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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

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
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