FAQ

EtherNet/IP is an open, ODVA-managed industrial Ethernet protocol widely used in the U.S. It combines CIP with standard Ethernet, enabling efficient data exchange, control, and integration of multi-vendor and legacy devices without proprietary systems.

Modbus, developed in 1979, is a simple, open-source industrial protocol commonly using serial connections like RS-232/485. It is easy and cost-effective to implement but offers slower speeds, limited data types, and lacks advanced diagnostics, making it best for simple applications.

Raw mode is the simplest communication method, passing incoming data directly as 8-bit bytes with no formatting or interpretation. Also called bit-shift mode, it lets applications freely interpret the raw data received from the communication line.

Synchronous Data Link Control (SDLC) is a simple yet robust communication protocol used between computers or remote devices. It uses well-defined frames with flag characters marking the start and end, ensuring messages are clearly structured and cannot be misinterpreted.

Bisynchronous communication uses a 16-bit synchronization sequence to start messages, followed by control characters like start of header and text. Originally designed for readable text, it uses non-readable characters as control signals.

Monosynchronous communication uses a single 8-bit sync character to mark message start. Because this pattern can also appear in data, receivers may lose synchronization, making the method prone to errors.

Asynchronous communication relies on precise bit timing and stability. Isochronous communication instead uses an additional signal with the data to indicate exactly when each bit should be read as a 0 or 1.

Asynchronous cards are lower cost, easier to use, and more software compatible. Synchronous cards are more expensive, not optimized for async communication, and require more configuration.

An interface defines how data is sent, while a protocol defines the message content and format. In serial communication, the interface is the electrical connection, and the protocol determines how information is structured and understood.

Sealevel’s COM Port Manager lets users assign a PCI or PCIe serial port a standard name like “COM1.” Once named, any application can open COM1 to communicate with the connected serial device.

Asynchronous communication is time-based and requires precise timing between transmitter and receiver to decode data bits correctly. Bit length determines data rate, typically 9,600 bps to 115.2 kbps, and is commonly used by standard computer serial ports.

To find an Ethernet Serial server, disable all unused network adapters in Windows except the one connected to the device. Once disabled, the SeaLINK Device Discovery utility should locate the unit so setup can continue. See the troubleshooting section of the SeaLINK Manual for additional tips.

Sealevel’s COM Port Manager allows a PCI or PCIe serial port to be assigned a standard name like COM1. Once assigned, any application can use COM1 to communicate with the connected serial device.

A serial tunnel is created when two Ethernet serial servers pass data from a local serial port across a TCP/IP network to a serial port on a remote device. There are two straightforward ways to monitor the data flowing between the servers.

One option is to run an end-to-end loopback test, which verifies both the serial settings on the local server and the network configuration between the two devices. This involves attaching a loopback plug to the remote server and using a null modem adapter on the local side to send data and check that it is properly returned.

WinSSD provides several tools for this process, including the terminal, BERT, and loopback test utilities. In some situations, the terminal and BERT tools offer more reliable results than the loopback test alone.

To observe data traveling from the remote server back to the local server, connect to the local serial port with a null modem adapter and view the outgoing data stream. The WinSSD terminal’s Hex/ASCII display makes it easy to analyze many different data formats. Both testing methods can be performed without changing network settings or using specialized hardware.

Slew rate describes how quickly a signal’s voltage changes over time. High-speed communication requires a fast slew rate for accurate data transfer, while slower data rates can suffer from increased electromagnetic interference if the slew rate is too fast.

Sealevel ultra high-speed serial adapters, such as the 7205ec and 7106e, include a software-selectable slew rate limiting feature. These asynchronous adapters support data rates above 1 Mbps, but when operating below 250 Kbps, enabling slew rate limiting in the Windows driver slows the signal’s edge transitions. This reduces EMI and improves signal integrity. Oscilloscope images typically show sharper transitions with slew rate limiting disabled and smoother edges when it is enabled.

“Gen Mod,” short for Generic Modification, allows a USB serial adapter to always use the same COM port assignment, no matter which physical adapter is connected to a computer. This is especially useful when a single computer, such as a laptop, is used with multiple USB serial adapters at different locations.

Normally, each USB serial adapter has a unique hardware identifier that lets the computer assign and remember individual settings and COM ports for each device. Gen Mod overrides this behavior by making the host system treat multiple adapters of the same type as one device, ensuring identical configuration settings and COM port assignments.

The main limitation of Gen Mod is that only one adapter of that type can be used per computer at a time, as multiple devices will not be distinguished correctly. In addition, software-configurable USB serial adapters are not compatible with Gen Mod due to their driver requirements.

USB serial adapters normally get unique IDs and COM ports, which can change between devices. Sealevel’s generic (-GEN) adapters use a shared ID so COM port numbers stay the same when swapping adapters. Only one generic adapter can be used per computer.

Most Sealevel serial adapters rely on standard Linux kernel serial drivers. Some USB and UART-based devices require extra driver details for proper access, while SeaLINK Ethernet serial servers use a dedicated Linux driver provided by Sealevel.

• To configure UART-based serial adapters, please read How to configure UART-based serial adapters in Linux.
• To configure USB serial adapters, please read How to configure USB serial adapters in Linux.
• For Ethernet serial servers, please download the Sealevel SeaLINK software driver for Linux.

Sealevel SeaLINK Ethernet serial servers handle 9-bit serial communication by packaging each frame into a 2-byte format. The first byte carries the ninth bit in its least significant position, while the second byte contains the standard 8 data bits. These servers also support transmitting 9-bit data across a network using serial tunneling.

SeaLINK devices use the RFC-2217 Telnet Com Port Control protocol, which adds non-serial data such as COM port settings and modem control signals to the data stream. Telnet control messages begin with the IAC byte (decimal 255). To avoid confusion, actual serial data with a value of 255 is sent as a doubled, escaped sequence, which the receiver interprets as a single serial data byte.

Asynchronous communication is commonly used with computers and relies on timing to read data. Synchronous communication differs by using a separate clock signal to indicate when data is valid, allowing hardware to directly read each bit as 0 or 1.

Sealevel provides two Linux software packages for specific serial controllers: SeaMAC for products using the Zilog Z85230 ESCC and Route56 for products using the Zilog Z16C32 IUSC. Both are available from the Sealevel website and include GPL-licensed, distribution-independent driver source code. While many Linux distributions can use these drivers as-is, others may require minor configuration changes, such as adjusting symbolic links, makefiles, or kernel build options, as outlined in the included documentation.

Sealevel synchronous serial adapters support three common non-encoded clocking modes:

1. The Sealevel serial adapter generates the clock using its baud rate generator (BRG), which the connected device uses for both transmitting and receiving data.
2. The connected device supplies an external clock that the Sealevel serial adapter uses for both transmit and receive operations.
3. The Sealevel serial adapter provides the transmit clock using the BRG, while the connected device supplies its own clock for transmitted data, allowing transmit and receive data rates to differ.

The Z16C32 functions like a UART and normally sends data least significant bit first. When operating in SDLC/HDLC mode with CRC enabled, the CRC is transmitted most significant bit first, while all other serial data remains least significant bit first.

ITU document O.153 states that the BERT pattern is intended for data rates up to 14.4 Kbps. However, Sealevel’s WinSSD utility supports using the BERT pattern at all available data rates and in all supported communication modes, including speeds above 14.4 Kbps.

A Cyclic Redundancy Check (CRC) is an error-detection value added to a data frame by the transmitter and verified by the receiver to identify transmission errors. If the calculated and received CRC values do not match, the data is considered corrupted. On Sealevel synchronous serial adapters, CRC is applied to the address, control, and data fields and is generated using defined polynomials with an initial sequence of zeros or ones.

Section 2.5 of the ITU O.151 specification explains that test patterns may be enclosed within a protocol’s framing bits when required. As a result, the BERT pattern can be used in both synchronous communication modes, such as SDLC/HDLC, and asynchronous modes.

Sealevel synchronous serial adapters appear in Windows as SeaMAC devices rather than standard COM ports, with the first port labeled SeaMAC0 due to zero-based indexing. This device-based enumeration supports advanced features not available with typical asynchronous COM ports. Many synchronous applications in industries such as banking, military, and aerospace rely on specialized protocols and do not use COM ports. The SeaMAC V5 API simplifies application development for these use cases, allowing the adapters to operate at peak efficiency.

The Set Configuration and Save Configuration options are available only in the synchronous version of the WinSSD utility included with the SeaMAC software suite. Set Configuration applies the current settings to the SeaMAC driver temporarily and reverts to defaults when WinSSD is closed. Save Configuration applies the settings and stores them as the new default, making them persistent across port openings and system reboots.

For Sealevel synchronous serial products, once the TX and RX pins are connected, the Clock Output pin (TSET) must be tied to the Clock Input pin (RXC). Typically, TSET is used as the board’s output clock, while Transmit Clock (TXC) is an input and should not be used.

MIL-STD-1553 is a military communication standard introduced in 1973 by the U.S. Department of Defense that specifies the electrical, mechanical, and functional requirements for serial networks used in avionics and aerospace systems. First deployed by the U.S. Air Force on the F-16, it quickly became the dominant standard for military avionics and is now used by all branches of the U.S. military and NATO across land, sea, air, and space platforms.

The standard defines a highly reliable synchronous serial data bus operating at 1 Mbps with an extremely low error rate of fewer than one fault per 10 million words. A single bus controller (BC) manages communication with up to 31 remote terminals (RTs) over redundant primary and secondary buses. Bus monitor (MT) devices may observe and log traffic but cannot transmit. Although only one BC is active at a time, redundant controllers can be implemented for failover.

Under normal operation, communication takes place on the primary bus, with the secondary bus serving as a backup if the primary is damaged or fails. System reliability can be further increased by using dual or triple redundant bus configurations.

Using a COM Express architecture offers significant advantages for embedded systems by combining a standardized computer module with a custom, application-specific carrier board. This approach reduces design time, cost, and lifecycle challenges compared to traditional ground-up designs, while allowing manufacturers to tailor solutions to specific applications.

COM Express modules provide core computing functions such as the CPU, memory, graphics, Ethernet, USB, storage, and expansion buses, enabling faster development and quicker time to market. Engineers can focus on designing the carrier board to meet unique I/O requirements, often reusing proven circuit designs to reduce risk.

The modular design also supports scalability and long-term availability. A single carrier board can support multiple COM Express modules, from low-power options to high-performance industrial processors, allowing tiered product offerings and easy upgrades. Many modules offer extended temperature support and lifecycle guarantees of up to 15 years.

Additionally, COM Express enables flexible mechanical designs suited for rugged environments. Carrier boards can be sized and configured to fit specific applications, while fanless, low-power modules support wide operating temperature ranges. As new processor technologies emerge, systems can be upgraded by replacing the COM module without redesigning the carrier board.

Rugged industrial computers are built to operate reliably in harsh environments, including extreme temperatures, heavy shock and vibration, high dust or moisture exposure, and unstable power conditions.

They are commonly used in military and aerospace systems, industrial automation, mining and oil exploration, public safety communications, transportation, and agriculture—applications where equipment must function consistently under demanding physical conditions.

Sealevel rugged computers, touch panel PCs, and COM Express solutions are designed for I/O-intensive applications and offer high performance, flexible configuration, extended temperature operation, and power tolerance. These systems are engineered to meet many commercial and military rugged computing standards.

A graphics processing unit (GPU) is a specialized processor built for rendering graphics and handling large volumes of data using parallel computing. Unlike CPUs, which process instructions sequentially and handle a wide range of tasks, GPUs use many smaller cores to perform calculations simultaneously, making them ideal for data-intensive workloads.

GPUs are well suited for applications such as video and audio processing, machine and computer vision, industrial automation, autonomous systems, and augmented or virtual reality. However, they are typically more expensive, consume more power, and generate more heat than CPUs, so they are best used when parallel processing provides clear performance benefits.

Intelligent Platform Management Interface (IPMI) is an out-of-band management standard that allows hardware monitoring and control independent of the CPU, BIOS, and operating system. It provides built-in capabilities for monitoring system health, logging events, managing power and reboots, sending alerts, and tracking hardware inventory.

IPMI’s key advantage is remote management, even when the system is powered off or unresponsive. Once mainly used in servers, IPMI is now included in embedded systems through the COM-HPC standard introduced in 2021.

UL certification is a widely recognized safety mark issued by Underwriters Laboratories (UL) that confirms a product has been independently tested for safety and performance. The process evaluates a product’s design, construction, and operation against established safety standards.

Although not mandatory, UL certification provides strong assurance to consumers, retailers, and regulators that a product is safe for normal use. The most common types are UL Listed, indicating a complete product meets defined requirements, and UL Recognized, which applies to components intended for use within a larger system.

CE certification, short for Conformité Européenne, is required for most non-food products sold in the EU and EEA. It applies to a wide range of product types and is governed by multiple CE Directives.

For electronic products, common directives include EMC for electromagnetic compatibility, RED for RF devices, LVD for electrical safety, RoHS for hazardous substance restrictions, and the Machinery Directive for industrial equipment.

FCC certification is legally required for electronic devices that use or emit radio frequency energy to ensure emissions stay within approved limits and do not cause harmful interference. This includes devices such as Bluetooth products, power adapters, telecom equipment, IT hardware, and other electronics that can oscillate above 9 kHz.

The FCC classifies devices as Class A or Class B. Class A devices are intended for commercial or industrial use, while Class B devices are designed for residential and public use and must meet stricter emission requirements.

A relay is an electrically operated switch that uses a low-power signal to control a higher-power circuit. It allows power to be turned on or off remotely without manual switching, making it a fundamental component in many electronic systems.

Relays work by opening or closing contacts to allow or block current flow and are available in many sizes, from high-current motor relays to small low-voltage reed relays. On printed circuit boards, the two most common types are electromechanical relays and solid-state relays.

Many reports come from users on Windows XP with Internet Explorer. Sealevel’s site uses modern SSL with SNI, which XP doesn’t support, so Internet Explorer may show a certificate error even though the connection is still encrypted and ordering is safe.

Since Microsoft ended XP support on April 8, 2014, it no longer receives security updates, so upgrading is strongly recommended. If you must use XP, try Firefox or Chrome to avoid the error. If you’re on a supported OS and still see errors, email [email protected] with OS/browser details and a screenshot.

Standard USB ports charge devices slowly, supplying only up to 500 mA at 5V. To support higher-current devices, the USB Battery Charging Specification (BC v1.2) defines dedicated charging ports (DCP) and charging downstream ports (CDP), which use standard USB Type A connectors but provide more power.

DCPs supply power only with no data transfer and are common in wall chargers, vehicles, and portable power sources. Sealevel’s USB 3.1 hubs include CDPs that deliver up to 2.4A on one port and up to 1.5A on others, enabling fast charging and reliable power for BCv1.2-compliant devices.

Many Sealevel products support Modbus, including SeaI/O, SeaDAC, eI/O, SeaRAQ, and SeaConnect modules, though the specific Modbus functions supported vary by module. This Sealevel software documentation page lists the supported Modbus functions for each applicable product category mentioned above.

COM Express architecture simplifies embedded system design by combining a standardized computer module with a custom carrier board, reducing development time, cost, and lifecycle challenges. Engineers can focus on application-specific I/O while relying on the COM module for core functions like CPU, memory, graphics, networking, and storage.

This modular approach enables faster time to market, easy scalability across processor options, and long-term availability, with some modules offering up to 15-year lifecycles. It also supports flexible, rugged mechanical designs and provides a clear upgrade path as new computing technologies become available, often without requiring carrier board redesign.

SMARC (Smart Mobility ARChitecture) is a compact, low-power Computer-on-Module standard designed for mobile and embedded applications. SMARC modules integrate the processor, memory, display, camera, networking, and serial interfaces on small boards that connect to an application-specific carrier via a single edge connector.

Supporting ARM, RISC, and x86 processors and typically consuming under 6 watts, SMARC solutions are well suited for space-constrained, battery-powered, and energy-efficient designs.

Many COM Express modules offer lifecycles of five years or more, and their modular design allows systems to be upgraded with newer processors or memory to extend usability even further. Because core computing functions reside on the module, the carrier board only needs updates when new interfaces are required, making future revisions faster and more cost-effective than a full system redesign.

COM Express video features vary by module, so choosing the right type is key to meeting application needs. The PICMG specification supports multiple graphics options, including VGA and TV output on most module types, LVDS for LCD panels, PCIe Graphics (PEG) for high-end graphics on select modules, and modern interfaces like DVI, HDMI, or DisplayPort on Type 6 and 10 modules.

Sealevel can help select the appropriate COM Express module and design a custom carrier board to support required video and I/O interfaces.

Managing the performance of a Tiger Lake module helps protect against issues caused by environmental conditions like temperature extremes or unstable power. In severe cases, such as significant heat changes, the processor may automatically reduce operation from four cores down to two or even one. Performance limits and control settings for Tiger Lake modules can be adjusted proactively through the system BIOS.

COM Express modules are designed for rugged use and are commonly available with operating ranges from –40°C to +85°C. The final system temperature range depends on factors such as enclosure design and power supply. Sealevel can help select the right module and design a COM Express system to meet wide-temperature and other application requirements.

The PICMG COM Express 2.0 specification defines three main module sizes: Basic (125 × 95 mm), Compact (95 × 95 mm), and Extended (155 × 110 mm), each offering different feature sets and capabilities. An even smaller Ultra form factor is also being considered, and custom sizes are available from some vendors.

In addition to size, COM Express modules are defined by six different Types, which specify pinouts and supported features.

Windows XP Professional is no longer offered on Sealevel computers.

9-bit data framing improves efficiency on multidrop embedded networks by reducing unnecessary data processing. Unlike standard 5–8 bit framing, which requires all devices to continuously examine incoming messages, 9-bit framing uses an extra bit—often the parity bit—to mark address messages.

Devices only process data after recognizing an address intended for them; otherwise, they ignore subsequent messages and continue normal operation. This approach minimizes wasted processing time and improves overall system performance on shared serial networks.

Optical isolation is used to protect electronic circuits from issues such as ground loops, voltage spikes, and electromagnetic interference. Ground loops occur when multiple ground paths exist between connected devices or when equipment powered from different sources has mismatched ground potentials. These conditions can create unwanted voltage differences and currents that may damage sensitive electronics.

This technique uses opto-isolators to pass signals between circuits without a direct electrical connection. Electrical signals are converted into light, transmitted across an optical barrier, and then converted back into electrical signals on the receiving side. Because there is no conductive path, the two circuits remain electrically separated.

The primary advantage of optical isolation is complete electrical separation, preventing noise, surges, and ground potential differences from propagating between circuits. Sealevel provides a broad selection of digital and analog I/O adapters with optically isolated inputs, along with serial I/O products featuring optically isolated ports.

SeaI/O Ethernet (SeaI/O-E) modules can achieve polling and latency times of about 30 ms at the default 9600 baud rate and roughly 6–10 ms at the maximum 115200 baud rate under ideal conditions. Actual performance varies based on system factors such as the operating system and overall application workload.

Form C electromechanical relays used in many Sealevel digital I/O products are well suited for switching highly inductive loads such as solenoids. Reed relays can degrade over time due to contact damage, and solid-state relays suffer from leakage current and power loss. Form C relays handle heavier loads and arcing more reliably and efficiently.

A flyback voltage spike occurs when power to an inductive load, such as a solenoid, is suddenly interrupted. To prevent high voltage from damaging relay contacts, inductive loads should include flyback protection that safely dissipates stored energy. A common solution for DC loads is a reverse-biased diode, such as those in the 1N4001–1N4007 family, which are inexpensive, fast, and well suited for this purpose.

No. Sealevel optically isolated and dry contact inputs use current-mode designs and typically do not require external pull-up or pull-down resistors. Unlike voltage-mode inputs found on lower-cost devices, these inputs remain in a known state without added components.

Their current-mode design also provides strong EMI resistance, reducing false triggers from electrical noise in industrial environments. This improves reliability and simplifies field wiring. In rare cases, such as when using open-collector or open-drain outputs, a pull-up or pull-down resistor may be needed to prevent a floating connection.

It depends on how the input is wired. A Sealevel input activates when a voltage difference of about 3 VDC or more is detected between the input terminal and the local common, regardless of polarity.

For active-high operation, connect the local common to ground or the negative reference. For active-low operation, connect the local common to the positive voltage reference.

All Sealevel TTL digital I/O products default to input mode at power-up, preventing any outputs from being unintentionally activated.

Open-collector outputs with built-in protection are ideal for controlling inductive loads such as DC motors, solenoids, and high-current relays. Turning off these loads can create damaging voltage spikes.

SeaI/O-530 and SeaI/O-540 modules feature isolated open-collector outputs with integrated flyback diodes, which protect the circuitry by safely suppressing these voltage spikes.

The SeaMAX Software package automatically installs several application samples with source code in the Example Projects subfolder.

To access the samples from the Start Menu, click the folder named Sealevel Systems – SeaMAX, and then click the subfolder named either Samples or SeaMAX Example Projects. Select your development platform from the available choices. Sample applications are supplied for Microsoft .Net C#, Microsoft VB.NET, and native C++.

The sample applications are designed to let you walk through the same integration steps that are required to integrate SeaMAX with your own project.

SeaIO is the legacy driver for Sealevel PCI Express, PCI, PC/104, ISA, and classic USB digital I/O devices. SeaMAX supports newer digital I/O and data acquisition products, including SeaI/O, SeaDAC, and SeaDAC Lite modules.

Many Sealevel products support Modbus. SeaI/O modules, SeaDAC modules, eI/O modules, SeaRAQ modules, and SeaConnect modules. That said, individual modules support different Modbus functions. This Sealevel software documentation page details the specific functions supported by each product category - https://www.sealevelsoftware.com/documentation/seamax/win/modbusbreakdown.html

The ssiEncodingNone and ssiEncodingNrz modes in SeaMAC are similar, but they are not the same. The None setting prevents the card from synchronizing the DPLL with incoming data, effectively disabling the DPLL. As a result, the DPLL cannot be selected as the RsetSource or TsetSource in this mode.

This option avoids limiting data rates, since the DPLL must operate at specific multiples of the data rate and can restrict maximum speed. The None mode is intended for applications that use the RXC/TXC pins instead of DPLL-based clock encoding, allowing higher data rates without unnecessary constraints. More information on the SeaMAC Software.

To reset the BIOS on a Relio R1 Embedded Computer, connect a USB keyboard, power on the system, and hold the Delete key for about 15 seconds to enter the BIOS. Press F9 to load optimal defaults and confirm, then press F10 to save and exit.

After rebooting, the display should be restored with DDI1 set to DisplayPort. If video is working, reenter the BIOS to disable the LVDS interface by setting Active LFP to No LVDS, adjust Power Loss Control as needed, and save the changes. If issues persist, contact Sealevel Technical Support. Step by Step Instructions

Start by checking the Base Part Number Range Guide or using Sealevel’s Software Driver Search tool to enter your product’s base part number or name. Each part number range corresponds to a specific Windows driver, such as SeaMAX, SeaCOM, SeaLINK, SeaMAC, or SeaIO Classic.

If you can’t find the correct driver, visit sealevel.com, use Site Search to find your product page, then open the Software + Documentation tab to view available drivers and software.

100-199, 400-699, 8100-8199, 8220-8239 | SeaMAX for Windows
2000-2999, 7000-7999 | SeaCOM for Windows
4100-4999 | SeaLINK for Windows
5000-5999 | SeaMAC for Windows
8000-8099, 8200-8219 | SeaIO Classic for Windows

SeaMAX for Windows includes both a .NET DLL and a native DLL with nearly identical functionality for device control. The .NET DLL works with any Windows language compatible with .NET 4, while the native DLL can be used by any Windows programming language that supports C data types and the stdcall calling convention.

WinSSD currently supports only the 511-bit test pattern specified in ITU O.153, which is widely used for BERT testing. For additional test patterns or algorithms, contact Sealevel Technical Support.

BERT, or Bit Error Rate Test, measures the quality of a serial communication link by identifying data errors. This testing capability is included in the Sealevel WinSSD utility.

WinSSD uses the 511-bit pseudo-random test pattern defined in ITU O.153 section 2.1. The pattern is one bit shorter than 64 bytes and shifts by one bit each time it repeats. WinSSD sends and receives eight full copies of this pattern using a 511-byte buffer, and the pattern is provided in the referenced text file.

SeaMAX for Windows includes both .NET and native DLLs with nearly the same device control features. The .NET DLL works with any .NET 4–compatible Windows language, while the native DLL supports any Windows language that can call C-based DLL functions using the stdcall convention.

Choosing a temperature sensor depends on accuracy, environment, and temperature range. RTDs measure resistance changes in metal and provide high accuracy, repeatability, long-term stability, and strong immunity to electrical noise, making them ideal for industrial and process control applications.

Thermocouples use two dissimilar metals to generate a small voltage based on temperature change. They support much higher temperature ranges at lower cost but with reduced accuracy and more complexity in selection. For sensor integration, Sealevel SeaRAQ I/O modules support both RTD and thermocouple inputs and connect directly to Relio industrial computers.

Resolution and accuracy describe different aspects of analog-to-digital conversion. Resolution is the smallest change an A/D converter can detect and is determined by the number of bits; for example, a 12-bit converter over a 0–10 V range divides the signal into 4096 steps. Increasing bit depth improves resolution by reducing the size of each step.

Accuracy refers to how close the measured value is to the actual input voltage. For example, with a 2.5 V signal, accuracy indicates how closely the A/D reading matches the true 2.5 V level.

We recommend the SeaI/O-570 module, which provides eight 16-bit A/D inputs designed to measure floating, or non-referenced, analog signals. Wiring instructions and schematics are available in the Floating Signal Source Wiring Guide section of the Interfacing Analog Signals to SeaI/O-570 Modules article.

A floating signal source has its own isolated ground reference and is not tied to the building ground. Common examples include transformer outputs, thermistors, battery-powered devices, and optically isolated outputs.

Unused analog inputs should be tied to the analog ground or common reference to prevent false readings. Leaving inputs unconnected allows electrical noise to affect the high-impedance circuitry, creating phantom data. Connecting them to ground eliminates this issue.

No. Medium loads wear away the gold plating on the contacts, which is required for micro-current switching. Once the gold is gone, the underlying PdRu alloy can handle medium loads up to 2 amps, but the relay will no longer reliably switch small loads.

The SeaConnect 370s feature advanced Form C electromechanical relays with gold-plated bifurcated contacts, offering lower contact resistance and improved reliability for micro-current switching compared to earlier designs. These relays also support medium loads up to 2 amps, combining precision and durability.

If the gold plating wears from repeated medium-load switching, the underlying Palladium Ruthenium (PdRu) contacts continue to perform reliably due to their low material transfer and resistance to welding, ensuring long-term operation.

For an overview of relay types, see John Titus’ discussion in his Control Systems Basics series.