Ahlborn ALMEMO 2390-3, Руководство по эксплуатации, Страница: 20 / 24

To perform zero-point adjustment the measured value must first be physical-
ly set to zero, i.e. :
Temperature sensors must be placed in icy water.
pH probes must be immersed in a buffer solution pH 7.0.
Conductivity probes must be withdrawn from the liquid and dried.
O
2
probes for water must be held in a zero solution.
Zero-point adjustment can also be activated by pressing the CLEAR key.
Gain adjustment can be performed for the following sensor types using the
same function, assuming the appropriate calibration value is available :
pH-probe FY A8PH-xx: pH 4.00 or pH 10.00
Conductivity FY A641-LF: 2.77 mS/cm
or FY A641-LF2: 147.0 uS/cm
or FY A641-LF3: 111.8 uS/cm
O
2
-saturation FY A640-O2: 101 %
Example pH-probe:
Zero-point adjustment in a buffer solution of 7.00 pH :
Measured value :
HOLD MIN MAX CORR
M
DIM
Zero-point adjustment :
CLEAR
HOLD MIN MAX CORR
M
DIM
Gain adjustment in a buffer solution of 4.00 pH:
Measured value :
HOLD MIN MAX CORR
M
DIM
Gain adjustment :
CLEAR
HOLD MIN MAX CORR
M
DIM
7.5 Differential measurement
If there are two sensors with the same units and same decimal point position
connected at measuring points M0 and M1, the difference M1 - M0 appears
automatically below measuring point M2. The sensors are electrically isolated
by means of photovoltaic relays. If the differential channel is not required, it
must be cleared via the interface. If further differential channels are to be crea-
ted, this is also possible via the interface using the appropriate reference chan-
nels; (see Manual, Section 6.3.4).
20 ALMEMO
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2390-3
Measuring operation