Powerful current measurement in the smallest of spaces

As small as possible, as light as possible: the miniaturization trend in electronic components continues unabated. In the automotive sector, in drive technology and in power electronics, the smallest electronic components that also offer high performance are in demand. Isabellenhütte specializes in low-ohm precision resistors that achieve very accurate measurement results in the smallest of spaces. With its latest WAx resistor family, which it will be presenting at the PCIM from 11 to 13 June in Nuremberg, resistance values of just 1 and 0.5 mOhm are possible in small sizes.

With the latest WAx resistor series, Isabellenhütte is closing a gap in its portfolio for very low resistance values in small sizes. In relation to their small size, the resistors in the WAx series measure relatively high currents and therefore offer a very good cost-benefit ratio. Resistance values from 2 mOhm were already possible with the last FMx series. With the new WAK (size 1206) and WAF (size 1213) resistors, Isabellenhütte can also offer resistance values of 1 and 0.5 mOhm. The WAF with a resistance value of 0.75 mOhm is also currently under development.

New roll cladding process

These low-resistance values in the smallest sizes are made possible by the production process of roll cladding, which Isabellenhütte has used here for the first time. In this process, a copper strip and a strip made from one of the company’s own resistance alloys, Manganin® or Zeranin®, are rolled together to form a mechanically very stable duo strip. The final component geometry is then punched out of the duo strip – the WAF is very small, measuring just 3.1 x 3.3 mm; the WAK is only half the size. Thanks to the resistor alloys used, the WAx resistors benefit from high long-term stability, a very good temperature coefficient and a high load capacity with low inductance (< 0.5 nH). All components are AEC-Q200 qualified and are also supplied in these small sizes with an initial tolerance of ±1 %; i.e. each component produced is individually trimmed at Isabellenhütte. In order to optimize the technical properties of the components, we recommend using the layout shown in the data sheet.

Small installation space and high-performance requirements

The WAx resistors are already in series production and are suitable for a wide range of applications. Example applications with limited space, where a low weight of all components is also required, are drives for e-bikes or e-scooters and drones, for example for land surveying, as well as BLDC motors, e.g. in white goods applications. 

WAK and WAF at a glance:

Size 1206Size 1213
Continuous current up to 90 A (0,5 mOhm)Continuous current up to 55 A (1 mOhm)
Rated power P70 °C: 6 WRated power P70 °C : 7 W
Two-terminal version
Excellent long-term stability (< 0,5 % after 2.000 hours at 110 °C)
Operating temperature from -65 to +175 °C
Very low inductance < 0.5 nH
Successful AEC-Q200 qualification
For high and medium power requirements