This article explains the correct method of wiring Q.bloxx Classic modules in a distributed system setup in an industrial environment.
Introduction
The Q.station 101 controller includes four UART interfaces for communication with Q.bloxx modules via an RS-485 bus. The RS-485 connection can be made through a backplane (integrated in the module socket) or wired for remote installations. All connected modules are automatically time-synchronized with ±0.5 µs jitter.
Each UART supports up to 16 modules, allowing a maximum of 64 modules per Q.station 101. The actual number of modules and data throughput depend on the configured baud rate, which is influenced by the RS-485 bus length. See Baud rate versus bus length for details.
How to connect Q.bloxx modules to a Q.station 101
The schematic below shows the RS-485 and power connections between the Q.station 101 and the first Q.bloxx module on a UART, using an 8-way pluggable terminal block (orange).
Each Q.station 101 includes one 8-way pluggable terminal block. Additional blocks must be ordered separately.
- Gantner Instruments Art. No. 757789 (Terminal block 8pol orange left for UART Q.series)
- Phoenix Contact MC 1,5/ 8-ST-3,81 OG
Please refer to the Q.station 101 or the Q.bloxx manual for more details about wiring a Q.bloxx Classic system.
Wiring requirements for a distributed measurement setup
To daisy-chain multiple modules on a single UART, each module’s right side requires an additional 8-way pluggable terminal block (black) for connecting the cable to the next module.
These terminal blocks must be ordered separately:
- Gantner Instruments Art. No. 930580 (Terminal block 8pol black right for UART Q.series)
- Weidmüller SCZ 3.81/08/180G SN OR BX
If voltage drop over the cable prevents powering all modules on one chain, an extension socket (Q.bloxx base extension, article number 792081) can be used to connect an additional 10–30 VDC power supply.
Please refer to Chapter 4 of the Q.bloxx manual for more details on calculating voltage drop and using the extension socket. Alternatively, contact your local Gantner Instruments representative for support.
How to connect e.bloxx modules to a Q.station 101
Q.bloxx modules must be addressed before e.bloxx modules on a UART. Skip an address in the sequence before addressing an e.bloxx module.
How to connect Q.bloxx modules to a Q.station X
To connect a Q.bloxx Classic module to a Q.station X, an extension socket is required. This adapter converts the Q.station X PCB backplane connector into a screw terminal connector for easy wiring. The extension socket provides connections for both RS-485 bus communication and power supply to the Q.bloxx modules:
Please also refer to this knowledge base article for more details about the extension socket pin assignment and wiring.
Baud rate versus bus length
Depending on bus length, the data transmission speed (baud rate) may need to be reduced. The factory default is 24 Mbps. See the table below for recommended baud rates.
The controller’s baud rate is configured in GI.bench (Controller → RS485 adapter → General → Baudrate). GI.bench verifies whether the configured modules, variables, and sample rate fit within the selected baud rate. If an error occurs, reduce the number of modules/variables on the UART or lower the sample rate.
The total bus length includes all cables between modules and the cable to the centralized controller. Regardless of cable length or baud rate, each UART supports up to 16 modules. For baud rates of 1.5 Mbps or lower, maintain at least 1 meter of cable between adjacent devices.
| Baud rate | Maximum bus length |
|---|---|
| 187.5 kbps | 1000 m |
| 500 kbps | 400 m |
| 1.5 Mbps | 200 m |
| 3 Mbps | 100 m |
| 6 Mbps | 20 m |
| 12 Mbps | 10 m |
| 24 Mbps | 10 m |
Cable requirements
The recommended baud rates apply only when using PROFIBUS cables compliant with the IEC 61158 standard. Using other cables may invalidate these recommendations and affect long-term reliability.
To reduce electrical interference, use cables manufactured to IEC 61158 (Type 3 or PROFIBUS cable). These are 2-wire shielded twisted pair cables, typically with Aluminum Polyester Tape shielding and either tinned copper wire braid (TCWB) or steel wire armor (SWA) to protect against crosstalk and electromagnetic interference.
Note that some cables designed for special environmental conditions may not meet the specified bus length or reliability requirements. Refer to the cable manufacturer’s datasheets for details.
Gantner Instruments recommends the UNITRONIC BUS PB cables from LAPP.