D521.02 / D521.04 / D521.10 / D521.12 / D521.14 Tachometer, Speed Monitor.

Series D521

Single Channel Speed Monitor D521 for increased safety requirements up to SIL1

The BRAUN Single Channel Speed Monitor Series D521.xx monitors motors, pumps, feeders, gears, rollers, and small turbines. It provides protection against overspeed at any required value of rotational speed, including standstill.
The universally designed signal input fits perfectly with BRAUN A5S… sensors or equivalent. However, it can also be used with NAMUR-type sensors, tacho generators, incremental encoders, or magnet-inductive sensors (MPUs).

With single-channel processing (1oo1) safety provision is solely determined by the device configuration. Therefore the use of sensor monitoring with integrated plausibility control is essential. In such a case no redundancy is provided. Should a fault be detected, the entire system will be shut down immediately.
With two-channel systems, there is a choice of implementation, dependent upon requirements. In principle, the two monitors operate in parallel yet independently. Alarm indication can be realized through the linkage of their Alarm Outputs.

For 1oo2 processing, we have system redundancy with enhanced safety through comparative diagnosis. In the case of fault detection, the entire system will be shut down. With 2oo2 processing, we still have system redundancy but with enhanced availability. Only if both monitors fail, the system as a whole will be shut down.
The D521 Speed Monitor permanently monitors the speed sensors for their correct function. During its complete lifetime cycle, the Monitor does not require any external proof tests and is completely maintenance-free.

Key Features

  • Single Channel Monitor with sensor monitoring and self-test function
  • Frequency range 0 Hz…50 kHz
  • Universal Signal Input, also for Magnetic Pick-Up sensors (MPUs)
  • 1 Analog Output 0/4…20 mA or 0/2…10 V (for versions D521.10, D521.12, D521.14)
  • Bright red digital LED display
  • 2 Alarm Outputs as SPDT relays (for versions D521.02, D521.04, D521.12, D521.14)
  • 2 Alarm Outputs as PhotoMOS relays (for versions D521.04, D521.14)
  • Square wave Pulse Output
  • USB 2.0 Data Interface
  • Two Monitors, suitably configured with their Alarm Outputs linked together, may provide a protection system with 1oo2 or 2oo2 redundancy
  • Universal Power Supply range 20…265 Vuc


  • Fast, precise, and safe
  • Maintenance-free during the lifetime, therefore minimized TCO
  • Universal range of application, throughout mechanical and electrical engineering, in the chemical industry, in power plants, and at test stands
  • Increased safety with 1oo2 architecture
  • Maximum availability with 2oo2 architecture

Product Brochures

Title Language File type
D521 Product Brochure English PDF

Technical Manuals

Title Language File type
D521 Manual English PDF
D521 Manual PDF

Product Certificates & Declarations of Conformity

Document type Language Scope File type
EU Declaration of Conformity English German European Union PDF
UK Declaration of Conformity English German United Kingdom PDF