Filter
Top Products
12
MODEL TF396 SECTION 5.0
MAINTENANCE
The Model TF396 Sensors require minimum mainte-
nance. The sensor should be kept clean and free of
debris and sediment at all times. The frequency of
cleaning by wiping or brushing with a soft cloth or
brush is determined by the nature of the solution being
measured. The sensor should be removed from the
process periodically and checked in buffer solutions.
If the sensor will not calibrate, refer to your analyzer/
transmitter instruction manual for proper test proce-
dures. If it is determined that the sensor has failed, it
should be discarded and replaced.
5.1 AUTOMATIC TEMPERATURE
COMPENSATOR.
The temperature compensator element is temp -
erature sensitive and can be checked with an ohm-
meter. Resistance increases with temperature.
The Pt100 will read 110 ohms at 25°C. Resistance
varies with temperature for a Pt100 element and can
be determined according to Table 5-2 or the following
formula:
R
T
=R
o
[l+R
1
(T-20)]
Where R
T
= Resistance
T = Temperature in °C
Refer to Table 5-1 for R
o
and
R
1
values.
5.2 ELECTRODE CLEANING
If the electrode is coated or dirty, clean as follows:
1. Remove the sensor from process.
2. Wipe the ISFET silicon surface with a soft, clean,
lint free cloth or tissue. If this does not remove the
dirt or coating, go to Step 3. (Detergents clean oil
and grease; acids remove scale.)
3. Wash the sensor tip in a mild detergent solution
and rinse it in clean water. If this does not clean
the ISFET, go to Step 4.
SECTION 5.0
MAINTENANCE
4. Wash the sensor tip in a dilute 5% hydro chloric
acid solution and rinse with clean water. Soaking
the sensor overnight in the acid solution can
improve cleaning action.
NOTE
Erroneous pH results may result immedi -
ately after acid soak, due to reference
junction potential build-up.
Replace the sensor if cleaning does not
restore sensor operation.
Resistance
Temperature °C (Ohms) ±1%
Pt100
0 100.0
10 103.8
20 107.7
25 109.6
30 111.5
40 115.4
50 119.2
60 123.1
70 126.9
80 130.8
90 134.6
100 138.5
Temperature
Compensation Element
R
o
R
1
Pt100 107.7 .00385
TABLE 5-2. Temperature vs. Resistance of Auto
T.C. Elements
WARNING
BEFORE REMOVING THE SENSOR,
be absolutely certain that the
process pressure is reduced to 0
psig and the process temperature is
lowered to a safe level!
CAUTION
The solution used during the following check is an
acid and should be handled with care. Follow the
directions of the acid manufacturer. Wear the proper
protective equipment. Do not let the solution come in
contact with skin or clothing. If contact with skin is
made, immediately rinse with clean water.
TABLE 5-1. R
o
and R
1
Values for Temperature
Compensation Elements