testo 340

Ready for the Job

The difficulty with a configurable analyser is that the customer has to know which sensors they need before they buy one, and getting it wrong is expensive.

The testo 340 Diesel Kit takes that decision away for diesel engine work. It arrives with O2, CO, NO and NO2 sensors, CO2 calculated from O2, an engine probe with thermocouple (335 mm long, up to 1,000°C), a power supply, carry case and Bluetooth. Talk to our Technical Consultants about configurations for boilers, burners and gas engines.

Sensors are plug and play and field changeable, so a configuration can be revised as the work changes.

Four Sensor Positions

Oxygen is the base sensor in all testo 340 analysers, and up to three more are added from CO, COlow, NO, NOlow, NO2 and SO2.

The combination matters. The standard CO sensor covers 0 to 10,000 ppm and suits tuning standard systems. The low range COlow sensor covers 0 to 500 ppm with 0.1 ppm resolution, and suits critical low CO limits, where the standard sensor lacks the resolution. The same applies to nitric oxide: NOlow measures 0 to 300 ppm with 0.1 ppm resolution, against 0 to 4,000 ppm with 1 ppm resolution on the standard NO sensor.

Sulphur dioxide (0 to 5,000 ppm) is the sensor to add for sulphur bearing fuels.

Why NO and NO2 Are Measured Separately

This decides whether a NOx figure is worth putting in a report.

NOx is nitric oxide plus nitrogen dioxide. Many analysers measure NO alone, then estimate NOx using an assumed ratio. That works where the ratio is stable. In engine exhaust, the NO2 share can vary a lot, so a NOx figure based on NO alone can be wrong.

Measuring both gives the real NOx value. On engine tuning, and on any measurement going into a compliance record, that’s the difference between a defensible number and an approximation.

To avoid absorption affecting NO2 readings, Testo recommends that a measurement doesn’t run longer than 2 hours.

Dilution to Fifty Thousand

Engine conditions often aren’t known when the instrument goes on, and an analyser that saturates gives you nothing while damaging its own sensor.

When the CO concentration exceeds a set threshold, the sensor in the dilution slot is automatically diluted with fresh air at a factor of 5. That extends CO measurement up to 50,000 ppm, NO up to 15,000 ppm and SO2 up to 25,000 ppm, with the corrected value calculated and displayed.

An optional dilution of all sensors, at a factor of 2, extends CO up to 20,000 ppm and NO up to 6,000 ppm.

The point isn’t the headline number. It’s that a measurement can carry on at an unexpectedly high concentration, without abandoning the test or shortening the sensor’s life.

Mass Emissions

This is the capability most likely to be the reason someone chooses the 340, and it’s easy to miss.

Concentration in parts per million tells you whether combustion is running correctly. It doesn’t tell you what the site actually emitted, because a low concentration in a very large gas flow can be more mass than a high concentration in a small one. Environmental licences and reporting are often written in mass terms, such as kilograms per hour or tonnes per year.

With a Pitot tube, the testo 340 measures flue gas velocity, and from that, plus the duct dimensions and gas concentration, it calculates the mass flow of pollutants including CO, NOx and SO2. Differential pressure and flow measurement are built in for exactly this.

So one instrument answers both the tuning question and the reporting question.

Probes, Reach and Protection

Modular flue gas probes come in 335 mm and 700 mm lengths, rated to 500°C or 1,000°C, with or without particle filters for dusty gas. Engine probes suit servicing and emissions work on stationary gas and diesel engines.

Hose extensions matter more than they sound. Two extensions plus the standard hose give up to 7.8 metres, which often means the measurement is taken standing on the ground rather than up a ladder at the sampling point.

Sensor protection goes beyond dilution. The condensate trap shows a warning when it reaches 90% full, and the filters protecting the CO and NO sensors can be replaced on their own, rather than replacing the whole sensor.

Where It Sits in the Range

It’s worth being direct, because all three Testo tiers overlap at the edges.

The testo 310 II covers boilers and hot water plant with oxygen and carbon monoxide. If that’s the work, it’s the right instrument, and the 340 adds cost without adding anything useful.

The testo 340 adds nitrogen oxides and sulphur dioxide, dilution, mass emission calculation and industrial probes. That covers boiler and burner tuning, engine work, and pre compliance testing.

The testo 350 takes up to six sensors, adding infrared CO2, hydrogen sulphide and hydrocarbons. It also adds gas preparation for wet gas, and the data bus, which measures before and after an after treatment system at the same time.

If you’re tuning engines and boilers and reporting emissions, the 340 is usually the answer. If you’re proving a scrubber works or running long term measurements in wet gas, it’s the 350.

Where It’s Used

Industrial burners and boilers. Stationary industrial engines. Gas turbines. Gas engines and cogeneration plant. Thermal processes. Generator sets. Pre compliance emissions testing. Functional testing of permanently installed emissions monitoring equipment. Marine engines.