новости компании о DPH890 User Manual Published: Modbus RTU Register Map and Calibration Guide for System Integrators

System integrators evaluating a pH sensor spend most of their time on questions that have nothing to do with the glass bulb: which register holds the value, what data format it uses, how the station address is changed, and how calibration is triggered from a controller. Daruifuno has published the DPH890 user manual to answer those questions before a purchase order is raised.

A Published Register Map, Not a Reverse-Engineering Exercise

The DPH890 is a Modbus RTU server device on an RS485 bus. The manual lists every parameter with its address, data format, permitted range and initial value, so commissioning does not depend on trial and error:

• Measurements (function code 04): pH at address 2 and temperature at address 4, both 32-bit floating point, formed from two consecutive 16-bit registers.
• Communication settings (function code 03 / 06): station address 1~254 (default 9), Baud rate 4800 / 9600 / 19200 / 38400 (default 9600), parity none / even / odd, stop bit 1 or 2.
• System settings: sampling buffer level 2 / 4 / 8 / 16 / 32, automatic or manual temperature mode, and the solution compensation type (none, natural water, pure water, other).
• Calibration (function code 16): write 4 to address 200 for the 4.01 pH point, 7 to address 206 for 6.86 pH and 9 to address 214 for 9.18 pH.
• Restore defaults: write 99 to address 400 - communication parameters are deliberately left untouched.

Calibration That Suits the Buffers You Stock

The three calibration point values are not fixed. Point 1 can be set between 3.5 and 4.51 pH, point 2 between 6.36 and 7.5 pH and point 3 between 8.68 and 10.5 pH, so a plant can calibrate with the standard solutions it already holds rather than ordering a specific set. Zero point, slope 1, slope 2, main measurement offset and temperature offset are all writable within published ranges, which gives maintenance teams a documented way to compensate for ageing before replacing an electrode.

Hardware Details Integrators Ask About

Commissioning Sequence Recommended by the Manual

1. Wire by colour: red V+ (DC 9~24 V), black V-, white RS485 A, green RS485 B. The aviation plug version arrives pre-wired.
2. Scan the bus at 9600 baud, 8 data bits, no parity, 1 stop bit on address 9 to confirm the sensor responds.
3. Read addresses 2 and 4 and verify both floats before mapping them into the controller.
4. Set the station address, Baud rate, parity and stop bit to the site convention.
5. Choose the sampling buffer level and the compensation coefficient for the process.
6. Soak the electrode in KCl solution, then calibrate at the three points and log zero and slopes as the service baseline.
7. Add a range alarm on pH and a watchdog on the temperature register - the cheapest fault detection available.

Installation Variants for Panel and Skid Builders

The same sensor body is supplied for five mounting arrangements: side wall installation on tank or channel walls, top flange mounting through a cover, flow-through installation in a bypass or sample line, submerged installation on a rail or bracket, and pipeline installation threaded into a tee. A 10 m cable is standard and can be customised, and the installation angle should stay within ±30° of vertical.

The DPH890 user manual, register map and dimension drawing are released for evaluation so an integrator can confirm wiring, protocol and mounting before the panel is designed. Contact the manufacturer's engineers to request the documentation set and a quotation.