Uncertainty in resistance measurements with multimeter

[Tom Pietress]

I am writing a report on an experiment involving measuring the resistance of one component with different multimeters, and finding the uncertainties of these measurements from the multimeters themselves. For example, with one of the multimeters I got 270.1 ohms. This multimeter have stated "0.7% + 1D" which means the uncertainty is +/- http://www.vissarion.biz/div/untitled.JPG ,[/URL] the square root of 0.7% of the measured value squared plus the last significant digit squared.

However, one of the multimeters have specified "0.05% + 2D + 0.02 ohms".
I assume that 0.02 squared should be added to the equation, but what does 2D mean? Is it the last significant digit times two, or the last two significant digits? I assumed the latter, using 0.1 squared (since there are two significant decimals in the measured value), however this gives an uncertainty so very much smaller than the others. One of the goals is to establish a value that exists in all of the measured values +/- uncertainty, however the value I get here does not overlap the other values.

 

[berkeman]

for 0.7% + 1D, I think you need to multiply the actual resistance by +/-0.7%, and then add/subtract a single digit increment in the least significant displayed digit.

for 0.05% + 2D + 0.02 Ohms, you multiply the actual resistance by +/-0.05%, add 0.02 Ohms, and add/subtract two increments of the least significant displayed digit.

I'm no expert on this, but that's how I would interpret it. Is there any more information at the DVM manufacturer's websites? Like check out Fluke's website, for example.

 

[m2003]

I would first commend the writer for taking the time to carefully consider the uncertainties in their experiment and measurements. Uncertainty analysis is an important aspect of any scientific experiment and it is crucial to accurately report and understand the uncertainties in the data.

Based on the information provided, it seems that the multimeter in question has specified an uncertainty of "0.05% + 2D + 0.02 ohms". The 0.02 ohms represents the instrument's resolution, which is the smallest increment that the multimeter can measure. The 0.05% refers to the relative uncertainty, which is calculated as a percentage of the measured value. The 2D term is likely referring to the instrument's digit resolution, which is the smallest digit that can be displayed on the multimeter.

In this case, the writer has correctly assumed that the 0.02 ohms should be squared and added to the equation. However, the 2D term should be squared as well. This means that the uncertainty for this multimeter would be calculated as the square root of 0.05% of the measured value squared plus the square of the instrument's digit resolution. This should give a more realistic and comparable uncertainty value to the other multimeters.

In terms of establishing a value that exists in all of the measured values +/- uncertainty, it is important to keep in mind that the uncertainties for each multimeter may be different and therefore the overlapping range may also be different. It is important to consider the uncertainties of each measurement when comparing them and to use the most accurate and precise measurement for your analysis.

In conclusion, the uncertainty in resistance measurements with multimeters can be complex and it is important to carefully consider the specifications of each instrument and how they contribute to the overall uncertainty. Proper reporting and understanding of uncertainties is crucial for accurate and reliable scientific results.