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5. Insert the 764 sensor probe into the side hole of the Magnesium Chloride chamber,
push it all the way in. A support stand is provided to place under the 764 so that it
and the sample chamber are level. Be sure not to get any paste on the sensor.
6. Leave for at least 2 hours, preferably overnight, in the constant temperature
environment. The 764 does not have to be on.
7. With the 764 probe still in the calibration chamber:
Press Set\Calibrate\Humidity\MgCl (33%). Sure?? will be displayed, the Set
button must be pressed again within 2 seconds to activate calibration. The display
will show “Working …” followed by either:
“Done” if the 764 has been calibrated before (usually the case)
“Not Done” if this is the first time any humidity calibration has been done on
this instrument. This indicates that the other salt still has to be used.
“xx Fail” Where xx is a code indicating the type of error:
Fail
code
Meaning Possible causes
10 RH for MgCl >
RH for NaCl
Calibration standards wrong way round,
missing or wrongly prepared.
Sensor damaged or disconnected
12 RH difference
between samples
too small
Calibration standards wrong way round,
missing or wrongly prepared.
Sensor damaged or disconnected
Other
Calculation
overflow
Sensor damaged or disconnected
Notes:
Even if “Done” is displayed the following steps still have to be performed to
complete the calibration.
If “Fail” is displayed clean out the chambers in running water, dry thoroughly
and do the whole procedure again ignoring any further “Fail” messages until
step 8 below. If step 8 still produces a fail message it indicates that the
humidity sensor is damaged requiring the return of the unit to the manufacturer
for repair.
8. Repeat steps 5, 6 & 7 with the Sodium Chloride chamber, selecting
Set\Calibrate\Humidity\NaCl (75%) in step 7.
NOTE: In later versions of the 764 there are menu options of “35%” and “75%”
that can be used with other calibration standards. Do not use these options with the
ELSEC calibration salts (MgCl and NaCl).
9. If the sample chambers are to be kept charged then put both top and side lids on
and keep on a level surface. Otherwise clean them in running water and dry
thoroughly.
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