Edgewise analogue level meter with optional integral input multiplexer, channel and parameter selection controls, intended for monitoring of periodic signals.

Incorporating a graphics liquid crystal display and microcontroller, the MU/04/E provides true RMS conversion together with provision to select up to eleven inputs.

The LCD is configured as a dual vertical 0/1, 0/3.16, (10 dB increment) scale with display of level (solid line), parameter (g RMS, g peak sine, etc), and selected channel number. Current channel and parameter data are retained on power down.

and pushbuttons with limit stops provide channel selection. Each channel may be preprogrammed with an acceleration, velocity or displacement parameter. Alternatively, an optional “Fn” pushbutton allows toggling between “g RMS” and “g pk.sine”. The latter is simply scaled √2 the RMS value hence its validity assumes low harmonic content. In the case of velocity and displacement derived from an acceleration source, the integration inherent in the process will usually provide harmonic reduction sufficient for the √2 scaling factor to be deemed valid, but waveform observation is always advisable.

RMS CONVERTER

This provides little impairment of accuracy for waveform crest factors (peak/RMS ratio) of up to 4:1, equivalent to a 1:16 mark/space ratio rectangular wave.

A 1/f frequency dependent ripple component is generated as a function of the averaging process, impairing low frequency accuracy. A 5 Hz sine input produces a 3% ripple content.

DISPLAY

This provides a scaled bargraph facsimile of the RMS converter output. Scaling is compatible with 04 module (CA, VV, VM, DM) range switch 10 dB increments.

Display reading is updated at 30msec intervals and is subject to a maximum 5mV (0.5% FSD) quantization error, and may be considered akin to a moving coil meter without the attendant parallax and hysterisis.

EXAMPLE : MU/04/E/dva

MU/04/E/dva monitors the three parameters acceleration, velocity, displacement, assumed to coincide with input channels 1, 2 and 3.

The input multiplexer is stopped to prevent excursion outside inputs 1 to 3. and pushbuttons allow dva selection. The “Fn” pushbutton is not available, parameters for each of d, v and a being selected from table 2.