Specifications

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5.0 MICROPROCESSOR TEMPERATURE CONTROLLER
5.1 System Description
The microprocessor temperature controller, with Model 554 RTD Temperature Sensor is
capable of controlling the temperature in the Model 518 Chamber by supplying a
proportionally controlled power output to the Heating System and/or Cooling System.
The controller provides low voltage (6 VDC) control signals to the HEAT and COOL
solid state relays, located on the ‘RELAY’ PC board. When the low voltage signal is
applied to the relay ‘Input’, the ‘Output’ of the relay ‘closes’ and allows AC Power to flow
to the connected device.
When the “TEMP” STANDBY switch on the front panel is in the ‘OFF’ (‘0’) position, AC
power is manually disconnected from the control relays and no heating or cooling may
take place until the switch is placed in the ‘ON’ (‘I’) position.
All devices in the Model 518 are connected through screw terminals on the ‘Relay PC
Board’. All relays and screw terminals are labeled.
5.2 Temperature Controller Operation
5.2.1 Set-Point Adjust
1. Press and hold the “∗” button. The letters ‘°C’ or ‘°F’ (depending on set-up)
will appear followed by the current set-point value. While holding the “∗”
button, the current set point value and ‘°C’ or ‘°F’ will alternately appear in the
microprocessor display.
2. To adjust the set point higher, press the “t” button. To adjust the set point
lower, press the “u” button.
3. Release the “∗” button.
5.2.2 Heating System
To operate the Model 518 Heating System:
1. Adjust the Temperature set-point to a value above the ambient temperature.
2. Turn on the “TEMP” STANDBY switch on the front of the Control Panel.