The need for speed

Optimizing Druck’s PACE pressure controllers

Introduction

Druck, a Baker Hughes business, has been developing anddelivering pressure measurement solutions to customers formore than 50 Years, across many applications in Aerospace,
Oil & Gas, Industrial, Metrological Laboratories and manyothers. One of Druck’s main areas of technical expertiseis Pressure Controllers. These are used in many different
industrial applications and by metrological laboratories ascalibration standards around the world.
Druck’s PACE pressure controllers are widely regarded as thefastest, most stable and accurate controllers on the market
in an extremely wide variety of applications. We have written
previously about the accuracy and stability of the PACE range
and a whitepaper that exists on our website, for free download,
discusses aspects to consider when accuracy and stability
are key to your application. This paper now focuses on how
best to optimize your PACE controller setup in order to achieve
the best results when speed is the most important factor.
In reality, applications often require a blend of all three
aspects of speed, accuracy and stability and the versatilityof Druck’s PACE product allows for fine tuning to find the best
possible set up to meet your application needs.
This paper presents the three main areas to focus on when
optimizing your PACE setup for speed:• Controller settings• Pneumatic connections• MaintenanceController settings

One of the easiest, quickest and cost-effective ways toimprove the PACE control performance is to optimise thesettings within the controller to match the application. Allcontrol settings can be found within the “control setup” menu.

Slew rate
For the majority of applications, the optimum setting isto configure PACE for “Max rate”. This will ensure the PACE
controls as fast as possible. However, for configurations that
contain complex loads/volumes it may be necessary to finda slew rate that hits the sweet spot for that application byconfiguring the slew rate as “linear” with a defined value in
mbar/second (example) that can be tuned to match theapplication. This setting is also useful should maximum
speed not be a requirement, but where a slower andprecisely controlled ramp might be more desirable

OvershootIn order to guarantee the fastest control speed it is necessary
to enable the overshoot setting. This does not guarantee thatthe controller will overshoot, but allows it to if necessary. If
the user requires the controller not to overshoot then the “noovershoot” setting can be enabled.

In-limits
PACE controllers are the most stable on the market andguarantee a control stability of 10ppmFS (0.001%FS)
minimum. Typically figures of 5ppm or even 1ppm arepossible. This can be compared to 30ppm from the closest
competitor products. However, if the user wishes to sacrificecontrol stability for enhanced speed-to-setpoint then the“in-limit” settings can be adjusted to higher values e.g.
50ppm. This will reduce the time it takes for PACE to reportback via remote communication (or on-screen) that it has
settled at the desired setpoint. In this case PACE can reachmost setpoints in as little as 1-2 seconds. This setting can befound within the supervisor setup menu. PACE also provides
feedback that you are within these specified control stability
limits for a user defined period of time. This feedback canbe provided on-screen or via the remote communicationinterface.

Active/passive/gauge mode
Although not related to control speed this setting allows theuser to potentially improve their uncertainty budget in a leakfree or low leak system. In active mode the PACE controller
is always responding to pressure fluctuations and so the
10ppm pressure stability figure must be included within theuncertainty budget. The reason for not including this term as
standard is because the PACE often achieves 1-2ppm control
stability and is therefore negligible in these situations. If theuser has a setup whereby the system has a very small leak,then PACE can be switched to passive mode whereby thecontroller turns off when reaching setpoint. This allows for theuncertainty budget to be improved. It’s extremely important
to consider this uncertainty budget if using a competitor
product with reduced control stability. Often, claims of very fast
control speed are offset by control stability specifications of>=250ppmFS. Consider this against a sensor uncertainty in theregion of 50-100ppmFS and the excellent sensor performanceis completely negated by the poor control stability.
Also, worth mentioning is gauge mode, this allows the user tocontrol PACE without the use of a vacuum pump by venting
the controlled pressure when close to atmospheric conditions
should a 0barg setpoint be required.

Pneumatic settings

This area can often be one of the most overlooked yet crucial
aspects to pressure control. In order to optimise pressure
control the following areas must be considered:

Source pressure
It is imperative for fast and precise pressure control that sourcepressure is accurately maintained during a pressure ramp. If
the source providing the pneumatic pressure to the PACE is notcapable of providing enough air into the PACE to pressurise
the load volume to the required pressure then the sourcepressure will ‘droop’ during a ramp and this will impact control
performance. For this reason, Druck recommends using hoses

as short as possible of 6mm or greater internal diameter andif necessary installing a volume several times bigger than theload volume in the source line. This has the benefit of being“charged up” by the source pressure in between pressure
ramps and the volume then supports the source pressureduring pressure ramps with a buffer of air (comparisons canbe drawn with a decoupling capacitor in an electrical circuit).

Controller performance

Similarly, the vacuum supply if used, which provides for faster
control around atmospheric pressure should have 6mm orgreater hosing and have the power to draw a strong vacuum
during negative pressure ramps. A volume in the vacuum line
will also benefit control speed. All volumes should be multiple
times larger than the load volume where possible in orderto maximise the benefits of installing a source volume. This
will give the added benefit of providing enough surplus air
in the event of several pressure ramps in quick succession.
It is recommended to install Druck accessory IO-VAC-SYS
for optimum performance also. This is a ‘check’ valve thatallows internal manifold pressure to be quickly exhausted toatmosphere during a negative pressure ramp as opposed
to going into the vacuum volume and causing a potential
pressure rise. The source pressure itself should be set toapproximately 120% full-scale to give the largest differential
pressure with respect to vacuum whilst also staying within
the pneumatic limits of the control module being used.

– Competitor A quotes 15 seconds for a 10%FS pressure
increase into a 50ml volume

Hose connections
As previously mentioned Druck recommends all thoseconnections to be 6mm or greater internal diameter so as toreduce the possible number of flow restrictors in the overallsystem. For this reason, it is important to also ensure that anypressure adaptors between hoses/volumes/equipment are
not restricting the flow more than necessary

1. Test and set-up description

As is widely known in the market the PACE controllers offer
industry leading speed-to-setpoint, but how much faster canbe hard to quantify based on datasheet figures. Examples
that you may see are:– Competitor B quotes 20 seconds settling time (typical)
The following graphs show a side by side comparison of a
PACE6000 controller against competitor A & B into variously
sized volumes and for different sized pressure ramps. Threepressure profile cycles were used as this accounts for any
pressure ramp variability. In practice each individual ramp
will never take exactly the same time. However, as you cansee from the graphs the PACE repeatability is extremely good
As can be seen the PACE is up to 7.5x faster for a given
pressure profile and this difference is even more pronounced
on larger volumes with larger ramps (due to the superior
ramp rate of the PACE controller). It is also crucial to consider
that PACE is settling to setpoints of 10ppm rather than 30ppm
of most competition. Remember also to consider speed
vs stability when analysing any potential claims maderegarding a fast controller.
All tests were performed with PACE set to maximum ramp
rate, overshoot enabled and with a 1 litre source volume
installed. An external sensor was used to log the pressure
independently and all setpoint changes were applied
via remote communications once a response from thecontrollers were received indicating that pressure was stable.
2. Presentation of results and observations

Barometric influence

MaintenanceIn order to guarantee the industry leading pressure control
performance, the Druck PACE controllers should be serviced atregular intervals (for example during yearly calibrations) andthis service can be provided in-house or at dedicated service
centres around the globe. This is one of the main advantagesof returning your Druck pressure controller to a recommended
service centre rather than a 3rd party. Returning the wholecontrol module as opposed to just a sensor module ensuresthat your control performance is always optimised

PACE CM2 S/N 11545593 10barg – 300cc volume

12000
10000

Pressure (mbarg)

On any gauge or pseudo-gauge pressure controller, theatmospheric pressure will have small influences on thepressure reading due to disturbances in the environment thePACE is controlling in such as doors opening/closing or air
conditioning for example. For this reason, Druck recommends
utilising the reference port snubber provided with all PACE
pressure controllers. The controller will still be able to reliably
measure barometric pressure, but the snubber prevents any
short-term disturbances from possibly affecting the PACE
controller during a pressure ramp or whilst maintaining its
industry leading control stability.

8000

6000

4000
2000
0050-2000

PACE

100

150

200

250

300

350

Time (seconds)
Competitor A

Competitor B

Observations:– PACE 82s typical (72s best case), A = 212s, B = 353s
(can be improved to 303s if uncontrolled vent is used
like in ramps 1 & 3).
– NB: If no-overshoot selected for the PACE then thetime taken increased to 101s, still significantly fasterthan competitor products. Competitor products wereboth configured to use their standard ‘fast’ settings.

PACE CM2 S/N 11545593 10barg – 300cc volume

12000

Observations:–P ACE 59s typical to 100%FS (38s best case), A = 102s, B = 217s

Pressure (mbarg)

10000

3. Conclusions

8000

6000

4000
2000
0050-2000

100150200

Time (seconds)

PACECompetitor ACompetitor B

Observations:– PACE 99s typical to 100%FS (75s best case), A = 158s, B = 202s
PACE CM2 S/N 11545593 10barg – 13cc volume

12000

Pressure (mbarg)

8000

As presented in this paper it is clear that PACE is by far thefastest pressure controller available on the market. From otherwhitepapers we have presented it can be seen that the PACE
product line also has the market leading accuracy and stability.

6000

4000
2000

050-2000

100

150200Time (seconds)

PACE

Competitor A

Competitor B

Observations:– PACE 37s typical (27s best case), A = 106s, B = 204s

In reality, a varying blend of speed, accuracy and stability
are required to optimize controller performance to meet theneeds of different applications. The excellence that PACE
demonstrates in these three key areas make it versatile
enough to optimize performance in numerous applications
across many different industries and applications withoutcompromising on performance. From Automotive to Aviation,from medical to metrological.
The benefits that this performance and versatility brings
from a profitability perspective as well as metrologicalperspective are self-evident.

PACE CM2 S/N 11545593 10barg – 13cc volume

12000

Contact your Druck sales representative to discuss
your application.

10000

Pressure (mbarg)

For a typical volume (50ml) on a production line
running 5 days a week 24 hours per day and based on
the performance data measured for this whitepaper it
can be seen that typical year 1 running costs would beapproximately 293% greater for competitor A and 656%
greater for competitor B.

Summary

10000

0As can be seen in the controller performance section thePACE controller performs very favorably compared to its
main competitors in the market. These performances also
hold true when control stability specifications are relaxed infavour of increased speed. You can see this performanceon many of our published Druck videos. If we equate thesesavings in production line operating time to monetarysavings, then it is clear to see the savings that can be made.

8000

6000

4000
2000
0050

-2000

100

200

Time (seconds)

PACE

Competitor A

Copyright 2023 Baker Hughes Company. All rights reserved.
BHCS39129		

150(04/2023)

Competitor B

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