Test and measurement

Calculation of Accuracy for HMC8012

Question

Please can you explain how to calculate accuracy for the digital multimeter HMC8012? I found the tables in the data sheet, but am not sure how to interprete these values.

Answer

Let's take a DC voltage measurement as example for the calculation. It is important to set the zero point of the measurement section (using the [NULL] key) for best accuracy. Zeroing is done. We measure a voltage of 13,85 V. To perform the calculation we need to refer to the following table:

Digital Multimeter HMC8012 DC specifications

For a result of 13,85V the 40V range has been selected.

This leads into

  • a standard deviation of 0,02% of the displayed value
    (13,85 V / 100 * 0,02 or 13,85 V * 0,02 % = 2,77 mV)
  • a standard deviation of 0,002% of the selected range
    (40 V / 100 * 0,002 or 40 V * 0,002 % = 0,8 mV)

If the environment temperature range is not within 18-28°C, an additional temperature coefficient must be factored in. In our example we choose the environment temperature to be 30°C, meaning a temperature deviation of 2 K.

For each Kelvin below or above those 18-28 °C

  • an addidional temperature coefficient of 0,001% of the displayed value
    (13,85 V / 100 * 0,001 or 13,85 V * 0,001 % = 0,1385 mV)
  • an additional temperature coefficient of 0,0005% of the selected range
    (40 V / 100 * 0,0005 or 40V * 0,005 % = 0,2 mV

must be added.

All in all we have an accuracy of 2,77 mV + 0,8 mV + 2* 0,1385 mV + 2 *0,2 mV = 4,247mV (2 times temperature coefficient each because of 2 K deviation from 28 °C).

Result: The real voltage value is in a range between 13.845753 and 13,854247 V.

Please find a certainty calculator for the HMC8012 in the attachment of this article. This article was written according to FW version 1.400

Name
Type
Version
Date
Size
Uncertainty_Calculation_HMC8012.xlsx
Type
FAQ
Version
Date
23-Jul-2020
Size
44 kB

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