Hach sc100, User Manual

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54
Modbus Protocol
A.6 Modbus Troubleshooting
Table 10 Troubleshooting
Problem Possible Causes Solution
No Modus Response
Baud rate, or stop bits does not
match settings of Modbus master
Verify sc100 settings match the Modbus master
settings.Verify Modbus master Parity setting is set to
None.
Bad RS232 or RS485 cable Replace/Repair cable
No or improper network biasing and
termination.
Check all network devices for termination or biasing
settings. Only the ends of the network should have
termination turned on and only one point on the
network should be providing biasing.
Slave Address incorrect or duplicate
address of another bus device. Verify all addresses are unique and between 1 and
247.
Modbus Exception
Response
Register not supported Verify register is supported
Data Type incorrect
Verify the requested register(s) Data Type matches the
Modbus Master Request e.g. do not access a Slave
Float value with a 2 byte Integer request. When
requesting a Float (2 registers/4 bytes), both registers
must be requested at the same time.
Table 11 sc100 Modbus Registers
Group Name Tag Name
Register
#
Data
Type
Length R/W Description
Measurements
Calculated
Value
40001 Float 2 R
Value calculated from two sensor
measurements
Setup Language 40003
Unsigned
Integer
1 R/W Current System Language
Setup Date Format 40004
Unsigned
Integer
1 R/W
Current Data Display Format
(0 = DD/MM/YY; 1 = MM/DD/YY;
2 = DD-MM-YY; 3 = MM-DD-YY)
Setup
Error Hold
Mode
40005
Unsigned
Integer
1 R/W
Error Mode Hold State (0 = Hold
outputs;
1 = Transfer outputs to predefined
value)
Setup/Analog Output 1 Source 40006
Unsigned
Integer
1 R/W
Selects data source for this output
(0 = None; 2 = sensor; 4 = Calculation)
Setup/Analog Output 1
Sensor
Select
40007
Unsigned
Integer
1 R/W
Selects sensor source when Source =
Sensor (0 = sensor1; 1 = sensor2)
Setup/Analog Output 1
Measuremen
t Select
40008
Unsigned
Integer
1 R/W
Selects measurement on the sensor
(0 = Meas1.. 3 = Meas4)
Setup/Analog Output 1 Type 40009
Unsigned
Integer
1 R/W
Selects output type
(0 = Linear output; 1 = PID control)
Setup/Analog Output 1
Transfer
Value
40010 Float 2 R/W Sets the transfer value
Setup/Analog Output 1 Filter 40012
Unsigned
Integer
1 R/W
Sets the output filter value in seconds
(0 to 120 sec.)
Setup/Analog Output 1
0mA - 4mA
Select
40013
Unsigned
Integer
1 R/W
Selects 0mA/4mA for min output
(0 = 0mA; 1 = 4mA)
Setup/Analog Output
1/Linear
Min Setting 40014 Float 2 R/W Sets the min output value
Setup/Analog Output
1/Linear
Max Setting 40016 Float 2 R/W Sets the max output value