Yokogawa SC72 Personal Handheld Conductivity Meter - Manual (Page 59)

IM 12D03D02-01E 7-4
7. Measuring Principles of this Instrument
␣ =
Temp. coef.
؋ 100 (%/؇C)
K
؊ K
K ( t
؊ 25 ) ؊ K ( t ؊ 25 )
1
1 2
1 1
2 2
2 2 1
2 1
where t , t : liquid temperature (
؇C)
K : conductivity at t
K : conductivity at t
(Calculation example)
To find the temperature coefficient of liquid with conductivity - 124.5 (S/cm at liquid
temperature 18.0
؇C and 147.6 (S/cm at liquid temperature 31.0؇C, substitute t
1
= 18.0,
t
2
= 31.0, K1 = 124.5, K2 = 147.6 in the equation above, thus we can obtain:
␣ = ؋ 100
147.6
؊ 124.5
124.5
؋(31.0؊25)؊147.6 ؋(18.0؊25)
=
؋ 100
23.1
747.0
؊(؊1033.2)
= 1.298
Set the temperature coefficient 1.30 in the SC72 meter (as meter allows three digits to be
entered).
• Checking if meter is working correctly
When the temperature coefficient already set is accurate, the conductivity displayed
should be constant regardless of liquid temperature (within permitted temperature range).
Check that the temperature coefficient already set is accurate. When the liquid
temperature is lowered, if a larger conductivity is indicated, the temperature coefficient
already set is too small; whereas, if a smaller conductivity is indicated, the temperature
coefficient already set is too large. In such a case, change the temperature coefficient
such that the measured conductivity does not change with temperature.
7.4 Wetted Part Materials of Sensors
• For general-purpose sensor
Titanium (sensor)
Polyphenylene sulfite resin, Polypropylene resin (insulated area and cover)
Fluoro rubber (O-ring)
• Sensor for high purity water measurement
SUS 316 stainless steel (electrode element)
Polypropylene resin (insulated area)
Fluoro rubber (O-ring)
• Chemical-resistant sensor
Glass, platinum black (electrode element)
Sensor for high-conductivity measurement
Glass, platinum black (electrode element)