Hamilton Electronics EPHUM011 - page 13

pH ARC SensorsModbus RTU Programmer’s Manual (EPHUM011)
624300/01 page 13/ 67
2.4.5.5 Reading theSelected Physical Unit for Analog Interface
Start
register Number of registers Reg1/ Reg2 Modbus function code Read access Write access
4376 2 Selected physical unitof AO1
(seechapter 2.5.1) 3, 4 U/A/S none
4504 2 Selected physical unitof AO2
(seechapter 2.5.1) 3, 4 U/A/S none
Figure 2.4.5.5.1:Definition of register 4376 / 4504.
Command: Avail unit AO1 Modbus address: 4376 Length: 2Type: 3Read
Parameter: Available unit
Format: Hex
Value: 0x001000
Figure 2.4.5.5.2:Example to read the selected unit of the selected PMC of AO1. The value returned is
“0x001000”,accordingly, the unit is pH. The physical unit for PMC is defined in Reg. 2090 or
2410 and applies automaticallyfor 4-20mA output.
2.4.5.6 Defining the MeasurementValues for 4, 12 and 20mA Ou tput
Start
register Number of registers Reg1/ Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus function
code
Read
access Write access
4378 6 Measurement
value at
Min Output
Current (4 mA)
for AO1
Measurement
value at
Max Output
Current (20
mA) for AO1
Measurement
value at
Mid Output
Current (12
mA) for AO1
3, 4, 16 U/A/S S
4506 6 Measurement
value at
Min Output
Current (4 mA)
for AO2
Measurement
value at
Max Output
Current (20
mA) for AO2
Measurement
value at
Mid Output
Current (12
mA) for AO2
3, 4, 16 U/A/S S
Figure 2.4.5.6.1:Definition of register 4378 / 4506.
Command: MinMaxMidv alue AO1 Modbus address: 4378 Length: 6Type: 16 Write
Parameter: Min value Maxvalue Mid value
Format: Float Float Float
Value: 3 10 7
Figure 2.4.5.6.2: Example to set the min value to 3 (for 4 mA), the max value to 10 (for 20 mA) and t he
mid value to 7 (for 12 mA). The corresponding physical unit can be read in register 4376 / 4504
and in 2090 / 2410.
Note:
Mid currentm ust alwaysbe defined. However, in linear output mode, the mid current value has no
physicalm eaningand will not affect the 4-20 mA output.