Chapter 7 Measurement Tutorial

Errors in High Resistance Measurements

Errors in High Resistance Measurements

When you are measuring large resistances, significant errors can occur due to insulation resistance and surface cleanliness. You should take the necessary precautions to maintain a “clean” high-resistance system. Test leads and fixtures are susceptible to leakage due to moisture absorption in insulating materials and “dirty” surface films. Nylon and PVC are relatively poor insulators (109 ohms) when compared to PTFE Teflon￿ insulators (1013 ohms). Leakage from nylon or PVC insulators can easily contribute a 0.1% error when measuring a 1 MΩ resistance in humid conditions.

DC Current Measurement Errors

When you connect the multimeter in series with a test circuit to measure current, a measurement error is introduced. The error is caused by the multimeter’s series burden voltage. A voltage is developed across the wiring resistance and current shunt resistance of the multimeter as shown below.

Rs

 

 

I

 

Vs

Vb

R

Ideal

Meter

 

 

 

 

 

LO

 

Vs = source voltage

Rs = DUT source resistance

Vb = multimeter burden voltage

R = multimeter current shunt

 

Error ( % ) = −100% x Vb

7

Vs

Teflon is a registered trademark of E.I. duPont deNemours and Co.

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Agilent Technologies 34401A manual Errors in High Resistance Measurements, DC Current Measurement Errors
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34401A specifications

Agilent Technologies 34401A is a highly reputable digital multimeter (DMM), renowned for its accuracy, versatility, and performance in a wide range of measurement applications. First introduced in the early 1990s, the 34401A has become a staple in laboratories, manufacturing environments, and educational institutions due to its robust build and comprehensive features.

One of the standout characteristics of the 34401A is its impressive accuracy, boasting a basic DC voltage accuracy of 0.0035%, making it ideal for precise measurements in electronic testing. The multimeter offers a wide range of measurement capabilities, including voltage (DC and AC), current (DC and AC), resistance, frequency, and continuity test, making it a highly versatile tool for engineers and technicians.

The 34401A utilizes a 6½-digit resolution, enabling the user to measure small changes in electrical signals with remarkable precision. With a sampling rate of up to 1000 readings per second, it can handle dynamic test requirements, providing timely results without sacrificing measurement integrity.

In terms of connectivity, the Agilent 34401A includes a GPIB (General Purpose Interface Bus) for remote operation, allowing users to automate their testing processes and integrate the multimeter easily into larger measurement systems. This feature is particularly beneficial in automated test environments, where speed and accuracy are paramount.

Additionally, the DMM incorporates advanced measurement functions, such as statistical analysis, including mean, standard deviation, and minimum/maximum readings, which provide users with valuable insights into their data. The instrument's user-friendly interface, complete with a clear digital display and intuitive controls, enhances usability and ensures that users can easily navigate its various functions.

Robust software support further extends the capabilities of the Agilent 34401A. It is compatible with a range of software tools for data logging and analysis, enabling users to efficiently document and analyze their measurements over time.

In summary, Agilent Technologies 34401A stands out in the realm of digital multimeters due to its high accuracy, extensive measurement functionalities, and user-friendly features. Whether for research and development, quality control, or educational purposes, the 34401A remains a preferred choice for professionals demanding reliable and precise measurement solutions. Its enduring legacy in the industry speaks to its performance and reliability, making it an essential tool for anyone involved in electronic testing and measurement.
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