Common Testing Questions

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

• 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.

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

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.