SX10507 Demo: Software Operation

Turn On

Whenever the program is down loaded to the board, the non volatile memory or permstore memory is erased, and this is where the calibration and setting are held. The program checks for valid contents of permstore memory on power up and will load some default values if the permstore memory has been erased. If this occurs, the display will read: "Default Values Loaded" and the operating parameters will be loaded with the following defaults:

• Temperature display mode: Fahrenheit
• Temperature Compensation source: USER
• PH signal filtering: OFF

In addition, the calibration values for the pH probe will be loaded with some values that will at least give an approximate reading on the pH display.

There after, the display will start with the normal status screen:

"pH= 7.01 T= 77.0"

"Filt:0 USER "

This screen shows that the measured pH is 7.01 (in this case) the compensation temperature is 77°F, the pH filter is set to zero (filter is off) and the temperature compensation source is USER, which means that the temperature value is being supplied by the user via the front panel push buttons on the MMi202.

Front Panel Push Buttons

None of the front panel LEDs are used. Some of the front panel push buttons have a dual function depending on which mode the program is operating in. There are three modes:

• Run Mode - pH and temperature status being displayed
• Edit Mode - system options and parameters being edited
• Calibration Mode - pH system being calibrated

Run Mode

In Run mode the buttons have the following functions:

• Input 12 - increment USER temperature value
• Input 11 - decrement USER temperature value
• Input 10 - ** no function **
• Input 9 - ** no function **
• Input 8 - Menu / Calibration mode entry button

If the temperature compensation source has been set to USER (by editing the parameter in the menu mode), then Input 12 and Input 11 increment and decrement respectively the compensation temperature, and the LCD screen value will be updated in real time.

Input 8 sets the software into one of two modes depending on how long the button is pressed for. If it is pressed for less than 6 seconds (short press), the parameter-editing mode (menu mode) is entered. If the button is pressed for 6 seconds or longer (long press), the unit enters the calibration mode. Once calibration mode has been chosen, the only way to abort it is to remove power from the unit. Progressing through the calibration mode without following the calibration procedure and using the correct buffer solutions will render the pH readings useless, hence the 6 second push to enter this mode. Calibration can always be repeated to restore the unit to correct operation.

Menu Mode

In Menu mode, operating parameters can be changed:

1. Temperature compensation source: USER, THERM (thermistor) or RTD. This selects the temperature source that will be used to calibrate the pH system when in calibration mode, and to temperature compensate the pH reading in Run mode.
2. Displayed temperature units: Celsius or Fahrenheit
3. pH filter setting: 0 (off) à 6 (heavy filtering). Allows the user to get a more stable reading in the presence of high electrical noise levels. With no noise sources present, the filter can be turned off (set to zero).

In Menu mode the front panel buttons have the following function:

• Input 12 - Parameter increment button - increments/changes the currently displayed parameter value
• Input 11 - Parameter decrement button - decrements/changes the currently displayed parameter value
• Input 10 - ** no function **
• Input 9 - Parameter select button - steps through parameters which can be changed
• Input 8 - Exit and store new parameter values