True RMS Voltmeter ⌁

⚡The Root Mean Square ( RMS ) voltage is a useful value to measure as it is related to the power  ( 'heating effect' ) of the voltage. The SpacerLabs "RMSDC-1" voltmeter described here is able to measure the true RMS value of complex periodic voltage waveforms, ( not just sinusoidal ∿ ), up to frequencies of  typically 8MHz, and even if a DC offset level is present.

Measuring the output voltage of a 3V DC precision source

Central to the operation of the RMSDC-1 is a highly accurate RMS to DC converter chip which produces a DC voltage equivalent to the RMS value of the input voltage. This DC voltage is sampled by a separate 10-bit analogue to digital converter ( ADC ) so that the voltage can be displayed. Also a dB output is available which has been calibrated to give the dB value of the input voltage being measured relative to 1V ( 1V = 0dBV ). For DC voltages the RMS value is the same as the DC value. So the RMSDC-1 can be used as a DC voltmeter. Both AC and DC input coupled signals can be measured; the latter allowing any DC offset to be retained. An active analogue filter of the Sallen-Key type can switched in to reduce any potential inaccuracy due to AC ripple at 2X input frequency.

An attractive 3-D printed front panel can be fitted

A front panel has been designed and printed to give the RMSDC-1 a very smart appearance. The front panel also serves to support the RMSDC-1 vertically. The display module is a 2X16 LCD with a white or yellow/green back-light.