Sigma C4 manual P1f, Fahrenheit Operation

3.4 Fahrenheit Operation

The C4 can use either Celsius or Fahrenheit temperature scales. Celsius is the default mode. When the controller is operating in Celsius mode it’s behavior is identical to the model CC-3 controller. When the controller is operating in Fahrenheit mode, both the displays and the bus communications are different. These differences are intentional and designed to prevent errors that might arise from a user using setpoints in one scale while the controller is operating in the other scale. Note, however, that there is no difference in the Program mode programming operation of the C4 when operating in either Fahrenheit or Celsius mode. It is incumbent upon the user to notice the differences in the temperature displays and program accordingly.

To change the temperature scale, use SETUP mode (See Section 8) to access setup parameter F16. Select either of these field values:

0Celsius

1Fahrenheit

When in Fahrenheit mode, temperature displays have an “F” following the probe identifier on the left side of the display. Example:

p1f 102.4

Likewise, temperature inquires over the bus (PT command - See Section 7.5.7) will return a string with an “F” as the third byte in the string. The string will therefore be 1 byte longer than the string returned in Celsius mode. This difference was intentional as it requires a modification of the parsing routine that will assure that Celsius and Fahrenheit data are recognized properly. Thus, if the current probe 1 temperature is 86.7/F, the result of a Fahrenheit mode get temperature query for probe 1 (query command = PT1) would be

T1F 86.7<CR><LF>

If the temperature at probe 1 was 55.4/C, the same command in Celsius mode would return

T1 55.4<CR><LF>

During Remote mode operation, the C4 may be queried to determine the current temperature scale by using the QS, Query Setpoint, command. See Section 7.4.4.

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