  Teaching about measurements and showing examples of instruments' non-ideal
behaviour are important in physics education. Digital multimeter input
impedance analysis is perfect for this, since these instruments are easily
available, precise enough, have good value/price ratio and represent modern
technology. A recent paper (2018 Phys. Educ. 53 053005) demonstrates how the
investigation of the input impedance of a digital multimeter can be used in
education. However, we think that some more discussion is needed to make it
more complete.
