Preferred Instruments PCC-IV, Instruction Manual

Page: 116 / 135

PCC-IV Instruction Manual (Rev. 0.1) Page 6-31 Section 6
– Blockware Functions
Technical Reference
Conditions that cause TTRIP to change to a "1" (Fault), and the resulting TCODE Output:
TCODE Condition:
Potential Reason with
"Fail Closed Wiring"
(+5 V wired to Pot Increase)
Potential Reason with
"Fail Open Wiring"
(+5 V wired to Pot Decrease)
0 % PCC-IV Reset or Power-up.
No Code in Memory.
1 % Scaled Position
greater than 105%
for more than P9 seconds Pot wiper wiring is "open circuit".
Pot "-" wiring is "open circuit".
Pot element is "open circuit". Pot "+5V" wiring is "open
circuit".
Pot element is "open circuit".
2 % Scaled Position
less than -5%
for more than P9 seconds Pot "+5V" wiring is "open circuit".
Pot element is "open circuit". Pot wiper wiring is "open
circuit".
Pot "-" wiring is "open circuit".
Pot element is "open circuit".
3 % Actuator stopped moving
for more than P9 seconds
(Note 1). Stalled, torque overload, jammed.
Blown fuse.
Any motor wire "open circuit".
Motor winding burned out.
Motor limit switch opened within
5-95% Scaled Position (Note 1).
Check Scaled Position
calibration.
Same as "Fail Closed"
4 % Actuator moving Slower
than 40% speed for more
than P9 seconds (Note 1) Binding linkage, damper, or valve.
Low AC line voltage.
Stroke Time (P6) set too low. Same as "Fail Closed"
Note 1: TTRIP will NOT "Fault" due to "Actuator Stopped" or "Actuator Slow" if any of the following are true:
▪
The TOUT channel is in S/M mode.
▪
Scaled Position is less than -5% or greater than 105%.
▪
The Decrease Triac is ON, and the Scaled Position is less than 5%
▪
The Increase Triac is ON, and the Scaled Position is greater than 95%
•
The last two exceptions prevent nuisance 'Faults' due to inaccurate travel limit
switch operation
All actuators that use Fault Detection require a "pull-up" resistor (330k or less) that is connected from the Feedback
Pot wiper to +5V, and it should be located inside the PCC-IV controller.
Review “Pull-Up/Down Resistor for Voltage
Inputs" in Section 2. If the pot wiper circuit field wiring goes open-circuit, or if the wiper loses contact with the pot
element due to wear or dirt, the PCC-IV analog input will ramp to +5V within 3 seconds. The PCC-IV "G" option
board includes an internal 330k pull-up resistor for each analog input. The CPU, "A", "B", and "F" board analog
inputs do NOT have internal pull-up resistors, and require external resistors.
FEEDBACK POT FAULT DETECTION WITH "PULL-UP" AND "BIAS" RESISTORS
FEEDBACK
POT
+ 5.0 Vdc
(+/- 0.1 V)
"+" AIN
SIGNAL
"-" (SIGNAL
COMMON)
A
330k
PULL-UP
in "G"
BOARD
PCC-III-Gxx0
75% 100%
25% 0%
0% -50%
100% 150%
U
N
SC
A
LE
D
(
A
IN
)
SC
A
LE
D
(
TO
U
T)
B
C
TYPICAL FEEDBACK POT WITH PARTIAL STROKE SETUP.
"G" BOARD INTERNAL "PULL-UP" RESISTOR USED.
FEEDBACK
POT
+ 5
"+"
"-"
A
330k
PULL-UP
in "G"
BOARD
PCC-III-Gxx0
94% 100%
6% 0%
100% (AIN)
107% (TOUT)
U
N
SC
A
LE
D
(
A
IN
)
SC
A
LE
D
(
TO
U
T)
B
C
FEEDBACK POT WITH FULL STROKE SETUP.
EXTERNAL "BIAS" RESISTORS FOR FAULT DETECTION.
0% (AIN)
-7% (TOUT)
BIAS RESISTORS.
APPROX. 7% OF FEEDBACK
POT OHMS ("A" to "B").
(METAL FILM OR WIREWOUND)