Agrowtek PHX pH Sensor
pH and temperature transmitter for nutrient solution, with ORP or oxygen on the PHX+.
The Agrowtek PHX is a hydroponics transmitter that measures pH and temperature, and on the PHX+ also ORP or dissolved oxygen, in nutrient tanks and fertigation systems. This Modbus RTU template reads all sensor values and identification, and lets you write pH and temperature calibration and the device address from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 24, read and write
- Brand
- Agrowtek
- Key readings
- pH · Temperature · ORP or dissolved oxygen
- Available commands
- pH calibration · Temperature calibration · Analog output calibration · Device address
- Compatible models
- PHX · PHXM · PHX+ · Agrowtek PHX and PHX+ hydroponics sensor transmitter, temperature and pH (+ORP or DO)
- Last updated
Registers (24)
14 read, 11 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| pH | pH | Read | |||
| Temperature | °C | Read | |||
| ORP or DO | Read | ||||
| pH Float | pH | Read | |||
| Temperature Float | °C | Read | |||
| ORP or DO Float | Read | ||||
| Temperature Offset Calibration | °C | Write | |||
| pH Offset Calibration | pH | Write | |||
| ORP Offset Calibration | Write | ||||
| Temperature Span Calibration | °C | Write | |||
| pH Span Calibration | pH | Write | |||
| ORP Span Calibration | Write | ||||
| Temperature Analog Output Calibration | Write | ||||
| pH Analog Output Calibration | Write | ||||
| ORP Analog Output Calibration | Write | ||||
| Clear Calibration | Write | ||||
| Device Address | Read and write | ||||
| Baud Rate | Read | ||||
| Data Format | Read | ||||
| Serial Number | Read | ||||
| Date of Manufacture | Read | ||||
| Hardware Version | Read | ||||
| Firmware Version | Read | ||||
| Device Model | Read |
Loading registers…
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Use cases
- Send an alert when the pH of a nutrient tank leaves its target band.
- Show pH and solution temperature of every tank on one dashboard.
- Compare pH drift over 365 days of history to plan probe cleaning or replacement.
- Check after a pH 7 and pH 4 calibration that the reading is back on track.
- Watch ORP in a disinfection loop on the PHX+ and alert on low values.
Installation
Fit the pH and temperature probes and connect the PHX GrowNET RJ45 port to an Agrowtek LX2 ModLINK, never to an Ethernet network.
Wire TX/RX+ and TX/RX- of the LX2 to RS485 A and B of the ModbusCloud Gateway, with termination at the bus ends.
Give the PHX a unique address in the SETUP menu and leave the LX2 at 19200 baud, 8 data bits, no parity, 1 stop bit.
In ModbusCloud, add a Modbus RTU device with that address and import this template.
Check pH in a pH 7 buffer and compare temperature with a reference.
Things to watch for
The transmitter does not answer Modbus requests.
The PHX speaks Modbus only through an LX2 ModLINK on its GrowNET port. Check the RJ45 cable, the LX2 power, A and B wiring and the address. Do not connect the GrowNET port to an Ethernet switch.
The pH reading is slow or off by more than 0.2 pH.
Clean and recondition the pH probe as described for the probe, then calibrate: pH 7 first, then pH 4.01 or 10. A probe that stays slow after cleaning is worn and needs replacing.
How do I calibrate pH from ModbusCloud?
With the probe in pH 7 buffer write 700 to pH Offset Calibration. Then rinse, put it in pH 4.01 buffer and write 401 to pH Span Calibration. Always do the offset first. Writing 1 to Clear Calibration restores the factory values.
What does the third sensor value mean?
On the PHX+ the third input reads ORP in mV or, with an oxygen probe, dissolved oxygen in hundredths of mg/L. The plain PHX has no third probe, so that value has no meaning there.
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