4–20 mA transducers
Transducers convert a measured quantity into a standard signal such as 4–20 mA, 0–20 mA or 0–10 V. CELSA offers power transducers for connection to current transformers with 1 A or 5 A secondary current and the DTVU20 isolating amplifier as a signal converter for standard signals.
Transducers on the current transformer
Pw-MU, Pnz-MU, Pz-MU, Pd-MU and Pdr-MU convert active power in single- and three-phase networks into an impressed DC current and DC voltage signal. The current input is designed for the secondary current of a current transformer, 1 A or 5 A. Outputs depending on version: 4–20 mA with 2–10 V, 0–20 mA with 0–10 V, or 0–10 mA.
Input and output are galvanically isolated by optocouplers; both outputs are open- and short-circuit-proof. Class 0.5, snap-on mounting on DIN rails (DIN EN 50022-35) or fixing with two M4 screws. An auxiliary supply is required for live zero (4–20 mA) or if the rated voltage fluctuates by more than ± 20 %: 24 V DC, 230 V AC or 36–265 V AC/DC.
4–20 mA signal converter: DTVU20 isolating amplifier
The DTVU20 universal isolating amplifier converts and isolates standard signals: input 0–10 V, 0–20 mA or 4–20 mA selected by a front rotary switch, output 0–10 V, 2–10 V, 0–20 mA or 4–20 mA via terminal assignment. Three-way isolation between input, supply and output (isolation voltage 2 kV), wide-range power supply built in.
Measuring direct current
Direct currents are measured via a shunt resistor, which delivers a fixed voltage drop at rated current, for example 60 mV. The digital panel meters with shunt input M2.96-145 SR4 and M3.96.2-145 SR4 display the current and are optionally available with an analogue output.
Frequently asked questions
What is a 4–20 mA transducer?
A device that converts a measured quantity – at CELSA, active power from current and voltage, or a standard signal – into an impressed current of 4 to 20 mA that controllers and control systems process directly.
Why 4–20 mA instead of 0–20 mA?
With live zero, a reading of zero corresponds to 4 mA. If the signal drops to 0 mA, a broken wire is detectable. Current signals are also insensitive to voltage drops on long lines.
Are there current transformers with a 4–20 mA output?
A current transformer supplies 1 A, 5 A or 333 mV. The 4–20 mA signal is generated in the downstream transducer or in the analogue output of a digital meter such as the M2.96-145 AC4EL for alternating current.