Extech Instruments Exstik EC500 Bedienungsanleitung Seite 13

Calibration - pH (I, 2, or 3 points)
Place the electrode into a buffer solution (4, 7, or 10). Press and hold the
I.
CAL/RECALL key until "CAL" appears in the lower (temp.) display.When doing a 2
or 3 point calibration.calibrate with pH 7 buffer first, then followwith pH 4 then the pH
10 buffer.
TheExStik' a utomatically recognizes thesolution andcalibrates i tselftothatvalue
2.
(the circlednumber on the LCD will match the solution). Note that if the solutionis
more than I pH unit off from the L (4), M (7), or H (10) pH buffer, or if the electrode
slopeislow, t heExStikO w illassume anerrorandabort t hecalibration ( END willbe
displayed,and the unitwill return to measure mode.)
3. Duringcalibration. t hepHreadingflashesonthe maindisplay.
Whencalibration i scomplete, theExStik@ automatically displays " SA",then"END"
4.
and returns to normal operation mode.
5. Theappropriate circledindicator(L, M,or H) appearsontheLCDwhena particular
calibration or seriesof calibrations hasbeencompleted withinonepoweron cycle.
When theExStik@is tumedoff,thecircled indicator configuration andthecalibration
data will be retained.
6. For a two or three point calibration,repeat steps 1-4.
CAL Reminder Display
Whenin pHmeasurement mode,a "CAL"iconwillappearafter15onloffcyclesof the
meterwithout performing a calibration. The CAL display is simply a reminder to calibrate
PH, and will turn off when the pH electrode is recatibrated. The reminder does not affect
function in any way.
RENEW Display
A flashing'RENEW' w arningindicates thatthe probeis notperforming to expected
specifications.If cleaning and recalibrationdoes not cause the RENEW icon to disappear,
replacethe probe (see optional accessories on the last page of this manual).The RENEW
displayappears as a result of the pH electrode slope fallingbelow 75% of a nominal slope.
Measurement and Display Considerations
If the unit appears to be locked (displayfrozen). It is possible thatthe Data Hold mode
has been inadvertentlyaccessed by pressing the MODEbutton.("HOLD"will be
displayedin the bottom let of the LCD.) Simply press the MODEbuttonagain or turn
the meter off and then on.
Ifthe meter does freeze. and no button presses revive it, perform a hard reboot as
follows: Removethe batteries,hold the "ON" buttondown for 5 seconds,then replace
the batteries. This resets the microprocessor. but does not clear stored readings or
calibration data from memory.
For maximum accuracy, allow sufficient time for the temperatureof the probe to reach
the temperature of the sample before calibrating.This will be indicated by a stable
temperature reading on the display.
8 EC500-EU V2.o 5/05
Calibration - Conductivity
Meter accuracy verification should be performed on a periodic basis. Once per month is
the recommended cycle for normal use. If calibration is required. a conductivity
standardizing solution must be obtained. The meter can be calibrated in any or all of the
three ranges.Standardizingsolutions of 84pS/cm, 1413pS/cm or 12.88mS/cm
(12,880gS/cm) are used for the automatic calibration recognition procedure. No other
calibration values are permitted.
Calibration is always done in conductivity mode. Since salinity and TDS values are
calculated from conductivity values, this procedure also calibrates the salinity and TDS
ranges.
Fill a sample cup with the standardizing solution.
2. Turn the meter ON and insert the electrode into the solution. Tap or move the
electrode in the sample to dislodge any air bubbles.
Press and hold the CAURECALL button (approximately 2 seconds) until "CAL"
3.
appears in the lower (temp) display. The main display will start flashing.
The meter will automaticallyrecognize and calibrate to the standardizingsolution.
4.
The display will briefly indicate "SA", END andthen return to the measurement mode
after a calibration.
Note: The "SANwill not appear if the calibration fails.
The Orange calibrated" symbol will appear in the display for each range that is
5.
calibrated during that power on cycle.
L Low range, 84uS/cm
Medium range, 1413pS/cm
H High range, 12.88mS/cm (12,880pS/cm)
Note: Each time the calibrationmods is entered all calibration symbols on the display are
cleared, but only the calibration data for the currently calibrated range is replaced. The
other two ranges keep the ehisting calibration data, just the symbols are removed.
Calibrationof all three ranges must be performed during one power on periodfor all three
range caribration symbols to appear.
Note: The meter allows for a 1, 2 or 3 point calibration. If calibration is done for more than
one point the lowest value standard should be done first to obtain the best accuracy.
Considerations and Techniques
Do not touch the inner surfaces of the conductivity electrodes. Touching the surface
•
of the platinized electodes may damage and reduce the life of the probe.
Store the electrode in the wetting cap with the sponge moistened with pH 4.01 buffer
•
solution.
Always rinse the electrode in de-ionized water between measurements to avoid cross
contaminationof the sample. Double rinsing is recommendedwhen high accuracy is
required.
Periodically, accumulated salt deposits from the reference electrode may build up in
•
the storage cap, and should be rinsed away. These deposits could affect measured
values of tow conductivity samples.
When measuring low conductivity samples, extra care is recommended in rinsing the
probe to avoid contamination of the sample with electrolyte from the pH reference
electrode. This will only be a factor when measuring in the low range. and can be
further minimized by increasingthe volume of the sample. (Example: Try a 200 to 500
mL sample.)
Ifthe 20mL sample cup is to be used, then the electrode should not be allowed to sit
in the sample for any longer than necessay, to avoid electrolyte leakage into the
sample, raising the conductivity value.
9 EC500-EU V2.0 5/05