Fairchild T79 Series Operating and maintenance manual

FAIRCHILD MODEL T79xx SERIES
ELECTRO-PNEUMATIC TRANSDUCERS
(Analog Output)
Operation and Maintenance Instructions
Software Version 3.45 and 3.46
SPECIFICATIONS
Figure 2. Model T7950 Keypad
Figure 1. Model T7900 Keypad
Figure 3. Model T79xx Series Transducer Keypad Functions

2
11-24 VDC
Less than 4 watts
Current mode input range 0-24 mA
35 mA maximum without damage
Voltage mode input range 0-12 VDC
Voltage mode input clamped at 13 VDC
150 psig
No less than 5 psig
above maximum output
11 SCFM @ 150 psig
supply at midscale output
2.0 SCFM @
15 psig output pressure
Instrument Air per ISA
S7.0.01 Recommended
Range 0 –160ºF
+(0.5%+0.06%/ºF)
of span
The Model T79xx Series includes Model T7900 and
Model T7950 Electro-Pneumatic I/P, E/P transduc-
ers Control Output Pressure in proportion to an
analog input signal.
When you apply initial power to the units, dis-
plays on the Main Menu. If the keypad is inactive for
three minutes, the unit returns to . If power is
disrupted, the unit returns to its last setting when
power is restored.
These devices use feed and bleed solenoid valve
control technology, digital feedback electronic con-
trol, and an internal electronic pressure sensor to
achieve high accuracy pressure control. Flexible
configuration and PID tuning capability ensure that
these pressure controllers can meet the most de-
manding air pressure control applications.
SPECIFICATIONS
Model T7900 Model T7950
Electrical
Supply voltage . . . . . . . . . . . . . . . . . . . . . . 11-24 VDC
Power consumption. . . . . . . . . . . . . Less than 4 watts
Analog input . . . . . Current mode input range 0-24 mA
35 mA maximum without damage
Voltage mode input range 0-12 VDC
Voltage mode input clamped at 13 VDC
Pneumatic
Maximum Supply pressure: . . . . . . . . . . . . 200 psig
Minimum Supply Pressure. . . . . No less than 5 psig
above maximum output
Forward Flow Capacity . . . . . . . . . . Up to 100
SCFM @ 170 psig
Exhaust Flow Capacity . . . . . . . . . . . . Up to 50 SCFM
Air Quality . . . . . . . . . . . . . . . . . . . . . . Instrument Air
per ISA S7.0.01 Recommended
Input signal / Impedance: . . . 4-20 mA / 246 ohms,
0-10 VDC / 500k ohms
GENERAL INFORMATION
Electrical
Supply voltage . . . . . . . . . . . . . . . . . . . . . . .
Power consumption . . . . . . . . . . . . . . .
Analog input . . . . .
Pneumatic
Maximum Supply Pressure . . . . . . . . . . . . . . .
Minimum Supply Pressure . . . . . . .
Forward Flow Capacity . . . . . . . .
Exhaust Flow Capacity . . . . . . . . . . . . . .
Air Quality . . . . . . . . . . . . . . . . . .
Environmental - T7900 AND T7950
Operating Temperature . . . . . . . . . . . .
Temperature Effect . . . . . . . . . . . .

Table 4. Tuning Menu (Option T on the Main Menu)
Table 3. Configuration Menu (Option C on the Main Menu)
Item Description Range
10% of full scale
0 - 10% maximum pressure
(Value displayed in pressure units)
0 - 6.399 seconds
0 - 9.99 repeats per second
0 - 63.99
Description Range
Item
0-30 psig, [0-2 BAR], (0-200 kPa)
0-75 psig, [0-5 BAR]. (0-500 kPa)
0-150 psig, [0-10 BAR], (0-1000 kPa)
0-30 psig, [0-2 BAR], (0-200 kPa)
0-75 psig, [0-5 BAR]. (0-500 kPa)
0-150 psig, [0-10 BAR], (0-1000 kPa)
Table 1. Main Menu (shown in red)
Description Range
Item
Item Description Range
90% of full scale
Table 2. Setup Menu (Option S on the Main Menu - shown in blue)
Output Pressure - Displays the actual output pressure.
Setpoint - Sets/displays the required process variable.
Control Units - Sets the operating units for control input.
Option Units - Sets the operating units for the analog output option
Look Ahead Function - 1Improves setpoint accuracy and response time.
Numerator - Sets/displays pressure unit conversion factor.
Denominator - Sets/displays pressure unit conversion factor.
mA or VDC
mA or VDC
Enable or Disable
0-9999
0-9999
Proportional - Sets the proportional gain.
Integral - Sets the reset time.
Derivative - Sets the rate of change.
Dead Band - Sets the amount of pressure centered on the setpoint which the
unit does not respond.
Control Value - Displays control input value.
Option Value - Displays the feedback option output value.
Control Value 1 - Sets the 0 % Control Input value.
Control Value 2 - Sets the 100% Control Input value.
Option 1 - Sets the value of the current or voltage proportional to P1.
Option 2 - Sets the value of the current or voltage proportional to P2.
2
Records the low pressure look ahead coefficient.
2
Records the high pressure look ahead coefficient.
Setup Menu - Accesses the Setup Menu.
Calibration Menu - Accesses the Calibration Menu.
Tuning Menu - Accesses the Tuning Menu.
1 and must be set for to work correctly.
2 Recommend 60% difference in the range (value) between and . A zero value is not recommended.
0-24 mA or 0-12 VDC
0-24 mA or 0-12 VDC
0-24 mA or 0-12 VDC
See Table 2.
See Table 3.
See Table 4.
OP or USEr
0-24 mA or 0-12 VDC
0-24 mA or 0-12 VDC
0-24 mA or 0-12 VDC
Sets the output pressure required at the existing
setpoint. Typically 100 %.
Output pressure 1 -
Output pressure 2 -
Sets the output pressure required at the existing
setpoint. Typically 0%.
0-30 psig, [0-2 BAR], (0-200 kPa)
0-75 psig, [0-5 BAR]. (0-500 kPa)
0-150 psig, [0-10 BAR], (0-1000 kPa)
0-30 psig, [0-2 BAR], (0-200 kPa)
0-75 psig, [0-5 BAR], (0-500 kPa)
0-150 psig, [0-10 BAR], (0-1000 kPa)
3
Control Input - Sets the mode of operation for the control input.
Remote or Local
Output Control - Sets the mode of operation for the analog output.

Figure 2. Model T7950 Menu System
4

Controlling Output Pressure with Analog
Setpoint Control
The Model T7900/T7950 is configurable for controlling
output pressure or a process variable. Use the
Control Input and Analog Output connection
menu items to set these operating modes. See Table
5, Quick Setup, for the 4 basic operating modes. Main
menu items are shown in red and submenus in
blue. Use Tables 1 through 4 and Figure 2 as
guides for operating and navigating through the
various menus.
OPERATING MODES
Controlling Output Pressure
Setting the Control Input to Local allows
the Setpoint on the Model T7900/T7950 to
control the output via the keypad. Note that the 2
character alpha display blinks in this setting. Setting
the Control Input to Remote configures
the Control Input channel as an analog setpoint
control.
Controlling output pressure: The Model T7900/
T7950 uses an internal pressure sensor for closed
loop control of output pressure. The Setpoint
and Deadband display in terms of output
pressure units. A “P” fitting adapter is provided to
remotely sense output pressure. The adapter
pipes the feedback pressure to the internal pres-
sure sensor from a remote location. The display
returns to if the keypad is inactive for three
minutes.
Control Input set to Remote : The Model
T7900/T7950 control input channel is configured to
accept an analog control signal to control the
setpoint. The Control Value displays the cur-
rent or voltage signal value at the control input
terminals under all configurations. The relationship
between the control input signal and the output
pressure is determined by , , and
settings in the Configuration menu.
Output Control - Analog Output Option
The Analog Output Option may be set to
output a current or voltage signal that is propor-
tional to the pneumatic output pressure or an
independant analog output channel controlled via
the keypad while in the menu.
Set the value of to for analog output that is
proportional to the Output Pressure. The relation-
ship between the analog output signal and the
output pressure set in the configuration menu
by entering the appropriate values for , , ,
and . See Tables 1 & 3 and Figure 2 for more
information. Set the value of to to control
the analog output from the keypad using the
menu item.
Table 5: Quick Setup
T79xx Configuration Settings for Operating Modes for Software Versions starting at V3.45
T79xx Configuration
Operating Mode
LR= LOCL
OC=USER
SP (Keypad) Controls
Output OP
Keypad Controls OV
LR= REM
OC= USER
CV Controls Output OP
Keypad Controls OV
LR= REM
OC=OP
CV Controls
Output OP
OV Follows OP
LR= LOCL
OC=OP
SP (Keypad) Controls
Output OP
OV Follows OP
Control Input Mode Switch Alpha characters blink in LOCL mode
5

MENU ITEM FUNCTIONS
6
Control Value ( )
Displays the control input value in mA or Volts.
Option Value ( )
The Option Value displays the current or voltage
value at the analog output option terminals.
Setup Menu ( )
See Table 2 and Figure 2 for setup options.
Tuning Menu ( )
See Configuring Menu Tuning Coefficients,
Table 4 & Figure 2 for setup and PID Tuning Infor-
mation.
Analog Output Connection ( )
Sets the mode of operation for the Analog output option to
or . Setting option to configures the Output
Option to proportinally follow the output pressure in mA or
volts. The value is displayed in Option Value . Setting
option to configures the Output Option to be used
as an independent keypad settable output signal in mA or
Volts and is displayed in the Option Value . See Table
5, Quick Setup Guide.
Output Pressure ( )
Displays the actual output pressure in the default
PSIG units. BAR and kPa units can be displayed
based on configuring ( ) and ( ) as discussed
in the Pressure Conversion section. See Table 6.
Setpoint ( )
Configuring the Model T7900/T7950 to control
output pressure , the Setpoint menu
item on the Main menu displays the setpoint in
terms of output pressure. Selecting Setpoint
with the control input channel in Local
mode causes the numberic characters to blink
unitl the value required is reached via the up/
down buttons and entered. Use Control Input
configured in Remote for controlling
the output pressure proportional to the signal
value at the control input channel terminals. This
is defined by the calibration relationship of ,
, , and in the Configuration Menu .
Setpoint displays the current pressure
setpoint value.
Control Input ( )
Control Input configures the control input chan-
nel function. Setting in Remote mode, the
control input channel functions as setpoint control
to the Model T7900/7950. Control Input set to
LOCAL chooses the Setpoint using the
keypad to control the output pressure. In this mode,
the Model T7900/7950 control functions disregard
the analog input channel.
NOTE: The Control Input and the
Analog Output Connection have
four setting combinations that confi-
gure the Model T7900/7950 operation.
See Table 5, Quick Setup.
Calibration Menu ( )
See section 'Control Input Used as Setpoint
Control' , Table 3 & Figure 2 for setup options.
Look Ahead Function ( )
Using the Look Ahead function can reduce the gain
error and enhance the Model T7900/T7950 response
characteristics in most linear control applications. To
improve response characteristics, the Look-Ahead
function predicts the required internal control correction
for a specific setpoint based on the characterizing
values and . To achieve optimum look-ahead
characteristics, the Configuration menu items
and must be set with the Model T7900/T7950
operating with the supply pressures they will use in their
applications.
Pressure Unit Conversion ( ) and ( )
The Model T7900/T7950 Output Pressure can
display in any required pressure unit. To convert to other
pressure units, set the values of menu items Numerator
and Denominator . Values entered in and
form a fractional conversion factor that converts the
base units of pressure (psig) in the Model T7900/T7950
into the required units. The converted (new pressure)
unit is determined by the expression Converted Pressure
Unit = (pressure in psig) x (N/D). Consult a conversion
table to obtain a conversion factor for the required units,
convert into a fractional form, and enter it into the Model
T7900/T7950 using and .
Setup Menu ( ) Operation
Control Units
Sets control input units in mA or volts .
Values are input in the Configuration Menu
as and .
Analog Output Option Units ( )
To change the Analog Output Option Units
between voltage and current enter the
appropriate unit on the menu.

7
The values of and are integers only and are
limited to the range of 1 to 9999. The Model T7900/
T7950 ship from the factory with units of psig, BAR, or
kPa determined by the part number. The Model T7900/
T7950 automatically determines the Output Pressure
Decimal Point location based on the maximum
Output Pressure after the N/D conversion.
NOTE:
Unit N/ /D Comments
psig 1 1 psig = psig x 1
BAR 100 1451 bar = psig x 0.0689
kPa 6895 1000 kPa = psig x 6.895
InHg 5000 2456 InHg = psig x 2.036
Table 6. Pressure Unit Values
The Setpoint and Deadband item
values display in terms of the converted
pressure units defined by the and
conversion factor.
For more information about and values for
common pressure units, see Table 6.
Pressure Unit Conversion ( ) and ( ) cont.
Configuration Menu Operation
Control Value used as Setpoint Control ( ), ( ),
() and ( )
The values in , , and set the relationship
between the control input signal and the output pressure.
Setpoint is displayed in terms of the output units. Config-
uring the control input for setpoint control, ( = ),
allows for the adjustment of the relationship between con-
trol input signal and the output. To make the adjustment,
set the appropriate values in , , and on the
Configuration menu. When the control input signal
varies between the values in and , the pressure
output varies proportionally between the values in and
. For example:
= mA, = 0.00, = 30.00, =
4.00, and = 20.00; Varying the control input
current between 4 mA and 2- mA varies the
pressure setpoint proportionally between 0 and
30 psig.
To achieve a reverse acting relationship, set
= 20.00 and = 4.00 or set = 30 and
= 0.
Option Value ( ), ( )
Sets the analog value of and proportional to
and , respectively.
= mA, = 0.00, = 30.00, =
4.00, and = 20.00; The Option Value will
vary between 4 mA and 20 mA proportinally
following the pressure output between 0 and 30
psig.
To achieve a reverse acting relationship, set
= 20.00 and = 4.00 or set = 30 and
= 0.
Look Ahead Items and
Configuring Menu - Tuning Coefficients
The Model T7900/T7950 ships from the factory with nomi-
nal PID values. Tune the PID coeffecients , and
for optimum performance in the Tuning menu .
There are several PID optimization routines used to adjust
the PID coefficients. The following is a basic procedure
that works in most applications:
1. Start with = 1.00, = 0, and = 0.
should be set to zero when optimizing PID. Re-
turn to the required value after optimizing PID.
2. Increment by 0.01 or other minimal value.
3. Change the Setpoint from 50% full-scale to
70% full-scale. Change the setpoint back to 50%
4. If the output stabilizes, go back to 1.
5. If the output does not stabilize, measure the pe-
riod (in seconds) of the oscillations and go to step
6.
6. Set to 50% of the final unstable value previ-
ously identified. Set to the period of the os-
cillations. Set = x 1/8.
To improve response characteristics , the Look Ahead
function predicts the required internal control correc-
tion for a specific setpoint based on the characterizing
values and . must be enabled in the Setup
Menu. The Look ahead function is pressure sup-
ply sensitive requiring the pressure supply be set at the
expected operating value. To set and , use the
following steps:
1. Set the Deadband on the Tuning
menu to zero.
2. Set the Setpoint to a value between 10
and 20 % of the maximum operating range.
3. Access the Configuration menu. Scroll
through the menu until displays. Press
the enter key, select . When flashes
on the display, the new value is set.
4. Repeat the procedure for with the setpoint
between 70 and 100 % of the operating range.
Option Value ( ), ( ) (cont)

Solution
Table 7. Messages
Messages Message
14, 15 Return the unit to the
factory.
Problem
Memory is corrupted
Restoring Original Factory Calibration
To restore the factory item values, use the following
steps:
1. GO to
2. Press and hold until appears.
3. While holding press and hold until the
display flashes.
At startup, message symbols can briefly appear on
the display. For an explanation of these message
symbols, see Table 7.
Deadband ( )
Deadband is the set amount of error, centered
about the setpoint where the unit will not take action
to correct. To achieve fine control, you can set the
Deadband to zero, however, this causes the con-
trol solenoid valves to operate continuously reducing
their life cycle.
When the Model T7900/T7950 is configured to con-
trol output pressure, the Deadband in terms of
output pressure.
The information set forth in the foregoing Operation and Mainte-
nance Instructions shall not be modified or amended in any respect
without prior written consent of Fairchild Industrial Products Com-
pany. In addition, the information set forth herein shall be
furnished with each product sold incorporating Fairchild's unit as
a component thereof.
LEGAL NOTICE:
1. If troubleshooting does not correct the problem,
return the transducer to the factory for repair.
2. To replace all elastomers and the supply filter in the
Model T7950, install Service Kit 19715-2.
3. To replace the solenoid valves in the Model T7950,
install Service Kit 19715-1.
4. For the Model T7900, install Service Kit 19375-1.
5. To replace solenoid valves in the Model T7900,
order quantity (2) of Part Number: 290-IPI-001-2.
Check the supply filter.
Check the supply pressure.
Check the inlet screen in the booster.
Check the power supply.
Check for an existing Input Signal.
Check for loose fittings.
Check for loose body screws.
Check for output pressure leakage.
Check calibration.
Check for liquid in the air supply.
Check for loose wires or connections.
Check for improper tuning.
Check proper settings for and .
The external pressure is not applied
to "P" port. ("P" option only).
Problem Solution
The device does not have power or is
not on line. Check the Module Status
LED.
The unit is near setpoint.
The unit is NOT near setpoint.
Near Setpoint (NS)
Off
Green
Red
No power - The device does not
have power.
Device operational - The device is
operating in a normal condition.
Unrecoverable fault - A RAM or
ROM error occured. Return the
unit to the factory.
LED Status Module Status (MS)
Off
Green
Red
Table 9. LED Status
MAINTENANCE
LED Status
•
•
•
•
•
•
•
•
•
•
•
•
•
•
The Model T7900 and T7950 Transducers use a supply
filter to prevent detrimental particles from entering the
pilot section of the unit. Clean or replace the supply
filter as necessary to ensure maximum performance.
For additional maintenance and troubleshooting infor-
mation, see Tables 8 and 9.
Table 8. Troubleshooting
No Output
Leakage
Improper
Output
Erratic
Operation
Constant
Maximum
Output
OM-500T79AO
Litho in USA
03/06