Datex-Ohmeda Anesthesia Delivery Unit S/5, Техническое справочное руководство

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Datex-Ohmeda ADU
B-30
Document No. 8502854
Reset causes the outputs to go into off state. On proportional valve drivers this is performed by
disabling the positive supply side on the current limit circuit. This means that the cassette valves will
be closed and sidegas selection valve is set into Air position. Thus no agent or N
2
O is delivered.
Digital inputs
The digital inputs consists of five cassette ID lines, two sidegas selection lines and two agent control
wheel input lines. All of the inputs have internal pull-up resistors and they are connected to open
collector type outputs or mechanical switches that connect the lines to ground. The agent control
wheel inputs also have Schmitt trigger circuits to adjust the signals suitable for the hardware decoder.
Analogue inputs
For analogue inputs there is a 16-bit A/D-converter on the board. Two eight-channel analogue
multiplexers are required to select and measure all the input voltage channels. In addition to the
pressure, flow, temperature and liquid level signals (only on the desflurane cassette), the supply
voltages are also measured for self diagnostics.
The input voltage range of the analogue channels of the board, is 0 to 10V. It is divided by two in a
resistor network to convert it to the input voltage range of the A/D-converter. The A/D-converter uses
+5 Vref reference voltage that is also employed in generating the +10V supply for the pressure
sensors.
As an exception to the previous, the temperature sensor inputs are connected directly to the sensors;
50 Kohm NTC-resistors. The two amplifiers on the board convert the temperature signals suitable for
the A/D-converter input voltage range.
Voltage supply
The CPU board requires several supply voltages:
•
+5V for the digital electronics, min. +4.75V max +5.25V
•
+15V and -15V for the analogue electronics,
+15V: min. +14V max +17V
-15V: min. -17V max -14V
•
VBUS for the valve power supplies.
The VBUS voltage is not used directly for driving the valves, there is +12V (min. +12.7V max 13.8V)
switching regulator on the board, supplying power to the valve drivers.
Hardware watchdog
The hardware watchdog resets the software and forces the hardware into a safe state in case of a
software failure.