Temperature Coefficient of Resistance, or TCR, refers to how the value of a resistor will vary with changes in temperature.  This temperature change can be from changes in the environment around the resistor as well the resistor heating itself as it dissipates power. Growing applications demand resistors with increasely lower TCRs. Resistor manufactures like Microhm Electronics attach great importance to the production of low TCR resistors.


With a typical TCR of 50ppm and a perfect tolerance, the resistance value will shift 0.25% at a temperature rise of only 50℃.   This shift could be on either side depending on whether the TCR is positive or negative.   Another way to think about the situation is that if the design criteria calls for a resistance tolerance of 0.1% then to remain within the design limits you should specify a 10ppm or better TCR.

An example of an application where this may be important is the measurement of mass.  This is typically accomplished using a scale.  Scales may be used to measure the mass of gems, pharmaceuticals, or even larger items like construction equipment or bricks.  Whether the scale is in a laboratory or located on a shop floor it is important that the instrument be accurate and consistent regardless of the environmental temperature.  Most scales operate use the principal of a Wheatstone bridge.
Based on our knowledge of how TCR effects resistance value it is clear that a low TCR solution would be advantageous in these applications.  Microhm offers a number of solutions to meet the most stringent requirements, including KSW series, PWS/PWP series and EE series.