8
8850-2 Conductivity/Resistivity Transmitter
Calibration Procedure
This instrument has been electronically calibrated at the factory.
• Procedure A veri
fi
es the accuracy and linearity of the instrument by simulating temperature and conductivity values with precision
(±0.1%)
fi
xed resistors.
• Procedure B is a wet calibration. This procedure uses the sensor input and NIST traceable test solutions. When done correctly, this
procedure offers the most accurate system calibration.
Iso. Gnd
(BLACK)
Temp. IN
(WHITE)
Signal IN
(RED)
13
12
11
Simulation resistor
TC resistor
B) Wet Calibration with NIST Traceable Solutions:
When using NIST traceable standards, review the temperature information provided with the test solution. Prevent
contamination of the test solution. The sensor must be at the temperature speci
fi
ed on the test solution label.
• Remove the sensor from the system. Rinse the sensor in a small amount of test solution.
• Place the sensor into the test solution.
• Place a reference thermometer into the same solution.
• Allow suf
fi
cient time for the temperature to stabilize.
• Set Temp: Adjust the temperature value based on the reference thermometer. (see Editing Procedure.)
• Set Cond: Adjust the conductivity value based on the test solution value. (see Editing Procedure.)
• Verify the linearity by placing the sensor into a second test solution of a different value.
• If the instrument does not display the correct value (Temperature ± 0.5 ºC, Conductivity ± 2% of reading), service is required.
A) Accuracy Veri
fi
cation with Precision Resistors (Electronic Calibration):
1. Simulate the Temperature
The temperature input to the 8850 is a PT-1000 thermistor, where 1000 Ohms (
Ω
) is equal to 0 ºC and a change of 3.84
Ω
equals a 1 ºC change. (1000
Ω
= 0 ºC, 1003.84
Ω
= 1.0 ºC, 1007.68
Ω
= 2.0 ºC. ... 1096
Ω
= 25 ºC)
• Connect a resistor (1000
Ω
to 1096
Ω
) between "Temp IN" and "Iso. Gnd" terminals.
• Set Temp; Adjust the temperature to exact value based on the measured resistance. (see Editing Procedure, Calibrate menu).
• To verify the temperature linearity, connect a second resistor value to the terminals.
• If the instrument does not display the correct value, service is required. ( ±0.5 ºC)
2. Simulate the Conductivity
You may calculate the exact Resistance needed to simulate a speci
fi
c conductivity value , or you may calculate the exact
Conductivity based on a resistor value:
(*1
μ
S = 1 X 10
-6
Siemens or 0.000001 Siemens)
• Connect the conductivity resistor between the "Signal IN " and "Iso Gnd" terminals.
• Set Cond: Adjust the conductivity value based on the resistor value. (see Editing Procedure
and Calibrate menu).
• Verify the linearity of the instrument by connecting a second resistor of a different value.
• If the instrument does not display the correct value (± 2% of reading), service is required.
Resistance =
Cell constant
e.g.
0.1 Cell
= 5,000
Ω
or 5 K
Ω
conductivity (Siemens*)
0.000020 (Siemens*)
Conductivity =
Sensor cell
e.g.
0.1 Cell
= 0.000001 Siemens* or 1
μ
S/cm
Simulation resistance (
Ω
)
100,000 (
Ω
)
