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  • 0563 4001



  • Measures temperature, humidity, pressure, CO2, rpm, current/voltage, velocity and volume flow
  • Calculation of all parameters in the Mollier (psychometric) chart
  • Input of duct cross-sections for volume flow calculations
  • Density calculations for velocity measurement
  • Optional attachable printer
  • Data communication via RS-232
  • 3 Fast function buttons
  • Backlit display
  • Save/print button
  • 2 freely assignable probe inputs


The Testo 400 reference meter and logger is a reference class meter that has everything the professional user needs to complete complicated measurement tasks efficiently and accurately. Utilizing a wide array of precision Testo probes and sensors, the 400 accurately measures humidity, CO2, rpm, current, voltage, air velocity and volume flow. The versatility of the Testo 400 makes it an indispensable instrument for specialists and professionals in industry and the trades.

The Testo 400 recognizes the whichever probe is connected and displays the steps necessary to ensure the measuring tasks can be carried out quickly, easily and efficiently. The drop down menus provide effortless operation and three fast function buttons, defined by the user, make it possible to quickly call up the most commonly used measurements or calculations at the touch of a button. The large display can show up to 6 readings simultaneously. Simple, one button operation can save data to the 45,000 point memory or to print with the optional printer.

The Testo 400 includes a number of advanced functions that truly separate it from similar meters. In addition to standard measurements, the 400 is capable of precise calculations including calculation of all parameters in the Mollier (psychometric) chart as well as density calculations for velocity measurement with reference to temperature, humidity and absolute pressure. Input of duct cross-sections for volume flow calculations can be added to aid HVAC technicians diagnose systems. The Testo 400 also easily calculates and displays minimum, maximum and mean values, such as, dew point, wet bulb, and absolute humidity.

Measurements are easily organized in the Testo 400 by creating files and folders either in the meter or on a PC. Numerous display formats and analysis options like calculations, tables, diagrams, histograms, and other forms are facilitated by the ComSoft 3 Software. All relevant parameters such as the beginning and end of a measurement, measurement intervals, limit exceeded and date/time can be programmed for long-term measurement.