RS-485 Nitrates (NO3) Probe AT-SB-PROBE-NO3-P
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Datasheet
1. Introduction
SENSBLUE RS-485 Nitrates (NO3) Probe AT-SB-PROBENO3-P can be used for environmental water quality monitoring, acid/alkali/salt solutions, chemical reaction processes, and industrial production processes, and meets the requirements for online ORP measurement in most industrial applications.
2. Features
- Signal output: RS-485 (Modbus/RTU protocol).
- Conveniently connects to third‑party equipment such as PLCs, DCS systems, industrial control computers, general controllers, paperless recorders, or touch screens.
- Double high‑impedance differential amplifier with strong anti‑interference capability and fast response speed.
- Durable ORP electrode: the internal reference fluid seeps out of the microporous salt bridge very slowly under a pressure of at least 100 kPa (1 bar), maintaining positive seepage for more than 20 months. This reference system is highly stable, and the electrode lifespan is doubled compared to ordinary industrial electrodes.
- Easy to install: the 3/4 NPT pipe thread allows convenient immersion installation or mounting in pipelines and tanks.
- IP68 protection level.
3. Technical Specifications
| Model | AT-SB-PROBE-ORP-P |
|---|---|
| Measuring Range | -1500～+1500mV |
| Accuracy | ±6mV |
| Resolution | 1mV |
| Temperature Range | 0 ~65℃ |
| Work Pressure | ＜0.1MPa |
| Output | RS-485, MODBUS protocol |
| Power Supply | 12～24VDC ±10% |
| Wetted Part Material | POM |
| Installation | Immersion mounting, 3/4 NPT thread |
| Cable Length | 15m |
| Calibration Method | One-point calibration |
| Power Consumption | ＜0.3W@12V |
| Ip Grade | IP68 |
4. Dimensions
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5. Installation and Electrical Connection
5.1 Install
Note: The sensor should not be installed upside down or horizontally when installed, at least at an angle of 15 degrees or more.
| Pinouts | |
|---|---|
| 1 - Pin 12-24V DC | 4 - RS485 B- |
| 2 - GND | 5 – NA |
| 3 - RS485 A+ | 6 - NA |
| 7 - NA | |
6. Maintenance
6.1 Use and maintenance
When measuring with the ORP electrode, rinse it with distilled or deionized water and gently dry it with filter paper to avoid introducing impurities into the test solution. Immerse one‑third of the electrode in the solution during measurement. When not in use, clean the electrode and store it in a protective cap or container filled with 3.5 mol/L potassium chloride solution.Ensure the terminal is dry; if dirty, clean it with absolute alcohol and let it dry. Avoid long‑term immersion in distilled water or protein solutions, and prevent contact with silicone grease.Over time, the glass membrane may become translucent or accumulate sediment; if so, clean it with diluted hydrochloric acid and rinse with water. If measurement errors persist even after calibration and proper maintenance, the electrode has likely failed and should be replaced.
6.2 ORP standard solution preparation method
a) Preparation method of ORP standard solution (256 mV):Weigh 2.1 g of quinhydrone and add it to 200 mL of a standard pH buffer solution with pH 4.00, then mix well.
b) Preparation method of ORP standard solution (86 mV):Weigh 2.1 g of quinhydrone and add it to 200 mL of a standard pH buffer solution with pH 6.86, then mix well.
c) Preparation method of ORP standard solution (–40 mV):Weigh 2.1 g of quinhydrone and add it to 200 mL of a standard pH buffer solution with pH 9.18, then mix well.
Please note that when preparing the pH buffer, a total of 250 mL is prepared, and 200 mL is used.
Method for preparing the corresponding pH standard solution:
Measure 250 mL of distilled water with a graduated cylinder, pour it into a beaker, add one packet of calibration powder (pH 6.86 / 4.00 / 9.18), and stir with a glass rod until the powder is completely dissolved.
6.3 Calibration
Place the sensor in the prepared 86 mV (or 256 mV or –40 mV) solution and wait for 3 to 5 minutes. After the value stabilizes, check whether the displayed value matches 86 mV (or 256 mV or –40 mV). If not, calibration is required. See the appendix for calibration instructions.
6.4 Precautions
- Avoid exposing the inner surface of the fluorescent film head to sunlight
- Please do not touch the fluorescent film with your hands
- Avoid bubbles adhering to the surface of the fluorescent film during measurement and calibration
- Avoid applying any mechanical stress (pressure, scratches, etc.) directly to the fluorescent film during use
7. Appendix data communication
7.1 Data Format
The default data format for Modbus communication is: 9600, n, 8, 1 (baud rate 9600bps, 1 start bit, 8 data bits, no parity, 1 stop bit).
7.2 Modbus Frame Format (xx represents a byte)
a) Read data instruction frame
| 06 | 03 | xx xx | xx xx | xx xx |
| Address | FC | Register start
address |
Number of Registers | CRC check code (low bytes in front) |
b) Read data response frame
| 06 | 03 | xx | xx xx | xx xx |
| Address | FC | Number of Bytes | Response data | CRC check code (low bytes in front) |
c) Write data instruction frame
| 06 | 06 | xx xx | xx xx | xx xx |
| Address | FC | Register address | Read-in data | CRC check code (low bytes in front) |
d) Data response frame
| 06 | 06 | xx xx | xx xx | xx xx |
| Address | FC | Register address | Read-in data | CRC check code (low bytes in front) |
7.3 Register Address
| Register Address | Name | Instruction | Number of Registers | Access
Method |
|---|---|---|---|---|
| 40001 (0x0000) | Measured value | Two double-byte integers are the measured value and the number of decimal places of the measure value. | 2 (4 bytes) | Read |
| 44097 (0x1000) | Zero calibration | Calibrate in the standard solution, the written data is the actual value of the standard solution. | 1(2 bytes) | Write |
| 44103 (0x1006) | Zero calibration value | Ther read data is the zero offset | 1(2 bytes） | Read |
| 48195 (0x2002) | Sensor address | The default is 6, and the write data range is 1-127 | 1 (2 bytes) | Write/Read |
| 48225 (0x2020) | Reset Sensor | The calibration value is restored to the default value, and the write data is 0. Note that the sensor needs to be calibrated again after reset before it can be used. | 1 (2 bytes) | Write |
Note:
a) The register address is the starting address of the register with register type defined according to the Modbus protocol (the actual starting address of the register represented by the hexadecimal system in parentheses).
b) When changing the sensor address, the sensor address in the return instruction is the new address after the change.
c) The data definition of the measured value returned when reading the data:
xx xx xx xx
2-byte measurement value 2-byte measurement value decimal places
The default data type is double-byte integer, high byte first; other types such as floating-point numbers are optional.
7.4 Command example
a) Start measurement command
Function: Obtain the ORP measured by the sensor, the unit of ORP is mV. Request frame: 06 03 00 00 00 02 C5 BC
Response frame: 06 03 04 00 78 00 00 0C EA Examples of readings:
| ORP value |
| 00 78 00 00 |
For example, the ORP value “00 78” represents the hexadecimal reading of the ORP value, and “00 00” indicates that the ORP value has no decimal places and no temperature value. When converted, the hexadecimal value 00 78 corresponds to a decimal value of 120.
b) Calibration instruction:
The ORP sensor only requires one‑point calibration. Before calibrating with another standard solution, the electrode must be cleaned with that solution; otherwise, it may cause significant measurement errors.Place the sensor in the prepared 86 mV or 256 mV standard solution and enter the corresponding calibration command.
The standard solution is 86mV:
Request frame: 06 06 10 00 00 56 0C 83;
Response frame: 06 06 10 00 00 56 0C 83;
The standard solution is 256mV:
Request frame: 06 06 10 00 01 00 8D 2D;
Response frame: 06 06 10 00 01 00 8D 2D
Note: The ORP value has a negative value, such as-40mV, its calculation method is:-{FFFF-FFD7 software test value)}=-28; decimal is-40mV.
c) Set the device ID address:
Function: set the MODBUS device address of the electrode. Change the device address 06 to 01, with the following example:
Request frame：06 06 20 02 00 01 E3 BD
Response frame：06 06 20 02 00 01 E3 BD
7.5 Error response
If the sensor does not execute the upper computer command correctly, the following format information is returned:
| Definition | Address | FC | CODE | CRC check |
| data | ADDR | COM+80H | xx | CRC 16 |
| Number of bytes | 1 | 1 | 1 | 2 |
a) CODE： 01 – Functional code error
03 – Data error
b) COM：Received function code
8. Applicable Accessories
| Name | Requirements | |
| PA000000076 | SENSBLUE MONARCH Solar Panel 1 Probe | |
| PA000000079 | SENSBLUE MONARCH Solar Panel 2 Probes | |
| PA000000080 | SENSBLUE MONARCH Solar Panel 1 Probe External Antenna | |
| PA000000074 | SENSBLUE MONARCH Solar Panel 2 Probes External Antenna | |
| PA000000081 | SENSBLUE MONARCH Opaque Case 1 Probe | |
| PA000000082 | SENSBLUE MONARCH Opaque Case 2 Probes | |
| PA000000083 | SENSBLUE MONARCH Opaque Case 1 Probe External Antenna | |
| PA000000084 | SENSBLUE MONARCH Opaque Case 2 Probes External Antenna | |
| PA000000020 | SENSBLUE MONARCH RS485 Probe Splitter Box (1 input -> 2 outputs) |
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| PA000000088 | SENSBLUE RS-485 ORP Probe AT-SB-PROBE-ORP-P-C1, w/ 15m cable w/connector | |
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10. Applicable certifications and standards
EMC Directive 2014/30/EU.
- EN IEC 61326-1: 2021
- EN 55011: 2016+A2: 2021
- EN IEC 61000-3-2: 2019+A1: 2021
- EN 61000-3-3: 2013+A2: 2021