Frequency Converter

Frequency converters are useful  for protecting rotating machinery by monitoring critical speed, over speed, and under speed. Commonly used with synchronous motors that turn or vibrate, the 4225 frequency converter can also match new speed sensors to original units and control process temperature, pressure, or flow without the use of a separate controller.

Speed Monitoring for Rotary Machinery

The 4225 frequency converter can be used to verify other tachometers and offers an independent alarm for critical, over, and under speed. Reliable speed monitoring improves processes by ensuring accurate performance while decreasing equipment wear and downtime. Additionally, the 4225 can transmit speed to an HMI control or PLC unit for data logging and more.

Speed Monitoring with a Frequency Converter

  • independent speed measuring with alarm to monitor critical equipment
  • verification of critical functions to ensure accurate measurement
  • frequency converters are a great alternative to other tachometers e.g. a variable frequency device (VFD), rotation speed monitor,  or frequency transmitter such as S1SD-1FI-1R, MCR-2-F-UI-2902056, Jumpflex 857-500, KFD2-UFC-1.D, and more
Frequency Converters Can Monitor and Verify Speed
Monitor Critical Speed, Under Speed, Over Speed

Synchronization and Modernization

Synchronize Industrial Processes for Efficiency
Frequency Converters are Critical for Gas Plant Modernization

Frequency converters measure the rotation of rotary machinery such as a generator, compressor, or gas turbine then generates a frequency that can be used to control pumps, fans, etc. By directly controlling equipment with the speed of rotation, systems can be synchronized thus increasing safety, reducing operating costs, and minimizing wear on equipment.

Rotary Machinery Frequency Conversion

  • gas turbines
  • power generation, wind turbines, cooling towers
  • aviation and marine
  • compressors, refrigeration, and HVAC
  • heat pump loop systems
  • manufacturing facility, gas and chemical plant modernization

Safety and Redundancy

To maintain a safe working environment and improve safety ratings, the 4225 universal f-l/f-f frequency converter can be used to measure equipment speed in addition to the existing tachometers that monitor critical functions. Having redundant speed monitoring increases the reliability of the system by providing a backup source for process data if the primary tachometer fails and ensures accurate measurement of rotation speed.

Redundant Speed Measuring Tachometer to Improve Safety

  • ultrasonic, photoelectric, and rotary frequency converters
  • variable frequency devices (VFD)
  • frequency transmitters
  • rotation speed monitors
Redundant Rotation Measuring Improves Safety
Wind Turbine for Renewable Power Generation
  • response time: <30 ms
  • six output relay settings including windows, setpoint, and latch functionality
  • universal power supply: 21.6…253 VAC / 19.2…300 VDC
  • display option with bluetooth communication
  • multifunctional, cost effective, compact design
  • measures NPN, PNP, Contact, NAMUR, S0, Tacho, and TTL sensors
  • programmable frequency input span of 0.001 Hz to 50 kHz
  • 5725D has two SPDT relays and one analog output
  • easy to read 4-digit, 14-segment LED display with scrolling help text
  • universally powered by 21.6…253 VAC or 19.2… 300 VDC

Real Time Process Data

  • Modbus RTU slave – RS485 interface
  • 2.5 kVAC galvanic isolation on the Modbus port
  • read and write configuration, calibration, process values, simulation
  • PR Preset Software (PPS) app (free download for iOS and Android)
  • easy programming
  • live process and error monitoring
  • data and event logging (30 days / 1 sec) with read-out
  • data retention and real-time clock backup
  • data analysis in your preferred program via .csv file data export

Universal f-l/f-f Frequency Converter

  • measures frequencies up to 100 kHz
  • 2.3 kVAC, 3-port galvanic isolation
  • custom U/I trigger levels
  • advanced input limits for increased safety
  • fast response time, <30ms
  • universal power supply
  • low power dissipation
  • bluetooth, data logging, modbus
  • NAMUR sensor error detection
  • low cut-off function (L.COF) enabled
  • all terminals over-voltage protected (24 VDC), polarity protected and short-circuit protected

Secure and Easy Programming

  • real time Modbus or Bluetooth communication for configuration, monitoring, and diagnostics
  • all programming can be password protected
  • 2-point process calibration
  • programmable trigger levels -0.05…6.5 V
  • programmable sensor supply 5…17 V
  • simulation of process value during commissioning and maintenance
  • linearization: linear or square root function

How A Frequency Converter Works

Frequency converters allow various instrumentation to communicate together by converting an AC frequency to a DC frequency. Through the use of a frequency converter, AC outputs from equipment like an engine can directly be used to signal operating conditions for other instrumentation, such as a fan that requires a DC frequency input. 

Converting Frequencies for Synchronization

Since many types of instrumentation require a DC input, frequency converters are commonly used in industrial processes, manufacturing, and power utilities to allow equipment to work as an integrated system.

AC Frequency Converter to DC

Sophisticated Frequency Changer

Signal Conditioning Frequency Changer
  • accuracy: <0.06% / span
  • temperature coefficient: 0.006%/°C
  • low power consumption 2.5 W
  • mounted side by side, horizontally, or vertically, without air gap, on DIN rail up to 140˚F
  • excellent signal/noise ratio (> 60 dB), 18-bit output converter
  • NAMUR NE21 and NE43, UK CA, UL-508 approvals

PR Electronics 4000 Series Product Line

Complements the 4000 series multifunctional product range with a highly flexible and universal frequency converter. Based on the strong foundation of the PR 4000 series products with the well-known and unique features such as front display programming, simulation, universal power supply and the PR 4500 series communication interfaces.

Multiple Configurations for Any Need

Common input with programmable trigger levels and sensor supply 4225A:
  • 4225A: 1 analog output and 1 relay
  • 4225B: 2 relays
  • 4225C: 1 analog output and 1 frequency output
AC Frequency Changer to DC

Input / Output and Specifications

Universal Power Supply for Frequency Converter 4225


  • input: NAMUR, NPN, PNP, Tacho, TTL, & S0
  • dual output with programmable bipolar mA / V frequency or relay
  • active/passive current output: ±23 mA / 0…23 mA
  • buffered voltage output: ±10 VDC
  • digital output: NPN & PNP; 0…100 kHz with programmable logic level 5…24 V

CProgram directly via the push-buttons and the unique PR Electronics menu structure.

The 4511 introduces Modbus RTU communication to your PR 4000/9000 device, an easy and cost-effective digital interface. With 4512 you can program your PR 4000/9000 devices or activate datalogging via Bluetooth, using an iOS/Android device running the free PR electronics PPS app.

(Video) Navigating Through Display of 4500 Communication Interfaces

Get attached to better asset management with detachable operator interfaces. Access your devices through detachable local operator interfaces, remote operator interfaces, and gateways. Our approach to asset management offers inexpensive future-proofing of your installed base to new communication protocols.

  • programming display for 4225 frequency converter and other 4000 and 9000 devices
  • Modbus RTU protocol interface over RS-485
  • display for system 4000 and 9000 devices
  • iOS & Android compatible Bluetooth version 4.2/4.1/4.0
  • mounting in Zone 2 / Div. 2

Get 50% off a 4512 bluetooth communicator

For a limited time only, we are offering half off a bluetooth communicator with the purchase of your first 4225 frequency converter