Special devices

The PR 2224 is a front-programmable valve controller designed for single-coil or double-coil hydraulic and pneumatic proportional valves. It accepts current (0-20/4-20 mA), voltage (0-10 V/±10 V), and potentiometer/joystick inputs, and provides a PWM (pulse-width modulated) output with programmable chopper frequency from 8 to 400 Hz. The output can deliver up to 3,000 mA mean current with 7 A peak. Features include programmable ramp times (0-10 seconds), jump values for valve breakaway, reversal control, and adjustable deadband (0-99.9%), making it suitable for precise proportional valve control in mobile hydraulics and industrial automation.

The PR 2261 converts low-level millivolt signals from load cells and strain gauge bridges into standard current or voltage outputs (4-20 mA or 0-10 V). It features a 3-digit LED display showing the measured value as a percentage, and is front-programmable with three pushbuttons. The device provides excitation voltage for the load cell bridge and includes auto-zero and tare functions. Typical applications include weighing systems, force measurement, torque monitoring, and other strain gauge-based measurements where the millivolt-level bridge output must be conditioned for transmission to a PLC or DCS.

The PR 5223A converts frequency/pulse inputs to analog current/voltage outputs with concurrent PNP/NPN transistor output and optional relay outputs. The PR 5225A adds concurrent frequency-to-current and frequency-to-frequency conversion capability, making it suitable for applications requiring simultaneous analog and pulse outputs from a single frequency source. Both devices accept NAMUR, NPN, PNP, TTL, Tacho, and S0 inputs. Universal AC/DC supply is standard. Applications include flow totalization, speed monitoring, production counting, and interfacing between pulse-based instruments and analog control systems.

The PR 5343A and 5343B are 2-wire loop-powered level transmitters that convert potentiometer or ohmic resistance inputs to a 4-20 mA output signal. They feature a unique process calibration function that allows zero and span to be set by physically positioning the sensor at the minimum and maximum levels, rather than entering numerical values. This greatly simplifies commissioning of level measurement systems using resistive float sensors or potentiometric level probes. The 2-wire loop-powered design requires only two wires back to the control system.

The PR 3405 is a slimline 6.1 mm DIN-rail device that distributes supply voltage from terminal connections to the DIN rail power bus, powering up to 100 slimline 3000-series devices from a single set of supply terminals. Instead of wiring power individually to each 6.1 mm isolator or converter, the 3405 feeds power through the DIN rail, dramatically reducing wiring time and terminal count in high-density installations. One PR 3405 can supply approximately 163 slimline units on a meter of DIN rail.

The PR 2224 uses a pulsating (dithering) current output — the PWM chopper frequency is programmable from 8 to 400 Hz in 1 Hz steps. This superimposed oscillation keeps the valve spool in constant micro-motion, preventing it from settling and sticking due to silt, contamination, or static friction (stiction) in the valve bore. The dither amplitude is inherent in the PWM waveform and does not affect the mean valve position. This is a critical feature for proportional valve applications in hydraulic systems where valves may remain at a fixed position for extended periods.

The PR 2224 features programmable ramp times from 0 to 10.0 seconds for both opening and closing. The ramp function limits the rate of change of the valve output, providing linear soft acceleration and deceleration for hydraulic and pneumatic actuators. Additionally, a jump value can be set to overcome the valve's initial breakaway force — the output jumps to a minimum current level before the ramp begins, ensuring the valve starts moving immediately rather than stalling at low drive levels. Reversal control manages the transition between opening and closing directions.

The PR 2224 valve controller features password-protected parameters to prevent unauthorized changes to critical settings such as ramp times, deadband, chopper frequency, and input/output configuration. The password must be entered via the front pushbuttons before any parameter can be modified. This prevents accidental or intentional misconfiguration in the field, which is particularly important for valve control applications where incorrect settings could cause equipment damage, process upsets, or safety hazards.