# How to estimate the measurement uncertainty of an oscilloscope ?

• nordmoon
In summary, the speaker is having difficulty determining the measurement uncertainty for the measured pulse area on their Textronics oscilloscope. The calibration sheet and manual do not provide clear information on this. The speaker also mentions the model number of the oscilloscope and provides a link to the datasheet. They mention that the manual has some information on vertical accuracy, but it is not clear how to apply it to determine measurement uncertainty for the pulse area.
nordmoon
TL;DR Summary
How to estimate the measurement uncertainty of an Textronics 500 MHz oscilloscope ?
I have an Textronics oscilloscope with 500 MHz sampling rate and using an 50 ohm cable for the measurement.

I can’t find the measurement uncertainty in the manual or the calibration sheet.

In the calibration sheet it says an ‘uncertainty’ for the used channel in divisions, for example 1m up to 10m (the scale) and with highest value being 1. It states the nominal value, upper and lower value and the measurement value. It also state an uncertainty (value between 1-2m) but not in %. I don’t understand how to determine the measurement uncertainty from this data. Anyone understand this?

The manual is even more cryptic .. no words on measurement uncertainty.

Do you have a model number?

Averagesupernova said:
Do you have a model number?

If I remember correctly it’s a DPO7054 or DPO7254.

nordmoon said:
Yes but I don’t understand how to determine the measurement uncertainty, for the measured pulse area, with this oscilloscope ?
Pulse area? Are you checking Eye Diagrams for communication circuits? What is the application?

I would think that you would combine the error specs for the vertical amplitude and horizontal time base jitter, but maybe there are other considerations. What frequency and rise/fall times are involved? What range of voltage amplitudes?

In the manual, for vertical accuracy see Appendix A, page A-8 "Effective bits, typical." Depending on frequency, the accuracy ranges between 5.2 and 6 bits.

Therefore, at 2.5GHz the vertical accuracy would be:
1/(25.2) = 1/36.76 = 2.7% of Full Scale reading

User Manual .pdf is available at:

Cheers,
Tom

dlgoff and berkeman

## 1. What is measurement uncertainty and why is it important for an oscilloscope?

Measurement uncertainty is the amount of error or variation that can occur in a measurement. It is important for an oscilloscope because it affects the accuracy and reliability of the measurements taken by the instrument.

## 2. How is measurement uncertainty calculated for an oscilloscope?

Measurement uncertainty is typically calculated by taking into account the specifications of the oscilloscope, such as its accuracy, resolution, and noise levels. It can also be calculated by performing repeated measurements and analyzing the variation in the results.

## 3. What are the sources of measurement uncertainty in an oscilloscope?

The sources of measurement uncertainty in an oscilloscope can include factors such as internal noise, external interference, and variations in the instrument's components. The quality and calibration of the probes used can also contribute to measurement uncertainty.

## 4. How can one minimize measurement uncertainty in an oscilloscope?

To minimize measurement uncertainty in an oscilloscope, it is important to use high-quality probes, properly calibrate the instrument, and perform multiple measurements to account for any variations. It is also helpful to reduce external interference and ensure the oscilloscope is used in a stable environment.

## 5. Are there any standards or guidelines for estimating measurement uncertainty in an oscilloscope?

Yes, there are international standards and guidelines, such as ISO/IEC Guide 98-3, that provide methods and recommendations for estimating measurement uncertainty in various instruments, including oscilloscopes. It is important to follow these standards to ensure accurate and reliable measurements.

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