User`s guide

Release E UMC800 Control Builder User’s Guide 261
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Appendix E – Measuring pH with UMC800 Controller and
Durafet II Cap Adapter
Introduction
The tradition approach to bringing pH measurements into a control system incorporated the use of a pH
transmitter or monitor/analyzer to condition the electrical signal, provide temperature compensation and to
provide the necessary zero and slope adjustments needed to properly range the pH sensor. With the
introduction of the Durafet II cap adapter (signal conditioner), a millivolt measurement representing pH can
now be directly connected to the analog inputs of a UMC800 controller. When combined with a new 100
ohm RTD temperature sensor built into the Durafet II electrode assembly, the two measurements needed to
calculate pH could now be directly connected to the inputs of the controller. To facilitate the
implementation of this application, a ± 15 volt power module is available for the controller to power up to 4
Durafet II cap adapters.
Equipment Needed
To perform a pH measurement with a UMC800 controller, the following controller and sensor hardware is
needed:
• 1 Durafet II pH sensor with 100 ohm RTD temperature sensor
• 1 Durafet II electrode cap adapter
• 1 UMC800 Power module (supports up to 4 sensors)
• 1 UMC800 Universal analog input module
Recommended Wiring
Figure 74 indicates the recommended wiring for one pH sensor input. Note that two analog input channels
are required, one for the pH sensor and one for temperature. Similar wiring may be used for additional
sensors. A UMC800 controller can accommodate 2 power modules for a total of up to 8 pH inputs.
1
12
1
12
1
C
Analog Input
Module
+
COM
-
pH 1 Sensor
MV
pH 1 Sensor
Temp
+
-
C
-
-
C
+
+
+
-
+
C
-
Mod 1
Mod 4
Green
Black
Blue
White/Black
(Unused)
Orange
Red/Black
Red
White
Jumper
UMC800 Shield Connector Kit
Part No. 51309814-501
Power Supply Module
UMC800 Controller
Figure 74 Recommended wiring for one pH sensor input