Teledyne T200, Руководство по эксплуатации, Страница: 316 / 425

Principles of Operation Teledyne API
– T200 NO/NO2/NOx Analyzer Operation Manual
314
13.3.4.4. HEATER CONTROL
For a variety of reasons such as, efficiency of certain chemical reactions, stabilization of
sample gas temperature and pressure, etc., various subcomponents of the T200 are
heated/cooled.
Two types of sensors are used to gather temperature data for the CPU:

THERMISTORS
: These are used in areas where the temperature control point is at
or near ambient temperature (e.g. the reaction cell temperature, internal chassis
temperate).

Thermistors change resistance as they heat up and cool down. A DC signal is
sent from the Mother board of a sent voltage and current. As the thermistor
changes resistance, the returning voltage rises and falls in direct relationship to
the change in temperature.

The output signal from the thermistors is received by the motherboard,
converted into digital data which is forwarded to the CPU.

THERMOCOUPLES
: These are used where the target temperature is high such as
the NO
2
 NO converter.

Thermocouples generate DC voltage that rises and falls as the thermocouple
heats up and cools down.

This DC signal interpreted, conditioned and amplified by the Relay PCA then
transmitted to the motherboard where it is also converted into digital data and
forwarded to the CPU.
All of the heaters used in the T200 are AC powered which are turned ON/OFF by AC
Relays located on the relay PCA in response to commands issued by the CPU.
Thermistor(s) –
Reaction Cell, Optional Internal
Span Gas Generator, Optional O
2
Sensor)
RELAY PCA
Preamplifiers
and Signal
Conditioning
MOTHER BOARD
A/D
Converter
(V/F)
CPU
J-type
Thermocouple
( NO
2
 NO converter)
THERMOCOUPLE
CONFIGURATION
JUMPER
(JP5)
Cold Junction
Compensation
Solid State
AC Relays
Thermistor
interface
Other Optional
AC HEATERs
(Internal Span Gas
Generator;O2 Sensor)
Reaction Cell
Heater
NO
2

NO
Converter
Heater
DC Control Logic
(for DC heaters)
Not used
on the T200
Figure 13-16: Heater Control Loop Block Diagram.
06858E DCN7057