Bio Instruments SD-xT-485M
Phyto-Sensor stem diameter sensor that measures micro-variations in micrometres over RS485.
The Bio Instruments SD-xT-485M is a Phyto-Sensor stem sensor that measures micro-variations of stem diameter in micrometres, used to follow plant water status and growth in greenhouses. This Modbus RTU template reads the stem diameter variation 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
- Stem diameter variation · Modbus address · Baud rate · Parity
- Available commands
- Modbus address · Baud rate · Parity
- Compatible models
- SD-5T-485M · SD-6T-485M · SD-10T-485M
- Last updated
Registers (5)
5 read, 3 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Stem Diameter Variation | µm | Read | |||
| Stem Diameter Variation Float | µm | Read | |||
| Device Address | Read and write | ||||
| Baud Rate Code | Read and write | ||||
| Parity Code | Read and write |
Loading registers…
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Plot stem diameter variation next to irrigation and climate data on a dashboard to see how the crop reacts during the day.
- Compare the daily stem shrinkage between greenhouse sections or irrigation strategies with 365 days of history.
- Get an email or webhook when the stem shrinks below a threshold you set, for example on a hot day with too little water.
- Let automatic monitoring flag a reading that stops changing for hours, for example after the brackets came loose.
- Give each sensor its own address from ModbusCloud before you add more sensors to the same RS485 line.
Installation
Open the jaws with the adjusting nut, place the stem between them and turn the nut until the jaws touch the stem without crushing it. Set the rod at the start of its stroke for a growing stem.
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.
Check that Stem Diameter Variation is well inside the range of your model, and reposition the sensor if it nears either end.
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.
The reading stays at the lower or upper end of the range.
The rod has run out of stroke, often because the stem has grown or shrunk. Reposition the sensor with the adjusting nut: near the start of the stroke if the stem keeps growing, near the end if it will shrink, otherwise in the middle. Fix the cable with a loose loop so it cannot pull on the sensor.
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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