A technical reference for common terms used in oxygen (O₂), carbon dioxide (CO₂), hydrogen sulfide (H₂S), moisture, and industrial gas analysis. Explore definitions related to gas measurement, analyzer specifications, sensor technologies, calibration, sample handling, hazardous areas, and process instrumentation.
| Термин | Category | Определение |
|---|---|---|
| 4–20 mA | Instrumentation | A common industrial analog current signal used to transmit a measurement to a PLC, DCS, recorder, or other control system. Typically, 4 mA represents the low end of the configured range and 20 mA represents full scale. |
| Точность | Measurement | The degree to which a measured value agrees with the actual or accepted value under stated conditions. Accuracy is typically expressed as a maximum error or uncertainty. |
| Alarm Relay | Instrumentation | An electrically isolated relay contact that changes state when an analyzer reaches a configured alarm condition. Alarm relays can be connected to horns, strobes, ventilation systems, shutdown circuits, PLCs, or other external devices. |
| Alarm Setpoint | Instrumentation | A configured gas concentration or operating value at which an analyzer activates an alarm indication or relay output. Depending on the instrument, an alarm may be configured to trigger above or below the selected value. |
| Aluminum Oxide Moisture Sensor | Sensor Technology | A moisture sensor that uses a porous aluminum oxide layer whose electrical properties change as water vapor is absorbed. Aluminum oxide sensors are commonly used for low dew-point and trace-moisture measurement. |
| Атмосферный воздух | Gas / Sampling | The air in the surrounding environment. Ambient air contains approximately 20.9% oxygen by volume throughout Earth’s atmosphere and may be used for a basic span calibration when appropriate. At higher elevations, the oxygen percentage remains approximately the same, while atmospheric pressure and oxygen partial pressure decrease. |
| Температура окружающей среды | Environmental | The temperature of the air surrounding an analyzer, sensor, or other device. Operating an instrument outside its specified ambient temperature range can affect performance or reliability. |
| Analog Output | Instrumentation | A signal or value that varies continuously rather than in discrete digital steps. Common analyzer analog outputs include 4–20 mA, 0 – 1 VDC, 1 – 5 VDC and 0–10 VDC. |
| ATEX | Hazardous Area | The European Union regulatory framework for equipment and protective systems intended for use in potentially explosive atmospheres. ATEX equipment requirements are established under Directive 2014/34/EU. |
| Audible Alarm | Instrumentation | An alarm that produces a sound when a configured measurement or instrument condition is reached. Audible alarms are often used with visual indicators and relay contacts in safety and breathing-air monitoring systems. |
| Auto-Range | Instrumentation | A function that automatically selects the most appropriate measurement range as the gas concentration changes, allowing the analyzer to maintain useful resolution across a wide measuring span. |
| Breathing Air | Gas / Sampling | Compressed air intended for human respiration in applications such as supplied-air respirators, diving, firefighting, and industrial breathing-air systems. Breathing air is typically monitored for contaminants and moisture to applicable quality requirements. |
| Bypass Flow | Gas / Sampling | A secondary sample-flow path used to increase total flow through a sample system while allowing only the required flow through the analyzer, reducing sample transport time. |
| Calibrate | Calibration | To compare and adjust an instrument using a known reference so its indicated value corresponds to the known value. |
| Calibration Gas | Calibration | A gas mixture with a known composition or concentration used to calibrate, verify, or check the performance of a gas analyzer. |
| Calibration Interval | Calibration | The established period between analyzer calibrations or calibration checks. The appropriate interval depends on the instrument, sensor technology, application, operating conditions, and quality requirements. |
| Coalescing Filter | Gas / Sampling | A filter that removes fine particulates, liquid aerosols and droplets from a gas stream by combining small droplets into larger droplets that can be separated and drained. |
| Cross Sensitivity | Sensor Technology | A sensor response to a gas other than the gas it is intended to measure. Cross sensitivity can create a positive or negative measurement interference depending on the sensor and gas. |
| Dead Volume | Gas / Sampling | Internal volume within tubing, fittings, valves, or cavities where gas exchange is slow or stagnant. Excessive dead volume increases purge, response, and recovery time. |
| Dew Point | Moisture | The temperature at which water vapor in a gas begins to condense into liquid water at a given pressure. Lower dew-point temperatures generally indicate drier gas. |
| Diffusion Sampling | Gas / Sampling | A sampling method in which the target gas reaches the sensor naturally by molecular diffusion rather than being drawn through the analyzer by a pump or supplied under pressure. |
| Digital Ground | Instrumentation | A reference connection used by digital electronic circuits and communication signals. Digital ground provides a common electrical reference and may be isolated from protective earth or analog ground depending on the instrument design. |
| Digital Output | Instrumentation | A discrete or digitally encoded output used to communicate analyzer readings, status, alarms, or other information to external equipment. Examples include relay contacts and serial communications such as MODBUS. |
| Dissolved Oxygen | Measurement | The amount of oxygen dissolved in a liquid, commonly expressed in mg/L, ppm, or percent saturation. Dissolved oxygen measurement is widely used in water, wastewater, aquaculture, and process applications. |
| Drift | Measurement | A gradual change in analyzer or sensor output over time while the measured gas concentration remains constant. Drift may affect zero, span, or both and is one reason periodic calibration checks are performed. |
| Dual-Channel Analyzer | Instrumentation | An analyzer that measures two parameters or uses two independent measurement channels within one instrument. Each channel may have its own display, output, calibration, and alarm settings. |
| Dual-Level Alarm | Instrumentation | An alarm configuration with two independently adjustable thresholds, commonly used to provide an initial warning and a second higher-priority or evacuation alarm. |
| Earth Ground | Electrical | A common electrical reference point, often connected to earth or used as the reference potential within an electrical system. |
| Electrochemical Sensor | Sensor Technology | A sensor that uses an electrochemical reaction to generate an electrical signal related to the concentration of the target gas. |
| EMI / RFI | Electrical | Electromagnetic interference (EMI) and radio-frequency interference (RFI) are unwanted electrical disturbances that can affect electronic instruments, signals, or communications. |
| Explosion-Proof | Hazardous Area | An enclosure construction designed to contain an internal explosion of a specified gas or vapor and prevent ignition of the surrounding hazardous atmosphere. |
| Fixed Gas Monitor | Instrumentation | A permanently installed instrument that continuously monitors the concentration of a gas in a room, process area, or other defined location and may provide local alarms or signals to external control systems. |
| Form C Relay Contacts | Electrical | Standard relay contact configurations. Form C is SPDT changeover. |
| Full Scale Range | Measurement | The upper limit of an instrument’s selected measurement range. For example, the full-scale range of a 0–100 ppm range is 100 ppm. |
| Galvanic Oxygen Sensor | Sensor Technology | A type of electrochemical oxygen sensor that generates an electrical current through a chemical reaction with oxygen. The output is generally proportional to the oxygen partial pressure reaching the sensor. |
| Gas Analyzer | Instrumentation | An instrument designed to measure the concentration or purity of one or more gases in a sample or surrounding atmosphere. |
| Gas Matrix | Gas / Sampling | The overall composition of the sample gas, including the target gas and all other major and minor components. The gas matrix can affect sensor selection, compatibility, cross sensitivity, and sample-system design. |
| Gas Sensor | Sensor Technology | The sensing element that responds to a specific gas and produces a signal that can be measured and converted into a gas concentration. |
| Hazardous Location | Hazardous Area | A location where flammable gases, vapors, liquids, combustible dusts, or ignitable fibers may be present in sufficient quantities to create a fire or explosion hazard. Equipment used in these areas must be suitable for the applicable classification. |
| High-Pressure Sample | Gas / Sampling | A gas sample supplied at a pressure higher than the analyzer or sensor can safely accept. A pressure regulator or other sample-conditioning components are typically used to reduce the sample to the required operating pressure and flow. |
| Horn and Strobe | Safety | An audible horn combined with a flashing visual indicator used to alert personnel when a gas concentration or oxygen level reaches a configured alarm condition. |
| IECEx | Hazardous Area | An international certification system based on IEC standards for equipment and services intended for use in explosive atmospheres. |
| Inert Gas | Gas / Sampling | A gas that is generally non-reactive under the conditions of use. Nitrogen and argon are common inert gases used for purging, blanketing, calibration, and as background gases in trace oxygen measurements. |
| IP Rating | Environmental | Ingress Protection rating. An IEC classification describing the degree of protection an enclosure provides against access to hazardous parts and the ingress of solid objects, dust, and water. |
| Isolated Output | Instrumentation | An electrical output that is electrically separated from other instrument circuitry or grounds. Isolation can help reduce ground loops, improve noise immunity, and protect connected equipment in industrial installations. |
| Leak Tightness | Gas / Sampling | The ability of a sample system or component to prevent gas from leaking into or out of the system. High leak tightness is especially important for trace and ppb measurements because very small atmospheric leaks can overwhelm the target concentration. |
| Linearity | Measurement | Often expressed as an error, the maximum deviation of an instrument’s response from an ideal straight-line relationship between the measured input and indicated output. |
| Lower Detection Limit (LDL) | Measurement | The lowest concentration that an analyzer or sensor is specified to reliably detect or measure under stated conditions. |
| Medical Air | Gas / Sampling | A regulated compressed gas used for patient respiration and medical applications. Medical air systems are controlled for oxygen content, moisture, carbon monoxide, carbon dioxide, and other contaminants according to applicable standards and regulations. |
| Micro-Fuel Cell Oxygen Sensor | Sensor Technology | A disposable electrochemical oxygen sensor in which oxygen diffuses through a membrane and reacts within the cell to produce an electrical current proportional to oxygen partial pressure. The term is commonly associated with Teledyne oxygen sensors. |
| Modbus ASCII | Communications | A serial version of the Modbus industrial communications protocol in which messages are transmitted as readable ASCII characters. |
| Modbus RTU | Communications | A widely used industrial communications protocol commonly transmitted over an RS-485 serial connection to exchange analyzer readings, status information, and configuration data with control systems. |
| Moisture Content | Moisture | The amount of water vapor present in a gas, commonly expressed using dew point, pressure dew point, ppm by volume, or other concentration units. |
| NDIR (Non-Dispersive Infrared) | Sensor Technology | An optical gas measurement technique that determines concentration by measuring the absorption of infrared light at wavelengths associated with a specific gas, commonly including carbon dioxide. |
| NEMA 4X | Environmental | A North American enclosure rating that provides protection against conditions including windblown dust, rain, splashing water, hose-directed water, and corrosion. NEMA 4X is an environmental enclosure rating and does not, by itself, indicate hazardous-location approval. |
| Non-Condensing | Environmental | An operating condition in which moisture may be present as vapor but does not form liquid condensation on or within the instrument or sensor. Condensation can damage components or affect measurement performance. |
| Non-Isolated Output | Instrumentation | An electrical output that shares a common electrical reference or ground with other instrument circuitry. Non-isolated outputs are generally simpler but may be more susceptible to ground loops or electrical interference in some installations. |
| NRTL | Hazardous Area | Nationally Recognized Testing Laboratory. An independent organization recognized by the U.S. Occupational Safety and Health Administration (OSHA) to test and certify products to applicable safety standards. NRTL refers to the recognition program and is not synonymous with a specific certification organization such as UL. |
| Online Analyzer | Instrumentation | An analyzer installed to continuously or routinely measure a process or gas stream rather than relying on a separate laboratory or occasional spot measurement. |
| Oxygen Deficiency | Safety | A condition in which the oxygen concentration in an atmosphere falls below the level considered safe for normal breathing. In workplace safety applications, atmospheres containing less than 19.5% oxygen by volume are commonly considered oxygen-deficient. |
| Oxygen Displacement | Safety | The reduction of oxygen concentration caused when another gas occupies or replaces part of the surrounding air. Leaks of nitrogen, argon, helium, carbon dioxide, and other gases can create an oxygen-deficient atmosphere without the displaced gas itself being toxic. |
| Oxygen Enrichment | Safety | An atmosphere containing a higher oxygen concentration than normal ambient air. Oxygen-enriched environments can significantly increase combustion and fire hazards. |
| Oxygen Partial Pressure | Measurement | The portion of total gas pressure contributed by oxygen in a gas mixture. Electrochemical oxygen sensor output is generally related to the oxygen partial pressure at the sensor. |
| Paramagnetic Oxygen Analyzer | Sensor Technology | An oxygen measurement technology that uses the paramagnetic properties of oxygen to determine concentration. Paramagnetic analyzers are commonly used for accurate percent-level oxygen measurement without consuming the sample gas. |
| Percent (%) | Units | A concentration unit representing parts per hundred. Normal ambient air contains approximately 20.9% oxygen. |
| Permeation | Gas / Sampling | The movement of gas molecules through a solid material such as polymer tubing, seals, or membranes. In trace analysis, oxygen or moisture permeation through unsuitable materials can cause measurement errors even when there is no conventional leak. |
| Portable Analyzer | Instrumentation | A compact analyzer designed to be carried between measurement points for temporary testing, troubleshooting, verification, or spot-check measurements. |
| PPB (Parts Per Billion) | Units | A unit used to express extremely low concentrations. One ppb represents one part of a substance per one billion parts of the total mixture. 1,000 ppb equals 1 ppm. |
| PPM (Parts Per Million) | Units | A unit used to express low concentrations. One ppm represents one part of a substance per one million parts of the total mixture. 100 ppm is equal to 0.01%. |
| PPMv Moisture | Moisture | Parts per million by volume of water vapor in a gas, commonly used to express low moisture concentrations in industrial and high-purity gases. |
| PPT (Parts Per Trillion) | Units | A unit used to express extremely low concentrations. One part per trillion represents one part of a substance per one trillion parts of the total mixture. 1,000 ppt equals 1 ppb. |
| Pressure Dew Point | Moisture | The dew point of a compressed gas measured at its actual system pressure. Because pressure affects the amount of water vapor a gas can hold, pressure dew point should not be confused with dew point referenced to atmospheric pressure. |
| Pressure Regulator | Gas / Sampling | A device used to reduce and control gas pressure from a higher-pressure source to a lower, stable pressure suitable for an analyzer or sample system. |
| PSIG (манометрическое давление в PSI) | Pressure | Pressure measured relative to local atmospheric pressure. A gauge reading of 0 PSIG is approximately equal to the surrounding atmospheric pressure. |
| Purity Measurement | Instrumentation | The measurement of the concentration of a primary gas, typically expressed as a percentage, to determine the overall purity of a gas stream. Common applications include oxygen, nitrogen, hydrogen, argon, and carbon dioxide production and quality control. |
| Range | Measurement | The span of values an instrument is designed or configured to measure, such as 0–10 ppm, 0–25%, or 0–100%. |
| Recovery Time | Measurement | The time required for an analyzer or sensor to return to a specified reading after exposure to a significantly different gas concentration. Recovery time is especially important in trace ppm and ppb measurements. |
| Удалённый датчик | Instrumentation | A sensor installed away from the main analyzer or display so the measurement can be made at a difficult, hazardous, or otherwise remote location while the display and controls remain accessible. |
| Repeatability | Measurement | The ability of an instrument to produce the same or very similar readings when the same input is measured repeatedly under the same conditions. |
| Resolution | Measurement | The smallest change in the measured value that an instrument can display or distinguish. |
| Sample Conditioning | Gas / Sampling | The preparation of a gas sample before it reaches the analyzer. Conditioning may include pressure regulation, filtration, moisture removal, flow control, cooling, or other steps needed to protect the analyzer and obtain a representative measurement. |
| Sample Flow | Gas / Sampling | The rate at which a gas sample passes through an analyzer or sample system, typically expressed in units such as SCFH, L/min, or mL/min. Proper sample flow helps ensure stable, accurate measurements and appropriate analyzer response time. |
| Sample Gas | Gas / Sampling | The gas stream delivered to an analyzer or sensor for measurement. |
| Sample Pressure | Pressure | The inlet pressure of the gas presented to the analyzer or sample system. Sample pressure should remain within the specified operating limits of the instrument and sensor. The outlet should be vented to atmosphere so the sensor itself is not under pressure. |
| Sample Pump | Gas / Sampling | A pump used to draw sample gas through an analyzer when the sample is at atmospheric pressure, under vacuum, or otherwise lacks sufficient pressure to flow through the sample system. |
| Sample System | Gas / Sampling | The tubing, valves, regulators, filters, flow controls, and other components used to condition and deliver a representative gas sample to an analyzer. |
| Sensitivity | Measurement | The degree to which an analyzer or sensor responds to a change in gas concentration. Higher sensitivity allows smaller changes in concentration to produce a detectable change in the instrument’s output. |
| Sensor Life | Sensor Technology | The expected useful operating period of a sensor before its performance no longer meets specification. Actual life can vary with gas exposure, temperature, pressure, storage, and application conditions. |
| Sensor Output | Sensor Technology | The electrical signal produced by a sensor in response to the measured gas. Depending on the sensor technology, output may be expressed as current, voltage, resistance, or another electrical quantity. |
| Sensor Shelf Life | Sensor Technology | The period a sensor can typically be stored before installation while still being expected to meet its performance requirements. Shelf life is different from operating sensor life and depends on storage conditions and sensor technology. |
| Shield | Electrical | A conductive covering around a cable or circuit used to reduce the effects of electrical interference. Shields are commonly connected to ground according to the equipment installation instructions. |
| Six-Wire Transmitter | Instrumentation | A transmitter configuration using separate wiring for power, measurement output, and additional functions such as alarms or communications. The exact wiring arrangement depends on the instrument design. |
| Span Calibration / Span Adjustment | Calibration | An adjustment made using a known non-zero reference gas so the analyzer reading matches the known gas concentration. |
| Span Gas | Calibration | A gas with a known concentration used to calibrate or verify an analyzer’s response. The span gas concentration is typically selected within the analyzer’s measurement range and should be appropriate for the intended application. |
| T90 Response Time | Measurement | The time required for a sensor or analyzer to reach 90% of its final response after a step change in gas concentration. |
| Temperature Coefficient | Measurement | A specification describing how much a sensor or analyzer output changes with temperature. Instruments may use temperature compensation to reduce this effect over the specified operating range. |
| Trace Measurement | Measurement | Measurement of a target gas present at very low concentrations, commonly expressed in parts per million (ppm) or parts per billion (ppb). |
| Trace Oxygen | Measurement | Oxygen present at low concentrations, typically expressed in ppm or ppb. Trace oxygen measurement is common in inert gases, gloveboxes, semiconductor processes, and specialty gases. |
| Two-Wire Transmitter | Instrumentation | A transmitter configuration in which the same two wires provide operating power and carry the measurement signal, commonly using a 4–20 mA current loop. |
| Ultra-High Purity (UHP) Gas | Gas / Sampling | A gas produced and handled to maintain extremely low impurity levels. UHP applications require careful materials, fittings, and sample-system practices to minimize contamination. |
| Wetted Parts | Gas / Sampling | The materials and components that come into direct contact with the sample gas, such as tubing, fittings, valves, seals, flow meters, and sensor housings. Wetted-part compatibility is important for corrosive, reactive, or high-purity gas applications. |
| Zero Calibration / Zero Adjustment | Calibration | An adjustment made using a zero reference so the analyzer indicates zero, or the appropriate baseline output, when the measured gas is absent. |
| Zero Gas | Calibration | A gas containing none, or a negligible amount, of the target gas and used to establish or verify the analyzer’s zero reading. The required zero gas depends on the measurement and application. |
| Zirconia Oxygen Sensor | Sensor Technology | A solid-state oxygen sensor based on zirconium oxide and typically operated at elevated temperature. Zirconia sensors are used in a variety of oxygen measurement applications and can provide fast response and long service life under suitable operating conditions. |
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