Industries Information

Weather instruments are designed to measure one or multiple components of weather including wind speed and direction, rain or snow fall, solar radiation, temperature, pressure and humidity.  In some cases, these instruments are designed for incorporation into a weather station arrangement and can be mounted on a pole or base and remotely monitored. In other cases, these are individual sensors or instruments that can measure one aspect of weather. In all cases, the instruments and sensors are designed for environmental type applications, and often housings are ruggedized for these applications.

Output options for weather instruments can include analog voltage, analog current, frequency or pulse signal and switch or alarm. These instruments can be connected to computers via serial, parallel, or other digital means for signal acquisition. Some models even have built-in modems and thus can act as event-triggered devices or can be programmed remotely in some cases. They can have local or remote analog, digital or video style displays. The user interfaces on weather instruments can be analog front panel type controls with switches, dials, potentiometers, etc.; digital interfaces with keypads, buttons and menus; or controlled by a remote computer with the same interfaces stated above.

Depending on the application the weather instruments are being used for, size and weight may be big constraints and should be examined carefully.

For very cold applications, some weather instruments come with an antifreeze reservoir for the instrument to sit in so that it does not completely freeze and stop functioning. Another method of battling the cold is to have a model with an integral heater. Heating the instrument this way is sure to run down batteries much quicker if a battery-powered model is being used. To adjust level and tilt, some weather instruments have a mechanical leveling fixture. Other common features are data logging or storage capability, programmability, built-in alarm and integral chart recorder.

Water quality testing instruments are used to test water for chemical and biological agents, and to measure variables such as clarity and rate of movement. There are many different types of products. Interface level analyzers are designed to detect the level of an oil and water interface. By contrast, oil in water monitors are designed to measure the amount of oil in water. Potential of hydrogen (pH) instruments measure pH levels. Voltammetry water quality testing instruments vary electric potential while measuring the resultant current, which can be used to determine the chemistry of the conducting medium. Devices use either anodic stripping voltammetry or cathodic stripping voltammetry. Water quality testing instruments that measure conductivity, dissolved solids, suspended solids, turbidity, dissolved oxygen, dissolved carbon dioxide, biological oxygen demand (BOD), chlorophyll, and algal pigments are also available.

Water quality testing instruments differ in terms of form factor or mounting style, user interface, and output options. Some devices are hand held, portable, or modular. Others are designed for laboratory, benchtop, in-situ, or field use. Panel-mounted water quality testing instruments are also commonly available. Like other types of products, they may include an analog meter, digital display, or video display; as well as manual controls, a digital panel, or computer interface. Output options for water quality testing instruments include analog voltages, analog currents, analog frequencies, and switches or alarm relays. An analog current or transmitter is recommended for applications that send signals over long distances. There are two main interface options for water quality testing instruments: serial and parallel. Serial devices use a standard serial communications protocol such as RS232, RS422, RS485 or universal serial bus (USB). Parallel devices use a standard parallel communications protocol such as general-purpose interface bus (GPIB).   

Features and functionality are additional considerations when selecting water quality testing instruments.  Some devices are temperature-compensated or provided some controller functionality. Others are battery-powered or include self-test features. Event-triggered water quality testing instruments can capture or log data only when a specific event occurs. Water quality testing instruments that are designed for extreme environments can withstand relatively high levels of temperature or humidity, and/or prevent the ingress of dust. Devices with special signal processing or filtering are also available.  

Opacity sensors, dust sensors and visibility sensors measure the amount of light transmitted through a sample. Opacity sensors, dust sensors and visibility sensors use two types of technology: transmissometry, where light is absorbed and scattered as it passes through a mixture of gas and particles, and compares the intensity of the emitted light with the received light, and the scattered light principle where a light beam emits infrared light that is scattered by particles in the gas. This method is used to detect very low concentrations.

These instruments work on a number of measuring principles. With extinction or extinction coefficient technology, the attenuation of light in its passage through an aerosol due to (light) scattering and absorption. Percent opacity devices use a measure, usually in percent, of light extinction, defined as one minus the transmittance of an aerosol cloud. They are used mainly to assess the obscuration by smoke plumes. Percent transmission is the ratio of the detected irradiance to the source irradiance for a beam passing through an attenuating medium. The relationship between transmission and opacity follows: % Transmission (light through the smoke) + % Opacity (light blocked by the smoke)= 100%. Optical density sensors report the logarithm (base 10) of the reciprocal of the transmittance. Dust density sensors report the concentration of dust in the sample volume.

Detector range, in terms of distance between transmitter and receiver, is one of the most important specifications for opacity sensors. Accuracy is expressed as a percentage of the full-scale output. Response time, the time between the sensor’s detection and output signal, is another important specification.

Some popular features for opacity sensors, dust sensors and visibility sensors are field calibration, built-in calibration, self-diagnostics, and heaters for outdoor or other cold temperature applications.

Electrical output types can be analog current or voltage, as well as a frequency. Output can also be a switch or an alarm. Displays for opacity sensors, dust sensors and visibility sensors can be analog, digital or video terminals. Control and programming the devices can be done through an analog or digital front panel or by using a computer interface, typically serial or parallel.

Turbidity instruments measure the average volume of light scattering over a defined angular range. Both particle size and the concentration of suspended solids, as well as the level of dissolved solids can affect the reading. Turbidity is defined as an expression of the optical property that causes light to be scattered and absorbed, rather than transmitted, in straight lines through the sample. Simply stated, turbidity is the measure of relative sample clarity.

Turbidity instruments can measure not only turbidity but also suspended solids. Turbidity is measured in Nephelometric Turbidity Units or NTU, which represents the average volume scattering over a defined angular range. Both particle size and concentration of suspended solids as well as dissolved solids can affect this reading. When measuring suspended solids, the instruments measure concentration, often in parts per million.

Mounting options for turbidity instruments are quite varied. They can be handheld meters, larger portable meters with wheels or handles for carrying, and modular for interfacing with sensors of different input ranges. Other styles commonly available are specially designed for lab or benchtop use and others for field or in-situ applications. Some of these meters are designed to be mounted in a panel.

Displays for the instruments can be analog meters, a numeric or alphanumeric digital display or video, CRT or LCD. Another option is to have no local display at all and have the data gathered by another instrument. Likewise, the user controls can also be analog or digital or can be operated through a host computer. To simplify the instruments, preprogrammed devices without user controls are available.

Electrical output options are the standard voltage and current outputs as well as an analog frequency or a change in state of switches or an alarm. Serial and parallel interfaces can help connect these instruments to a host computer.

Some features available for many turbidity instruments include battery power for greater portability and built-in signal processing filters. Built-in calibration ability and self-test functions are also available, as are event triggering and ratings for extreme environments. These instruments can also have some controller functionality such as set limits, regulator, or P/PI/PID control.

Generally, all total organic carbon (TOC) analyzers employ the same basic technique. A liquid sample is initially introduced to an inorganic carbon (IC) removal stage, where acid is added to the sample. At this point the IC is converted into carbon dioxide gas that is stripped out of the liquid by a sparge carrier gas. The remaining inorganic carbon-free sample is then oxidized and the carbon dioxide generated from the oxidation process is directly related to the TOC in the sample.

The analysis methods total organic carbon analyzers use to oxidize and detect the organic carbon may be combustion, UV persulfate oxidation, ozone promoted, or UV fluorescence. With the combustion method, analysis is determined when carbon compounds are combusted in an oxygen-rich environment, resulting in the complete conversion of carbon-to-carbon dioxide. In UV persulfate oxidation, the carbon dioxide is purged from the sample and then detected by a detector calibrated to directly display the mass of carbon dioxide measured. This mass is proportional to the mass of analyte in the sample. Persulfate reacts with organic carbon in the sample at 100 degrees Celsius to form carbon dioxide that is purged from the sample and detected. The ozone promoted method oxidizes the carbon by exposing it to ozone. UV fluorescence is a direct measurement of aromatic hydrocarbons in water. Fluorescence occurs when a molecule absorbs an "excitation" energy of one wavelength to be measured as concentration of the hydrocarbon. This may also be referred to as spectrophotometry or colorimetry.

One method for introducing the sample to the analyzer is via syringe. Another is loop sampling, in which the sample loop introduction system allows repeatable analysis over a wide range of concentrations while avoiding the inherent dead volumes of syringe-based systems. On-line total organic carbon analyzer systems have an analyzer that is mounted in a process line and the sample is introduced via a connection to the process. Vial auto samplers are another way to introduce the sample. The liquid-sample transfer auto-sampler removes specific sample volumes from a standard vial and transfers the sample to the common analysis vessel. A sample carousel is loaded with up to fifty vials and placed in the auto-sampler for unattended analysis. In addition to measuring total organic carbon, total organic carbon analyzers may sometimes be used to detect total carbon, total inorganic carbon, and purgeable and nonpurgeable organic carbon.

One of the most important specifications for total organic carbon analyzers is the measuring range. Carrier gas flow rate, average analysis time and process temperature are important as well. Accuracy and resolution are important to consider also.

User interfaces for total organic carbon analyzers can be analog, with dials, switches and potentiometers; digital, with menus, keypads and buttons; or computer interfaces connected to the analyzers by a serial or parallel or other connection. Displays can be analog meters, numeric or alphanumeric digital displays or video terminal. Outputs from TOC analyzers, aside from computer-readable data, can be analog voltage, current or frequency. Another option is to have the output be an alarm or change in state of switches.

Typical features that may be available for some models of TOC analyzers are measurement of solid samples and display of temperature and resistivity. Other handy features are programmability, self-calibration, data storage options, self-test diagnostics and extreme environment ratings.

 Titration instruments are used to determine the concentration of dissolved substances. Titration is based on a complete chemical reaction between the analyte and a reagent or titrant of known concentration that is added to the sample. The analyte is the substance which a laboratory test is designed to measure. The reagent or titrant is the substance that produces a chemical reaction in order to determine the presence of the analyte. There are two basic titration methods: manual and automatic. Manual titration is performed with a burette, a piece of laboratory glassware that has volumetric graduations along its length and a tap or stopcock on its bottom. Automatic titration is performed with an auto-titrator, an electrically-powered laboratory instrument that can be interfaced to a personal computer (PC). Typically, automatic titration instruments are used for repetitive titrations.

Titration instruments differ in terms of addition and indication methods. There are two titrant addition methods: volumetric and coulometric. Volumetric devices add the titrant directly to the sample. Coulometric devices generate the titrant electromechanically. There are many different titration indication methods. Voltametry, a technique also known as the Karl Fischer water determination method, measures the concentration-dependent potential of a solution against a reference potential. Potentiometry, redox and precipitation measure the potential at a constant electric current. Photometry, complexometry, and turbidimetry measure the light transmission of a colored or turbid solution with a photometric sensor. With amperometry, the current flowing in a sample is measured at a constant potential. Titration instruments that measure conductivity include a conductivity meter while devices that measure temperature include a sensor.

Selecting titration instruments requires an analysis of product specifications, features, display types, and computer interfaces. Product specifications for titration instruments include concentration range and reaction time. Some instruments provide data storage and temperature-compensation features. Others measure solids or gases. In terms of display types, titration instruments with analog or digital front panels are commonly available. Analog user inputs include potentiometers, dials and switches. Digital front panels can be setup or programmed using a digital keypad or menus. Titration instruments that can be controlled or monitored via a computer interface use serial or parallel communications and may include application software. RS232, RS485 and universal serial bus (USB) are common serial interfaces. The general-purpose interface bus (GPIB) is a common parallel interface.

 Thermal imagers detect heat patterns in the infrared wavelength spectrum.  Thermal imagers rely on the emission of thermal or infrared energy by all objects above 0 Kelvin. They detect energy emissions (heat) in the infrared wavelength spectrum of 1 micron to 100 microns.  Thermography, thermology, thermal wave imaging, thermovision and thermal infrared night vision use thermal imagers, some of the actual devices appear like slightly oversized video cameras, while others appear a bit bulkier. They have been getting smaller since the introduction of Focal Plane Array (FPA) detectors.  The specific uses of the imagers are widespread. Several major cost saving uses depend upon the temperature measurement capability of the specific imaging equipment and a great many commercial and industrial uses produce significant cost savings or cost avoidance.  Thermal imaging devices provide the observer with instruments that can collect ( just like a video or still camera) and convert the thermal infrared radiation emitted (and also reflected) by objects into images that can be seen on a view screen or computer display.

There are several parameters important in specifying thermal imagers, measurement temperature range, spectral range, accuracy, resolution and maximum frame rate.  The measurement temperature range is the temperature range of object to be measured.  Spectral range can be broken into one of four ranges, near IR:  0.75-3 microns, middle IR: 3-6 microns, far IR: 6-15 microns  and extreme IR: 15-30 microns.  The accuracy value represents the accuracy or measurement uncertainty expressed as a percent of the reading value.  The temperature resolution represents the smallest unit of temperature uncertainty.  Maximum frame rate is the speed or image update rate.

Thermal imagers may have one of three common detector types, flying spot, scanning and line array.  A flying spot detector is a single point detector scanned to build image.  A scanning detector is a line detector that scans to produce an image.  An array detector is a two-dimensional array of sensors or detectors.

Most IR detectors must be kept at a constant temperature ranging from -100C to -196C, therefore they have cooling mechanisms in their design.  These may be thermoelectric, liquid nitrogen, active built-in cryogenic cooling or the detector may not be cooled at all.  Thermoelectric designs cool via Peltier cooling.  Liquid nitrogen cooling may be used to absorb any unwanted heat and associated noise.  With built-in cooling the infrared imager is supplied with on-board cooling to cryogenic temperatures.

Thermal imagers have both a horizontal and vertical spatial resolution that represents the number of pixels in either direction.  The greater the resolution, the smaller the unit of temperature that can be measured.

Features common to thermal imagers include batteries, built-in cameras, built-in microphones, frame grabbers, portability, protective cooling jacket, remote heads, removable data storage, and infrared or spectral filters.

 Temperature instruments, all types are used in many industrial and non-industrial applications for the measurement of temperature.  Thermometry is the measurement of temperature. There are two basic methods for temperature measurement, contact and noncontact. Within these two groupings, an engineer is likely to come into contact with six types: thermocouples, resistive temperature devices (RTDs and thermistors), infrared radiators, bimetallic devices, liquid expansion devices, and change-of-state devices. This is a generic search form for the selection of instruments, probes and elements used for the temperature measuring industry. Both contact and noncontact style devices are listed. Specific temperature device search forms are also available.

Specific temperature instrument types include contact temperature instruments, non-contact temperature instruments, digital thermometers, dial thermometers, laboratory glass thermometers, temperature and humidity process controllers, and temperature probes.  Contact temperature instruments are instruments and Indicators designed for temperature monitoring and displaying. These instruments either require a sensor input or come equipped with an integral sensor. Non-Contact temperature sensing devices are typically infrared devices.  Digital temperature sensing instruments are portable, have permanent probe(s) and a digital display. These thermometers are typically battery powered.  A dial thermometer is a bimetal, gas-actuated, or vapor-tension-based thermometer. They display temperature and possibly min/max readings and/or other ‘extras’.  Laboratory thermometers are standard glass thermometers for laboratory settings and applications.  Process controllers can be configured specifically for temperature and humidity processes.  Temperature probes include probes for various temperature sensing applications.  Common sensor types include thermostat or thermal switch, thermocouple, RTD element, thermistor, and thermal cutoff.  The temperature measurement range is also important to consider.

Display style choices for temperature instruments include analog meters or indicators, digital readouts, and video display terminals.  A Fahrenheit display is defined by 32 degrees at the ice point and 212 degrees at the boiling point of water at sea level. A Celsius display is defined by 0 degrees at the ice point and 100 degrees at the boiling point of water at sea level.  Common outputs for temperature instruments include analog voltage, analog current, resistance, frequency or modulated frequency, switch output, serial interface, and parallel interface.  Application software may be included for process monitoring and control.  Options and features for temperature instruments include explosion proof, splash proof or waterproof, HVAC applications, and sanitary applications.

 Temperature instruments and temperature indicators are designed for temperature monitoring and analysis. Temperature instruments and temperature indicators either come equipped with an integral sensor, or require sensor input.  Approximately 16% of all process instrumentation measures, indicates, or controls temperature. In many industrial applications it is necessary to collect temperatures as a permanent record due to government or manufacturing requirements, or to provide historical data that may later be used to determine problems within a system. Data collection methods in industry vary from simple manual systems using inexpensive portable indicators to sophisticated DCS (Distributed Control Systems) that both log and control data. The most inexpensive portable indicators do not provide any "recording" or memory features. Readings from portable temperature instruments and temperature indicators must be recorded by hand. Some portable indicators are available with memory so that a number of measurements may be collected and later downloaded into a personal computer.  A chart recorder is another device used to record temperature data.  These recorders usually offer digital readouts and give a digital indication of the process temperature of selected points or of scanned points. Distributed control systems also offer datalogging as a part of their overall capabilities. Since these systems are computer based, the datalogging functions are programmable to almost any needed configuration.

Important general specifications to consider when searching for temperature indicators and temperature instruments include the sensed temperature range, input options and number of inputs or channels.  The sensed temperature range refers to the temperature range the device is rated for sensing.  Choices for input options include permanent sensor or probe, thermocouple inputs, RTD inputs, thermistor inputs, and solid-state inputs.  The number of inputs or channels specifies the number of inputs available for probe or sensor attachment.  Interface and display options are also important to consider.  Local interfaces include digital front panels and analog front panels.  Display options include digital readouts, analog meters or indicators, video display terminals or no displays.  Communications interfaces for devices that can be controlled remotely by a computer include serial and parallel interfaces.

Mounting is also important to consider when searching for temperature indicators and temperature instruments.  Mounting choices include portable or hand held, self-contained or stand-alone, panel mount or meter, and rail or track mounted.  The display scale can be Fahrenheit or Celsius.  Fahrenheit is defined by 32 degrees at the ice point and 212 degrees at the boiling point of water at sea level. Celsius is defined by 0 degrees at the ice point and 100 degrees at the boiling point of water at sea level.  Additional specifications to consider when searching for temperature indicators and temperature instruments include battery powered, detachable probes, datalogger or data collection capabilities, recording of minimum or maximum values, internal timers or counters, controller functionality, math or statistical function performance, and self-test diagnostics.

Sound level meters and noise dosimeters are used in many kinds of sound and noise analysis including industrial safety, traffic and transportation noise quantification, and scientific noise measurement. They are frequently hand-held and battery-powered. Sound level meters measure real-time sound and can have functions such as signal analysis, noise dose measurement, and different time and frequency weighting.

Sound level meters and noise dosimeters are used for measuring Sound Pressure Level (SPL) and different weightings such as A-weighted SPL, C-weighted SPL, Sound Exposure Level, etc. Noise dosimeters are used for specific measurement capability for defined industrial safety criteria. A typical measure is sound exposure for an 8-hour period. These instruments can be found either individually or as one unit that covers capabilities of both products.

Two critical specifications for sound level meters and noise dosimeters are frequency range and sound level range. Frequency Range is the range of frequencies for which the meter maintains a constant sensitivity within defined boundaries. Functionally, this is the operational range of the meter. Sound level range is limited on the low end by the inherent noise of the acoustic system and on the high end by the maximum sound pressure level.

Many sound level measurement modes are available for these devices. Flat or unweighted SPL measures the straight physical quantity with no weighting. A-weighting is a frequency domain weighting based on human hearing response. This filters out low frequency sound to approximate the response of the human ear. C-weighting filters less low frequency sound than A-weighting, providing a closer representation of acoustic energy across all frequencies. A-weighted sound exposure level measurement is used for short or one-time sounds as the equivalent 1-second level. Equivalent continuous SPL is the noise level of a continuous steady sound whose time-averaged power equals that of the fluctuating noise under measurement. Percentile SPL measures the percentage of time during a given measurement period that the instantaneous measurement exceeds a given value.

Some typical features for sound level meters and noise dosimeters include ratings for outdoor use and auxiliary outputs for measurement with other instruments. These devices can also have human and hand-arm vibration measurement for industrial, environmental or occupational vibration such as power tools, nearby trains, etc. Data storage and spectrum or frequency analysis are also available.

Control panel options include analog, digital front panel or computer control. Typical machine interfaces for sound level meters and noise dosimeters are parallel and serial, although other possibilities, such as RF transmission, may be available. Displays on these instruments can be local analog or digital readouts or else can be read through a host computer or video display terminal.