Schiller AT-102 Service Handbook page 109

AT-102 ECG Service Handbook
Service Screen (cont.)
ECG Reference Voltage
Electrode dc offset
TPH TEMP
EPROM
Article Number 2. 540 028
SCHILLER AG 2002
This provides measurements and setting facilities for the reference
voltage used for accurate measurement of ECG signals
Uref+ This gives the value of the reference voltage used in the
multiplexer circuit on the ECG Amplifier. The value of the
reference voltage is 2000 mV ±20 mV.
Uref- This is a negative reference voltage used on the ECG
Amplifier board. The value of this voltage should be -2000
mV ±20 mV.
Udif This is the sum of the two reference values above (Uref+
and Uref -). This value must be 4000 mV ± 20 mV.
Uoff This is the value of offset voltage on the multiplexer circuit.
This value should be in the range ± 150mV
Calib This value is the Udif value divided by 4. The nominal value
is 1000 ±5 mV.
This gives the voltage drop in the patient cable and can indicate any
faults in the patient cable or patient electrode. The value given is the dc
voltage between the left leg electrode and all other electrodes. The
measurements obtained will indicate any cable short circuits or open
circuits. The measured voltage value will depend on where the
electrodes are connected. The voltage readings that can be expected
are as follows:
With patient connected - ± 100mV
With patient simulator connected - ± 20 mV - this will depend on
the patient simulator used and must be taken as a flexible
measurement.
With all electrodes shorted together: - ± 20 mV
No patient cable connected: -350 to -500mV
This is the measured thermal print head temperature that the processor
uses to correct print quality. When the printer has not been used for
some time this should read ambient tempertaure + 5
quickly when the printer is used.
This is the checksum for the EPROM. Its value varies from one unit to
another and may change after a software upgrade.
Section 5
Adjustments
o but will rise
5.13