The ITZ series of transducers from LEM is for galvanically-isolated, ultra-accurate precision DC, AC and pulsed current measurements in industrial and laboratory applications. The high-accuracy product range comprises a series of transducers for nominal current measurements from 600 A to 24 kA, that provide overall accuracies at ambient temperature (25°C) of only a few ppm.
Achieving such extreme accuracy at very high current levels is a challenging problem in measurement technology. LEM used closed-loop Fluxgate technology – which the company has developed extensively in recent years – to address the problem. This provides initial offset error of under 2 ppm; linearity in the range of 1 – 10 ppm; and extremely low thermal drift of 0.1 to 0.6 ppm/K (ppm per degree Kelvin).
The ITZ transducers deliver measurements as an output current or voltage. In addition to these normal signal outputs, the transducers also provide outputs indicating the transducer state. Indications include whether the transducer is operational or not; if the measured current is extremely low or high, or if the transducer is in overload condition – each state being signalled via normally-open or closed contacts and each of these conditions being supported by a dedicated LED. Further operational information regarding the measuring head range that is in use, and about the status of the power supply, is also indicated by an LED.
600 A and 2000 A models are available as programmable units with either current or voltage outputs (from 40 A to 620 A in steps of 20 A for the 600 A model, and from 125 A to 2000 A in steps of 125 A for the 2000 A model). ITZ-series transducers have very low output noise and bandwidth varying from 2 to 500 kHz (+/- 3 dB) according to the model.
The transducers tolerate substantial overload currents (to over 30 kA in the case of the highest-rated unit) for up to 100 msec. They are powered by standard AC mains supplies of 100-240VAC, 50/60 Hz and operate over a temperature range from 0 to +55°C for the measuring heads and from +10 to +40°C for the electronics rack.