Gossen MetraWatt R2080 - Page 19

GOSSEN METRAWATT GMBH 19
Evaluating the Actuation Test
– Apply a tangent to the curve at the intersection of the actual value and the setpoint, or at the cut-off point of
the output.
– Measure time ∆t.
– Measure oscillation amplitude x
ss
, or overshooting for step-action controllers ∆x.
MRS = Measuring range span of the configured sensor type (compare Configuration, see page 25), not the
measuring range according to C Designation
Performing the Oscillation Test
If an actuation test is not possible, for example if neighboring control loops influence the actual value too greatly,
if switching output II must be active in order to maintain the actual value (cooling operating point), or if optimiza-
tion is required directly to the setpoint for any given reason, control parameters can be determined by means of
sustained oscillation. However, calculated values for tu may be very inaccurate in this case under certain cir-
cumstances.
– Same preparation as for actuation test. The test can be performed without a recorder if the actual value is
observed at the display, and if times are measured with a stopwatch.
Parameter Values
tu 1,5
• ∆t ∆t – (tY / 4)
tc tu / 12 tY / 100
Pb 1 (x
ss
/ MRS) • 100 % (∆x / MRS) • 50 %
Pb 11 – Pb 1
• (T
I
/ T
II
)–
Parameter 2-step controller 3-step controller Step-action controller
P
∆ t
∆ x
x
ss
T
I
T
II
dbnd = 0dbnd = MRS
(3-step controller only)