to whether any reduction (or
increase) is due to the measurement circuit or
filter response.
50.102.2
Input dynamic
range and
differential
offset voltage
The standard asks to “adjust the sensitivity” of
the equipment so that a 10mVpp signal covers
80% of the display. However, most patient
monitors do not have continuously adjustable
sensitivities, and come with fixed values such
as 2, 5, 10 and 20mm/mV.
