Service manual
Specification Data
1-4
1
Meets or exceeds AAMI EC11-1991 standard for Diagnostic Electrocardiographic Devices.
2
Meets or exceeds AAMI EC11-1991 standard for Diagnostic Electrocardiographic Devices. Tested according to AAMI
EC11-1991 test method 4.2.7.1.
Sampling Characteristics of Cardiograph
Physiological factors such as breathing can cause variation in amplitudes of heart beats,
independent of the heart rate. In addition, sampled systems (as opposed to continuous
systems) may show changes in the apparent height of the R-wave when sampling of the R-
wave occurs slightly off-peak. Because the sampling rate and the heart rate are
asynchronous, the time between the peak and an adjacent sample can vary from one QRS
complex to the next. This results in a slight variation of displayed QRS amplitude. This
effect is more pronounced with narrower signals, more commonly found in some pediatric
electrocardiograms and in pacemaker pulses. The M177XA family of cardiographs
minimizes this effect by:
• using an integrating-type A/D converter
• sampling all leadwires simultaneously
• oversampling the signals
• processing the oversampled signals with appropriate digital signal processing techniques
Table 1-2 Electrical Specifications
Parameter Specification
Resolution
ECG (internal)
display
5 µV
128 row pixels by 240 column pixels
display sweep speed
23.1 mm/sec
± 1%
Input impedance greater than 2.5 MΩ@ 10 Hz, typically greater than 100MΩ @ DC
1
Gain accuracy
±5% of input signal or ±40 µV, whichever is greater
2
Input bias less than 40 nA for input leadwire, less than 500 nA for Right Leg output
leadwire
1
Common mode rejection
110 dB or greater with AAMI test circuit
1
Defibrillator recovery
System recovery 8 seconds after 360 joule discharge, no damage
1
Crosstalk rejection
Less than 2% channel crosstalk
1
Sample rate 4.096M samples per second per input leadwire (unfiltered)
DC offset tolerance
≥ ±300 mVdc with less than 5% gain change
1
Noise
≤ 30 µV peak-to-peak RTI
1
Standardizing voltage
1 mV
± 5% for 100 mSec ± 5 mSec
1
50/60 Hz notch filter 50/60 Hz AC line rejection filters are always active.
Pacemaker pulse display > 0.2 mV indication for pace pulses between 0.5 and 2 ms duration at amplitude
2 to 250 mV
1