Bio Instruments SF-xT-485M
Phyto-Sensor sap flow sensor for leaf petioles and small shoots, read over RS485.
The Bio Instruments SF-xT-485M is a Phyto-Sensor sap flow sensor that tracks relative changes in sap flow in a leaf petiole or small shoot, used for crop monitoring in greenhouses. This Modbus RTU template reads the relative sap flow and the communication settings, and lets you change the address, baud rate and parity from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 9600 baud
- Registers
- 5, read and write
- Brand
- Bio Instruments
- Key readings
- Relative sap flow · Modbus address · Baud rate · Parity
- Available commands
- Modbus address · Baud rate · Parity
- Compatible models
- SF-4T-485M · SF-5T-485M
- Last updated
Registers (5)
5 read, 3 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Sap Flow | Read | ||||
| Sap Flow Float | Read | ||||
| Device Address | Read and write | ||||
| Baud Rate Code | Read and write | ||||
| Parity Code | Read and write |
Loading registers…
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Use cases
- Plot relative sap flow next to irrigation and greenhouse climate data on one dashboard to see how the crop responds during the day.
- Get an email or webhook when sap flow drops below a threshold you choose, for example after an irrigation fault.
- Keep 365 days of sap flow history to compare days, crop stages and irrigation strategies.
- Let automatic monitoring flag a sap flow value that stays exactly the same for hours.
- Give each sensor its own address from ModbusCloud before you add more sensors to the same RS485 line.
Installation
Mount the probe on a petiole or small shoot with the red mark pointing in the direction of the upward sap flow, and wrap it completely in two or three layers of aluminium foil.
Connect black to ground, yellow to RS485 B and white to RS485 A of the ModbusCloud Gateway, and red to a 5 to 24 Vdc supply. Terminate both ends of the bus with 120 Ω.
Give every sensor on the bus its own address with the Bio Instruments address tool or by writing Device Address. All sensors leave the factory with address 247.
In ModbusCloud, add a Modbus device with protocol RTU, the sensor address, 9600 baud and 8E1, and import this template.
Allow 15 minutes of warm-up, then check that Sap Flow shows a value between 0 and 2.
Things to watch for
The sensor does not answer. What should I check?
Check 9600 baud, even parity, 1 stop bit and address 247 in ModbusCloud; many tools default to no parity. Swap A and B if nothing comes back, connect the black ground wire to the bus ground, and terminate both ends of the bus, because the sensor has no termination resistor inside.
Sap flow reads about 0.4 and hardly changes. Is that normal?
The output has a zero offset of about 0.4 relative units, so read changes against the course of the day rather than the absolute number. If it stays flat, check that the red mark points upward with the sap flow, that the foil covers the whole sensor and that the probe has had 15 minutes to warm up.
Why do I see every measured value twice?
The sensor gives each measurement as a scaled whole number and as a floating-point value. Both carry the same reading. Keep the one you want on your dashboards and remove the other from the Modbus device in ModbusCloud if you do not need it.
Can I change the address, baud rate or parity from ModbusCloud?
Yes, these three registers are writable. Writing is off per gateway by default; request it for the gateway in the portal. After a new address the sensor only answers on that address. Change baud rate or parity only when every device on the bus gets the same setting, and update the Modbus device in ModbusCloud right away.
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