Hanna Instruments HI 98140 - Manual (Page 11)

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GLP AND RS232
All the GLP data can be retrieved (if the electrode is connected) from
a PC through the RS232 communication feature. The calibration data
are transferred to the PC along with measurement data (see "Data
transfer to PC" paragraph).
LAST CALIBRATION DATA
Last calibration data are stored automatically after a successful
calibration and they can be displayed by pressing the GLP key.
to view pH calibration data
• Press ALT and GLP when the meter displays pH reading.
• The LCD will then display the last pH calibration date.
• Press RANGE to scan remaining data, in the following order:
last calibration time
electrode offset value in mV ("OFF" appears in the lower LCD)
electrode slope in mV/pH ("SLP" appears in the lower LCD)
first point calibration buffer
second point calibration buffer (only if a 2-point calibration has
been performed).
If calibration was performed with an old or dead probe, the
message "Old probe" or "Dead probe" will scroll on LCD.
• The meter will then return to normal operational mode. Press ALT
and GLP to escape before viewing all the data.
to view mV calibration data (HI98150 only)
• Press ALT and GLP when the meter displays mV reading.
• The LCD will then display the last mV calibration date.
• Press RANGE to scan remaining data, in the following order:
last calibration time
first calibration point
second calibration point
third calibration point (only if a 3-point calibration has been
performed).
• The meter will then return to normal operational mode. Press ALT
and GLP to escape before viewing all the data.
GOOD LABORATORY PRACTICE (GLP)
GLP is a set of functions that allows the storage or retrieval (when
necessary) of data regarding the maintenance and status of the
electrode. HI98140 and HI98150 use electrodes with a built-in
EEPROM in which calibration data are read at start-up and stored
after calibration. The meter can automatically analyze the data and
advise the user if a problem is found with a clear message.
PROBE LIFE VERIFICATION
At the end of calibration, the meter checks if offset is between -30 and
+30 mV and the slope between 53.5 and 62 mV/pH. If the values
are not within these parameters, the message "old probe" scrolls across
the LCD. The electrode is still working, but it will be necessary to perform
a cleaning procedure (see electrode cleaning and maintenance para-
graph) or replace it.
If the offset is outside the -60 and +60 mV range or the slope is
outside the 40 to 70 mV/pH interval, the "dead probe" message will
scroll across the LCD; the readings will blink on the upper LCD to warn
the user that they are not reliable.
ELECTRODE IDENTIFICATION
At start-up the meter checks if the electrode is inserted. If not the
message "no probe" scrolls across the LCD and a dashed line "----" will
be displayed in place of the reading.
If the meter detects a "dead probe" the readings will blink.
The meter checks the electrode only at start up. If an electrode
replacement is needed, turn the meter off before disconnecting the
electrode. Then replace the electrode and turn the meter on again.
CALIBRATION ALARM TIME-OUT
The calibration alarm time-out is available only for pH calibration.
It is possible to set (through setup code 10) the number of days
before the next required calibration procedure. User can set a value
from 01 to 99 days. The default value is 07. Set the parameter to
"OFF" to disable this feature.
When turned on, the meter checks if the time-
out time has expired. If the time has run out,
the message "Cal date" scrolls across the LCD.
The "DATE" symbol will blink as a reminder.
Alarm time-out is also signaled when viewing logged data through
the "Cal date" message.