Delta OHM HD2205.2, Manual

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Conductivity measurement
The HD2206.2 and HD2256.2 work with direct conductivity/temperature probes (input
j
), direct
4-electrode and 2-electrode only conductivity probes (input
j
), or combined conductiv-
ity/temperature probes with SICRAM (input
i
). The 4 wire Pt100, 2 wire Pt1000 sensors may be
used for measuring temperature, which is used for the automatic compensation of the conductivity.
If a temperature only probe is connected (connector
5
), the measured temperature becomes
the reference value for the measurement system, and has priority on the one supplied by the
combined conductivity probe.
Probes with SICRAM and without SICRAM
The combined conductivity probe with SICRAM is fitted with a Pt100 temperature sensor and an
electronic module. The module has a memory circuit that enables the instrument to recognize the
type of probe connected. It stores also the serial number, the factory calibration of the Pt100 sensor,
the manufacturing date and the last calibration performed by the user.
The combined conductivity probe with SICRAM is connected to input
i
, the direct probe
without SICRAM is connected to input
8
: if the inputs are exchanged, the instrument does
not measure and displays 0.0
μ
S/cm. If you connect simultaneously two conductivity probes
(one with SICRAM and one without SICRAM) to the respective inputs, the displayed meas-
urement is not correct.
The conductivity probes with SICRAM use the cell constant stored in their memory, the
probes without SICRAM use the cell constant stored in the instrument during calibration
.
A new calibration updates the cell constant. If the probe is fitted with a SICRAM module, the
new cell constant is saved in the probe’s memory. If the probe is not fitted with a SICRAM
module, the cell constant is saved in the instrument’s memory.
The instrument stores the nominal cell constant entered manually in the menu. If you perform a
calibration using a probe without SICRAM, the instrument updates the constant in the memory with
the new one resulting from the calibration of the new probe without SICRAM.
If you connect and disconnect a probe with SICRAM, and later you connect a probe without
SICRAM, the instrument reloads the cell constant of the last calibration performed using the probe
without SICRAM. If the conductivity probe is the one used for the last calibration without
SICRAM, the cell constant proposed is correct. If the conductivity probe is different, to obtain a
correct measurement you have to manually set the cell constant and perform a new calibration.
For the direct probes (non SICRAM), the cell constant nominal value must be entered in the
“
Conductivity Measurement Options
” >> “
Conductivity Cell Nominal Value
” menu item. You
cannot modify the cell constant value of a probe with SICRAM directly from the menu.
The instrument obtains the following from the measurement of conductivity:
•
the liquid resistivity measurement (
Ω
, k
Ω
, M
Ω
),
•
the concentration of total dissolved solids (TDS) according to the
χ /TDS conversion factor,
which can be modified using the menu,
•
the salinity (NaCl quantity in the solution, expressed in g/l).
By repeatedly pressing “ F2 = cond. ” you can select the quantity.