Table of Contents
Advertisement
301/303/305/306/307 Flowmeters and Controllers Instruction Manual
Gain Potentiometer
On the top left of inlet side of the flow controller there is a hole through
which the gain potentiometer is accessible (See right). This gain
potentiometer affects the gain of the closed loop controller. Normally
this potentiometer will be set at the factory for good stable control. It
may be necessary to adjust this potentiometer in the field if the system
varies widely from the conditions under which the controller was setup.
Turning this gain potentiometer clockwise will improve stability. Turning
the potentiometer counter-clockwise will speed up the valve reaction
time to changes in the command signal.
Temperature Coefficients
As the ambient temperature of the instrument
changes from the original calibration
temperature, errors will be introduced into the
output of the instrument. The Temperature
Coefficient of Zero describes the change in the
output that is seen at zero flow. This error is
added to the overall output signal regardless of
flow but can be eliminated by adjusting the zero
potentiometer of the flow meter/controller to
read zero volts at zero flow conditions. The
Temperature Coefficient of Span describes the
change in output after the zero error is
eliminated. This error cannot be eliminated but
can be compensated for mathematically if
necessary. The curve pictured in Figure 2.8
shows the span error in percent of point as a
function of temperature assuming 23°C is the
calibration temperature.
EAR99 Technology Subject to Restrictions Contained on the Cover Page
Page 21 of 32
Advertisement
Table of Contents
