Contacting Conductivity Calibration - Emerson Rosemount 1066 Instruction Manual

Instruction Manual
LIQ-MAN-1066
9.4

Contacting Conductivity Calibration

New conductivity sensors rarely need calibration. The cell constant printed on the label is
sufficiently accurate for most applications.
CalIBRaTING aN IN-SERvICE CONDuCTIvITy SENSOR
After a conductivity sensor has been in service for a period of time, recalibration may be necessary.
There are three ways to calibrate a sensor.
a. Use a standard instrument and sensor to measure the conductivity of the process stream. It is
not necessary to remove the sensor from the process piping. The temperature correction used
by the standard instrument may not exactly match the temperature correction used by the
1066. To avoid errors, turn off temperature correction in both the transmitter and the standard
instrument.
b. Place the sensor in a solution of known conductivity and make the transmitter reading match
the conductivity of the standard solution. Use this method if the sensor can be easily removed
from the process piping and a standard is available. Be careful using standard solutions having
conductivity less than 100 µS/cm. Low conductivity standards are highly susceptible to atmos-
pheric contamination. Avoid calibrating sensors with 0.01/cm cell constants against conductiv-
ity standards having conductivity greater than 100 µS/cm. The resistance of these solutions
may be too low for an accurate measurement. Calibrate sensors with 0.01/cm cell constant
using method c.
c. To calibrate a 0.01/cm sensor, check it against a standard instrument and 0.01/cm sensor while
both sensors are measuring water having a conductivity between 5 and 10 µS/cm. To avoid drift
caused by absorption of atmospheric carbon dioxide, saturate the sample with air before
making the measurements. To ensure adequate flow past the sensor during calibration, take the
sample downstream from the sensor. For best results, use a flow-through standard cell. If the
process temperature is much different from ambient, keep connecting lines short and insulate
the flow cell.
To calibrate the conductivity loop with a connected contacting conductivity sensor, access the
Calibration screen by pressing ENTER from the main screen and press ENTER.
The following calibration routines are covered:
1. Zero Cal Zero the transmitter with the sensor attached
2. In Process Cal Standardize the sensor to a known conductivity
3. Cell K: 1.00000/cm Enter the cell Constant for the sensor
4. Meter Cal Calibrate the transmitter to a lab conductivity instrument
5. Cal Factor: 0.95000/cm Enter the Cal Factor for 4-Electrode sensors from the sensor tag
To calibrate contacting conductivity:
1. Press the MENU button
2. Select Calibrate. Press ENTER.
3. Select Conductivity. Press ENTER.
The adjacent screen will appear. To calibrate Conductivity or Temperature, scroll to the desired
item and press ENTER.
Calibration
Section 9: Calibration
April 2017
1.234 µS/cm 25.0 ºC
SN Calibrate?
Conductivity
Temperature
71