(2) This calibration should be performed after five minutes of a warm up
interval to ensure tracking between the voltage to frequency converter and the phase lock
c. Calibrate the Manual Size Control and 1mv Calibration Chart Recorder.
Refer to Appendix B, Monitor Board Analog Schematic, sections B-7 and B-9.
(1) Be sure the ECG simulator and lead selector switch are in the lead 1
configuration, the simulator output is exactly 1.0mv with 60 to 80bpm, and the size control
is in its center position.
(2) Turn the unit on and wait five minutes for stabilization. Depress the 1mv
calibration button several times. A positive going pulse should appear on the CRT with
sharp rising and falling edges.
(3) By adjusting R111 (one-turn control), make the positive deflection above
the base line exactly the same height as the peak of the QRS complex of the incoming
Now switch the chart recorder selector to DIAGNOSTIC.
(5) Adjust R138 (four-turn control) so as to obtain exactly 20mm of pen
deflection at the peak of the QRS complex.
(6) Push the 1mv calibration button for 1/2 second at a time. During each
interval the button is pushed, the input signal is removed, and a square pulse appears on
the chart which should have the same amplitude (20mm) as the QRS complex. If you
notice a deviation of more than 2mm between the amplitude of both signals, check the
frequency response of the chart recorder. It may have changed from the original settings
because of differences in paper or pen pressure.
d. Calibrate the Display and Chart Recorder Amplitude. Refer to Appendix B,
Monitor Board Analog Schematic, sections
B-8, B-9, and B10.
Reconnect the ECG simulator to the input.
Adjust the output to 1mv and 60bpm.
Turn the size control to its center position.
(4) Now turn R123 until the oscilloscope connected to pin 14 of U102 shows a
signal of 1.5v P/P. Disregard the superimposed dc voltage. If there is a difference in
amplitude between the signal on the chart recorder and the CRT in diagnostic operation,
R138 has to be adjusted until both are identical.