Operation; Oxygen - Hach LDO AQS sensors User Manual

Operation

Modbus registers
Use the Modbus registers in the control system to configure and get data from the sensor. Refer to
Table 2. Set the communication parameters to RTU (Zf), 19.2 Kpbs, 8 bits, no parity and 1 stop bit.
The data type for all registers in
Register Name
40001 Dissolved oxygen
40002 Temperature
(Celsius)
40003 Software version
40004 Sensor cap lot
number
40005 Serial number
40012 Percent
saturation (%)
40013 Altitude (meters)
40014 Salinity (PSU)
49998 Sensor address
Configure the sensor
Use the Modbus registers to enter the altitude and salinity values for the sample.
1. Enter the altitude in meters at the location where the sensor is installed (default: 0 meters).
2. Enter the salinity value of the sample in PSU (practical salinity units). Use the steps that follow to
get the salinity value.
a. Use a conductivity meter to measure the conductivity of the sample in mS/cm at a reference
temperature of 20 °C (68 °F).
b. Find the salinity value in PSU from
mS/cm PSU
5 3
6 4
7 4
8 English
Table 2 is unsigned integer.
Table 2 Modbus registers
Description
mg/L O × 1000 (e.g.,
2
8.082 mg/L O shows as
2
"8082")
°C × 100 (e.g., 26.41 °C shows
as "2641")
Version × 100 (e.g.,
4.56 shows as "456")
Year and day (e.g., 2015, day
136 shows as "15136")
Hexadecimal number from
ASCII code (e.g., Registers
40005–40010 are "3133",
"3132", "3330", "3030", "3030",
"3937", in ASCII code "13",
"12", "30", "00", "00", "97",
combined shows as
"131230000097")
Dissolved oxygen as %
saturation
Altitude in meters (default:
0 meters)
Salinity in PSU (default: 0 PSU)
Sensor address (default: 247)
Table
Table 3 Salinity (PSU) per conductivity value (mS/cm)
mS/cm
16
17
18
Minimum/maximum
0/65535
0/5000
3.
PSU mS/cm
10 27
11 28
12 29
Length
(bytes)
–5/21 2
0/50 2
0/100 2
2
— 12
0/200 2
2
0/250 2
1/99 2
PSU mS/cm
18 38
19 39
20 40
Access
Read
Read
Read
Read
Read
Read
Read/Write
Read/Write
Read/Write
PSU
27
28
29