External Functions - Hanna Instruments HI 24 Series Instruction Manual

EEPROM SELFTEST
The EEPROM selftest procedure involves verifying the stored
EEPROM checksum. If the checksum is correct the "Stored
data good" message will be shown for a few seconds be-
fore exiting selftest procedure.
If not, the message "Stored data error - Press
stored data or
If is pressed the EEPROM selftest procedure terminates
with no other action. Otherwise, EEPROM is reset with de-
fault values from ROM as when a device with a virgin EE-
PROM is switched on.
During EEPROM reset a blinking message
"Set" is shown on primary LCD; the sec-
ondary LCD displays "MEM".
At the end of this operation all the param-
eters are reset to their default values. The
calibrated cell constant is also reset. For
this reason the "CAL" flag blinks until the
EC/TDS calibration is performed.
RELAYS AND LEDS
Relays and LEDs selftests are executed as follows:
First all of the relays and LEDs are switched off, then they are
switched on one at a time for a few seconds and cyclically.
User can interrupt the otherwise endless cycle pressing any
key, as indicated by the scrolling message.
Note
Relays and LEDs test has to be carried out with the relay
contacts disconnected from external plant devices.
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to reset
to ignore".
WATCHDOG
When a dead loop condition is detected a reset is auto-
matically invoked.
The effectiveness of watchdog capability can be tested
through one of the special setup items. This test consists of
executing a dummy dead loop that causes watchdog reset
signal to be generated.

EXTERNAL FUNCTIONS

HOLD FUNCTION
This function allows to perform the mainte-
nance procedures. When the relevant digital
insulated input (terminals #11 on page 8) is
on, the analog output is frozen at its last value
and the control and alarm relays are dis-
abled. The "Hld" indication is displayed on the secondary
LCD when the function is active. A 5 to 24 VDC voltage
can be applied to this input.
While in hold state, it is possible to display
the temperature reading on the secondary
LCD pressing the right arrow key. Only when
the key is released, the secondary LCD re-
turns automatically after a few seconds to
the "Hld" indication.
PRESETTABLE TIMER (CLEANING FUNCTION)
A timer is presettable by software to close a
digital insulated contact (terminals #12 on
page 8) after a user programmable time in-
terval with a minimum interval of 1 day (e.g.
for probe cleaning function). The time inter-
val is programmable in number of days through setup code
72.
This output is ON for the period set through setup code 77
(this period can be also changed when the output is ON).
The starting time of the cleaning timer can be set through
setup codes 73, 74, 75 and 76.
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