Let’s start with the R5 scale, which can be represented mathematically as follows: In Renard’s system, the interval from 1 to 10 was divided into 5, 10, 20, or 40 steps, which we now refer to as the R5, R10, R20, and R40 scales. In this case, Renard realized that if a product is to be manufactured in a range of sizes, then one way to minimize the number of different sizes that need to be manufactured or kept in stock is to choose them such that they are roughly equally spaced on a logarithmic scale. People like Renard amaze me because I could never see myself conceiving the things they do. Renard was tasked with somehow reducing this number to a more manageable quantity.
Before Renard appeared on the scene to keep their balloons in the air, the army was obliged to maintain 425 different ropes, which was a logistical nightmare. At that time, the French army had a bunch (not the technical term) of hot-air balloons that they used to spy out enemy positions and drop bombs on anyone who criticized French cuisine. In 1877, a French military engineer called Charles Renard was presented with a poser. Now, hold onto your hats because we are about to take a journey back in time. Note: Type this formula into the spreadsheet cell as a continuous entry without carriage returns.Related: The CrowPi2 is Like STEM on Steroids The Excel formula calculates the two nearest standard values and tests them with the desired resistor value to select the closer. Mantissas of the 96-value-per-decade sequence are derived byĮach mantissa is then rounded to three significant digits, which creates small deviations from perfectly spaced values. Also, it will sometimes yield a more accurate design than if "perfect" calculated values are converted to nearest standard 1% values following the completion of all other calculations. This approach avoids a buildup of tolerance errors. When calculating interdependent component values, standard resistor values can be used to calculate subsequent component values. This formula can be copied and replicated to other cells just like any standard Excel cell formula.Ī properly constructed spreadsheet used to calculate standard circuit values can produce more accurate designs.
The formula will calculate the nearest 1%-resistor for the value in cell A1. Type or electronically paste the text below into any cell (other than A1). The Excel cell formula below calculates the nearest standard 1%-resistor value without using a lookup table or macro.