Tibbo > Hardware > RS485 Modbus Sensors

RS485 Modbus Sensors (Bus Probes)

Bus Probes are a family of low-power environmental sensors with an RS485 interface. The probes communicate using the standard Modbus RTU protocol.

Tibbo offers six types of probes: an ambient temperature sensor (BP#01), an ambient temperature and humidity sensor (BP#02), an ambient light sensor (BP#03), a three-axis accelerometer (BP#04), a flood/leak sensor (BP#05), and an opto-isolated digital input (BP#06).

Bus Probes are typically wired to a twisted pair cable that distributes power and carries RS485 "+" and "–" lines. All probes accept a supply voltage from 4V to 15V, allowing you to power them with 5V sources (for example, the 5V output of Tibbit #00-3) or standard 12V power supplies. The wide supply voltage range also means that you can allow for a significant voltage drop along the bus (e.g., when using a bus cable of considerable length).

Bus Probes are very compact (measuring only 40x36mm externally) and sport an attractive look and feel. Each sensor has two mounting holes for attaching it to walls and other surfaces.

Bus Probes can be configured and tested using our web-based test app (you will need to connect the probes to your PC or Android smartphone via our Web485 board). Tibbo also offers a browser-based test kit (see BP-TEST-WEB-KIT below), which consists of four Bus Probes (#01, #02, #03, and #04), a Web485 board, and the necessary cables.

Two Tibbo Project System (TPS), Gen. 2-compatible Tibbo BASIC applications for the setup and testing of Bus Probes are available: BP-Tester-UI and BP-Tester-Web. We also offer a TPS-based test kit (see BP-TEST-KIT below), which consists of four Bus Probes (#01, #02, #03, and #04), a TPS2L(G2) preloaded with the BP-Tester-UI app, and the necessary cables.

Here is How You Can Use Bus Probes

Use the probes in your
Modbus system

Tibbo Bus Probes feature an RS485 interface and support the industry-standard Modbus RTU protocol. Therefore, existing Modbus systems can use them as general-purpose environmental sensors.

To aid in the creation of sophisticated Modbus systems and network-enablement of serial Modbus devices, Tibbo also offers Modbus Gateways.

Deploy the probes as a part of our
TPS-based Remote I/O solution

Our Remote I/O solution supports the use of Bus Probes. Connect the probes to the RS485 port on a standard TPS-based controller and collect environmental data via the RS485 bus.

Combine TPS devices with Bus Probes to create environmental monitoring systems.

Key Features

Half-duplex RS485
interface

Modbus RTU
protocol

4V to 15V power

Available Probes

BP#01: Ambient temperature
sensor

BP#02: Ambient temperature
and humidity sensor

BP#03: Ambient
light sensor

BP#04: Three-axis
accelerometer

BP#05: Flood/leak sensor

BP#06: Opto-isolated digital input (DI)

Hardware

Specifications:

Half-duplex (two-wire) RS485 interface
Communications parameters:
- User-selectable baudrate
  - Default: 38,400bps
  - Minimum: 1,200bps
  - Maximum: 115,200bps
- 8-bit
- User-selectable parity: none, odd, even, mark, and space
- One stop bit⁽¹⁾
Modbus RTU protocol
BP#01 (ambient temperature sensor)
- Measurement range: –40°C to 125°C⁽²⁾
- Measurement resolution: 0.25°C
- Measurement accuracy: ±1°C⁽³⁾
BP#02 (ambient temperature and humidity sensor)
- Temperature measurement
  - Measurement range: –25°C to 50°C
  - Measurement resolution: 0.5°C
  - Measurement accuracy: not specified⁽⁴⁾
- Humidity measurement:
  - Measurement range: 10 to 90% RH
  - Measurement resolution: ±0.1% RH
  - Measurement accuracy: ±5% RH⁽⁵⁾
  - Temp. range for valid humidity measurements: 5°C to 50°C
BP#03 (ambient light sensor)
- Measurement range: 1 to 65,528 lux
- Measurement resolution: 1 lux
- Measurement accuracy: 1 lux
BP#04 (three-axis accelerometer)
- Independent X, Y, and Z axes
- Measurement range for each axis: ±6G
- Measurement resolution for each axis: 0.003G
- Measurement accuracy for each axis: 0.1G
BP#05 (flood/leak sensor)
- Reliably detects the presence of water and water-diluted liquids⁽⁶⁾
  - While the companion sensor cable is designed for immersion in liquids, the Bus Probe's body is not waterproof
- Two sensitivity levels: normal and reduced⁽⁷⁾ (controlled via a non-volatile register)
- Companion sensor cable supported length: 30cm to 30m
- Inductor-less isolation of the detection circuit from the power and RS485 bus for improved reliability and safety
- ±65V fault and short-circuit protection for the RS485+ and RS485– lines
- ±40V common-mode voltage range for the RS485+ and RS485– lines
- Hot-swap protection
BP#06 (opto-isolated digital input)
- Unidirectional optically isolated digital input (DI) suitable for 2/3-wire sensors with reduced power consumption
- Optimized for 24VDC industrial inputs, especially Type-3 sensors
- Input V-I characteristics:
  - Wide input range compliant with IEC 61131-2 Type 3 criteria
  - Input current clamped to 3.5mA
  - V_in (threshold): 11VDC ~ 12.4VDC (depending on temperature)
  - I_in (threshold): 2.2mA±0.3mA (complete voltage and temperate range)
- Protection and safety features:
  - Protection against high-voltage transients on the line
  - Digital input reverse polarity protection up to –80VDC
  - Digital input isolation voltage: 2.5kV
  - ±65V fault and short-circuit protection for the RS485+ and RS485– lines
  - ±40V common-mode voltage range for the RS485+ and RS485– lines
  - Hot-swap protection for all terminals
- Sampling time:
  - Instant
  - 0.25ms filtered
Green and red status LEDs
Power: 4V to 15V DC
Current consumption:
- BP#01 ~ BP#04 — 2.5mA average @5V/12V with spikes of up to 6mA
- BP#05 — 16mA average @5V/12V with spikes of up to 25mA during Modbus communications
- BP#06:
  - Idle — 4mA average @ 5V/12V
  - Polling — 7mA average @ 5V/12V with spikes of up to 20mA
Dimensions, excluding connectors (L x W x H): 40 x 36 x 19mm
Operating temperature range: –40°C to +85°C⁽⁸⁾⁽⁹⁾
Internal firmware is upgradeable through XModem file transfer protocol over RS485
CE- and FCC- certified.⁽¹⁰⁾

If two stop bits are required, the parity can be set to the mark mode, which is equivalent to 8-N-2 (8 bits of data, no parity, and two stop bits).
The actual measurement range is limited by the operating temperature range of the Bus Probe itself, which is from –40°C to +85°C.
Independent lab tests commissioned by our Romanian distributor found BP#01's measurement accuracy for ambient temperature to be ±0.45°C or better.
Independent lab tests commissioned by our Romanian distributor found BP#02's measurement accuracy for ambient temperature to be ±0.5°C or better.
Independent lab tests commissioned by our Romanian distributor found BP#02's measurement accuracy for relative humidity to be ±3.8% or better.
After immersion in any liquid that can leave a residue, BP#05's companion sensor cable should be cleaned, inspected, and tested to ensure that it remains conductive. Contact with highly acidic or alkaline substances can permanently damage the cable.
The normal sensitivity mode can detect even small amounts of water on the companion sensor cable. The reduced sensitivity mode helps to avoid false positives due to condensation or high levels of humidity in the operating environment.
While the sensor is capable of operating from –40°C to +85°C, BP#05 will only reliably detect water in its liquid phase.
BP#05 and BP#06 were tested according to procedures I, II, and III of MIL-STD-810H Method 501.7 and MIL-STD-810H Method 502.7.
CE and FCC certification for BP#05 and BP#06 are pending.

See Also:

Apps, Files, and Documentation

Test Applications	Bus Probe Web-based Tester App Bus Probe Web-based Firmware Updater App TPS-based Test App (UI version) TPS-based Test App (web interface version)
Probe Firmware	bp_application_firmware_v1_07.bin
Documentation	Bus Probe Manual
CE Certificate	bp01_02_03_04-ce.pdf
FCC Certificate	bp01_02_03_04-fcc.pdf