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This presentation is a systematic
procedure to isolate problems in your conductivity measuring system.
Troubleshooting
Equipment
The following tools are recommended to assist you in problem identification:
- A DVM (digital volt meter)
A DVM will help to check for electrical continuity
from the measuring electrode to its connector
and to measure resistance between the conductive
pins to see if a short circuit is present.
It will also verify that the temperature sensor
in the electrode is working based on resistance
reading at room temperature.
- Conductivity Simulator or
resistor and loop of wire
Simulators (not available from Sensorex) will
help test the ability of the conductivity system
(electrode + meter/controller) to read properly.
A resistor connected via wires to the conductivity
instrument in place of conductivity sensor inputs
can also help simulate measurement of conductivity
if no conductivity standards are available.
Use the following formula to figure out which
resistor(s) to choose:
Resistor (R) = Cell constant
x 1,000,000 / conductivity value to simulate
(uS)
Example: R = 1.00 x
1,000,000 / 2000us = 500 Ohms
- Conductivity
Standards
A wide range of conductivity standards/calibration
solutions are available. Use at least 2
standards that are at the high and low end of
the range in which you need to measure.
Meter/Controller
Troubleshooting
The meter or controller
is the easiest component to eliminate as a possible cause of your
problem. Disconnect conductivity sensor from meter/controller
and connect conductivity simulator in its place. Input conductivity
readings and make sure controller/meter display matches the reading
from the simulator. Use fixed resistor if a simulator is not
available. If readings do not match, the problem is in the
meter or controller. Contact meter/controller supplier for
help or refer to meter/controller troubleshooting section.
If simulator inputs are correctly displayed on the meter/controller,
then the electrode is the most likely cause of the problem.
Conductivity
Electrode Troubleshooting
Check electrode in conductivity calibration/standard solutions as
recommended above. Compare results to those on the following
table:
| No output |
a) Conductivity sensor not connected to instrument
b) bad connection at connector
c) break in cable or internal connection broken in sensor |
a) check all connections from electrode to instrument
b) Check for electrical continuity from conductivity pin to connector using Ohms setting
on DVM (should be <1 Ohm)
c) Contact Sensorex |
| output in standard solution is more
than 10% different than value of solution< |
a) solution is not fresh, contaminated or labeled wrong
b) Electrode is dirty
c) Standard solution is outside of cell range** |
a) use fresh solutions or new lost of solution
b) Clean electrode per instruction manual. Do not abrade measuring surface.
c) pick standards based on ranges shown below** |
| Unstable or drifting reading |
Bubbles in electrode or flow cell |
a)shake or stir electrode to remove bubbles if testing solution in beaker.
b)Mount electrode horizontally so bubbles rise up and away from electrode. |
| Readings in line do not change but
electrode calibrates in conductivity standard solutions |
a) Electrode not completely immersed in process fluid
b) Electrode not connected to controller |
a) Check installation fittings and make sure sensor is complete installed.
b) Check wiring to instrument |
Conductivity
Cell Ranges**
| 0.10 |
5-5,000 uS |
| 1.0 |
50-50,000 uS |
| 10.0 |
500-20,000 uS |
If you are still having problems after
trying the above diagnostics, fill out our Application
Questionnaire and e-mail it to us for assistance. |
