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Instrumentation - DD/04/DVA

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Autoranging 3½ Digit • 3 Ranges Configurable For 1, 10, 100mV/g etc... I/P's 3 Channel I/P Option • True rms Conversion From 2Hz

Flexible format LCD display provides a variety of scaling options, plus autoranging over three decades and three channel input, for quasi steady state periodic signals. True wide band rms conversion produces accurate measurement for waveform crest factor Vpeak/Vrms ; up to 5 (equiv. to 25 : 1mark/space ratio symmetrical rectangular wave).


May be either 1, 10, or 100mV/measurement unit (mu), peak sine or rms, on any input channel, 1mV/mu sensitivity requires display rescaling from 199.9 to 1999 mu’s max. Full scale reading (any range) corresponds to an rms converter output of either 2 or 2.8V DC. Crest factor > 5 will cause limiting (symm. rect. wave, rms scaling, Vs ±15V). The 100mV/mu option will in addition impose a further Vs determined constraint on maximum reading.

Minimum Operating Frequency

Rms conversion applied to periodic signals generates a 1/f frequency dependent ripple component of averaging. This in turn introduces a 1/f dependent error component, thus defining minimum frequency in terms of averaging time. The integrating A/D converter updates the display every 400m.sec.

In addition, the autorange logic samples for over-range (O/R), under range (U/R) at a rate which is determined by minimum signal frequency. Autoranging and display malfunction may be associated with noise and modulation products additive to the signal; it may be necessary to further increase rms converter averaging time and A/D update times to compensate.


0.5" high char. display is readable from 10 mtrs subject to good background lighting. Input signals must conform to the 1, 10, 100mV/mu format which are available (O/P1) from the various 04 series transducer interface amplifiers. Inputs may also be derived from sources such as VM/04 and DM/04 providing these modules are configured as fixed rather than switched gain format.