Information in this document is subject to change without notice. No part of this document may be reproduced or transmitted in any
form or by any means, electronic or mechanical, for any purpose, without the express written permission of DH Instruments, Inc.
4765 East Beautiful Lane, Phoenix AZ 85044-5318, USA.
DH Instruments makes sincere efforts to ensure accuracy and quality of its’ published materials; however, no warranty, expressed
or implied, is provided. DH Instruments disclaims any responsibility or liability for any direct or indirect damages resulting from the
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DH Instruments, DH, DHI, PPC, PPC2 and PPC2 AF are trademarks, registered and otherwise, of DH Instruments, Inc.
Document No. 550090C-01
980812, 021025
Printed in the USA.
1.2.3 POWER SUPPLIES................................................................................................................................... 3
3.2 DIRECT FUNCTION KEYS....................................................................................................................23
3.2.1 RANGE .................................................................................................................................................... 23
3.2.2 UNIT ........................................................................................................................................................ 24
3.4.4.4 DATE ................................................................................................................................................... 48
5.1.5 ILLUSTRATED PARTS BREAKDOWN................................................................................................... 82
5.1.5.1 PARTS LISTS...................................................................................................................................... 82
PPC2 AF is a high precision pressure controller/calibrator intended to apply and measure accurate values
of gas pressure for the calibration and testing of pressure measuring instruments.
PPC2 AF measures and controls pressures in the range of 0 to 1 000 psi (0 to 7 MPa) in both gauge and
absolute mode. Six pressure measuring ranges are available using two high accuracy reference
transducers and an on-board barometer. Internal valving chooses the appropriate transducer for the
desired range and protects the lower pressure transducer when working at high pressures. Pressures are
controlled by a pneumatic module consisting of fast and slow inlet and exhaust solenoid valves and
differential pressure regulators.
PPC2 AF can be controlled locally by the operator using a front panel display, keypad and special function
keys or remotely by a computer using ASCII character command strings over an RS232 interface.
A Self Purging Liquid Trap (SPLT) can be used to protect PPC2 AF from liquid contaminants in the device
or system being tested.
1.2 SUBASSEMBLY DESCRIPTION AND LOCATION
1.2.1 FRONT PANEL ASSEMBLY
1. Display
2. Multi-Function Keypad
The front panel assembly provides a 2 X 20 vacuum fluorescent display of PPC2 AF
operating status and a membrane keypad for local user control.
The rear panel assembly provides pressure connections, the host communications interface
and the power on/off module, and product and warranty labeling. Pressure fittings are
internally secured to prevent loosening when making and breaking connections.
1. + 12 V DC (± 2 %) @ 3.3 Amps: for internal and external valve execution.
2. + 5 V DC (± 2 %) @ 3.0 Amps; + 15 V DC (± 10 % / - 3 %) @ 2.0 Amps; - 15 V DC
(± 5 %) @ 0.35 Amps: for the supply of the micro board and driver board electronics.
1.2.4 MICRO CARD
Internal Layout
The micro card supports a Motorola 68302 microcontroller; EPROM, EEPROM, NVRAM and
flash memories; RS-232 communications; the front panel keypad and display control; and a
two channel frequency counter for reading reference pressure transducers. An I/O port
controls other boards and devices in PPC2 AF.
The driver board is controlled by the micro card (see Section 1.2.4). It supports the
12 V drivers for the internal and external solenoid valve actuation and the barometer board
(see Section 1.2.6). It also supplies power to the cooling fan.
1.2.6 BAROMETER BOARD
Internal Layout
The barometer board supports a board mounted, barometric range, micromachined silicon
sensor and an ambient temperature sensor. The barometer readings are used for dynamic
atmospheric pressure compensation when measuring gauge pressure with an absolute
reference transducer.
The pneumatic module is an integrated assembly that includes two inlet (fast and slow) and
two exhaust control valves and differential pressure regulators. The differential pressure
regulators use pressure feedback to maintain a constant differential pressure across the
control valves. The control valves are solenoid type actuated by 12 V.
The transducer selection module includes solenoid valves to connect and disconnect the low
pressure (secondary) reference transducer from the test system and to independently vent
the low pressure reference transducer.
1.2.9 REFERENCE PRESSURE TRANSDUCERS
Internal Layout
There are two reference pressure transducers. Their basic sensing principle is the
measurement of the change in the natural oscillating frequency of a quartz tuning fork with
temperature and with mechanical stress resulting from the change in pressure applied to a
connecting bellows or bourdon tube. Two independent quartz elements are used: one subjected
to pressure related stress; the other is used only to monitor temperature.
The low pressure reference transducer has a full scale range of 35 psi (220 kPa)
in gauge mode and 50 psi (330 kPa) in absolute mode.
1.2.10 SOURCE PRESSURE RELIEF VALVE
Internal Layout
The source pressure relief valve is a factory set, adjustable, spring loaded pressure relief
valve with a brass body, Viton O-ring seal and stainless steel internal parts. The valve is set
to relieve at 1 200 psi (8.3 MPa).
The SPLT is a free standing accessory designed to protect the PPC2 AF from liquid
contamination returning form the system or device under test. It is made up of a stainless
steel body with an internal X-Type coalescing filter and a bottom drain port fitting with an
electrically actuated purge valve. The filter valve assembly is installed in a mounting stand.
85 to 264 VAC, 47 to 440 Hz, 30 VA max consumption.
15 to 35 °C
- 20 to 70 °C
Meets MIL-T-28800D
12.8 kg (28.2 lb)
7.1" H X 12.6" W X 15.8" D (18 cm X 32 cm X 40 cm)
Motorola 68302, 16 MHz
RS232 (COM1)
-15 to 1 000 psi (7 MPa) gauge/0 to 1 000 psi absolute in six ranges using two
reference pressure transducers and a barometer
Clean, dry, non-corrosive gas
Supply: 1/8 in. NPT F
Test: 1/4 in. NPT F
Vent: 1/4 in. NPT F
Exhaust: 1/4 in. NPT F
AutoZero: 1/4 in. NPT F
1.3.2 PRESSURE MEASUREMENT SPECIFICATIONS
PPC2 AF measures pressures in gauge and absolute mode in six ranges using two reference
pressure transducers and a barometer.
The reference pressure transducers are of the absolute pressure type using an evacuated,
permanently sealed reference. They are used to measure gauge pressures by atmospheric
offset determined by direct measurement when the reference transducer is vented. The
atmospheric offset is dynamically compensated while operating in gauge mode using
measurements of the changes in atmosphere provided by a separate barometer.
1.3.2.1 HIGH PRESSURE REFERENCE TRANSDUCER (HI REF)
Ranges
Measurement Precision
(Combined Linearity, Hysteresis
and Repeatability)
Stability (6 Month with Use of
AutoZero Function)
Resolution
High (3): 0 to 1 000 psi (7 MPa) gauge/absolute
Mid (2): 0 to 600 psi (4 MPa) gauge/absolute
Low (1): 0 to 300 psi (2 MPa) gauge/absolute
± 0.01% F.S. of each range
± 0.005% F.S. of maximum range
1 ppm of maximum range
1.3.2.2 LOW PRESSURE REFERENCE TRANSDUCER (LO REF)
Ranges
Measurement Precision
(Combined Linearity, Hysteresis
and Repeatability)
Stability (6 Month with Use of
AutoZero Function)
Resolution
High (3): - 15 to 35 psi (250 kPa) gauge
0 to 50 psi (350 kPa) absolute
Mid (2): - 15 to 15 psi (100 kPa) gauge
0 to 30 psi (200 kPa) absolute
Low (1): - 15 to 0 psi gauge
0 to 15 psi (100 kPa) absolute
The barometric sensor is not used to provide absolute accuracy, it is used only to
measure the changes in atmospheric pressure to provide dynamic compensation
of the reference pressure transducer atmospheric pressure offset measurements
when using a reference pressure transducer to make gauge pressure
measurements.
Range
Accuracy (Nominal)
Resolution
1.3.3 PRESSURE CONTROL SPECIFICATIONS
11 to 16 psia (70 to 110 kPa)
± 0.5 % of reading
0.001 psi (7 Pa)
Control Modes Available
Control Volume
Control Limits
Static and dynamic
0 to 30 in
System defaults provided for each pressure measurement
range but can be customized by the user using the CUSTOM
CONTROL function.
3
(500 cc), ideal 7 to 15 in3 (125 to 250 cc)
1.3.3.1 STATIC PRESSURE CONTROL
Default Hold Limit
Default Stability Limit
± 1 % of F.S. of the active pressure measurement range
± 0.005 % of F.S./sec of the active pressure
measurement range
1.3.3.2 DYNAMIC PRESSURE CONTROL
Default Hold Limit
Default Stability Limit
± 0.05 psi (138 Pa) for Hi Ref ranges (1 to 3)
± 0.0025 psi (7 Pa) for Lo Ref ranges (1 to 3)
± 0.05 psi (350 Pa)/sec for Hi Ref ranges (1 to 3)
± 0.0025 psi (18 Pa)/sec for Lo Ref ranges (1 to 3)
PPC2 AF is delivered in a molded medium density polyethylene shipping case with a custom
foam insert for holding the PPC2 AF, SPLT if included, documentation and accessories.
Remove all PPC2 AF elements from the shipping case and remove each element from its
protective plastic bag.
2.1.2 INSPECTING CONTENTS
Check that all items are present and have no visible damage.
PPC2 AF includes:
DESCRIPTION PART NO.
PPC2 AF Pressure Controller/Calibrator 401270
Calibration Certificate 550200
Test Report 550102
ACCESSORIES: 401273
User’s Manual 550090
Power Cord (7.5 ft.) 100770
(4) Rubber Feet Caps 400202
1/4 in. NPT Male X KF 16 SS Vacuum Adaptor 102519
Male Electrical Connector for Drivers 102478
SPLT on Stand (with filter) * 401271
(1) Spare SPLT Filter Element * 102502
Shipping Case with Inserts 401272
* If supplied.
2.2 SITE REQUIREMENTS
The PPC2 AF can be installed on any flat, stable surface at a convenient height. The front feet can be
extended so that the unit can be inclined slightly for easier viewing. The PPC2 AF can also be mounted in
a standard 19" rack mount using the optional rack mount kit.
Minimizing the length of tubing between the PPC2 AF to the device or system to be tested will
enhance control performance and reduce pressure setting times.
Ready access to the PPC2 AF rear panel should be considered to facilitate making and breaking
pressure connections.
The SPLT, if used, needs to be mounted vertically at the low point of the pneumatic system.
• An electrical power source of 85 to 264 VAC, 47 to 440 Hz.
• A continuous regulated source pressure of 1 100 psi (8 MPa) clean, dry, non-corrosive gas
to connect to the pressure supply. Lower gas pressure sources can be used but should
exceed the maximum desired test output pressure by 10 to 20%.
• A vacuum source of less than 1 psia (7 kPa) and at least 3 cfm (90 lm) is needed to control
under 2 psi (14 kPa) gauge.
When supply pressure is applied to the PPC2 AF supply port, there is a constant gas exhaust through
the EXHAUST port of PPC2 AF to which the vacuum source will be connected. Therefore, the vacuum
source should either be continuously "on" or should bypass to atmosphere when the vacuum source is
"off" to avoid building up pressure on the EXHAUST port and/or the vacuum pump. To conserve gas,
vent the test volume and shut off the pressure supply when PPC2 AF is not in use.
2.3 INITIAL SETUP
2.3.1 PREPARING FOR OPERATION
To prepare PPC2 AF for check out and operation:
• Remove the plastic caps from the five (5) PPC2 AF rear panel pressure connections.
• Remove the protective plastic sheet from the front panel display.
• Install the rubber feet caps onto the bottom case feet, if desired.
2.3.2 POWER CONNECTION
• Check that the PPC2 AF power switch is off.
• Connect the supplied power cable to the rear panel power module.
• Connect the other end of the power cable to an electrical supply of 85 to 264 VAC, 47 to 440 Hz.
2.3.3 CONNECTING TO A PRESSURE SUPPLY (SUPPLY PORT)
Using a pressure connecting hose of appropriate pressure rating, connect the pressure supply
to the SUPPLY connection on the rear panel of PPC2 AF. The PPC2 AF SUPPLY connection
is 1/8 in. NPT female.
Never connect a pressure supply greater than 1 200 psi (8 MPa) to PPC2 AF.
2.3.4 CONNECTING A VACUUM PUMP (EXHAUST PORT)
For PPC2 AF to set pressures under atmosphere and/or to reliably set pressure under 2 psi (914 kPa)
gauge other than zero gauge, a vacuum pump must be connected to the exhaust port.
Never connect a pressure supply to or plug the PPC2 AF EXHAUST port.
When changing the pressure applied to the EXHAUST port from vacuum to atmosphere, be
sure to change the control reference setting (see Section 3.3.1).
2.3.5 CONNECTING TO THE DEVICE UNDER TEST (TEST PORT)
See Section 2.3.5.1 before proceeding to connect the device under test.
Using a pressure connecting hose of appropriate pressure rating, connect the device or system to
be tested to the TEST port of the PPC2 AF. The PPC2 AF TEST connection is ¼ in. NPT female.
Minimizing the length of the test connection hose will enhance control performance and
reduce pressure setting time. For normal operation, the total volume of the device of
3
system under test including connecting tubing should be less than 30 in
(500 cc).
PPC2 AF pressure control will not operate properly if there are excessive leaks in the test
system (see Section 3.2.8).
PPC2 AF pressure may be adversely affected if the test connection hose is too restrictive.
For optimum results, the inner diameter of the connecting hose should be > 0.07” (1.75 mm).
NEVER apply pressure to the TEST port without having a pressure supply equal to or great than
the applied pressure connected to the SUPPLY port. When controlling pressure externally, or
measuring external pressure through the SUPPLY port, NEVER
cause the pressure to change at
a very rapid rate. For example, do not vent suddenly by opening an external valve. Internal
PPC2 AF damage may result.
2.3.5.1 INSTALLING THE SPLT
The SPLT (if provided) is intended to collect and exhaust liquid contaminants that may be
present in the device or system under test so that they do not return to the PPC2 AF.
The SPLT is installed in the test connection line at a low point between PPC2 AF and
the device or system under test. The SPLT pressure connections are 1/4 in. NPT female.
Teflon tape or another sealing material should be used to assure leak free
connection of adapters installed in the SPLT pressure connections.
Proper SPLT operation is dependent on the gas flowing through it in the correct
direction. Be sure to connect the SPLT to the device or system under test and
the PPC2 AF following the connector port labels on the SPLT.
Connect the SPLT electrically to the PPC2 AF rear panel DRIVER connection and to the
SPLT terminal blocs. See Appendix 9.2 for information on preparing the SPLT
electrical cable and connection to the SPLT terminal blocs.
The SPLT must be mounted vertically with the purge valve at the bottom to
perform properly. It must be at a lower point in the system than the PPC2 AF
and/or the device under test. In operation, liquid contaminants collected from the
device or system under test will be exhausted through the SPLT purge valve.
Liquid contaminants will be forcibly ejected from the SPLT purge tube. Provision
for collecting the purged liquids should be considered when installing the SPLT.
Excessively dirty or wet filter elements can adversely affect pressure control.
The PPC2 AF VENT connection is the system vent to atmosphere point used to set zero
gauge pressure and obtain reference pressure transducer measurements of atmospheric
pressure. Though a pressure hose can be connected to the VENT connection to direct the
vented gas flow, a completely unobstructed connection to atmosphere must be obtained for
PPC2 AF reference pressure measurements to operate normally.
The PPC2 AF VENT connection is 1/4 in. NPT female.
Never plug, obstruct or connect a supply pressure to the PPC2 AF vent connection.
2.3.7 THE AUTOZERO CONNECTION (AUTOZERO PORT)
The PPC2 AF AUTOZERO connection is used for the AutoZero by Vacuum function and is
not needed at start up. It should be left open to atmosphere.
2.4 POWER UP AND VERIFICATION
2.4.1 SWITCH POWER ON
Actuate the power switch on the PPC2 AF rear panel. Observe the front panel display as
PPC2 AF initializes, error checks and goes to the main run screen (see Section 3.1.1).
PPC2 AF operating condition at power up is VENT valve closed, Hi reference pressure
transducer active.
If the PPC2 AF fails to reach the main run screen, service is required. Record the sequences
of operation and displays observed.
If the active range on power down was a Hi reference transducer range, the same range will
be active on the next power up. If the active power down range was a Lo reference
transducer range, range H3 will be active on power up. This is to protect the Lo reference
transducer from accidental overpressure (see Section 3.1.2.5).
PPC2 AF's front panel interface provides the means to access all PPC2 AF data and
functions including functions which, if used inadvertently or incorrectly, could change critical
metrological and/or operational parameters. The USER LEVEL function (see Section 3.4.4.6)
allows these areas to be password protected. The "low" security level protects only the most
critical internal calibration data. It is recommended that this level be set on all PPC2 AF's
even if no special security precautions are desired.
2.4.3 CHECK PROPER PRESSURE MEASUREMENT
OPERATION
2.4.3.1 CHECKING ABSOLUTE PRESSURE MEASUREMENT
If the PPC2 AF is not vented, press the VENT direct pressure control key to vent
it (see Section 3.1.2.2).
Press the UNIT function key (see Section 3.2.2). Select psi and then select
absolute mode.
Using the RANGE function key to change ranges (see Section 3.2.1), observe the
current value of atmospheric pressure displayed by each range. Check that
these values agree within ± 0.2 psi (1.4 kPa). If they do not agree, PPC2 AF may
need calibration or repair.
2.4.3.2 CHECKING GAUGE PRESSURE MEASUREMENT
If the PPC2 AF is not vented, press the VENT direct pressure control key to vent
it (see Section 3.1.2.2).
Press the UNIT function key. Select psi and then select gauge mode.
Using the RANGE function key to change ranges, observe that zero psi, ± 0.01 psi
is indicated for each range within 10 seconds. If it is not, PPC2 AF may need repair.
2.4.4 LEAK CHECK
If desired, perform a leak check of the test system (see Section 3.2.8).
2.4.5 PURGE
If the SPLT is included and installed in the test line, perform a purge of the system if it may be
liquid contaminated and descending pressures will be controlled (see Section 3.2.8).
Operating the PPC2 AF connected to a system with liquid contaminants without taking
proper precautions to purge the system and test line may cause contamination of the
PPC2 AF that will require non-warranty service.
PPC2 AF is designed to offer a balance between simple, straight forward operation and the
availability of a wide variety of functions with a high level of operator discretion if desired. The local
operator interface is through a 2 X 20 display, a 4 X 4 keypad and 4 direct pressure control keys.
3.1.1 THE MAIN RUN SCREEN
The PPC2 AF main run screen is its home display that is reached on power up and from
which other functions and menus are accessed. It is the very top level of all menu structures.
The main run screen is where the operator works with PPC2 AF to set and read pressures.
It provides complete information on the system's current configuration and operating status.
1. * Ready/Not Ready indication (See Section 3.1.2.4).
* when Ready,
if Not Ready.
2. PRESSURE1: Numerical value and sign of pressure
currently measured by currently active transducer and range.
3. UNIT: Current unit of measure of pressure indication
(see Section 3.2.2).
4. M: Pressure measurement mode: g for gauge, a for
absolute (see Section 3.2.2).
5. H: Indicates if a head correction is applied. H if applied,
blank if not (see Section 3.2.7).
6. SR: Indicates active reference transducer (H for high, L for low) and range (1 = low, 2 = mid, 3 = hi)
(see Section 3.2.1).
7. T: Indicates whether number following is target pressure (T), rate of change of pressure (R) or deviation
from target value (D) (see Section 3.2.3).
• Target pressure (T) will be indicated when:
- Dynamic control is active and pressure is NOT READY.
- Static control is active and valves are operating.
• Deviation (D) will be indicated when:
- Dynamic control is active and pressure is READY.
• Rate of change (R) will be indicated when:
- No control is active, i.e. control is suspended or
system is vented.
- Static control is active, and no valves are active.
8. PRESSURE2: Numerical sign and value of either target pressure, rate of change of pressure or deviation
from target. Target value and deviation in the same pressure unit as the current unit in 3. above. Rate of
change of pressure is in current unit per second (see Section 3.2.3).
9. CC: Pressure control mode (S for static, D for dynamic) with a (C) appended if custom control settings are
in use. These characters flash when the system is controlling. In static mode, if control is active they flash
even if no valve is operating, for example while inside the hold limit and waiting for stability. Characters flash
while controlling pressure down to vent but not when vent valve is open (see Sections 3.2.3 and 3.2.6).
10. NN/NN: Used only when running a sequence. Indicates number of increment currently being worked on
over total number of increments in the sequence or enter when “ready”. Changes to a countdown time during
count down when next increment of sequence is on timed delay rather than enter.
or indication direction of pressure evolution
*PRESSURE1 UNITMH SR
TPRESSURE2 CC NN/NN
PPC2 AF has a screen saver function which causes the display to dim if no key is pressed
for 10 minutes. Pressing a key restores full power to the display.
The PPC2 AF has a 4 X 4 keypad for local operator access to direct functions,
function menus and for data entry.
3. The Editing and Execution keys are for causing execution, suspending execution, backing up
in menus and editing entries.
1. The Function/Data keys allow very
commonly used functions to be
accessed directly by a single
keystroke when pressed from the
main run screen. The name of the
function is on the bottom half of the
key (see Section 3.2). These keys
enter numerical values when editing.
2. The Menu/Data keys provide access
to function menus when pressed
from the main run screen. The menu
name is on the bottom half of the
key. The SETUP menu is for more
frequently used functions (see
Section 3.3). The SPECIAL menu is
for functions that are not generally
used as a part of normal operation
(see Section 3.4). These keys enter
numerical values when editing.
Keypad
The ENTER key generally causes execution or forward movement in the menu tree.
ENTER from the main run screen allows an automated pressure control
command to be given.
The ESCAPE key moves back in the menu tree and/or causes execution to
cease or suspend. Pressing ESCAPE repeatedly always eventually brings you
back to the main run screen and from there will allow a momentary viewing of the
PPC2 AF introduction screen.
The
key changes a numerical sign when editing. It also toggles through
multiple screens when available.
The
and keys allow reverse and forward cursor movement when editing
data entry.
Some screens go beyond the two lines provided by the display. This is
indicated by a flashing arrow in the second line of the display. Use the ←
→ arrow keys to move the cursor to access the lines that are not
and
visible or directly enter the number of the desired menu choice if you know it.
3.1.2.2 DIRECT PRESSURE CONTROL KEYS
Direct Pressure Control Keys
The direct pressure control keys provide direct manual control of pressure
increase, decrease and vent. They can be useful in adjusting pressure when
automated pressure control to a target value is not needed.
The direct pressure control keys interrupt and override automated pressure control.
The VENT key causes the system to control pressure to near atmospheric
pressure and then open the system vent valve (see Section 1.2.7). Vent valve
open is indicated by lighting a red LED just above the VENT key. The vent valve
will remain open until the VENT key is pressed again or pressure is changed by a
direct pressure control key or an automated pressure control command. The VENT
key also causes the purge function to execute when the PPC2 AF LEAK
CHECK/PURGE function is active (see Section 3.2.8).
and keys cause pressure to increase or decrease at the slow slew rate.
The
Pressing the FAST key while pressing an
increase or decrease speed to change from slow to fast.
or key will cause the pressure
3.1.2.3 AUTOMATED PRESSURE CONTROL
PPC2 AF automated pressure control provides automated adjustment and control
of pressure to a user designated target value. This feature allows pressure
values to be set simply and precisely by simple numerical entry. Pressing
ENTER from the main run screen allows a pressure control target value to be
entered and executed. Pressing ESCAPE or a direct pressure control key will
cause pressure control to be interrupted.
PPC2 AF supports two pressure control modes, static and dynamic, to meet
different pressure setting and controlling requirements. Pressure control
parameters for each control mode are automatically adjusted to optimal values
for each PPC2 AF range when the control mode is selected in that range (see
Section 3.2.3). If desired, control parameters can be customized by the user
using the CUSTOM CONTROL function (see Section 3.2.6).
Control parameters:
Target Value: The pressure setpoint specified by the operator.
Hold Limit: A symmetrical positive and negative limit around the target value.
Stability Limit: A rate of change of pressure limit in units of pressure/second.
See Sections 3.1.2.3.1 and 3.1.2.3.2 for a detailed explanation of each control mode
and its advantages, the default control parameters and the Custom Control options.
3.1.2.3.1 Static Control
Static control mode is designed to set the pressure near the target value and then
stop controlling to allow pressure to stabilize naturally. The advantage of this
control mode is that pressure can be measured without interference from a
pressure control system. In a system without excessive leaks, the pressure
stability achieved, especially at low pressures, may be greater than the stability
with which the pressure control system can actively control pressure. Using static
control to control pressures near the desired set point and then measuring back
the stabilized pressure without interference of the control function, can allow
control errors to be eliminated. However, the final pressure achieved will be
different from the target value.
During static pressure control, the hold limit is active. If the pressure goes
outside of the hold limit, a "not ready" condition will occur (see Section 3.1.2.4)
and pressure will be readjusted to the target value (see Section 3.2.3 for default hold
and stability limit values and Section 3.2.6 for setting the hold and stability limits).
Static Pressure Control Operation
3.1.2.3.2 Dynamic Control
Dynamic control mode is designed to set the pressure to the target value and
control continuously to keep pressure within the hold limit and as close to the
target value as possible. The advantage of this control mode is that the final
pressure achieved will be the same as the target value. However, unlike static
control, in dynamic control, a control error will be included in the pressure
achieved. The maximum value of the control error is equal to the hold limit. The
average value of the control error is generally well inside the hold limit.
During dynamic pressure control, the hold limit is active. If the pressure goes outside
of the hold limit, a "not ready" condition will occur (see Section 3.1.3.4; see
Section 3.2.3 for default hold limit values and Section 3.2.6 for setting the hold limit).
The far left character of the display provides a pressure "Ready/Not Ready" indication.
This indication is intended to provide the user with a clear and objective criterion
for determining when a valid pressure measurement can be made.
Ready/Not Ready indications are:
* : Pressure "ready".
: Pressure "not ready" and decreasing.
: Pressure "not ready" and increasing.
When pressure control is not active, a "ready" condition will occur any time no
control valve is operating and the pressure rate of change is inside the stability
limit. The stability limit is defined in terms of rate of change of pressure in current
pressure units per second.
The determination of the "ready/not ready" condition is different for static and
dynamic pressure control. Pressure Ready/Not Ready parameters are set by
default when a control mode is selected and can be customized (see Sections
3.2.3 and 3.2.6).
3.1.2.4.1 Static Control Ready/Not Ready
When static pressure control mode is active a "ready" condition will occur when:
1. No control valve is operating.
2. The current measured pressure is inside the hold limit.
3. The rate of change of pressure is less than the current stability limit.
When dynamic pressure control mode is active a "ready" condition will occur when:
1. The current measured pressure is inside the hold limit.
Ready/Not Ready in Dynamic Pressure Control Mode
3.1.2.4.3 Ready/Not Ready When Automated Pressure
Control is Not Active
When no automated pressure control is active, "ready" is indicated whenever the
rate of change of pressure is less than the current stability limit.
3.1.2.5 MULTIPLE PRESSURE RANGES
PPC2 AF has two reference pressure transducers each of which has three
ranges for a total of six pressure ranges. This multiranging feature allows
accuracy to be optimized for the range of pressure in which you are working.
Generally, the best range to select (see Section 3.2.1) is that whose full scale is
closest to, but not less than, the maximum pressure at which you need to work.
PPC2 AF handles all of the data and internal valving operations needed to make
range changes occur transparently to the operator when the RANGE function is
used to select a range. Ranges available can be viewed at any time but changing
ranges can only occur when PPC2 AF is vented.
When ranges are changed, the upper limit is automatically changed to the default
for that range or to the last upper limit that was set for that range (see Section 3.2.4).
In addition, most other functions are range specific (see Section 3.2.1 below).
PPC2 AF has six ranges on two transducers. In general, user settings and
operational adjustments are specific to the range currently in use, as if you
had six instruments rather than one.
The PPC2 AF internal valving for handling of the two reference transducers is:
The currently active reference transducer and range is continuously displayed in
the upper right hand corner of the main run screen. Ranges available and main
run screen indication are as follows:
REFERENCE TRANSDUCER
AND RANGE NUMBER
Lo, 1 (Lo) 0/15 L1
Lo, 2 (Mid) 15/30 L2
Lo, 3 (Hi) 35/50 L3
Hi, 1 (Lo) 300/300 H1
Hi, 2 (Mid) 600/600 H2
Hi, 3 (Hi) 1 000/1 000 H3
RANGE (PSI)
GAUGE/ABSOLUTE
MAIN RUN SCREEN
INDICATION
All ranges start at zero in absolute mode and in gauge mode go negative by the
current value of atmospheric pressure.
3.2 DIRECT FUNCTION KEYS
3.2.1 RANGE
PURPOSE
To change the currently active pressure measurement range.
PRINCIPLE
PPC2 AF uses a 1 000 psi (7 MPa) absolute transducer and a 50 psi (350 kPa) absolute
transducer to measure reference pressures. In addition, each one of these transducers is
triple ranged providing a total of six pressure ranges over the 1 000 psi pressure range of the
PPC2 AF (see Section 3.1.2.5).
The RANGE function keys allows ranges to be selected including automated switching of
transducers when necessary with built-in logic to prevent accidental overpressure of the low
pressure transducer.
PPC2 AF functions and settings such as pressure unit of measure (UNIT) and control mode
(CONTROL) are range specific. Only the HEAD function is not range specific (see Section 3.4.2).
Changes made while in one range apply to that range only and will not affect the other ranges.
OPERATION
Pressing the RANGE function key activates the range viewing and selecting function.
Pressing the +/- key or the RANGE key again while in the RANGE functions steps through
displays of available ranges, Lo to Hi. Pressing ENTER while in the RANGE function when
PPC2 AF is vented makes the currently displayed range the active range. Pressing ESCAPE
while in the range function returns to the main run screen with no range change having been made.
When the RANGE function key is first pressed, the current reference transducer and range
being used are displayed, for example:
1. Identifies reference transducer in use (Lo or Hi).
2. Identifies range of that reference transducer currently in use
(1, 2 or 3, Lo to Hi).
3. Abbreviated range designation.
4. Units of measure and pressure range for that transducer and
range number when used in gauge (g) or absolute(a) mode.
Pressing the
key or pressing the RANGE key again causes the screen to step through
the other available ranges in sequence Lo to Hi, for example:
Current LO, Rng3 L3
psi 35 g/50 a
1. Identifies reference transducer (Lo or Hi).
2. Identifies range of number on that reference transducer (1, 2 or 3).
3. Abbreviated range designation.
4. Units of measure and pressure range for that transducer and
that range when used in gauge (g) or absolute(a) mode.
Select HI, Rng1 H1
psi 300 g/300 a
Range limits are given in the pressure unit that is currently active for that range.
To protect against overpressure of the Lo pressure reference transducer and avoid
accidentally exceeding range upper limits, the active range can only be changed when the
system is vented. If ENTER is pressed while in the RANGE function when PPC2 AF is not
vented, the display will indicate "Vent system fully to change range". Press ESCAPE or ENTER
to reach the main run screen and vent using the VENT direct pressure control key. Once
the system has fully vented, use the RANGE function to make the desired range change.
RANGE SPECIFIC FUNCTIONS AND SETTINGS
In general, PPC2 AF functions and settings are channel specific. They are set and stored for
each range so that changing them when in one range does not change them in the other
ranges and when you return to a range, you will find the settings you left.
The only functions and settings that are not range specific are:
Functions: HEAD, ANALOG
Setup Menu: 1ControlRef, 4Drivers
3.2.2 UNIT
PURPOSE
To specify the pressure unit in which PPC2 AF displays pressure values.