Temperature Coefficient of Resistance (TCR) is an important parameter that measures the degree of change in resistor resistance value with temperature, and is measured in ppm\/\u00b0C (parts per million per degree Celsius). For a precision measurement element such as a shunt, the TCR directly determines the stability of the measurement accuracy in different temperature environments.<\/p>\n
The TCR is calculated by the formula:<\/p>\n
TCR = (R\u2082 - R\u2081) \/ R\u2081 \/ (T\u2082 - T\u2081) \u00d7 10\u2076 ppm\/\u00b0C<\/strong><\/p>\n Where R\u2081, R\u2082 are the resistance values at temperature T\u2081, T\u2082 respectively.<\/p>\n For example, a shunt with a TCR of 50 ppm\/\u00b0C will have a resistance change of 50 \u00d7 50 = 2500 ppm = 0.251 TP3T when the temperature is increased from 25\u00b0C to 75\u00b0C. This change is unacceptable for applications requiring 0.11 TP3T accuracy.<\/p>\n Different alloy materials have different TCR properties:<\/p>\n The TCR can be adjusted by precisely controlling the proportions of the elements in the alloy. e.g. Changes in manganese content in manganese-copper alloys can significantly affect the TCR.<\/p>\n The structural design of the shunt also affects the temperature distribution and TCR performance during actual operation:<\/p>\n In two temperature points (such as 25 \u2103 and 85 \u2103) were measured resistance value, according to the formula to calculate the TCR. method is simple but can not reflect the change rule of TCR with temperature.<\/p>\n Resistance values are measured at multiple temperature points and R-T curves are plotted for a more complete understanding of TCR characteristics. Differences in the TCR of certain materials can be found in different temperature intervals.<\/p>\n In accordance with national standards, TCR tests are usually performed under the following conditions:<\/p>\n Assume an energy storage BMS system:<\/p>\n Maximum temperature change: 60\u00b0C - (-20\u00b0C) = 80\u00b0C If the system requires a total accuracy of 0.51 TP3T, the TCR alone takes up an error budget of 0.41 TP3T, leaving little room for other error sources.<\/p>\n In practice, the shunt itself heats up as a result of the current passing through it, causing the resistive element to be warmer than the ambient temperature. This self-heating effect exacerbates the effects of the TCR.<\/p>\n Under operating conditions such as charge\/discharge switching, the temperature of the shunt changes rapidly, which can lead to dynamic errors in the measured value if the TCR is large.<\/p>\n Inverse TCR requirements based on system accuracy requirements and temperature range:<\/p>\n TCR (max) = allowable error \/ temperature range \u00d7 10\u2076.<\/strong><\/p>\n Example: Allow 0.1% error, temperature range 50\u00b0C Low TCR means higher material costs and manufacturing process requirements. A balance needs to be struck between performance and cost to avoid over-design.<\/p>\n For cost-sensitive applications, a shunt with a slightly higher TCR can be selected and temperature compensated by a software algorithm:<\/p>\n This approach effectively reduces the impact of TCR, but increases system complexity.<\/p>\n BMS current detection requirements for an OEM:<\/p>\n Energy metering requirements for an energy storage plant:<\/p>\n Temperature coefficient is one of the most important performance indicators of shunt, which directly affects the accuracy and stability of current measurement. When selecting a product, it is necessary to consider the temperature range of the application scenario, the accuracy requirements and the cost budget, and choose a product with the appropriate TCR rating. For demanding applications, hardware selection and software compensation strategies can be combined to optimize system costs while meeting performance requirements.<\/p>","protected":false},"excerpt":{"rendered":" In-depth analysis of the technical principle of the temperature coefficient of the shunt, the test method and the impact on the system accuracy, to provide practical selection advice.<\/p>","protected":false},"author":1,"featured_media":771,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-724","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tech-articles"],"yoast_head":"\nII. Factors affecting the TCR<\/h2>\n
2.1 Resistance Alloy Materials<\/h3>\n
\n
\n makings<\/th>\n Typical TCR (ppm\/\u00b0C)<\/th>\n specificities<\/th>\n<\/tr>\n \n pure copper<\/td>\n +3930<\/td>\n Extremely high TCR, not suitable for precision measurements<\/td>\n<\/tr>\n \n Copper (CuNi)<\/td>\n \u00b140<\/td>\n Common materials, moderate cost<\/td>\n<\/tr>\n \n Manganese copper (MnCu)<\/td>\n \u00b120<\/td>\n Excellent low TCR characteristics<\/td>\n<\/tr>\n \n Zeranin\u00ae<\/td>\n \u00b110<\/td>\n High-end precision applications<\/td>\n<\/tr>\n \n Manganin\u00ae<\/td>\n \u00b15<\/td>\n Measurement grade applications<\/td>\n<\/tr>\n<\/table>\n 2.2 Material ratios<\/h3>\n
2.3 Manufacturing processes<\/h3>\n
\n
2.4 Structural design<\/h3>\n
\n
III. Measurement Methods of TCR<\/h2>\n
3.1 Two-point method<\/h3>\n
3.2 Multi-point approach<\/h3>\n
3.3 Standardized test conditions<\/h3>\n
\n
IV. Analysis of the impact of TCR on system accuracy<\/h2>\n
4.1 Example of error calculation<\/h3>\n
\n
\nMaximum resistance change: 50 \u00d7 80 = 4000ppm = 0.4%<\/p>\n4.2 Temperature gradient effects<\/h3>\n
4.3 Dynamic temperature changes<\/h3>\n
V. Low TCR shunt selection strategy<\/h2>\n
5.1 Define accuracy requirements<\/h3>\n
\nTCR (max) = 0.1% \/ 50 \u00d7 10\u2076 = 20ppm\/\u00b0C<\/p>\n5.2 Material selection<\/h3>\n
\n
5.3 Cost considerations<\/h3>\n
5.4 Alternative: software temperature compensation<\/h3>\n
\n
VI. Practical application cases<\/h2>\n
6.1 Electric Vehicle BMS<\/h3>\n
\n
6.2 Metering of energy storage plants<\/h3>\n
\n
VII. Summary<\/h2>\n