Yokogawa EXA ISC202 2-wire Conductivity Transmitter/Analyzer - Manuel (Page 61)

4.3 Overall Accuracy Test
This test can be performed by the end-user to check the overall accuracy of the instrument. The data
specified on the Test certificate are results of the overall accuracy test performed during production
and can be reproduced by performing similar tests with the following test equipment:
1. A variable resistor (resistor decade box 1) to simulate the temperate element. All tests are
performed simulating 25ºC (77 ºF).
2. A second variable resistor (box 2) to simulate the conductivity. Recommended is a resistor decade
box in steps of 1 Ω, between 125 Ω and 188 kΩ. (accuracy 0.1%)
3. A fixed resistor of 300 Ω to simulate the mA-output load.
4. An inductive conductivity sensor (ISC40)
5. An insulated wire with a length of approximately 1 mtr and a minimum cross-section of 0.75 mm 2
to be connected through the ISC40 to the box 2.
6. A stabilised voltage supply unit : nominal 24 Volt DC
7. A current meter for DC currents up to 25 mA, resolution 1µA, accuracy 0.1%
Connect the ISC202 as shown in Figure 1. Set box 1 to simulate 25ºC
(1097,3 Ω for Pt1000, 30 kΩ for NTC).
Before starting the actual test, the ISC202 and peripheral testing equipment has to be connected to
the power supply for at least 5 minutes, to assure the instrument is warmed up properly.
*note: For low ohmic input values (box 2) it is necessary to compensate for the wiring resistance.
The number of windings through the inductive sensor needs to be increased from 1 to 10. As
a result the range will be extended by a factor 100. For the low ohmic input range (1.25Ω to
37.60 Ω) the value should be multiplied by hundred (e.g. 2.51 Ω becomes 251 Ω).
Figure 1. Connection diagram for the overall accuracy test
The tolerances specified relate to the performance of the ISC202 with a calibrated sensor and
purpose built test equipment under controlled test conditions (humidity, ambient temperature). Note
that these accuracy’s are only reproducible when performed with similar test equipment under similar
test conditions. Under other conditions, the accuracy and linearity of the sensor and test equipment
will be different. The display may show values, which differ as much as 1% from those measured
under controlled conditions.
5. Accuracy test mA output circuit
Our automated testing facility checks the output accuracy of the instrument with simulated
mA-output values.
mA
meter
G
11
12
13
14
15
16
17
300W
Fixed
Resistance
L .R.
EXA ISC202
Box 2 (conductivity)
Electrode cabel
Resistance box
ISC40
+
-
Box 1 (temperature)
Resistance box
Supply
24 VDC
+
-
Test Certificate 12-2
IM 12D8B3-F-E