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15. Addendum 4: Calculating Temperature Coefficients
To determine the temperature coefficient of your sample solution use this formula:
C
T2
- C
T1
TC
= 100 x _________________________
C
T1
(T
2
- 25) - C
T2
(T
1
- 25)
TC
= Temperature coefficient
C
T1
=Conductivity at Temp. 1
C
T2
= Conductivity at Temp. 2
T
1
= Temp. 1
T
2
= Temp. 2
25
= 25°C
NOTE:
A controlled temperature water bath is ideal for this procedure.
1.
Immerse the probe into a sample of your solution and adjust the temperature
coefficient to 0% (that is, no compensation) by performing the following:
A. From measurement mode, press the SETUP key to enter Setup mode.
B. Press the
▼
key until the lower display reads P5.0.
C. Press the ENTER key twice. The lower display reads tCO and the upper
display shows the temperature coefficient value.
D. Press the
▼
key until the upper display shows 0.0.
E. Press ENTER key to confirm the value.
F. Press CAL/MEAS key twice to return to measurement mode.
2.
Wait for 5 minutes. Note T
1
and C
T1
(conductivity at T
1
).
3.
Condition the sample solution and probe to a temperature (T
2
) that is about 5°C
to 10°C different from T
1
, and note the conductivity reading C
T2
.
NOTE:
Record your results for future reference. Ideally T
1
and T
2
should bracket
your measurement temperature, and should not differ by more than 5°C.
4.
Calculate the temperature coefficient of your solution according to the formula
shown above.
5.
Enter the temperature coefficient you calculated into the meter.
A. From measurement mode, press the SETUP key to enter Setup mode.
B. Press the
▼
key until the lower display reads P5.0.
C. Press the ENTER key twice. The lower display reads tCO and the upper
display shows the temperature coefficient value (should be 0, per step 1
above).
D. Press the
▲
key until the upper display shows your calculated temperature
coefficient.
E. Press ENTER key to confirm the value.
F. Press CAL/MEAS key twice to return to measurement mode.
The calculated temperature coefficient will now be applied to all the meter readings.