Hirschmann OZD Profi G12D repeater explosion-proof installation configuration

Hirschmann OZD Profi G12D Series PROFIBUS Fiber Optic Repeaters Explosion proof Installation and Ring Network Redundancy Configuration Guide

Introduction: Safe Crossing of Explosion proof Zones from Electrical to Optical Fiber

In environments with explosive gases or dust such as petrochemicals, pharmaceuticals, and gas transportation, PROFIBUS fieldbus networks must not only meet high-speed data transmission requirements, but also strictly comply with explosion-proof regulations. Traditional RS-485 electrical signals face inherent safety limitations and electromagnetic interference issues in Zone 1/21, while fiber optic transmission has become an ideal choice due to its electrical isolation and anti-interference advantages. The Hirschmann OZD Profi G12D series (including three variants of G12DU unprotected housing, G12DK plastic housing, and G12DE stainless steel housing) is a PROFIBUS fiber optic repeater designed for this purpose. It supports adaptive rates from 9.6kbit/s to 12Mbit/s and is ATEX/IECEx certified (Ex e mb op is [ib] IIC T4 Gb). It can be used as an electrical PROFIBUS signal to fiber optic network conversion interface in Zone 1, 2, 21, and 22. This article is based on the official manual, systematically reviewing the explosion-proof installation specifications, DIP switch mode configuration, fiber/electrical wiring, redundant ring network parameter calculation, and fault diagnosis methods of this series of repeaters, to assist engineers in safely and efficiently deploying PROFIBUS fiber networks in hazardous areas.

Chapter 1 Product Overview and Selection Analysis

1.1 Three shell variants and application scenarios

The core functionality of the OZD Profi G12D series is consistent - providing one electrical RS-485 channel (CH1) and two fiber optic channels (CH2, CH3), both supporting BFOC/2.5 (ST) connectors to achieve bidirectional conversion of electrical/optical signals. The difference lies in the form of the shell:

OZD Profi G12DU ATEX 1 (without protective casing): DIN rail installation (35mm) or flat installation, to be installed in the explosion-proof enclosure provided by the customer with IP54 or above, suitable for integration into existing control cabinets.

OZD Profi G12DK ATEX 1 (plastic shell): IP66 protection level, comes with cable sealing joints (PG glasses), can be directly installed in Zone 1/21 area (the shell itself is explosion-proof shell), optional transparent window cover (accessory OZD SFK ATEX) for easy observation of LED.

OZD Profi G12DE ATEX 1 (stainless steel housing): IP66, higher mechanical strength and corrosion resistance, suitable for harsh chemical or marine environments.

Selection key: If there is already an explosion-proof junction box on site, choosing G12DU has a lower cost; If independent outdoor installation is required, choose G12DK/G12DE. Stainless steel shell is more corrosion-resistant but heavier (about 3.7kg vs 2.4kg).

1.2 Interpretation of Explosion proof Markings

G12DU：II 2 G Ex e mb op is [ib] IIC T4 Gb

Ex e: increased safety terminal; MB: Sealed type; OP is: Optical isolation is inherently safe; [ib]: Associated with intrinsic safety circuits; IIC: Suitable for high-risk gases such as hydrogen and acetylene; T4: Maximum surface temperature ≤ 135 ° C.

G12DK/DE: II 2 G Ex e mb [ib] op is IIC T4 and II 2 D Ex tD A21 IP66 T130 ° C (dust explosion-proof).

Important restrictions: Maximum ambient temperature ≤ 60 ° C, pollution level 2, overvoltage category II. Only allowed to open the increased safety terminal cover in power-off state.

Chapter 2: Mandatory Regulations for Explosion proof Installation

2.1 Installation Requirements for Zone 1/21

G12DU: It must be installed in a casing that meets one of the following explosion-proof types: increased safety (e), explosion-proof (d), or enclosure protection (t), and the casing must be ATEX certified. The shell protection level should be at least IP54 (gas) or IP6X (conductive dust).

G12DK/DE: Can be installed directly, but all cable sealing joints must use certified models, and unused inlet ports must be sealed with certified plugs. The tightening torque should be executed according to the manual table (M16=2.5Nm, M20=3.5Nm, etc.), as over tightening or over loosening will damage the IP66 protection.

Live operation restrictions: In Zone 1, maintenance can be carried out while the shell cover is open (but the increased safety terminal cover cannot be opened). In Zone 21 (dust), the shell cover can only be opened after power failure or obtaining a "hot work permit". All terminal covers are strictly prohibited from being disassembled when live.

Dust deposition: The thickness of dust accumulation on the surface of the equipment shall not exceed 5mm (IEC/EN 61241-1).

2.2 Zone 2/22 Installation Requirements

Similar to Zone 1 but loose: the housing cover can be opened for maintenance while live (Zone 2), but Zone 22 still requires power off.

IP54 (gas) or IP6X (dust) requirements are the same as Zone 1.

2.3 Safety Zone Installation

G12DU can be directly installed in distribution cabinets located in safe areas (non explosion proof areas) without the need for additional enclosures. At this time, the shell cover can be opened at any time.

Chapter 3 Mechanical Installation and Grounding

3.1 DIN rail and flat installation

G12DU: The top buckle hangs on the 35mm guide rail and is locked by pressing down; Unlock with a screwdriver during disassembly. Alternatively, the rail adapter can be removed and installed flat using three M4 screws (see Figure 14 for drilling dimensions).

G12DK: Four semi-circular slots at the bottom, fixed to the plane with M4 screws (see Figure 16 for drilling dimensions).

G12DE: Two brackets at the bottom, fixed with M5 screws (see Figure 18 for drilling dimensions).

3.2 Functional Grounding (FG)

Important: The reference ground (FG) of the RS-485 interface is directly connected to the functional ground terminal without electrical isolation. Therefore:

The FG terminal must be connected to the equipotential grounding bar of the control cabinet.

If different control cabinets are connected through RS-485 cables, their grounding bars must be interconnected with low resistance.

It is strictly prohibited to lead RS-485 cables out of buildings (lightning protection), and optical fibers must be used to pass through building boundaries.

Wiring: The FG terminal of G12DU is located at the front single terminal (see Figure 24 in the manual); The FG terminal of G12DK/DE is located outside the housing (Figure 25) and requires a toothed washer to ensure good contact.

Chapter 4 Detailed Rules for Electrical and Fiber Optic Wiring

4.1 RS-485 Electrical Channel (CH1) Wiring

Terminals: DI A, DI B (receive input), DO A, DO B (send output). In practical use, A-A and B-B are usually short circuited to form a "loop in loop out" structure (as shown in Figure 22).

Shielding treatment: The cable shielding layer must be extensively connected to the equipotential busbar at the entrance of the control cabinet, and the shielding layer must be grounded at both ends (note that the potential difference may cause excessive shielding current, and equipotential compensation wires may be laid if necessary).

Terminal resistor: If the repeater is located at the end of the RS-485 bus segment, the internal terminal resistor needs to be connected through DIP switch S7 (OFF=connected, ON=disconnected).

Indoor wiring only: RS-485 cables shall not be laid outside buildings.

4.2 Fiber Channel (CH2/CH3) Wiring

Connector: BFOC/2.5 (ST), requiring cross connection (send receive, receive send).

Fiber type: multimode G 50/125 or G 62.5/125, wavelength 860nm, maximum segment length 3000m (attenuation budget: G50/125≤3.0dB/km，G62.5/125≤3.5dB/km）。

Wall sealing: The PG sealing joint of G12DK/DE is equipped with a slotted sealing ring, allowing the fiber optic cable pre installed with the connector to pass through (by breaking the sealing ring and fitting it onto the fiber optic cable).

Unused ports: must be sealed with protective caps to prevent environmental light interference and dust pollution.

4.3 Signal contact (relay) wiring

Terminals: F (common), FNC (normally closed), FNO (normally open). When there is no fault, F and FNC are conductive; When there is a malfunction or power outage, F and FNO are conductive.

Electrical limits: Maximum switching voltage 60V DC/42V AC, maximum current 1A, capacity 30W. SELV power supply must be used.

Reportable faults: fiber breakage, power loss, self-test error, ring network fault, etc. (indicated by LED and contacts simultaneously).

4.4 Redundant power supply

Terminal: Two independent 24V inputs (24V 1, 24V 2) and a 0V common terminal. Internal diode decoupling, automatic switching to higher voltage, no load balancing.

Voltage range: 18~32V DC (typical 24V), power consumption ≤ 5W.

Redundancy meaning: If the main power supply fails, the backup power supply will automatically take over, and the signal contacts will not be lost and trigger an alarm (requiring external monitoring).

Chapter 5 DIP Switch Working Mode Configuration

The front end of the device has 8-bit DIP switches (S0~S7, with S5/S6 having no function). The power must be disconnected before configuration.

5.1 Electrical Channel Mode (S0)

OFF (factory): Segment monitoring of electrical channels - detects error frames or continuous occupancy on RS-485, and blocks the channel if any abnormalities are found until normal operation is restored.

ON: Non segmented monitoring of electrical channels - only used in the electrical star segment of the star coupler to avoid accidental blocking.

5.2 Fiber Channel Mode (S1~S4)

Each optical channel is set independently, but the two optical channels must have the same mode (if both are used for ring, they must all be ring).

Mode S1/S3 S2/S4 Description

Line type OFF with fiber optic monitoring enables echo sending, echo monitoring, echo suppression, and segmentation functions

Line type ON/OFF without fiber optic monitoring only transparent forwarding, no fiber breakage detection (used to connect third-party devices that do not support echo)

Redundant halo ON Two optical channels form a ring network, which automatically switches to linear mode after fiber breakage

Important: The two ends of the optical channel (i.e. the corresponding optical ports of the two repeaters) must be set to the exact same mode, otherwise communication cannot be achieved.

5.3 Internal Terminal Resistance (S7)

OFF: Connect the terminal resistor (for RS-485 segment end)

ON: Disconnect the terminal resistor (for intermediate nodes)

Chapter 6 Parameter Calculation of Redundant Halo Network

In the ring network topology, due to the additional delay introduced by fiber optics and multiple repeaters, it is necessary to adjust the "Slot Time" parameter of the PROFIBUS master station, otherwise communication timeout and system LED red green flashing may occur.

6.1 Calculation Formula

Slot Time=a+(b x total fiber length in km)+(c x number of repeaters)

The coefficients a, b, and c are queried according to the data rate in Table 2a (DP standard) or Table 2b (DP/FMS universal mode) of the manual. For example:

12Mbit/s：a=1651，b=240，c=6

1.5Mbit/s：a=351，b=30，c=5

500kbit/s：a=251，b=10，c=5

Example: Rate of 1.5Mbit/s, total fiber length of 5km, number of repeaters 8:

Slot Time=351+30 × 5+5 × 8=351+150+40=541 bit times.

6.2 Other necessary configurations

Set a non-existent station address: The main station will send polling messages during the GAP query cycle, and the relay will use this idle gap to re close the fiber optic cable into a ring shape. A non-existent slave address must be configured, otherwise the ring cannot be automatically restored after fiber breakage recovery.

Retry count: It is recommended to set it to at least 3 times to smooth out brief interruptions during the switching process.

Slot Time must be large enough: if it is too small, it will cause the system LED to flash red and green, and needs to be recalculated and increased according to the formula.

Chapter 7 Fiber Optic Receiving Level Measurement and Diagnosis

The device provides analog voltage output terminals (CH2, CH3, CH0V), and a high impedance voltmeter can be used to measure the voltage value corresponding to the received light power (Figure 33 in the manual shows the corresponding relationship between voltage and signal quality).

7.1 Measurement Method

It is necessary to ensure that the peer repeater is sending valid PROFIBUS messages (with its LED flashing yellow).

Use a floating high impedance voltmeter (do not connect the reference potential to the shell).

Read the voltage value and compare it with Figure 33 to determine:

Good (normal operation): The voltage is in a high region and the system has sufficient margin.

Critical (decreased system margin): Fiber attenuation increases, and it is necessary to check the cleanliness of the connector or the bending radius of the fiber.

Poor (function not guaranteed): The voltage is too low, and it is necessary to check whether the optical fiber is damaged, whether the connection is loose, or whether the transmitting power at the opposite end is insufficient.

7.2 Fault localization process

If a certain light channel has a red LED light, follow the steps below:

Check if the two end modes are consistent.

Check if the optical fibers are cross connected.

Measure the receiving level:

If the voltage is in the "difference" zone, check the fiber attenuation and replace the fiber segment if necessary.

If the voltage is normal, it may be a hardware failure of the repeater. Try replacing one of the repeaters in that section.

Chapter 8 LED Status and Troubleshooting Quick Check

8.1 Meaning of System LED and Channel LED

System LED (yellow/red/green):

Yellow flashing: No rate detected (no bus message).

Green: The speed has been recognized and the system is functioning properly.

Red and green flashing alternately: Slot Time configuration is too small (incorrect ring network parameters).

CH1 (Electrical) LED:

Yellow: Receiving data.

Red: Segment monitoring detected an error (blockage).

CH2/CH3 (Light) LED:

Yellow: Receiving data (normal in monitoring mode).

Red: fiber breakage or receiving error (with monitoring mode). If the line is still red after restoration, the HSA parameters (ring network configuration) need to be checked.

Red/yellow alternation: periodic interference or loose connections.

8.2 Signal contact triggering conditions

The situation of contact disconnection (F and FNC disconnected):

Any optical channel fiber breakage (with monitoring mode)

Ring network configuration error

Equipment self-test failed

Power loss (all)

Chapter 9 Maintenance and Safety Warning

Repair strictly prohibited: There are no user repairable parts inside the equipment, and if damaged, the original parts must be replaced as a whole.

Sealing integrity: Damaged sealing rings must be replaced every time the housing is opened, and screws must be tightened with torque to maintain IP66.

Dust environment: It is strictly prohibited to open the dust explosion-proof enclosure (Zone 21/22) while it is electrified. The dust must be removed first and the power must be turned off.

Cable sealing: Only use certified cable sealing joints to ensure that the cable diameter is within the allowable range (G12DK/DE power connectors allow 5.5-13mm, signal/bus connectors 5.5-10mm, fiber optic connectors 6.4-13mm).