Schiller AT-2plus - Paper mark Detector Check

Page 5.7
Chapter 5
Adjustments
SCHILLER AT-2plus 6-Channel ECG Unit
SERVICE HANDBOOK Issue d May 2002
Paper mark Detector Check
Tools, Equipment and Material
• Digital voltmeter
• Small flat bladed screwdriver
• 70% alcohol solution and clean lint free cloth
Procedure
To adjust the paper-mark Schmitt trigger sensitivity proceed as follows:
• DISCONNECT THE MAINS SUPPLY
• Open the paper tray lid and clean the photocell (situated on the opposite side to the dc
motor) with a 70% alcohol solution. Allow to completely dry.
• Disassemble the unit as detailed in Chapter 4.
• Reconnect the keyboard to the Control board and place the top assembly on its side in front
of the Base assembly .
• Switch the unit on and set the speed of the printer to the slowest setting of 5mm/s (5mm/s
key).
• Press the MAN START key to activate the printer. The paper is now moving at low speed
(through the roller and paper mark detector).
• Check the pulse amplitude at P8 pin 1. (Measure with AC setting, signal is noisy.)
• no paper-mark (white paper) between -80mV and -200mV
• paper mark (black paper) between -5mV and -30mV
• Reassemble the unit as detailed in Chapter 4.