indoor with uncontrolled climate must be considered. Both
gain and offset values of analogue- to-digital converters might
be affected by temperature, and offset might also be affected
for instrumentation amplifiers. Therefore the temperature
dependence must be kept to a minimum for these circuits, and
internal temperature measurement and correction schemes as
well as reference voltage circuits with low drift should be
considered.
H. Frequency range
Although DC is theoretically zero Hz, both the voltage and
current may vary more or less rapidly and they may both
contain certain amounts of higher frequency components due
to for instance the AC to DC conversion as well as transients.
Therefore a frequency range up to at least 2 kHz and hence a
sampling rate of minimum 4 kHz and a proper anti-alias filter
should be considered.
VI. PRELIMINARY MEASUREMENTS