Multichannel recorder for equidistant recording of significant changes of a measured variable in each channel

DETAILED DESCRIPTION An object of the present invention is to provide an improved multichannel point recorder by which in each event a substantially complete and readable curve is recorded, whereat only meaningful values of the measured variables which are equidistant from each other are selected and recorded.
In accomplishing these and other objects, there has been provided, in accordance with the present invention, a multichannel recorder, whereat per channel the measured input values are cyclically scanned and said scanned values serve to drive and control a print head being displaceable transversely across a movable recording chart forming a time base with respect to the measured value by memorizing for each channel the data with respect to the measured value and the time base of the last printed point (P.
sub.
n), first testing whether a newly measured value (P.
sub.
n+1) differs from the last measured and printed value (P.
sub.
n) by an amount k (.
vertline.
P.
sub.
n -P.
sub.
n+1 .
vertline.
.
gtoreq.
k), and in the event where this test is satisfied, memorizing said newly measured value (P.
sub.
n+1) together with its time base (.
SIGMA.
.
alpha.
), and in the event where this test is not satisfied secondly testing whether the time base (.
SIGMA.
.
alpha.
) exceeds a certain amount (.
SIGMA.
.
alpha.
.
gtoreq.
k), and in the event where the second test is satisfied memorizing the newly measured value (P.
sub.
n+1) together with said time base (.
SIGMA.
.
alpha.
), and in the event where the second test also is not satisfied, cycling to the next channel and making the same tests with a subsequent recording of the stored values.
An apparatus for implementing the invention includes a discriminator means arranged between a multiplex scanning device (14) and a buffer memory and evaluating at each scanning cycle whether the difference between the last memorized value and the presently scanned value is equal or greater than a given constant (k) or, if this is not the case, whether the summed displacement of the recording chart is equal or greater than said constant (k)