Teledyne 501 TRS, Operation Manual, Page: 64 / 111

THEORY OF OPERATION Teledyne API - T102/501 TRS, Addendum to T101 Operation Manual
62
10.4.2.
M501-TRS Electronics
Electronically the M501-TRS is a simple device. The nucleus of the instrument is a
programmable, P-I-D temperature controller that manages the temperature of the
instrument’s AC powered converter oven based on analog input from the thermocouple
attached to the converter’s chamber.
HEATER
AC Heater
Control Relay
Quartz Converter Tube
Thermocouple
P-I-D
CONTROLLER
SPST ALARM
Thermal
Switch
Alarm Output
Connector
M501-TRS
Figure 10-4. M501-TRS Electronic Block Diagram
The P-I-D controller determines the differences between the actual temperature (called
the Process Value or PV) of the oven, compares it to the target temperature (called the
Set Point or SV) and changes the percentage of time the heater is turned on versus the
time it is turned off accordingly. The higher the proportion of ON-time versus OFF-time
the faster the oven is heated. For instance, if the PV is much lower than the SV the P-I-D
will keep the heater turned on 100% of the time resulting in a relatively rapid increase in
the temperature of the oven. As the PV approaches the same temperature as the SV the
ON cycles get shorter compared to the OFF cycles.
The M501-TRS’s P-I-D controller includes sophisticated software that allows the
controller to track the rate change in temperature of the oven compared to the percentage
of heater ON-time and predict the proportion needed to reach and maintain the proper
oven temperature with a minimal amount of overshoot or fluctuation.
10.4.2.1. Thermal Switch
While the M501-TRS’s P-I-D Controller includes many safeguards that prevent runaway
heating of the converter oven, as an additional safety backup the M501-TRS includes a
heat sensitive switch which automatically interrupts power to the heater before the oven
temperature reaches critical levels.
07267B DCN6485