Bio Instruments LT-xT-485M
Phyto-Sensor contact sensor that measures leaf temperature with one or four probes over RS485.
The Bio Instruments LT-xT-485M is a Phyto-Sensor contact sensor that measures the true temperature of a leaf, or the average of four leaves, in greenhouses and controlled environments. This Modbus RTU template reads the leaf temperature 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
- Leaf temperature · Modbus address · Baud rate · Parity
- Available commands
- Modbus address · Baud rate · Parity
- Compatible models
- LT-1T-485M · LT-4T-485M
- Last updated
Registers (5)
5 read, 3 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Leaf Temperature | °C | Read | |||
| Leaf Temperature Float | °C | 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
- Show leaf temperature next to greenhouse air temperature on a dashboard to see when the crop heats up under sun or lamps.
- Get an email or webhook when leaf temperature rises above a threshold you set.
- Keep 365 days of leaf temperature history to compare climate strategies, screening and lighting.
- Use the four-probe model to follow the average temperature of several leaves with one sensor and one address.
- Give each sensor its own address from ModbusCloud before you add more sensors to the same RS485 line.
Installation
Clip the thermistor to the shaded underside of a healthy, fully expanded upper leaf, and fix the cable with tape near the base of the leaf, leaving a little slack.
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 Leaf Temperature shows a value close to the air temperature around the plant.
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.
Leaf temperature jumps or reads far from the air temperature.
Check that the thermistor still touches the shaded underside of the leaf and that the cable has some slack, so wind or plant work cannot pull the clip off. A probe in direct sun or hanging in the air does not give leaf temperature.
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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