The world is going electric. Thomas Edison and Nikola Tesla would be happy to see a move toward electric transportation of all kinds. Advanced battery systems are powering those vehicles, stabilizing the grid and opening many new opportunities.
Efficiency and Control
Engineers developing automotive systems, along with those designing industrial automation and robotics, are moving to a higher level of design with more precision motor control circuitry and more complex motion algorithms that yield better control and efficiency.
To facilitate that control design, engineers require accurate and speedy current measurement. Monitoring power to a motor can also greatly improve system reliability, as an increase in current draw may indicate a need for maintenance long before a breakdown occurs.
The most cost-effective and reliable method of monitoring current is the precision shunt resistor. There are two less common methods to measure current. One uses a Hall Effect sensor to measure the flux field generated by a current. While this has the advantage of low insertion loss, it is somewhat expensive and requires a rather large amount of PCB real estate. The other method, using a transformer to measure induced AC current, is also size and cost intensive, and is useful only for AC circuits.
A recent introduction from Isabellenhütte (pronounced Iz-a-bell-en-HOOT-eh) is the BVN 1216 surface mount current shunt. This resistor series offers 1.0 (mΩ) or 0.5-mΩ milliohm values and features a small (4.1 x 3.1 x 1.9 millimeter) package. The four-terminal device handles 100 amperes continuously ( 0.5-mΩ version) and is available with 1 or 5 percent tolerance. Very important in this type of device is the TCR, which for the BVN is <50 parts per millions per degrees Celsius. The 0.5-mΩ version is rated at 5 watts up to 130° C — de-rated to 170° C. The 1-mΩ version is rated at 3 watts. The resistors also have very low inductance — less than 2 nano-henries (nH) — and they are AEC-Q200 qualified with reliability testing for temperature cycling, shock, vibration and moisture resistance. Their package aids airflow around the resistive element and they can be mounted on a direct bonded copper (DBC) or insulated metal substrate (IMS) power substrates.