Yokogawa EXA PH202 2-Wire pH/ORP Analyzer - Manuel (Page 85)

IM 12B6C3-F-E
Test Certificate 11-2
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 box 1 (resistor decade box) to simulate the temperate element. All tests are
performed simulating 25ºC (77 ºF).
1. A fixed resistor of 300 Ω to simulate the mA-output load.
2. A millivolt source ranging from -1500 to +1500 mV with an accuracy of 0.1%.
2. A stabilised voltage supply unit : nominal 24 Volt DC
3. A current meter for DC currents up to 25 mA, resolution 1uA, accuracy 0.1%
3. A multimeter capable of measuring megohm ranges to check insulation impedance.
4. Screened cable to connect the input signals.
5. Single core flexible cable for liquid earth connection.
Connect the PH202 as shown in Figure 1. Set box 1 to simulate 25 ºC (1097,3 Ω for Pt1000)
Before starting the actual test, the PH202 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 PH202 with calibrated 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.
4.4 Accuracy test mA output circuit
Our automated testing facility checks the output accuracy of the instrument with simulated
mA-output values.
Resistance Decade Box
16
15
14
13
17
11
12
PH202
-
+
millivolt
source
- + G
mA Meter
300 Ω
+ -
24 Volts
DC Supply