General calibration & maintenance procedure – Yokogawa FU20/PH20 All-in-One pH/ORP Sensor User Manual
Page 10
IM 12B6J3-02E-E
8
5-1. Calibration for pH measurement
To calibrate a pH sensor, two buffer
solutions with known pH values are
required. It is recommended that one
buffer solution has a value near to pH
7.00. Depending on the process value to
be measured, the second buffer solution
should be either acidic (below 7.00) or
alkaline (above 7.00). Normally, the IEC
buffers (4.01, 6.87 and 9.18) are used.
The following is a very general 2-point
calibration procedure.
1. Clean the sensor (deposits may be
removed using a 5% (approximate)
solution of HCl).
2. Rinse sensor thoroughly with clean
water.
3. Immerse the sensor in the first buffer
(6.87 pH is recommended).
4. Refer to appropriate Instrument
Instruction Manual for Calibration
procedures (Auto; Manual; Sample, etc.),
5. Rinse sensor thoroughly with clean water.
6. Immerse the sensor in the second buffer
(4.01 or 9.18 recommended).
7. Repeat Step 4.
During calibration the temperature
compensation should be active. The
instrument automatically compensates for
the sensitivity change of the pH sensor at
different temperatures. After the calibration
is complete replace or re-install the sensor
into the process.
5-2. Calibration of ORP
and rH measurements
For calibration of ORP and rH the
procedures for MANUAL CALIBRATION
can be used as described in the instruction
manual of the analyser. The commonly
used standards for ORP and rH calibration
are made from Chinhydron (Quinhydrone)
powder dissolved in pH buffer solutions.
(1 gram/200 ml) The ORP value is a function
of the Reference cell of the measurement
and the pH value of the buffer solution.
4.2.1. Settings for PH402G and PH202G(S)
Function
pH
pH&ORP
pH&rH
ORP
pH compensated
Setting
(default)
ORP
code 01
0(pH)
0(pH)
0(pH)
1(ORP)
1(ORP)
code 02
0(off)
1(ORP)
2(rH)
0(off)
0(off)
code 03
1.1.1
1.1.1
1.1.1
0.0.1
0.0.1
code 04
0.0.1
0.0.1
0.0.1
0.0.1
1.1.1
code 31
0
2
2
jumper input 1
no
no
no
yes
yes
jumper input 2
yes
yes
yes
yes
no
4.2.2. Settings for PH150 and PH450G
Function
pH
pH&ORP
pH&rH
ORP
pH compensated
Setting
(default)
ORP
sensor setup
pH
pH+ORP pH+ORP
ORP
ORP
measurement
setup
pH+ORP
pH+rH
Impedance
setting
input1
High
High
High
Low
Low
input 2
Low
Low
Low
Low
High
jumper input 1
no
no
no
yes
yes
jumper input 2
yes
yes
yes
yes
no
5. GENERAL CALIBRATION & MAINTENANCE PROCEDURE