Hanna Instruments HI 700 Series - Manual (Page 23)

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FAULT CONDITIONS AND SELFTEST PROCEDURES
The fault conditions below may be detected by the software:
• EEPROM data error;
• I2C internal bus failure;
• date lost;
• code dead loop.
EEPROM data error can be detected through EEPROM test
procedure at startup or when explicitly requested using setup
menu.
When an EEPROM error is detected, user is given the option
to perform a reset of EEPROM.
Note When an EEPROM reset has been per-
formed calibration data are reset to default
(every range). An intermittent CAL will blink
on the display to advise the user of this status.
A I2C failure is detected when the I2C transmission is not
acknowledged or a bus fault occurs for more than a certain
number of attempts (this can be due, for example, to dam-
age sustained by one of the ICs connected to I2C bus).
If so, the controller stops any tasks and displays a perpetual
sliding message “Serial bus error” (i.e. this is a fatal error).
If an invalid date is read from RTC, it is initialized back to the
default date and time (01/01/98 - 00:00).
The error detection for dead loops is performed by watchdog
(see below).
You can use special setup codes, perform selftest procedures
for LCD, keyboard, EEPROM, relays and LEDs, watchdog.
The operation of these functions is outlined in the setup sec-
tion. The selftest procedures are described in detail in the
following subsections.
DISPLAY SELFTEST
The display selftest procedure consists of lighting up all of the
display segments together. The Display test is announced by a
LAST CALIBRATION DATA
The meter can display the following last calibration data:
• Date
• Time
• Cell constant
While displaying these data, the controller remains in control
mode. The data are related to the selected range only.
The procedure below indicates the flow. Displaying of the
items follows the above sequence.
• To begin the cycle press CAL DATA. The last calibration
date will appear on the primary LCD as DD.MM format,
while the secondary display will show the year.
If the meter has never been calibrated or an EEPROM reset
has occurred, no calibration data are shown when CAL
DATA is pressed. The “no CAL” message will blink for a few
seconds, then the meter skips back to normal mode.
• Press or to cycle through
the data forward or backwards
respectively.
Note In any moment, by pressing LCD or CAL DATA the meter will
return to the regular operating display.
• Press or to view the time of last
calibration. The secondary display will
show "HOU".
• Press or again to view the cell
constant at the time of last calibra-
tion. The secondary display will show
"CEL".
• Press or again to return to the first CAL DATA display
(date) at the time of last calibration.