Rosemount 396R, Instruction Manual

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Startup and Calibration 43
5.1 Sartup
To obtain best accuracy, the sensor must be calibrated as a loop with the transmitter. Please refer
to the respective transmitter instruction manual for proper calibration procedures.
5.2 pH Calibration
1. After a temporary connection is established between the sensor and the instrument, a
buffer calibration may be performed.
2. Consult appropriate pH/ORP transmitter instruction manual for specific calibration and
standardization procedures or see below for recommended two point buffer calibration
procedure.
5.2.1 Recommended two point buffer calibration procedure
Select two stable buffer solutions, preferably pH 4.0 and 7.0 (pH buffers other than pH 4.0 and
pH 7.0 can be used as long as the pH values are at least two pH units apart).
1. Immerse sensor in the first buffer solution. Allow sensor to adjust to the buffer
temperature (to avoid errors due to temperature differences between the buffer solution
and sensor temperature) and wait for reading to stabilize. Value of buffer can now be
acknowledged by transmitter.
2. Once the first buffer has been acknowledged by the transmitter, rinse the buffer solution
off of the sensor with distilled or deionized water.
3. Repeat steps 1 and 2 using the second buffer solution.
4. Once the transmitter has acknowledged both buffer solutions, a sensor slope (mV/pH) is
established (the slope value can be found within the transmitter).
5. The slope value should read about 59.1 mV/pH for a new sensor and will decrease over
time to approximately 47 - 49 mV/pH. Once the slope reads below the 47-49 mV/pH range,
a new sensor should be installed to maintain accurate readings.
Section 5: Startup and Calibration
Instruction Manual Wiring Rosemount 396RVP
LIQ-MAN-396R-396RVP March 2017
A pH 7 buffer solution reads a mV value of approx. zero, and pH buffers read approx. +/- 59.1 mV for each
pH unit above or below pH 7. Check the pH buffer manufacturer specifications for millivolt values at
various temperatures since it may affect the actual value of the buffer solution mV/pH value.
NOTICE