pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.2Primary Measurement Channel 1 (pH)

2.5.2.1Description of PMC1

In register 2080, a plain text ASCII description of PMC1 is given.

Start

Number of

 

Reg1 … Reg8

Modbus

Read

Write

 

register

registers

 

16 ASCII characters

function code

access

access

 

2080

8

 

 

Description of PMC1

3, 4

 

U/A/S

none

 

Figure 2.5.2.1.1: Definition of register 2080.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Command: PMC 1 text

 

Modbus address: 2080

Length: 8

 

Type: 3

Read

Parameter:

Text

 

 

 

 

 

 

 

 

Format:

 

Character

 

 

 

 

 

 

 

 

Value:

 

pH

 

 

 

 

 

 

 

 

Figure 2.5.2.1.2: Example to read the description. It is “pH”.

2.5.2.2Selecting the Physical Unit for PMC1

In register 2088, the available physical units for this channel are defined.

Start

Number of

 

Reg1 / Reg2

 

 

Modbus

 

Read

Write

register

registers

 

(bitwise defined)

function code

 

access

access

2088

2

 

 

Available physical units of PMC1

3, 4

 

U/A/S

none

Figure 2.5.2.2.1: Definition of register 2088.

 

 

 

 

 

 

 

 

 

 

 

 

Command: PMC1 available units

Modbus address: 2088

Length: 2

Type: 3

Read

Parameter:

Units

 

 

 

 

 

 

 

 

Format:

 

Hex

 

 

 

 

 

 

 

 

Value:

 

0x201000

 

 

 

 

 

 

 

 

Figure 2.5.2.2.2: Example to read the available physical units of PMC1: pH (0x001000) + mV (0x200000), total 0x201000.

In register 2090, the active physical unit for this channel can be selected, by choosing one of the physical units that are defined in register 2088.

Start

Number of

Reg1 / Reg2

Modbus

Read

Write

register

registers

(bitwise defined)

function code

access

access

2090

2

Selected active physical unit for the

16

none

S

 

 

PMC1

 

 

 

Figure 2.5.2.2.3: Definition of register 2090. Only one bit can be set.

Command: PMC1 set unit

Modbus address: 2090

Length: 2

Type: 16

Write

Parameter:

Unit

 

 

 

 

 

 

Format:

Hex

 

 

 

 

 

 

Value:

0x1000

 

 

 

 

 

 

Figure 2.5.2.2.4: Example to set the physical unit of PMC1 to pH (0x1000).

Attention:

Changing the physical unit has also an influence on the output of AO1 / AO2, as the same physical unit is active for the analog outputs. All limits of the 4-20 mA analog output have to be redefined after changing the physical unit!

624300/01

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Hamilton Electronics EPHUM011 Primary Measurement Channel 1 pH, Description of PMC1, Selecting the Physical Unit for PMC1