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Basic Techniques for Accurate Resistance Measurement

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CLEVELAND - eTradeWire -- Reduce Measurement Errors in your Application

CAS DataLoggers receives calls about resistance measurement applications, offering various techniques for accurate results. Callers can resolve odd readings by understanding the different measurement ranges. This white paper covers improving accuracy.

Use the Right Measurement Technique For Your Range

Resistance measurements are represented in ohms (Ω). 1 ohm is the resistance between 2 points with a 1V potential difference producing a 1A current, without any internal voltage. Resistance varies widely in electronics. Different ranges require different measurement techniques.

Ohm's Law

Ohm's Law states that the ratio of potential difference to current in a conductor is constant, as long as temperature remains constant. The basic equation is I = V/R.

Low Resistance Measurement

When measuring small resistances, a common technique is to force a known current and then measure the voltage across the Device Under Test (DUT–see Figure 1 below). This is by Ohm's Law since you're using the current and voltage to determine the resistance. Let's assume you have a precision current source (for example 2 milliamps or 200 microamps), and you've got a highly accurate voltmeter.

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For low resistance measurements, try 3-wire measurement as an alternative to 4-wire. Measure voltage across the resistor and test the current conductor, then adjust for error. Many data loggers, including dataTaker and Grant Squirrel, can perform 3-wire measurements.

High Resistance Measurement

Specialized devices or materials can have high resistances, requiring a different measurement technique. One approach is to force a voltage and measure the current to calculate the resistance, using precision instruments.

Intermediate Resistance Measurements

Intermediate resistance measurement typically falls between a few hundred ohms and 100,000 ohms. The technique used depends on the measuring device. Errors are less common in this range, and lower-cost loggers may use a voltage source while more expensive devices use a current source and voltmeter.

Summary

To obtain accurate resistance readings, it's important to use the appropriate techniques based on the resistance range. For values below 10,000 ohms, the low resistance techniques can be used, while for values above 100,000 ohms, the force voltage technique is recommended. This will ensure higher accuracy in measurements.

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For more information on resistance measurement or resistance data loggers, or to find the ideal solution for your application-specific needs, contact a CAS Data Logger Applications Specialist at (800) 956-4437 or visit us at https://www.dataloggerinc.com.

Contact
CAS DataLoggers
Elizabethe Zala
***@dataloggerinc.com


Source: CAS DataLoggers
Filed Under: Industrial

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