Common Testing Questions

Questions on Sensors

What can I measure with the testo 350 emission analyzer?

The 350 can measure O2, CO, NO, NO2, SO2, H2S, Hydrocarbons, CO2, pressure, temperature, flow, and velocity.

What are Electrochemical sensors?

Electrochemical sensors are devices that measure flue gas constituents (O2, CO, NO, NO2, SO2, H2S) through the principle of ion selective potentiometry The sensor contain a electrolytic matrix that is designed for a specific gas to be detected. Two or three electrodes (again gas specific) are placed in this matrix and an electrical field is applied. Flue gas enters the sensor and chemically reacts (oxidation or reduction) on the electrode releasing electrically charged particles (ions). This reaction causes the potential of this electrode to rise or fall with respect to the counter electrode. With a resistor connected across the electrodes, a current is generated which is proportional to the concentration of gas present. The output is converted then displayed as a concentration (typically in ppm, percent, or as a mass unit (i.e. lbs/hr or mmbtu).

Standard electrochemical sensors are affected by various environmental factors including: temperature, pressure, and other combustion gases. However, Testo sensors are designed to eliminate these effects. Mounted on each sensor is a circuit board that contains calibration data, linearity data, and other critical information. This technology enables the sensor to be pre-calibrated at Testo and installed in the field as a simple plug-in device. No need to have calibration gases on site. Additional technological advancements in sensor and analyzer design include the use of:

  • Continuous temperature compensation to provide accurate response regardless of ambient temperature fluctuations.
  • Control of sample pressure and automatic flow rate monitoring to eliminate pressure related effects.
  • Sensor temperature control by using heated thermoplastic sensor blankets.
  • Integrated on-board interference filter media that eliminates the hassle of replacing NOx beads.
  • Automatic cross compensation for interference gases.

Are the sensors temperature compensated?

Yes. Most electrochemical analyzers use temperature compensation to eliminate drift due to temperature change. Analyzers typically base their compensation on the temperature when the analyzer is first turned on. The sensor output will remain linear within a limited temperature range depending upon the analyzer and sensor configuration. The Testo 350 emission analyzer continuous temperature compensation and sensor temperature control to ensure accuracy. Sensor temperature measurement integrated circuit boards on each sensor provide the mechanism to apply a continuous temperature compensation based on sensor temperature monitoring.

Can you use a NO standard range and NO low range sensor simultaneously?

Not at the same time. Instead, you can switch or swap them in the field. This is easily done without tools and usually takes less than a minute. This innovative feature is made possible by the integrated circuit board and plug & play connectors mounted on every 350 sensor. The circuit board memory contains critical calibration, linearity, and performance information that enables the sensors to be pre-calibrated before shipping. This eliminates the downtime and shipping cost of returning the analyzer to the factory.

What is the error message "NO measurement not possible for 2 hr?

This is a result of the Nitric oxide sensor losing its "bias" charge. All electrochemical NO sensors require a tiny amount of electrical current in order for the sensor to measure accurately. When an analyzer is off, this current is supplied by a trickle charge from the battery. If the battery goes completely dead, then the NO sensor will loose its bias charge.

How are sensors protected?

The analyzer will automatically turn-off the sampling pump at a predefined over-range concentration. In addition, by simply pressing a function button, a fresh air purge or CO shut off or sensor zero can be started. Lastly, when the analyzer is turned off it will go through a shut-down sequence that purges residual gases from the analyzer resulting in longer sensor life and more stable output.

What is a CO dilution system?

The dilution system extends the measurement range of the CO sensor and protect it from high eoncentrations (x40). The system has user-selectable factors (2, 5, 10, 20, 40); an automic feature and an overall analyzer function.The analyzer automatically calculates and displays the corrected concentration based upon the dilution factor. Basically, the dilution system introduces a precise volume of ambient air into a mixing chamber that contains the flue gases thereby reducing the concentration by a specific quantifiable factor. This system has many advantages over older technologies in that: it protects and extends the life of the sensor by reducing the concentration and it eliminates the cost for additional replacement sensors.

What is the reason for fresh air purges?

Periodic fresh air purges rejuvenate electrochemical sensors. Without a fresh air purge electrochemical sensors will become "saturated' and the output will drift. The amount of time for the purge is generally dependent upon the flue gas concentration and the time of exposure. The higher the concentration and longer the exposure, the more often the fresh air purge is needed. The fresh air purge function can be started manually or automatically in the program mode.

How does the Hydrocarbons (CxHy) sensor work?

A heated sensor that measures total hydrocarbons. Also know as a catalytic or heated bead sensor. It consists of specially matched pair of precision resistive thermal devices (RTDs) overlaid with two different coatings. The first one is covered with a propriety catalyst that creates an exothermic reaction to the presence of targeted hydrocarbons. The second RTD Pellister CxHy Sensoris covered with an inert coating and acts as a reference. Both RTDs are heated to approximately 950°F to increase the catalytic reaction rate. In the presence of hydrocarbons the catalytic RTD will have higher heat value than the reference. The RTDs are tried to two legs of a "Wheatstone Bridge" to maximize the output and stability. Testo's unique cross calibration techniques essentially make the HC module blind to interference gases such as carbon monoxide and free hydrogen.

Questions on Testing

What is NOx?

NOx is a term used to describe nitrogen oxides. NOx is a reactive gaseous compound that is one of the criteria air pollutants regulated by the USEPA Clean Air Act. The two primary oxides of nitrogen involved in air pollution are NO and NO2. Nitric oxide (NO) is colorless and essentially odorless. Nitrogen dioxide (NO2) is a reddish-brown gas with a pungent smell. NOx (NO & NO2) can irritate the lungs, cause bronchitis and pneumonia, and lower resistance to respiratory infections. NOx is also a precursor to the formation of ground level ozone (smog) and a contributor to acid rain.

NOx emissions are produced during the combustion of fuels. The primary man-made sources of atmospheric NOx include; area mobile sources (cars and trucks), off-road sources (construction and agricultural machines, trains, etc.) and stationary sources (power plants, industrial boilers & heaters, etc,).

In a combustion process, three types of NOx can be formed:

  • Thermal NOx, from high temperature combustion in the presence of free oxygen.
  • Fuel NOx – from the nitrogen bound in the fuel when it is oxidized during combustion.
  • Prompt NOx – from the combustion flame and the ambient nitrogen in the ambient air.

Can my Testo 350 emission analyzer be used for compliance testing?

Yes. The Testo 350 emission analzyer is used for compliance testing across the country. Testing for regulatory compliance is performed according to approved protocols. The EPA has a variety of methods specifically for electrochemical analyzers, CTM-030, CTM-034, and ASTM designation D 6522-00. Some state and local "air boards" also have "approved" test protocols. We recommend you contact your local regulatory agency to determine which testing protocol best fits your application.

Is the Testo 350 approved by the U.S. EPA? By state agencies?

Portable emission analyzers are not "approved" by the U.S. EPA. Instead of granting "approvals", the EPA publishes test methods for specific applications. The test methods contain performance specifications the analyzer must meet during the actual test in order for the test to be valid. This requires the operator of the analyzer to be competent and knowledgeable regarding the test method and the analyzer. The Testo 350 emission analyzer meets the performance specification of these methods.

State and local regulatory agencies may have greater flexibility regarding "approvals". Some adopt EPA's requirements and others may approve analyzers instead of test methods. You can learn more about the EPA's test methods by going to their website.

Is the Testo 350 emission analyzer EPA verified?

Yes. The Testo 350 emission analyzer has been verified by U.S. EPA's Environmental Technology Verification Program under the Advanced Monitoring System (Air). Refer to the EPA's ETV Testo 350 verification page for more information.

Can I correct my values to an oxygen reference (O2 ref)?

Yes. The Testo 350 emission analyzer will automatically calculate, NOx, NO, CO and SO2 to a corrected oxygen reference. The "O2 ref." can easily be changed from 0% to 25%. Regulatory agencies typically require the pollutant gas to be reported to a specific "oxygen reference" to ensure uniformity in the reports. Additionally, this calculation is used to eliminate the consequence of adjusting the controls to subtract or add air to the combustion system thereby changing the ppm reading. Typical oxygen reference levels are: 3% or 7% for boilers and burners, 12% or 15% for engines and turbines.

Can I do long-term monitoring?

Yes. Special design features enable the Testo 350 emission analyzer to perform long-term testing. With a huge internal memory (250,000 data points), your testing can go on for weeks if not months. The automatic program has extensive testing capabilities. Start and stop a test on a certain date or for a defined length of time. Simply define the time for sampling, the rate for data logging, and the length of time for the fresh air purge. The analyzer can print the test with a calculated mean average or as single discreet measurements or download to either of Testo's software programs.

Can I do 10 minute or 15-minute tests?

Yes. Just define the test program, push the start button, and the analyzer will do all the work. With a huge internal memory, you do not need to have a computer on-site. Testing time, fresh-air time, data logging rate are all user-defined. Data will be automatically saved to any location specified by you. The test data can be printed on site or downloaded to a computer in the comfort of your office.

Questions on Maintenance & Calibration

How often must I calibrate my analyzer?

The short answer is "as often as required". Electrochemical cells in good condition should not drift more than 5% per year. However, as the sensor ages the output diminishes, therefore the calibration frequency may need to be increased. Once or twice per year is usually adequate for most applications. Testing for regulatory purposes will often require a calibration before and after each test. This self-calibration is easily performed with calibration gases.

What basic maintenance can I perform myself?

  • Sensors are field-replaceable and are pre-calibrated.
  • Sampling pumps
  • Particle filters (0554.3381) should be replaced when discolored or obvious particulate buildup occurs. This is a function of usage, frequency and sample conditions.
  • Condensate water should be removed by either attaching a hose to the port on the condensate trap and letting the water drain by gravity or removing the trap from the Analyzer Box and shaking the water out.
  • The O-rings on the probe hose barbs should also be checked and replaced as needed.

Can I replace sensors in the field?

Yes! Replacement sensors come from Testo pre-calibrated and ready for installation. Most people can install the sensor in less than one minute.

How long will the Testo 350 emission analyzer operate on battery?

The Testo 350 emission analyzer will operate for 2-4 hours on a single full battery charge. This includes operating a complete sample gas conditioning system and all other analyzer parameters in the portable mode. If needed, an additional battery can be swapped out or an AC power cord connected for longer-term or semi-continuous monitoring.

Questions on Software

Testo offers two different types of software:

easyEmmisions Software

The easyEmissions software package allows the user to control every function of the Testo 350 emission analyzer. The software provides extraordinary data management capability and the ability to import/export data from a number of different formats, effectively increasing the versatility and flexibility of the 350 to meet the user's testing and data management needs easyEmission has the intuitive user interface of today's common Windows® based applications. Display screens can be customized to match the most commonly used functions. Prepare custom reports and documents with the powerful data management features.

easyReport Software

easyReport is an Excel-based program that communicates with the Testo 350 emission analyzer using a Microsoft Excel toolbar application. By utilizing this toolbar, data can be logged in two different formats, a basic module and a reporting module. Features easyReport provides include: compliance-type reports generated in Microsoft Excel, pre- and post-test calibration data logging, Source test data collection, bias check testing (under construction), and linearity check (under construction).

Microsoft Excel® based Import Tool

The simple Testo 350 Import Tool lets you use your existing Excel® program to collect real time data or download tests directly into your Excel® spreadsheet. It provides simple operation and only the necessary functions for easy report writing.

Questions on Sampling

What sample conditioning is used?

A Peltier cooling system cools the flue gas and condenses the water for removal by an on-board peristaltic pump. The analyzer incorporates a powerful sample pump for high velocity sampling. By combining high velocity sample rates, minimized surface areas, and reduced residence time, the system offers the performance of a stack testing reference system. Heated sample lines and heated hose adaptors are also available for those test methods that require it.y report writing.

General Questions

Can I buy my emission analyzer direct from Testo?

The 350 can be purchased through Testo's distribution network. Our distributors provide product demonstrations and on-site training as well as extensive application knowledge.Contact us directly and we can help you find a distributor in your area.