Determination of measurement accuracy of a digital meter.

Each electronics specialist uses a universal meter. It is an available and very helpful tool in everyday work. Analog versions have practically been replaced by digital versions. Unfortunately, many people have a problem with the correct estimation of the measurement error. Therefore, I will show on the example of my meter how to do it.

SANWA PC5000a

The meter I have is SANWA PC5000a. The instruction manual for this meter is available at this link:

https://www.sanwa-meter.co.jp/japan/pdf/manual/digital_multimeters/PC5000a_EN.pdf?channel=sanwa

Let’s measure with this meter and estimate the measurement error.

DC voltage measurement.

I set the power supply to 5 V DC and measured the voltage at the power supply terminals.

Let’s now look at the meter manual, where there is information about the accuracy of DC voltage measurements.

The measured voltage was 5,0280 V. So we look at the first position and read the formula for calculating the accuracy with which we measured:

0.03% rdg + 2 dgt

  • 0.03% rdg means 0.03% of the read value.
  • 2dgt means the 2 least significant digits displayed on the display.

So the measurement accuracy is:

5.0280 V * 0.03% + 0.0002 V = 0.0017084 V ≈ 0.0017 V

So the measured value is: 5.0280 V ± 0.0017 V.

So the actual voltage value is between: 5.0263 V ÷ 5.0297 V.

Resistance measurement.

I took a random THT resistor and measured its resistance:

Let’s check the measurement accuracy according to the instruction manual:

The value we measured is 6.790 kΩ, so we use the formula: 0.2% rdg + 6 dgt. The measurement accuracy is:

6790 Ω*0.2% + 6 Ω = 19.94 Ω ≈ 20 Ω

The measured value is: 6790 Ω ± 20 Ω. The actual resistance value is between: 6770 Ω ÷ 6810 Ω.

Capacity measurement.

Finally, I will measure the capacity. I took a 100 µF / 25 V electrolytic capacitor and measured its capacity:

Let’s check the measurement accuracy according to the instruction manual:

The value we measured is 94.5 µF, so we use the formula: 3.5% rdg + 5 dgt. The measurement accuracy is:

0.0000945 F*3.5% + 0.0000005 F = 3.807 5 µF ≈ 3.8 µF

So the measured value is: 94.5 µF ± 3.8 µF. The actual capacity value is between: 90.7 µF ÷ 98.3 µF.

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