testo 435-3 - Multifunction meter w/ integrated differential pressure

Order-Nr.  0560 4353

  • Integrated differential pressure measurements for flow velocity

  • Optional wireless (RF) temperature probes for remote measurement

  • Backlit LCD for easy viewing

  • Optional printer allows for easy documenting of measured data

The testo 435-3 multifunction meter is perfect for monitoring, analyzing, and diagnosing indoor air quality, wherever you need to take important IAQ measurements. In addition, you can easily pinpoint and troubleshoot airflow problems with HVAC systems, and immediately see the results of corrections. Commissioning, validating, benchmarking, or simpy adjusting HVAC systems are all easy with the testo 435-3.

Product Description

The testo 435-3 multifunction meter allows you to carry out the measurements that are necessary to check and adjust the airflow of air conditioning systems, and assess the quality of indoor air. The testo 435-3 multifunction meter accepts a wide variety of probes to measure and record airflow, temperature, and indoor air quality readings.
Probe dependent menus and selectable user profiles ensure that the testo 435-3 multifunction meter is always ready to use.  Easy setup of user defined IAQ and airflow / duct profiles allow for fast measurement of many different tasks, and with a wide variety of probe choices available, the testo 435-3 is ready to handle a vast array of indoor air quality applications.
testo 435-3 highlights:
  • Integrated differential pressure measurement for airflow
  • Ideal for spot check measurements
  • Wired, or wireless temperature probes
  • IP54 Protection class


Delivery Scope

testo 435-3, batteries, and conformity certificate

Temperature - NTC

Measuring range

-58° to 302 °F / -50 to +150 °C


±0.4 °F (-13° to 166.8 °F) / ±0.2 °C (-25 to +74.9 °C)

±0.7 °F (-58° to -13.2 °F) / ±0.4 °C (-50 to -25.1 °C)

±0.7 °F (167° to 211.8 °F) / ±0.4 °C (+75 to +99.9 °C)

±0.5 % of mv (Remaining Range)


0.1 °F / 0.1 °C

Temperature - Type K TC

Measuring range

-328° to 2498 °F / -200 to +1370 °C


±0.5 °F (-76° to 140 °F) / ±0.3 °C (-60 to +60 °C)

±(0.4 °F + 0.5 % of mv) (Remaining Range) / ±(0.2 °C + 0.5 % of mv) (Remaining Range)


0.1 °F / 0.1 °C

Temperature - TC Type T (Cu-CuNi)

Measuring range

-328° to 752 °F / -200 to +400 °C


±0.5 °F (-76° to 140 °F) / ±0.3 °C (-60 to +60 °C)

±(0.4 °F + 0.5 % of mv) (Remaining Range) / ±(0.2 °C + 0.5 % of mv) (Remaining Range)


0.1 °F / 0.1 °C

Humidity - Capacitive

Measuring range

0 to +100 %rH


See probe data


0.1 %rH

Absolute Pressure

Measuring range

0 to 800 InH₂O / 0 to 2000 hPa


See probe data


0.1 InH₂O / 0.1 hPa

Velocity - Vane anemometer

Measuring range

0 to +11811 fpm / 0 to +60 m/s


See probe data


0.01 fpm (60 + 100 mm Vane) / 0.01 m/s (60 + 100 mm Vane)

0.1 fpm (16 mm Vane) / 0.1 m/s (16 mm Vane)

Velocity - Hot wire anemometer

Measuring range

0 to +3937 fpm / 0 to +20 m/s


See probe data


0.01 fpm / 0.01 m/s

Differential pressure (internal sensor) - Piezoresistive

Measuring range

0 to +10 InH₂O / 0 to +25 hPa


±0.01 InH₂O (0 to +1 InH₂O) / ±0.02 hPa (0 to +2 hPa)

±1 % of mv (Remaining Range)


0.01 InH₂O / 0.01 hPa


80 InH₂O / 200 hPa

General technical data


9 x 3 x 2 in. / 220 x 74 x 46 mm

Operating temperature

-4° to 122 °F / -20 to +50 °C


ABS / TPE / Metal

Protection class


Battery type

Alkaline, type AA

Battery life

200 h (typical vane measurement)

Display ligthing


Storage temperature

-22° to 158 °F / -30 to +70 °C


15 oz. / 428 g

Air Probes

CO probes

Ambient CO probe

Order Number: 0632 1235

Immersion / Penetration Probe


Absolute pressure probe 29 psi

Order Number: 0638 1835


Additional Accessories

Flow measurement in the ventilation duct using a thermal anemometer and vane anemometer

Testo offers compact anemometer probes and pitot tubes for measuring the flow and volumetric flow in the ventilation duct.

Selecting a suitable probe or measuring instrument depends on the flow velocity in the ventilation duct. This can be broken down into three sub-ranges:

  • Low flow velocities: 0 to 5 m/s => thermal anemometers and thermal probes are suitable for this (order no. 0635 1535, 0635 1025)
  • Medium flow velocities: 5 to 40 m/s => best results are achieved by the 16 mm vane anemometer und Flügelrad-Sonden (order no. 0635 9535)
  • High flow velocities: 40 70 100 m/s => the pitot tube provides the best prerequisites (see following application)

The flow sensors for duct measurement are all equipped with telescopes making them easy to use in large air ducts. Air temperature and humidity can also be measured with the same probe as the flow velocity if required. According to the required application, choose between a thermal probe, vane probe or pitot tube for measuring the flow measurement in the duct.

Measurement at the air outlet

Every duct inlet and outlet should only contain the volumetric flow that according to calculations is a basic prerequisite to an efficient functional system.

Large vane anemometers with 100 mm diameters are suitable for measuring the volumetric flows at duct outlets (order no. 0635 9435), as it integrates the flow velocity over a larger area thereby determining disturbance from the air grille (loop method).

To measure the suction or blowing vents of air grilles and poppet valves our volumetric flow rate funnel set is ideal (order no. 0563 4170) as is the large 100 mm vane anemometer (order no. 0635 9435) The entire volumetric flow is recorded with the aid of the funnel without the need for conversion on the basis of the flow velocity and area. This method of flow measurement is simple and reliable.

Measurement of the air and surface temperature

For human beings to be comfortable and perform at their best, it is crucial that the rooms they occupy are correctly air conditioned. As well as the structural conditions and personal perception, the following factors also contribute significantly to the existence of a pleasant indoor climate: the indoor air and surface temperature of walls, windows, floors and ceilings.

There is a range of optional temperature probes available for the testo 435. Our temperature probes with a sprung cross-band sensor element for measurement on surfaces are outstanding. The sprung cross-band sensor element fits on any surface, taking the actual temperature of the measured object in just a few seconds (for example the fast-reaction surface probe, order no. 0602 0393).

In order to allow a fast measurement of air temperature, the temperature sensor is free in our air probes (e.g. precise, robust NTC probe 0613 1712). Immersion/penetration probes can also be used for measurements in air. However, the response time is then about 40 to 60 times higher than the indicated value which was measured in water.

Measurement of radiated heat

The multi-functional measuring instrument testo 435 is your reliable aid to measuring thermal comfort. The optional, attachable globe thermometer (order no. 0602 0743) enables measurement of radiated heat (that is, the operative or perceived temperature). The operative temperature measured with a Globe thermometer with a 150 mm diameter preferably corresponds with people's perceived temperature to ± 0.41 K.

The temperature measurements in a room (air temperature and operative temperature) are to be taken in the same place and same general conditions as the measurement of indoor air velocities.

Differential pressure measurement on filters

Air conditioning systems are equipped with filters which prevent dirt from the outside air entering the indoor air. These filters are to be inspected regularly to make sure they are still fully functional. To do this, the pressure is measured in front of and behind the filter. The result is the differential pressure. If it is too high, the filter is contaminated and needs changing.

testo 435-4 uses the integral sensor to measure the differential pressure within the 0 to 25 hPa range. The differential pressure measurement is temperature-compensated for exact readings. Magnets on the rear of the instrument allow hands-free work.

Measurement in the ventilation duct using a pitot tube

Observance of air flows in the ventilation duct is of utmost importance for the function of the ventilation and air conditioning system.

The internal differential pressure sensor of the testo 435-3 is used for measuring in the case of high flow velocities and very contaminated flows, and the pitot tube for an air velocity ranging from 0 to 64 m/s. The testo 435-3 simultaneously displays pressure, flow and volumetric flow.
Magnets on the rear of the instrument allow hands-free work.

Measurement of indoor air quality (CO2)

Bad indoor air quality due to high concentrations of CO2 can cause tiredness, lack of concentration and even illness. Therefore, to ensure sufficient indoor air quality the CO2 concentration should generally not exceed 1 000 ppm. Values of 700 to 1 500 ppm can be viewed as the "reference range".

The IAQ probe (order no. 0632 1535) is particularly suitable for monitoring indoor air quality controls. This probe can be used to record CO2, temperature and relative humidity at the same time.

CO measurement

Carbon monoxide (CO) is an odourless, invisible and tasteless gas, but also poisonous. It is produced during the incomplete combustion of substances containing carbon, such as coal, wood, oil, natural gas, etc., in heat sources and combustion engines. The CO concentration will increase quickly, particularly if there is not enough oxygen available. This may have adverse effects on health.

The ambient CO probe (order no. 0632 1235) and testo 435-1 are able to detect even the smallest quantities of CO in ambient air.

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