Yokogawa EXA PH202 2-Wire pH/ORP Analyzer - Manual (Page 111)

IM 12B0702-01E
11-14 Appendix
11-6-2. On-line impedance checks
This check can be applied to a sensor with liquid earth electrode. In using a sensor having no liquid
earth electrode, set impedance check off on service code 3 and 4.
T5.3.1E.eps
Code Display Function Function detail X Y Z Ddefault values
Parameter specific functions
03 *Z1.CHK Impedance check 1 Low 0 1.1.1
High 1 High
Temp comp off 0
Temp comp on 1 On
Imp check off 0
Imp check on 1 On
*Z.L.x V Low impedance limit Press NO to step through choice of units. 1 M 7
x=None, K, M or G press YES to select units, then use the
, ENT keys to set the value
*Z.H.x V High impedance limit Press NO to step through choice of units. 1 G 7
x=None, K, M or G press YES to select units, then use the
, ENT keys to set the value
04 *Z2.CHK Impedance check 2 Low 0 0.0.1 Low
High 1
Temp comp off 0 Off
Temp comp on 1
Imp check off 0
imp check on 1 On
*Z.L.x V Low impedance limit Press NO to step through choice of units. 100 7
x=None, K, M or G press YES to select units, then use the
, ENT keys to set the value
*Z.H.x V High impedance limit Press NO to step through choice of units. 200 7
x=None, K, M or G press YES to select units, then use the
, ENT keys to set the value
Yokogawa sensors with the liquid earth electrode include the PH8EFP, PH8ERP, PH8EHP,
OR8ERG, OR8EFG and FU20.
The liquid earth electrode is inside the sensor, and at the potential of the measured solution. The
liquid earth electrode is also used for an impedance check (to determine if a functional sensor
is connected). Be sure to connect the wire from the liquid earth electrode to terminal 14 on the
transmitter.
The impedance check detects when the glass electrode is broken, and also provides a check of
junction contamination and junction clogging. Such checks are qualitative rather than absolute , and
relatively loose high/low limits for "acceptable" values are usually set.
In the measurement in low conductivity water such as pure water, the impedance check does not
work. Set the impedance check function for the reference electrode to off in Service Code 04.
If the sensor doesn't have a liquid earth electrode, it's not possible to perform an automatic
impedance check to determine if the sensor is connected. Turn the functions of Service Codes 3 and
4 off when using such a sensor.
Yokogawa sensors without liquid earth terminals include the HA405, HA406, DPA405, DPAS405,
DPA406, HF405, HA485, DPA485 and DPAS485.
CAUTION