KROHNE OPTISENS PAS 2000 EN - Manual (Page 33)

TECHNICAL DATA
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OPTISENS PAS 2000
www.krohne.com 11/2008 • MA PAS 2000 R04 en
Technical data
7.1 Measuring principle
The pH value is normally measured with an electrode where pH is expressed as a function of
voltage. Today's electrodes often contain both a measuring electrode and a reference electrode,
which in combination provide a voltage in linear proportion to the pH value. Electrodes internally
combined with a reference and measuring cell are divided into two categories: gel electrodes
and refillable electrodes. The gel electrode is the simpler and less expensive type. There are a
number of different types of refillable electrodes for different applications, each with different
internal solutions that are to be added at regular intervals. KROHNE provides gel-filled glass
electrodes.
To compensate for the temperature dependence of the electrode, the temperature of the media
is measured by the transmitter and compensated automatically via the MAC 080 software. The
temperature can also be read in the MAC 080 converter and used as secondary value when a
transmitter is configured to use two analogue outputs.
The temperature compensation can also be set manually to a fixed value via the MAC 080 menu.
All settings are made in the MAC 080 converter using a self-instructing menu controlled by just
three keys. The output signal is frozen when you switch to menu mode so that the output signal
will not change during procedures such a re-calibration.
The MAC 080 has two 4-20 mA outputs (extendable to four), and relay outputs for alarm and
cleaning of the electrode. The current pH/mV values and the temperature measurement of the
active sensor are continuously displayed in the MAC 080 display. Maximum, minimum and
average values for the last 24 hours can be obtained by pressing two buttons.
NOTE!
The build in temperature measurement is not a precision measurement, but shall be seen as an
indication.
.book Page 33 Friday, November 28, 2008 2:32 PM