Linear Input Calibration - Omega Engineering CN9400 User Manual

Calibration to Another Instrument (continued)
To make a correction when there are different errors across the scale.
2 Adjust using the
SPAN
2.1 Chose a temperature near the bottom and
another near the top of the scale.
2.2 Run the process at the lower temperature (T
Note the error (E ) between the controller and the
1
instrument readings.
2.3 Repeat at the upper temperature (T
error (E ).
2
2.4 Substitute the values for T
expression below to calculate
E -E X hi.SC = SPAn
2 1
T -T
2 1
For hi.SC settings see level 2.
Example:
Instrument reading
Controller reading
Error
(-15) - (-2) x 450 = (-13) x 450 = (-)17.9
385 - 58
function
).
1
) and note
2
, T , E and E in the
1 2 1 2
SPAN
T T
1 2
58° 385°
60° 400°
E (-) 2° E (-) 15°
1 2
327
2.5 Therefore adjust SPAn to (-) 18 to correct error.
Notes: (1) After making the adjustment the reading will
immediately change. Allow time for the temperature
to stabilise at T before making any further adjustment.
2
At this point, a ZEro adjustment may be needed, refer
to step 1 above.
(2) Check that the temperature correctly stabilises at T
and then adjust setpoints to T
at T repeat from step 2.
1

LINEAR INPUT CALIBRATION

In addition to the ten temperature inputs, the controller has five
linear input ranges which can be calibrated to display a range of
engineering units. This procedure involves making adjustments to
the controller's hi.SC , ZEro and SPAn adjustments found in
function menu levels 2 and 3.
Note: The controllers linear inputs are in mV. If your transducer
provides an output in mA this should be converted to mV
by feeding the controller input via a high stability one ohm
resistor, see figure page 26. Other low Vdc signals can be
connected via a suitable voltage divider network to match
the controller input requirements.
2
. If an error is present
1
25