Dräger Isolette C2000 Service Manual

Theory of Operation
Chapter 3: Theory of Operation
Isolette® Infant Incubator (Model C2000) Service Manual Page 3 - 19
3
analog temperature selector. The microcontroller selects a new
temperature channel every 21 milliseconds.
The resistor R14 provides the constant voltage drive required for each
thermistor as it is selected from the appropriate multiplexer. This
voltage is amplified by a factor of 2.1083, and is sent to the A/D
converter as signal TCOM.
To provide automatic calibration of the circuit and eliminate temperature
and aging drifts, R44 and R45 introduce precise calibration values into
each multiplexer. These values are read through the multiplexers and
are used in software processing to eliminate the gain and offset errors
of each multiplexer/amplifier combination. These values equate to
120.87 °F (49.37 °C) and 72.72 °F (22.62 °C), which allow for precise
circuit calibration.
Resistor R43 is an additional check to the circuit, which provides a
resistance simulating 98.57 °F (36.98 °C).
The sensor module supports the following three air temperature
sensors on the sensor board:
•AIRTE
•AIRTC
•AIRTM
These signals interface through J2-6 to J2-8. The thermistors then route
to temperature multiplexers U5 and U6, which provide analog signal
processing into the A/D converter.
The skin temperature probes contain dual thermistors. The sensor
module supports two probes that plug into connectors J6 and J7. The
two thermistors connect to SKNT1M and SKNT1C or SKNT2M and
SKNT2C, with a common connector at AGND. Both probes have high
frequency filtering by inductor networks LN1 and LN2. In addition, each
skin probe has a resistor that is input to the multiplexers. The
microcontroller uses these signals, SKNT1D and SKNT2D, to
determine if the probes are installed.
Humidity Measurement
Humidity measurement originates with the humidity sensor on the
sensor P.C. board, connected to J2-5 and J2-14 (AGND and HS2,
respectively). The sensor is a capacitive-type that changes capacitance

Dräger Isolette C2000 Specifications

General

Brand	Dräger
Model	Isolette C2000
Category	Medical Equipment
Language	English