VPG Releases New Ultra-High-Precision Current Sensing Resistors With Low TCR to ±0.05 ppm/°C, Tolerances to ±0.01%, and High Power Ratings to 7 W

Vishay Precision Group, Inc. (NYSE: VPG) today announced that its Vishay Foil Resistors division has released two new ultra-high-precision Bulk Metal® Foil power current sensing resistors with very low TCR of ±0.05 ppm/°C from 0°C to +60°C and ±0.2 ppm/°C from -55°C to +125°C, +25°C ref., and resistance tolerance to ±0.01. For high-power applications, the VPR5Z offers a power rating of 5 W at +25ºC, while the VPR7Z offers a power rating of 7 W and load life stability of ±0.01% at 70 °C for 2,000 hours at rated power.

The VPR5Z and VPR7Z feature a wide resistance range from 5 Ω to 100 kΩ. Vishay Foil resistors are not restricted to standard values, and specific as required values (e.g. 1001.23 Ω vs. 1.0 kΩ) can be supplied at no extra cost or delivery time. The resistors feature a rise time of 1 ns, with effectively no ringing, thermal EMF of 0.05 μV/°C typical, a thermal stabilization time of < 1s (nominal value achieved within 10 ppm of steady state value), current noise of <- 40 dB, and a voltage coefficient of <0.1 ppm/V. Offering the utmost in ESD immunity, the devices withstand electrostatic discharges up to at least 25 kV for increased reliability, and offer a non-inductive (< 0.08 μH), non-capacitive design.

Typical end products for the resistors will include battery chargers, current regulators, dc-to-dc converters, diagnostic equipment, electronic scales, motor controls, motor drivers, over current protection, pressure sensors, PWM input circuits, remote monitoring, satellite receivers, and voltage regulators in military/aerospace and surveillance applications.

The Bulk Metal Z-Foil power current sensing resistors released today are designed to be direct replacements for certain wirewound devices. This Bulk Metal Foil resistor has the bulk alloy metallurgical characteristics of wire but is formed into an unstressed flat planar resistive path instead of being subjected to the internal stresses of wire wound around a bobbin. Bulk Metal Foil resistors thus have much greater stability through thermal cycling and better load life characteristics than wirewound resistors.

Both the VPR5Z and the VPR7Z have four-terminal construction for tapping precision voltages from the resistors. Each resistor has heavy fixed leads to carry current through the resistor and flexible wire leads for tapping the precision voltage directly from the resistor element, thereby isolating the measured voltage from the voltage drop errors in the current leads.

Unlike evaporated or sputtered thin metal films, the Bulk Metal resistor element undergoes no change of state from its bulk metal alloy state and, consequently, has none of the stability-limiting re-formation defects present in thin film resistors. In comparison to thick film or thin film devices, Bulk Metal Foil resistors require a minimal allowance for errors — and even devices purchased at a relatively loose tolerance still exhibit a tighter cumulative end-of-life total offset from nominal resistance than any other resistor technology.

Samples and production quantities of the new current sensing resistors are available now, with lead times of five days for samples, and eight weeks for standard orders.