Flow and pressure control tailored for you

Highly customized flow and pressure control for demanding applications

You know your process. We know the parts you need to help get you there.

An Alicat PC-15PSIG-D pressure controller

At Alicat, we are not only focused on accuracy but customizability. We give our customers the best solution for their application, whether that be in a humid, corrosive or heavily regulated environment. Every Alicat pressure, liquid or mass flow controller is completely tailored to the customer’s needs, from flow rates to communication protocols.

Alicat devices are as diverse as the applications they are used in. For example, one customer needed to control pressure in a test environment to adjust humidity. They purchased this device: PC-15PSIG-D/5P, 5IN; a 15 PSIG pressure controller. For many customers, this level of customization is enough to satisfy the application needs.

However, some customers need more.

A customer called us looking for a pressure controller that could control gas at 155 PSIG and handle flow up to 5,000 SLPM. The controller needed to be placed in an OEM box system but not lose interactivity from outside of the box. Within the box, the system was set to operate at temperatures up to 70 oC, and to be consistent with the rest of the equipment the device required analog signals and connections.

They also expressed some concerns to us: the system included pressure sensitive instruments which would break above 155 PSIG. Since the supply pressure was 180 PSIG this would damage or break the instruments, so the controller needed to measure pressure precisely at these sensitive instruments to ensure the pressure limit was not exceeded. While the operating temperature was 70 oC, the storage temperature of the box dropped down to -50 oC making condensation a big concern. With previous Alicat devices they’ve purchased, they noticed that the devices retained the last setpoint in its memory at power up, which was a security concern.

The instrument we designed for this customer addresses all of these concerns and is represented by the part number below:

PCRH3-100PSIG-RD-REMOTE-M12-40×55-SAE24-CC/CP, 5IN, RANGE (155 PSIG), P1: 180 PSIG, FLOW (5000 SLPM), GT[1], PUSP: 0, RD: 1.5’, REM: 1’

Now, this might look a lot like alphabet soup, but every letter and number lets us know exactly what this Alicat will look like.

Alicat PCRH3-100PSIG-RD-REMOTE high flow pressure controller with remote sense port and panel-mounting

Let’s walk through the part number:

High-flow pressure control: PCRH…40×55…P1: 180 PSIG, FLOW (5000 SLPM)

The first letters, simply put, designate that the device is a pressure controller, shown as PC. The RH afterwards means that this device has a pair of Rolamite valves in Hammerhead configuration. This allows for 5,000 SLPM high flow capacity. Hammerhead valves open and close simultaneously which doubles the surface area of the valve orifices, allowing more flow. Additionally, we built the valves with a custom size of 40×55, 40 being the orifice size (0.040”) and 55 being the number of holes in the Rolamite hole pattern. This specific hole pattern was determined to afford the greatest control across the expected range of inlet pressures (P1: 180 PSIG) and desired maximum flow rate (FLOW: 5000 SLPM).

Remote pressure sensing: 3

The customer wanted to maintain pressure after a delicate system of other instruments, but needed to regulate the airflow before it reached this system. The 3 signifies a remote sense port, which allows such pressure controllers to sense flow in a different area than where the valves are controlling the flow. This system is ideal in applications with limited space because the valve does not need to be located where pressure is being measured.

Customized pressure range: 100 PSIG…RANGE (155 PSIG)

The maximum pressure that the customer intended to control was 155 PSIG, so we modified the sensor range from the 0-100 PSIG stock sensor range to 0-155 PSIG.

Designed for panel-mounting: RD-REMOTE…RD: 1.5’, REM: 1’

This pressure control system was located inside of a box, but needed to be controlled from the outside. A remote display, noted as RD, allows the display to be mounted outside of the box, giving user access to all of the functions inside. RD: 1.5’ is the length of the cable that connects the remote display to the rest of the controller. The remote display was tested to withstand temperatures down to -50 oC, the lowest anticipated storage temperature.

With operating temperatures within the boxed system as hot as 70 oC, a REMOTE electronics package was specified. In high temperature scenarios which would damage the standard electronics, we separate the sensor assembly from the rest of the electronics package, so only the sensor interacts with high temperatures and the electronics are kept safe. REM: 1’ is the custom length of the cabling needed to connect the electronics to the sensor and flow body of the device.

Locking industrial connector: M12

The customer requested a locking M12 electrical connector to keep their system from coming unplugged inside the box.

Coated to protect against condensation: CC

Moving from the -50 oC storage temperature to room temperature would sometimes lead to condensation within the system, and this could short out the electronics. To prevent this, we added a protective conformal coating (CC) on the circuit board to protect against any condensation.

SAE24 fittings

The customer was already using SAE24 threaded process connections, so we matched it.

Mismatched analog signals: CP, 5IN

Another customization for this device is a mismatched analog input and output: a 4-20 mA output pressure data (CP) and a 0-5 Vdc setpoint input signal (5IN). Typically customers use an input and output that match, but this customer needed a mismatched setup to make this pressure controller work with their existing system signals, including a PLC that has an output of 0-5Vdc.

Remote analog tare: GT[1]

Because the customer was not using a digital interface for communications with the PLC, they needed a way to remotely tare the controller using analog signals. To satisfy this need, we designed this device to be tared by grounding Pin 1 of the M12 connector.

Preconfigured setpoint: PUSP: 0

To avoid revealing potentially sensitive information, this pressure controller will always bring up a setpoint of 0 PSIG (PUSP: 0).


Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

Tough environments call for tougher instruments

Alicat instruments are built specifically for the conditions under which they will operate and the environments where they will be used, according to each customer’s needs. We work directly with customers to understand the stressors that will be placed on the instrument to ensure that every Alicat is up to the challenges they may experience in the field, lab or factory. Because the best repair is the one you never need, Alicat has a number of options to keep your process flowing smoothly.

In a precision test setting, it is unlikely that errant particulates, changes in ambient conditions or back flow of water will ever reach instrumentation. But Alicat instruments are often used far from the clean room. They are used to calibrate air monitors where the weather is a factor. They are used to maintain pressure and control gas mixtures in bioreactors, where cleaning means running the risk of splashing instruments. Some processes require the use of gases far more aggressive than air and other such nonreactive gases.


In ambient air monitoring applications, humidified air can make it difficult to achieve the required accuracy in the field, especially when it is hot and humid. That is why we developed the FP-25. This flow meter incorporates a live humidity sensor that ensures accuracy of measurement at any temperature and humidity.

Recently we worked with an air monitoring customer who needed to control the flow of ambient air in humid areas at a high level of accuracy. We developed a flow controller that uses the same internal relative humidity sensor and software to correct readings based on relative humidity that we use in the FP-25. This allows for accurate sampling of ambient air as temperature and humidity change.


Water outside the process line can cause issues as well. While some solutions might include creating some sort of protective box around process control instrumentation, or simply placing a plastic bag over the equipment and hoping for the best, we can build units to be rated up to IP66. Because our gas flow bodies are the same as our liquid flow bodies, a little water in the system won’t cause complete failure of the device, provided that it can be dried out later. Additionally, we have a conformal coating option to protect the interior electronics for situations where changes in temperature can cause condensation. Rain, back splash from a hose or conditions that might lead to condensation on or within the instrument are non-issues for Alicat instruments equipped with these options.

And if water or other damaging conditions are anticipated to a point where the electronics are at risk of damage greater than what can be protected with an IP66 rating or coating, we can build the device with the sensor and the electronics package as a separate remote option. This option is most frequently used in high heat environments, but can efficiently remove the more sensitive electronics away from wet conditions.

Corrosive Gases

Some processes throw more at the device than the forces of Mother Nature, and not all gases are as gentle as air, nitrogen or other common gases. Many customer processes require corrosive gases like ammonia or sulfur dioxide that could cause damage to the instrument. Depending on the gas being used, we can use FFKM or EPDM elastomers and stainless steel components. For some applications, we can customize from there, too. Our S series instruments are built with 316L stainless steel sensors, and in many cases the flow bodies and valving can also be ordered as 316L.

Hazardous Environments

For processes and environments that are potentially explosive, most Alicat instruments can be built with a CSA Class 1 Division 2/ATEX Zone 2 area certification. These instruments can be used in oil and gas applications where exposure to combustible gases is possible.

Your process can be messy, rough, jarring and abrasive. The last thing you want to worry about is your process control instrumentation being too delicate to handle the task. That’s why at Alicat we custom-build each unit with the customer’s process in mind. These Alicats are not just built to withstand tough process conditions; they can be configured to thrive in harsh ambient conditions as well. Backed by annual recalibrations and our limited lifetime warranty, an Alicat instrument will keep your process running smoothly, even in challenging environments, for years to come.

Your process, your project and the end results are what are most important. Spend your time on the things that matter, not worrying about your instrumentation.


Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

How can I take advantage of PID Tuning?

How can I take advantage of PID Tuning?

Posted by: Jas Gill

Alicat flow and pressure controllers use closed loop control algorithms to achieve their highest degree of control stability. The algorithms are a mathematical relationship that dictates the response of the valve to the flow or pressure conditions. It assesses the difference between the set point and the process value—whether it be mass flow, volumetric flow, or pressure—as an error. The degree of error determines what kind of input to send to the valve, reaching the correct value in the quickest time possible. The amount of time expended to minimize the error—and therefore the control response of the controller—depends on what type of loop is being used (PD or PD2I) and what P, D and I values are used.

When you order your controller, we set the Proportional and Derivative values by trying to replicate the application parameters (process conditions) to the best of our ability before we ship it to you. This customization to your system is one reason our controllers are fast.

No worries

If process conditions change, the valve response may change drastically depending on how much you deviate from the conditions the valve was tuned at. You need not worry about erratic response from your controller if the conditions change, since PID tuning can be done in field to get better control at the new process conditions. You can change PID terms through the display panel buttons, or through electronic commands using digital or analog communications.

You’ll get optimal performance from your controller when you select correct values for all three parameters (two in case of single valve controllers). The ‘P’ term opens the valve to achieve the set point, ‘D’ term applies a damping influence to eliminate the overshoot and ‘I’ function helps the system settle to the set point.

A previous blog describes the P, D, I terms:
Achieving Responsive and Stable Valve Control with PID Tuning

  1. Proportional (P): The P term applies power to the valve as it tries to decrease the error between the set point and the process value position to achieve the set point.
  2. Derivative (D): Think of this as a damping term which tries to reduce the rate of change. The larger the D term, higher the damping influence on the valve drive.
  3. Integral (I): Integral in calculus is the area under the curve, it determines the output of the valve as a function of the sum of all the errors. I term takes into account previous readings to reduce the error and correct the process value to the set point.


Oscillating around the set point

If your controller shows signs of oscillations about the set point, or is unstable in its control response, it is a sign that the P term is too large. The greater the P value, the greater the range of oscillation. To get rid of the oscillation (settle the controller to set point), you would need to decrease the P term.

Let’s say you have a 10 SLPM controller set to 10 SLPM for Hydrogen. The controller is oscillating between 8 and 12 SLPM. Hydrogen is a low viscosity and a very light gas compared to Air. This being the case, the valve—which is tuned with air—should be re-tuned. So, starting with the factory P value (for example, it may be 1000), try decrements of 10% and keep on going down until you see the controller settle to the set point quickest. Generally, we only touch the D terms after you have altered the P term, so if you still have small oscillations, you can increase the D value with 5-10% increment. This should help the controller become more stable.

PID response shown graphically, by varying P

Excessive P (purple) produces oscillation. Low P (red) slowly rises to the setpoint. Optimal (green) settles quickly.

Delayed setpoint

A second situation is when your controller takes too long to get to the set point or never achieves the set point, but settles to a flow rate or pressure below the set point value. This implies either too small a P value being used or too large a damping influence. Using the analogy of a car, imagine you want to get to 70 miles per hour. but when you start increasing the speed, someone applies brakes which decreases the acceleration of the car. The car may never get to 70 mph if the deceleration is larger than acceleration, and the car may settle at a speed of 60 mph when acceleration = deceleration, or the opposite forces are equal.

In this case, try increasing your P value in 10-15% increments until you see the controller getting close to your set point. Next step would be to decrease the D value to help the controller get to the set point in a quicker time. If you start seeing some oscillations, that means the D value has been set too low.

Control loop adjustment is all about getting a good feel of how the controller responds to changes in the P and D terms. The gas viscosity, inlet pressure, back pressure can greatly influence how the valve responds. Tuning the valve is an art rather than science and the more familiar you get with your controller, the better you’ll be able to tune it.





Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

7v Firmware Update Makes Interface More Intuitive for Alicat Flow and Pressure Instruments

Posted by: Danielle Adams

We’ve just made it easier to use your Alicat mass flow meters and pressure controllers from their front panels. This post has all the details on our 7v firmware update, which features a more intuitive user interface.

If you’ve been with Alicat for very long, you’ve seen us add new menu selections to our flow and pressure instruments from time to time. We incorporated these features into a set of “Miscellaneous” menus (MISC1 and MISC2) in order to preserve the existing interface. However, after filling up MISC1 and MISC2 with new functions, we decided it was time to give the entire menu system an intuitive update.

Alicat mass flow controller showing new basic configuration menu

Alicat mass flow controller showing new basic configuration menu

Here to explain the motive behind these changes is Brian Clandenon, Alicat’s Senior Software Engineer:

“As Alicat has added more functionality to our instruments, the idea was to make minimal changes to existing buttons in the menus. While this was reasonable for each small change, so many changes built up over the past few years that some related functions became scattered across multiple menus. This made the menus more challenging to navigate and to remember.

Alicat mass flow controller showing new advanced setup menu

Alicat mass flow controller showing new advanced setup menu

One goal of a good menu system is to make settings easy to find, so it became time to review the overall structure of the menus. We endeavored to organize the settings in ways that would be more intuitive to new and existing users alike, so that the changes would outweigh the inconvenience of learning the new locations.”

The following FAQ describes the changes to Alicat’s menu structure in the new 7v firmware.

Which instruments are affected by this change?

All Alicat-branded instruments manufactured on or after May 22, 2017, will ship with 7v firmware, with the exception of no-change customers who have not yet approved this update.

Can I update my existing instruments to 7v?

Alicat’s 7v firmware update is compatible with most Alicat instruments that have serial numbers of 135,000 or higher. Some instruments with serial numbers between 80,000 and 135,000 may also be compatible with 7v. Upon request, we can update your firmware to 7v during your instrument’s next annual recalibration at no charge. Alternatively, we can update instruments outside of the recalibration process for a firmware update bench fee of $80 (USD).

Will my new 7v Alicat communicate the same as my existing 6v Alicats?

Yes. Communications protocols and commands have not changed in the move from 6v to 7v, so your command set will remain the same, no matter which protocol you have been using.

Which changes will I notice?

Alicat mass flow controller showing new main menu

Alicat mass flow controller showing new main menu

The new menu map is reproduced on the following page. Below, you will find a listing of changes to the menu structure. Please see your new operating manual for more details.

  • A new BASIC CONFIG menu allows easy access to GAS SELECT, DEVICE UNITS and STP/NTP options. The GAS menu option also displays the currently selected gas.
  • A new TARES menu gives you access to flow and pressure tares, plus AUTO TARE.
  • A new ABOUT menu collects DEVICE INFO, DEVICE STATE and MFG INFO in one place.
  • The contents of the old MISC, MISC1 and MISC2 menus can now be accessed via the ADV SETUP menu, with the exception of STP/NTP, which is now in BASIC CONFIG.
Feature New Menu Location (7v Firmware) Old Menu Location (6v, 5v or 4v)

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com