Adjusting and Using the
Set all of the trim pots to their center position. Stand
the U channel upright in the slot of the base as shown in
Figure 12. Download and install the Zietnitz Soundcard
Scope app (version 1.46). Connect the ECG unit, SCOPE
OUT, to the microphone input of a laptop computer using
a short stereo 1/8” to 1/8” patch cable/cord. Connect the
input cable to the ECG unit.
Open the settings tab of the Soundcard Scope app.
Set the scope input to the external microphone (Figure
13). Adjust the channel 1 amplitude to 400m per division.
Setthe trace time to five seconds. Set the trigger amplitude
to 200 mV. Adjust the ECG pre-amp gain pot to the 2:00 or
3:00 position between the center and max gain setting (this
yields roughly a gain of 2,000).
Connect the red and black input leads together and
hold them with your fingers. Adjust CMR2 until the scope
trace is a minimum amplitude. Adjust CMR1 until there is
a minimum amplitude. The unit is now ready for final
testing and adjustment.
If the noise amplitude is too large, hold the common
clamp in one hand and the ± clamps in the other hand.
Then, adjust CMR2 and CMR1 for the smallest noise
Using rubbing alcohol and a folded paper towel, clean
three electrode areas as shown in Figure 14. Allow the
areas to dry. Remove the backing from an adhesive
electrode and place one on each cleaned area with the
electrode tab (no adhesive) pointing down. Connect the
S.E., common lead to the patient’s left shoulder; the black
lead, minus to the right center chest area; and the red lead,
plus to the lower left rib area. This electrode configuration
is shown in Figure 15.
After a few seconds, the scope should show a pattern.
Adjust CMR2 to minimize the noise in the pattern, then
adjust CMR1 to further reduce the noise pattern. Adjust
the GAIN pot so that the heart beat signal (QRS complex)
has about a 1V amplitude.
The last adjustment is the heartbeat LED level. Turn the
HB pot until the LED lights, then back off the adjustment
to where the LED turns off but flashes each time the QRS
complex is observed (on each heartbeat). It is important
to note that the results are dependent on clean firmly
30 February 2017
■ FIGURE 12. ECG setup for adjustment.
■ FIGURE 14. Nikotab elctrode placement.
■ FIGURE 13. Zietnitz scope setup screen.