Yokogawa DO202 2-Wire Dissolved Oxygen Analyzer - Manual (Page 24)

IM 12A00A01-61E
Foundation Fieldbus 3-19 3-19
DO202
1: Dissolved Oxygen,
2: Temperature,
3: Percent Saturation,
4: Sensor Current
Channel Value Unit
1 primary_value primary_value_range.units
2 secondary_value secondary_value_unit
3 percent_saturation %
4 sensor_current nA
XD_SCALE/OUT_SCALE:
Scaling information is used for two purposes. Display devices need to know the range for bar graphs and
trending, as well as the units code. Control blocks need to know the range to use internally as percent of
span, so that the tuning constants may remain dimensionless. This is converted back to a number with units
by using the range of OUT_SCALE. The AI block has the parameter XD_SCALE to define the units expect-
ed from the transducer.
Transducer scaling (XD_SCALE) is applied to the value from the channel to produce the FIELD_VAL in per-
cent. The XD_SCALE units code must match the channel units code.
The EXA transmitter does this automatically when the Service Codes are changed. See table 3.18 to 3.21
for the Service codes and their results.
If L_TYPE is set to Indirect or Ind Sqr Root, OUT_SCALE determines the conversion from FIELD_VAL to
the output. PV and OUT always have identical scaling. OUT_SCALE provides scaling for PV. The PV is
always the value that the block will place in OUT if the mode is Auto.
Table 3.18 Unit Index by XD_SCALE PH202
Channel FF parameters Service code XD_SCALE.UNITS
1 - SC01 (set to 0) pH
2 2029 SC11 (set to 0) ºC
2 2029 SC11 (set to 1) ºF
3 - SC01 (set to 1) mV
3 - SC01 (set to 0), SC02 (set to 1) mV
3 - SC01 (set to 0), SC02 (set to 2) rH
Table 3.19 Unit Index by XD_SCALE SC202
Channel FF parameters Service code XD_SCALE.UNITS
2 2023 SC11 (set to 0) °C (1001)
2 2023 SC11 (set to 1) °F (1002)
1, 3 - SC01 (set to 1)
Ω•cm (1295)
1, 3 - SC01 (set to 0) S/cm (1594)
4 - Default % % (1342)
Table 3.20 Unit Index by XD_SCALE ISC202
Channel FF parameters Service code XD_SCALE.UNITS
2 2023 SC11 (set to 0) °C (1001)
2 2023 SC11 (set to 1) °F (1002)
1, 3 - Default S/cm S/cm (1594)
4 - Default % % (1342)