testo 521-3 - Differential pressure measuring instrument (up to 2.5 hPa)

Order-Nr.  0560 5213

€ 873,00
sa PDV-om € 1091,25
  • Integrated temperature-compensated differential pressure sensor with accuracy of up to ± 0.5 Pa

  • Calculation of the flow velocity and the volume flow via Pitot tube (optional)

  • Direct zeroing of the display values of pressure probes

  • 2 probe inputs for additional pressure and temperature probes

The testo 521-3 high-precision differential pressure measuring instrument easily determines even the smallest differential pressures (up to +2.5 hPa). Its high accuracy and a resolution of 0.1 Pa make the instrument ideal for differential pressure measurements in clean rooms or for flue inspections.


Product Description

The testo 521-3 differential pressure measuring instrument is designed for high-precision differential pressure measurements in air conditioning and ventilation technology. It can be used, for example, for measurements in clean rooms and for flue inspections – thanks to a high level of accuracy and outstanding resolution. In conjunction with a Pitot tube (optional), the integrated pressure sensor measures flow velocities of +1 to +20 m/s.
The integrated temperature-compensated differential pressure sensor performs measurements to an accuracy of up to ± 0.5 Pa. In addition, you can attach up to 2 further optional probes to the measuring instrument. This means you can flexibly adapt the differential pressure measuring instrument to your application. You have the choice of the following probes:
  • Differential pressure probes
  • Absolute pressure probes
  • Relative pressure probes
  • Temperature probes (e.g. surface probes or immersion and penetration probes)

The practical features of the testo 521-3 differential pressure measuring instrument

The integrated differential pressure sensor enables the testo 521-3 measuring instrument to calculate flow velocity and volume flow using a Pitot tube (which can be ordered separately). The differential pressure measuring instrument also offers timed and multi-point mean calculation.
The optional ComSoft software enables you to save the measurement data so that it is linked to the measuring location and analyze it on the PC. You can use the optional testo fast printer to print out measurement data directly at the measuring location.
You can choose between the following units for pressure measurement: mbar, hPa, bar, Pa, kPa, inH2O, mmH2O, torr and psi. The mean value, the last measured value and the min./max. values can be displayed at the press of a button.

Delivery Scope

testo 521-3 differential pressure measuring instrument, including calibration protocol and batteries.

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Technical Data

Temperature - NTC

Measuring range

-40 to +150 °C


±0,2 °C (-10 to +50 °C)*

±0,4 °C (Remaining Range)*


0,1 °C

*Accuracy information applies only to instrument without probes connected

Temperature - TC Type K (NiCr-Ni)

Measuring range

-200 to +1370 °C


±0,4 °C (-100 to +200 °C)*

±1 °C (Remaining Range)*


0,1 °C

*Accuracy information applies only to instrument without probes connected

Differential pressure (internal sensor) - Piezoresistive

Measuring range

0 to 2,5 hPa**


±0,5 Pa (0 to 20 Pa)

±(0,5 Pa ±0,5 % of mv) (20,1 to 250 Pa)


0,1 Pa

Static pressure

1000 hPa


50 hPa


to 0,5 hPa

**Sensor is not suitable for long-term measurements

Differential pressure (external probe) - Piezoresistive

Measuring range

0 to 2000 hPa


±0,1 % of mv*


0,1 Pa (0638 1347)

0,01 hPa (0638 1547)

0,001 hPa (0638 1447)

0,1 hPa (0638 1847 / 0638 1647)

*Accuracy information applies only to instrument without probes connected

Differential pressure (external probe) - Ceramic

Measuring range

-1 to 400 bar


±0,2 % of fsv*


0,01 bar

*Accuracy information applies only to instrument without probes connected

General technical data


219 x 68 x 50 mm

Operating temperature

0 to +50 °C

Product-/housing material



2; 1

Measuring rate

0,04 s


Hose: inner Ø 4 mm outer Ø 6 mm

Battery type

9 V (6LR61)

Battery life

Continuous operation w/ internal pressure sensor: 30 h; With rech. battery: 10 h; With carbon battery: 18 h

Display type

LCD (Liquid Crystal Display)

Display function

7 segment display and point matrix

Display update

2x per second, in fast measurement 4x per second

Power supply

Battery/Rechargeable battery,Mains unit 12 V




100 kB; 25.000 measuring values

Storage temperature

-20 to +70 °C


300 g


Accessories for probes

€ 115,00
sa PDV-om  € 143,75
Connection cable

Order Number: 0430 0143

€ 59,00
sa PDV-om  € 73,75
€ 45,00
sa PDV-om  € 56,25

Additional accessories and Spare parts

9V rech. battery for instrument

Order Number: 0515 0025

€ 111,00
sa PDV-om  € 138,75

Printer and accessories

testo fast printer IRDA

Order Number: 0554 0549

€ 248,00
sa PDV-om  € 310,00
€ 27,00
sa PDV-om  € 33,75

Software and Accessories

RS232 cable

Order Number: 0409 0178

€ 77,00
sa PDV-om  € 96,25

Transport and Protection

TopSafe (protection case)

Order Number: 0516 0446

€ 873,00
sa PDV-om € 1091,25