(3) Another way of testing without the defibrillator is to apply an external 12 dc
power source to pin 4 of J3 with the positive through a 1 kilo (k) resistor to pin 4 of J3, and
the negative to the ground. As soon as the external source is turned on, the marker pulse
is present. By observing the signal at pin 4 of J3 on the oscilloscope, a negative-going
pulse of about 4.0 volt amplitude and 5.0 milliseconds (msec) duration should appear for
each QRS recognition. The pulse should not be present during the time the hold button is
(1) Select paddle pick-up mode and apply a
(ground) of J3.
(2) A clean recorder sine wave should be displayed on the CRT and on the
chart records when in the delayed mode of operation. This signal should diminish rapidly
in amplitude above 30Hz.
i. Calibrate the Heart Rate Meter and Alarm. Refer to Appendix D, Monitor
Board Heart Rate Meter Schematic, sections C-17, C-18, and D-18.
(1) Since the heart rate meter takes its signal from the QRS recognizer, it is
necessary to verify that the recognizer circuit functions properly. Calibrate the reference
voltage which appears at TP1 pin 1 to exactly 1.000v +\-1.0mv by turning R186.
(2) Drive the patient cable input with an ECG simulator at 1.0mv and 240bpm.
The following repetition rates of the signal have to be accurately known: 30, 60, and
240bpm, for this test.
(3) Once the read out number has stabilized within 2 beats plus or minus, turn
R190 (four-turn control) so as to obtain a read out of 240bpm, + or - 2bpm.
(4) Now switch to 60bpm. The read out should stabilize at + or - 1bpm. After
this test, switch to 30bpm. The read out should, again, stabilize at + or - 1bpm.
This concludes the calibration and verification of its linearity. Let us proceed to
the heart rate alarm circuits.
(5) Connect an oscilloscope probe between TP1 pin 3 and TP1 pin 4 (ground).
An absolutely linear, positive ramp should appear at the repetition rate of four times per
second, approximately, when the input to the unit is driven by an ECG signal of 240bpm.
Adjust R197 (one-turn control) until the peak value of the ramp is 4.0v in