Yokogawa EXA SC202 2-Wire Conductivity Transmitter/Analyzer - Manuel (Page 70)

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 2 Ω and 1200 kΩ. (accuracy 0.1%)
3. A fixed resistor of 300� U to simulate the mA-output load.
4. Screened cable to connect the input signals (a WU20 cable with a length of 2 metres is preferred)
5. A stabilised voltage supply unit : nominal 24 Volt DC
6. A current meter for DC currents up to 25 mA, resolution 1μA, accuracy 0.1%
Connect the SC202 as shown in Figure 1. Set box 1 to simulate 25 oC (1097,3� U for Pt1000).
Before starting the actual test, the SC202 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.
Figure 1. Connection diagram for the overall accuracy test
The tolerances specified relate to the performance of the SC202 with calibrated 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 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.
12-1 Test Certificate
IM 12D7B3-F-E