Flame Guard Circuit; Flame Ignition Circuit; Proportional Temperature Control Circuit - Teledyne 4020 Operating & Maintenance Manual

Operational Theory
nominally 125 volts. Output tolerance is ±10 volts from the specified
125 volts.

2.3.3 Flame Guard Circuit

A thermistor-controlled, transistorized switching circuit is employed
to operate a relay in the event of a flame-out condition. A panel indicator
light and fuel shut-off solenoid valve are operated by the relay to alarm
personnel that a flame-out condition has occurred. The fuel shut-off
solenoid valve stops the hydrogen flow.

2.3.4 Flame Ignition Circuit

The flame ignition circuit includes the anode-igniter electrode (in the
detector cell), a transformer, and processor controlled relay. The circuit
is automatically energized after the warm up count down timer expires.
If automatic ignition fails, there will be a message that reports this,
and the flame can be manually ignited by pressing simultaneously the
Up and Down key.

2.3.5 Proportional Temperature Control Circuit

The temperature of the isothermal chamber containing the sampling
components is regulated by a thermistor-directed electronic circuit. The
thermistor and heating element are located in the chamber, and the
balance of the circuit components are mounted on the temperature
controller printed circuit board. A temperature limit switch protects the
isothermal chamber against excessive temperature, which may occur if
the temperature controlling system fails.
Teledyne Analytical Instruments
Model 4020
12