Bimba PCS - Manual (Page 18)

www.bimba.com Technical Assistance: 800-44-BIMBA 18
14. PRELIMINARY “SPAN” ADJUSTMENT
PFC cylinders and PTF rotary actuators greater than 180 degrees of
rotation (See below for PTF’s less than 180 degrees)
Use the Span adjustment to set the intended fully extended position to be the same
as the full scale (maximum) analog command input signal. Using the Main
Control (or equivalent), command the actuator to go to the analog command input
signal full scale position. (Set the analog command input signal to 10 volts, or 20
mA depending on the PCS Model.) Look at the LEDs and make the adjustments
described in one of the appropriate following paragraphs.
If the Green LED is on or continuously flickering - (Span is currently set beyond
the extended hard stop.) Slowly adjust the Span potentiometer CW, until the green
LED goes off. (If the Span potentiometer was adjusted too far and the actuator
moved, adjust the Span potentiometer CCW just enough to move the actuator
back to the full scale position. If adjusted too far, the Green LED will come back
on). Both LEDs should be off when set correctly. This ends the preliminary Span
adjustment.
If neither LED is on - (Span is currently set somewhere in mid-stroke.) Slowly
adjust the Span potentiometer CCW to move the actuator rod or shaft toward the
full scale position. When the actuator hits the full scale position, the green LED
will continue to flicker even when the adjustment is no longer being turned. Now
adjust the Span CW just enough to turn off the green LED. Both LEDs should be
off when set correctly. This ends the Preliminary Span adjustment.
PTF rotary actuators less than 180 degrees of rotation
Using the command signal (CS) formula defined in the Main Control section of
the Glossary, calculate the full scale analog command signal setting the d
parameter = full rotation of your actuator, and setting the t parameter = 180
degrees.
For
Example:
The calculation for a 45 degree PTF with Voltage input would be:
CS = 45 x (10/180) + 0 = 2.50 VDC Full Scale Analog Command
Input Signal
And the calculation for a 45 degree PTF with a 4-20mA input would be:
CS = 45 x (16/180) + 4 = 8 mA Full Scale Analog Command
Input Signal
Now set the analog command input signal to the calculated full scale command
signal for your PTF rotation (i.e., 2.50 volts for a 45 degree unit with voltage
command input signal) and perform one of the following adjustments:
If the Green LED is on or continuously flickering - (Span is currently set beyond
the extended hard stop.) Slowly adjust the Span potentiometer CW, until the green