VCS101, VCS103, VCS401 High Precision Bulk Metal Foil Power Current Sensing Resistors with 3 A and 15 A Maximum Current, TCR to 15 ppm/C from 0.005 FEATURES Temperature coefficient of resistance (TCR): 20 ppm/C (available to 15 ppm/C) Resistance tolerance: to 0.1 % Resistance range: 0.005 to 0.25 (for higher or lower values please contact us) INTRODUCTION Power rating: to 1.5 W at + 25 C (free air) Model VCS101, VCS103 and VCS401 resistors are available in 2 configurations. This Bulk Metal resistor can serve as a low ohm, Maximum current: to 15 A high power resistive shunt or as a medium power current sensing Maximum operating temperature: + 175 C resistor. Resistors are non-insulated. The art of current sensing calls for a variety of solutions based on Load life stability: 0.5 % at 25 C, 2000 h at rated power application requirements. Current sensing is best achieved with a Vishay Foil Resistors are not restricted to standard values Kelvin connection, which removes the unwanted influences of lead specific as required values can be supplied at no extra cost or resistance and lead sensitivity to temperature. Other requirements delivery (e.g. 0R123 vs. 0R1) such as high stability and short thermal stabilization time when the power changes may dictate a special resistor design. Non-inductive, non-capacitive design High-precision resistors used for current sensing are usually low 4 leads for Kelvin connection ohmic value devices suitable for four terminal connections. Two terminals, called current terminals, are connected to conduct Rise time: 1.0 ns effectively no ringing electrical current through the resistor, while voltage drop VS is Thermal EMF: 0.05 V/C typical measured on the other two terminals, called sense or voltage drop terminals. According to Ohms law, the sensed voltage drop Voltage coefficient: < 0.1 ppm/V VS divided by the known resistance RS gives the sensed current Non-inductive: 0.08 H IS. The accuracy of measurement depends on the stability of ohmic resistance RS between the nodes, i.e. the points of connection of Terminal finish: lead (Pb)-free or tin/lead alloy* the sense leads. Since the voltage leads feed into an infinite Prototype quantities available in just 5 working days or sooner. resistance circuit, there is no current flowing through the voltage For more information, please contact foil vpgsensors.com terminals and, therefore, no IR drop in the voltage sense leads. Thus, the four-terminal system eliminates the voltage drop errors For better performances, see VCS201, VCS202 and VCS301, originated in the leads when the voltage terminations are VCS302 datasheets or contact application engineering connected close to the resistance element (excluding significant portions of the leads that carry the current). Real life resistors exhibit two types of reversible changes: This arrangement, called a Kelvin connection, reduces, especially 1. When they are cooled or heated by a changing ambient temperature, and for low ohmic resistance values, a measurement error due to the resistance of the lead wires and the solder joints as the sensing is 2. By self-heating due to the power they have to dissipate (Joule performed inside the resistor, in or close to the active resistive bulk effect). metal foil element. Of the commonly used methods of measuring the When a high precision is required, these two effects induce a change magnitude of electrical current, this current sensing resistor method in the resistive element s temperature, T due to ambient and T a sh provides the most precise measurement. According to Ohms law, due to self heating, both of which must be considered. V = IR, the voltage drop measured across a resistor is proportional to The ambient temperature changes slowly, and all parts of a resistor the current flowing through the resistor. With the known and stable follow uniformly the change of the ambient temperature, but the effect value of the resistance R, the voltage drop sensed on the resistor of the dissipated power is different. The temperature of the resistive indicates the intensity of the current flowing through it. element - the active part of the resistor - will change rapidly with the Assuming an ideal current sense resistor that doesnt change change of the intensity of current. The power it has to dissipate will its resistance value when there is a change in the magnitude change proportionally to the square of the current and a rapid increase of the current or a change in environmental conditions, like in current will cause a sudden increase in the temperature of the the ambient temperature or self heating, the measured voltage resistive element and in the heat that must be dissipated to the drop will yield a precise value of the current: I = V/R. But with ambient air. These two effects of resistance changes are quantified by a real-life resistor, such as a metal film resistor or a manganin TCR - Temperature Coefficient of Resistance and by PCR - Power bar, a change in current intensity (and in the dissipated power) Coefficient of Resistance (called also Power TCR). will cause a change in the resistor s value which will involve a Our applications engineering department is prepared to advise thermal transient period taking a few seconds or longer to and to make recommendations. For non-standard technical stabilize. Therefore, the key to a fast and precise measurement requirements and special applications, please contact us. of current is the use of a real life current sensing resistor which approaches, as closely as possible, an ideal resistor. That is, a resistor that is not influenced by changes in the magnitude of the current flowing through it nor by changes in ambient temperature or any other environmental condition. * Pb containing terminations are not RoHS compliant, exemptions may apply Document Number: 63016 For any questions, contact www.vishayfoilresistors.com Revision: 2-Mar-15 foil vpgsensors.com 1VCS101, VCS103, VCS401 FIGURE 1 - DIMENSIONS AND SCHEMATIC Model VCS101 Current Sensor Model VCS401 Current Shunt 0.520 0.020 W W H I I 1 2 R I I 0.500 Min. Leads 0.032 Diameter H I E E I 1 1 2 2 Solder Coated Copper V ( 20 AWG) Leads (1) Leads 0.520 0.020 0.040 x 0.005 0.500 Min. 0.040 x 0.005 E E Tin Plated Copper 1 2 Tin Plated 0.200 0.030 Model VCS103 Current Sensor Copper W 0.920 0.020 0.040 Diameter Lead H Solder Coated Copper ( 18 AWG) I E E I 1 1 2 2 0.630 0.500 Min. 0.032 Diameter Lead Solder Coated Copper ( 20 AWG) 0.689 0.020 0.200 0.030 1.083 0.020 (1) TABLE 1 - CHARACTERISTICS AND DIMENSIONS RESISTANCE TIGHTEST DIMENSIONS MODEL POWER RATING MAXIMUM RANGE RESISTANCE NUMBER at + 25 C CURRENT INCHES (mm) () TOLERANCE (%) H 0.130 (3.30) VCS101 1 W 15 A 0.005 to 0.01 1 W 0.080 (2.03) 0.01 to 0.05 0.5 H 0.130 (3.30) 0.05 to 0.2 0.1 VCS401 1 W 3 A W 0.080 (2.03) 0.005 to 0.01 1 H 0.190 (4.83) VCS103 0.01 to 0.05 0.5 1.5 W 15 A W 0.080 (2.03) 0.05 to 0.25 0.1 Note (1) Tighter performances are available, please contact our application engineering department (1)(2) TABLE 2 - VCS101, VCS103 AND VCS401 PERFORMANCE - MIL-PRF-49465 VCS101, VCS103 AND VCS401 TEST OR CONDITION TYPICAL LIMITS MAXIMUM LIMITS Maximum Ambient Temperature at Rated Power + 25 C Maximum Ambient Temperature at Zero Power + 175 C Temperature Coefficient See table 3 Thermal Shock, 5 x (- 65 C to + 125 C) 0.02 % 0.05 % Short Time Overload, 5 x P 5 s 0.05 % 0.5 % nom Terminal Strength 0.05 % 0.1 % High Temperature Exposure, 2000 h at + 175 C 0.05 % 1.0 % Moisture Resistance 0.05 % 0.1 % Low Temperature Storage, 24 h at - 65 C 0.02 % 0.05 % Shock (Specified Pulse) 0.05 % 0.1 % Vibration (High Frequency) 0.05 % 0.1 % Life (Rated Power, + 25 C, 2000 h) 0.5 % 3.0 % Resistance Tolerance 0.1 %, 0.5%, 1 %, 3 %, 5 %, 10 % Note (2) Rs plus additional 0.0005 for measurement error www.vishayfoilresistors.com For any questions, contact Document Number: 63016 2 foil vpgsensors.com Revision: 2-Mar-15