MTL2000 series isolation barrier

The core hub of industrial explosion-proof safety: MTL2000 series intrinsic safety isolation barrier

In modern industrial automation control systems, the signal transmission between process instruments and control equipment faces extremely severe challenges, especially in hazardous areas such as petroleum, chemical, and natural gas where explosive gas mixtures exist. In such an environment, any small electric spark or overheating can lead to catastrophic consequences. Therefore, intrinsic safety (IS) isolation technology has become the key to ensuring the lifeline of industrial production. As a classic product with milestone significance in the industry, the MTL2000 series intrinsic safety barrier has built an absolutely reliable safety bridge between hazardous and safe areas with its excellent high integrity design, innovative isolation mechanism, and comprehensive functional coverage.

Disrupting the isolation design concept of traditional architecture

In the early stages of the development of intrinsic safety explosion-proof technology, Zener diode safety barriers were widely used. However, the Zener gate has a fatal limitation - it must rely on a "high integrity safety ground" with extremely low impedance. In actual complex industrial sites, building and maintaining such a perfect grounding system is not only extremely costly, but also almost impossible to achieve in certain specific ships, offshore platforms, or mobile devices.

The MTL2000 series completely breaks this technological barrier. This series of devices provides electrical isolation of up to 250V between the input, output, and power terminals, and has undergone a voltage withstand test with a minimum effective value of 1500V before leaving the factory. This true "three port isolation" design directly eliminates the system's dependence on the ground network. The circuit in the hazardous area can be completely suspended or grounded at any single point according to actual needs. This not only greatly simplifies the logical complexity of system wiring, making system hook up exceptionally simple, but also fundamentally reduces the expensive cost of grounding construction, making many explosion-proof projects that could not be implemented due to inadequate grounding conditions a reality.

Unparalleled high integrity and fault protection mechanism

'High integrity' is the core product gene of the MTL2000 series. In industrial sites, wire breakage caused by cable aging, mechanical damage, loose or corroded terminals, and grounding faults caused by insulation degradation are extremely common hazards. At the beginning of its design, the MTL2000 series prioritized preventing these extreme working conditions.

1. Breakage and power-off protection

Taking the temperature trip amplifier in this series as an example, if any of the three leads of the on-site RTD sensor breaks, the internal detection mechanism of the equipment will instantly identify the abnormality and immediately cut off the excitation energy of the relay, triggering an alarm. This logic of 'disability alarm' also applies to power supply. Whether using 240V AC, 120V AC, or 24V DC power supply, once the main power supply fails, all relays will automatically de energize to ensure safe shutdown of the system in case of loss of control.

2. Dual mode grounding fault protection

Ground leakage current is an invisible killer that can cause unknown sparks. The MTL2000 series provides users with two distinct and flexibly configurable ground fault protection strategies:

Fault safety mode: By directly connecting the designated terminal to the ground, the system enters a highly sensitive monitoring state. When the total resistance of the three lines to ground is less than 1k Ω, the relay immediately activates and alarms; The system only recognizes the fault as resolved when the resistance to ground is restored to 7.5k Ω or above. This mode is suitable for shutdown protection scenarios with extremely high safety requirements.

Non fault mode: Through an external dedicated grounding fault detection relay (such as MTL4220), when a grounding fault occurs in the cable, the isolation barrier itself will not cut off the output, but will declare the fault signal to the upper computer or control system. This is crucial in the continuous production process of chemical engineering, as unnecessary sudden shutdowns may lead to more severe process loss of control (such as material solidification, pipeline pressure buildup, etc.). Non fault modes allow the system to operate with problems until a suitable process window is found for intervention.

Analysis of Switching Values and Digital Signal Processing Modules

MTL2000 series has launched a variety of highly targeted switch operation relays to meet the needs of various light load switches, proximity switches, and motor control on site.

MTL2210B: Single channel intelligent motor control hub

MTL2210B is a single channel device, but its internal logic is extremely rich. It can control two independent 500VA loads in the safe area simultaneously through a touch switch in the dangerous area. What is even more commendable is its built-in "self-locking" function: by short circuiting specific terminals, it can be configured as a standard motor start stop control circuit. The start switch is closed to close the relay and lock it, and the stop switch is opened to release the lock. More importantly, the stop command has absolute priority in logic. Even if the start circuit is in a short-circuit closed state, as long as the stop circuit is disconnected, the motor will still be reliably cut off, which fully complies with the safety operation regulations of heavy machinery. Its response time is only 50ms, and the contact life can reach 200000 times.

2. MTL2211: Dual channel high reliability independent control

Unlike the cascade logic of 2210B, MTL2211 provides two completely independent and floating input channels. Each channel can independently control a set of 500VA loads. In order to pursue ultimate reliability, its internal double pole double throw contacts are physically connected in parallel, effectively reducing the risk of poor contact. Each channel provides 2.5V DC voltage (internal resistance 680 Ω) to the on-site switch. When the circuit resistance is less than 200 Ω, it is pulled in, and when it is greater than 500 Ω, it is released. The 100 Ω hysteresis design effectively prevents misoperation caused by contact shaking.

3. MTL2213: Three channel hybrid sensor fusion terminal

In scenarios that require high-density wiring, MTL2213 provides three channels with an extremely compact volume. Its most prominent feature is the support for mixed access of switches and NAMUR standard proximity sensors. Sensors that comply with DIN 19234 standards will experience a surge in current from less than 1.2mA to greater than 2.1mA when detecting metal targets. MTL2213 accurately captures this current change to drive the relay. In addition, it also provides a unique "reverse phase" function, which can invert the alarm logic of all three channels (from "power off alarm" to "power on alarm") through simple terminal short circuiting, greatly improving the flexibility of on-site debugging.

4. MTL2215: Reverse Control of Intrinsic Safety Output

In traditional isolation barrier applications, signals always flow from hazardous areas to safe areas. MTL2215 breaks this convention by allowing the intrinsic safety circuit of hazardous areas to be controlled through switches or logic levels from safe areas. Its output contacts are strictly certified as' non energy storage devices', which means it can be directly connected to any certified IS circuit without additional evaluation. This feature makes it the perfect tool for testing on-site IS fire alarms, changing the tone of IS sound and light alarms, or injecting test signals into IS alarms without isolated inputs.

Analog Signal Processing and Energy Transmission Center

In process control, 4-20mA analog signals are the "blood circulation system" of industrial sites. The MTL2000 series has also demonstrated a strong foundation in analog processing.

1. MTL2441B: 4-20mA repeater power supply

The transmitter requires a stable energy supply to operate in hazardous areas. MTL2441B can provide a fully floating DC power supply for 2-wire or 3-wire transmitters. For a 2-wire transmitter, it can provide a terminal voltage of 17.5V at 20mA, and its internal input resistance is extremely low (less than 32 Ω), which means it hardly consumes signal energy. At the same time, it isolates and relays the current signal of the transmitter 1:1 to a safe area. The load capacity of its safe area is as high as 1k Ω, and the output impedance is greater than 1M Ω, effectively blocking ground loop interference between different control circuits.

In terms of accuracy, its transmission error at 20 ℃ is better than 20 µ A, temperature drift is controlled within 1 µ A/℃, and a response time of 200ms can fully meet the requirements of the vast majority of slow process control. It is worth noting that this model only supports AC power supply (240V or 120V), and DC power supply scenarios need to be switched to other models.

2. MTL2442B: 4-20mA isolated driver

If 2441B is the "receive" signal, then MTL2442B is the "send" signal. It receives 4-20mA instructions from the safety zone controller and drives high load equipment in hazardous areas, such as electrical positioners, I/P converters, or electrical valve positioners, after isolation. Its input impedance is less than 200 Ω, and it can provide up to 800 Ω load driving capability to hazardous areas（ 16V@20mA ）. It also has extremely low temperature drift and extremely high output impedance, ensuring the purity and integrity of control instructions.

3. Signal transmission through dangerous areas

The combination of MTL2441B and MTL2442B provides a highly creative solution when it is necessary to connect signals from two safe zones and cross a dangerous zone between them. 2441B receives and demodulates the signal on one side of the danger zone, while 2442B receives and re modulates the signal on the other side of the danger zone, achieving complete electrical isolation and physical crossing throughout the entire process.

Ultimate mechanical craftsmanship and global compliance

In addition to excellent electrical performance, the MTL2000 series also fully considers the harsh environment of industrial sites in its physical structure design. All units are encapsulated in sturdy injection molded plastic shells, with anti vibration terminals inside that can withstand severe mechanical impacts. The terminal block supports two rows of 18 digit alphanumeric markings, greatly facilitating complex on-site identification work.

In terms of installation, the equipment can be directly inserted into the standard 35mm symmetrical guide rail (top cap rail), or fixed on a flat surface with SMC2 installation fixtures. Its accessories and housing system are fully compatible with the higher end MTL3000 series, providing great convenience for users' spare parts management and system upgrades. For extreme environments, the equipment can operate stably within the range of -20 ℃ to+55 ℃ (some models are+50 ℃) when closely arranged. If a heat dissipation gap of more than 5mm is maintained, the upper limit of operating temperature can be increased to+60 ℃, and the storage temperature has reached a wide temperature range standard of -40 ℃ to+80 ℃.

In terms of explosion-proof certification, the MTL2000 series has been certified by all major authoritative organizations worldwide and can seamlessly integrate into the most stringent hazardous areas of Zone 0, IIC, T4 (some models reach T6) and North American Div 1, Group A. In order to guide engineers in safe on-site wiring, the manual provides a detailed list of the maximum cable parameters (capacitance and inductance values) based on BASEEFA (CENELEC) and FM standards. For example, in IIC gas environment, MTL2211 allows a maximum cable capacitance of 13 µ F and an inductance of 69mH for connection, providing accurate calculation boundaries for on-site cable selection and laying.