Yokogawa SC4A 19mm Conductivity Sensors - Manual (Page 13)

IM 12D7J4-E/D/F-H
ENGLISH
7
3. OPERATION AND MAINTENANCE
3-1. Checking the cell
If a fault occurs, first check the cell for visi-
ble damage. If damage is not apparent,
check the cell resistances measuring
between the cable connections.
a. 11 and 12 (or connector pins 1 and 2)
b. 11 and 13 (or connector pins 1 and 3)
c. 12 and 13 (or connector pins 2 and 3)
d. 12 and 15 (or connector pins 4 and 5)
e. 15 and 16 (or connector pins 5 and 6)
f. 13 and 14 (or connector pins 3 and 4)
g. 13 and 15 (or connector pins 3 and 5)
Celltype a b c d e f g
SC4A Pt1000 > 100 > 100 > 100 0 0 >100
value M Ω M Ω M Ω M Ω M Ω M Ω
If the cell has become fouled resistance will
be developed across the electrodes. These
resistances can be measured as shown in
fig. 3-1 by making contact directly with the
electrode and the relevant pin of the con-
nector.
3-2. Calibration of the cell
The cell constant is determined in laborato-
ry conditions. It is possible that slight varia-
tions in the cell constant may occur depen-
dant on the installation. This possible error
can be corrected by recalibrating with a
solution of known conductivity value
(according to DIN 53779).
NOTES :
The specific conductivity value of the solu-
tion of known value must be near the value
of the liquid to be measured. Specific con-
ductivity is highly temperature dependent,
therefore in the above calibration procedure
the temperature of the cell and the liquid
should be allowed to equalise and should
be accurately measured with a calibrated
thermometer.
3-3. Cleaning of the cell
If the cell becomes fouled an insulating
layer may be formed on the electrodes and
consequently, an apparent increase in cell
constant may accur, giving a measuring
error. This error is:
2 • x 100 %
Where:
Rv = the resistance of the fouling layer
Rcel = the cell resistance.
Cleaning methods
1. For normal applications hot water with
domestic washing-up liquid added will
be effective.
2. For lime, hydroxides, etc. a 5...10%
solution of hydrochloric acid is recom-
mended.
3. Organic foulings (oils, fats, etc.) can be
easily removed with acetone.
4. For algae bacteria or moulds, use a
chlorinated solution (domestic bleach*).
* Never use hydrochloric acid and
domestic bleach simultaneously. The
liberation of the very poisonous gas
chlorine will result.
3-4. Spare parts list
Spare part nr. Description
K1500BE O-ring set -PR
K1542DK O-ring set -SA
K1542DG Seal rings -SB1
K1542DH Seal rings -SB2
K1542DJ Seal ring -SC1
K1542DF 1” Stainless steel
adapter
K1542CW 1” PVDF Adapter
K1520EK Angled welding socket
15º
K1520EJ Straight weld in adapter
K1542FC Welding clamp 1”
K1542FF Welding clamp 1 1/2 ”
K1542FE Welding clamp 2”
(Rv)
(Rcel)