1) What is Krystal Bond^™ Technology?

Krystal Bond Technology is a diffusion process developed by AST to inorganically bond micro-machined semiconductor strain gauges to metallic diaphragms in the presence of high temperatures.

Krystal Bond^™ Technology offers two distinct advantages to AST’s customers:

• AST customers get the sensitivity of MEMS silicon based piezo resistive gages, which can be more than 10 times higher than the sensitivity of other technologies. The combination of AST’s high performance strain gauges and Krystal Bond^™ Technology result in a gauge factor of 140 with low operating strain. (Operating stain is typically 275 microstrain @ 100% pressure!)
• AST sensors, with Krystal Bond^™ Technology, offer high electrical isolation (up to 1000VDC), low pressure & thermal hysteresis (<0.05% of FS), high frequency response. (High frequency response = fast response to changes in pressure, < 1mSec)
• Krystal Bond^™ Technology can be used with a wide range of materials, such as Stainless Steels, Inconel & Hastelloy (High Strength Nickel Alloy for high corrosion applications), and Titanium.

2) What is so unique about AST's technology in comparison to other technologies?

In addition to the advantages mentioned above, the combination of Krystal Bond™ Technology with high quality metallic, one-piece diaphragms offer many advantages to the AST customer that other technologies can not deliver:

• a. Excellent long-term stability (<0.25% of FS per year)
• b. High temperature operation (Media temps up to 250°C)
• c. No leak paths (Most AST products have a one-piece sensor element with No O-rings, process connection welds, or fluid filled cavities)
• d. High cyclic life ( >100,000,000 Full Pressure Cycles)
• e. High overload and burst pressure capabilities for safe operation even in extreme applications.

3) What are the current pressure ranges offered by AST?

Absolute Pressure: 0-15, 0-30, 0-50, 0-100, 0-300 PSIa

Gauge Pressure: 0-5 thru 0-60,000 PSIg (0-0.33 thru 0-4000 BARg)

Sealed Gauge Pressure: 0-100 thru 0-60,000 PSIs (0-7 thru 0-4000 BAR)

Differential Pressure: 0-15 thru 0-1000 PSId (0-1 thru 0-70 BAR)

4) What pressure units does AST commonly calibrate sensors to?

• PSI (pounds per square inch)
• BAR (1 BAR = 14.504 PSI)
• Kg/cm2 (1 Kg/cm2 = 14.223 psi)
• Inches of H2O (1 “H2O = 0.0361 Psi. Also, 1.0 psi = 27.68 “ of H2O)

5) I want to measure the level of water. How do I convert FEET to PSI?

• 1 foot of water = 12 inches H2O
• 12 inches H2O = 0.4335 PSI
• Multiply 0.4335 by the height [in feet] of the measuring range

6) Can Pressure Sensors and Transducers utilizing AST's Krystal Bond Technology measure from vacuum to positive pressure?

Yes, Krystal Bond Technology can be used in this type of application. AST refers to this as a Compound Sensor. A compound sensor is a gauge or sealed gauge sensor that is calibrated to emulate an absolute range. For example:

0-100 PSIA sensor = -14.7 to 85 PSIg sensor

or

0-7 BARa sensor = -1 to 6 Barg sensor

This option offers the ability to measure in PSIg ranges below 0 PSIg, avoiding the errors of absolute sensors that are seen during changes in daily barometric pressure or changes in altitude.

Applications where this is particularly useful are:

• refrigeration applications (separation and compressor)
• suction compressors
• reciprocating compressors
• pressure spike/transients monitoring in pipes and pipelines
• water pumps (especially where the pumps are made in used in different altitudes)

7) What is the difference between a pressure sensor, pressure transducer, pressure transmitter, pressure switch, and digital pressure gauge?

Please note that these terms are often interchanged without regard to the meaning below, and that the exact definitions may differ from source to source. AST uses these general definitions.

• Pressure Sensors
  Millivolt (mV) output signal (also a general term for all pressure types); a device that measures pressure. The millivolt output signal can typically be used ten (10) to (20) feet away from the electronics without significant signal loss.
• Pressure Transducers
  High level voltage or frequency output signal including 0.5 to 4.5V ratiometric (output signal is proportional to the supply) and 1-5V. These output signals should be used within twenty (20) feet of the electronics.
• Pressure Transmitters
  Current output signal, i.e. 4-20mA (4 to 20mA); the current is measured on the device, rather than the voltage; all AST pressure transmitters are two wire devices (red for supply. black for the ground). 4-20mA pressure transmitters offer good electrical noise immunity (EMI/RFI).
• Pressure Switches
  A pressure sensing device that has contacts at set points to open or close a circuit; all AST pressure switches are solid state with Open or Closed contacts.
• Digital Pressure Gauges
  Pressure measurement with a display; digital pressure gauges originated as battery powered gauges, but now feature output signals as well.

8) What is the media compatibility of AST's pressure products?

Below is a small chart that shows some of the wetted materials for AST’s pressure products and the media most commonly designated for each one. The chart is a guideline and can not factor all application variables. If you have a question about media compatibility, call us for some advise (that’s what we’re here for!) and we’ll provide our input into your material selection.

• 17-4 PH Stainless Steel
  Hydraulic fluid, Air (nitrogen, oxygen, etc), Natural Gas, Freon, Paint, Steam, Plastic Molding, Diesel Fuel, CO2
• 316 L Stainless Steel
  Hydrogen* applications, chlorinated water, ammonia refrigerants, Petroleum products (crude or processed)
  *Only Krystal Bond™ Technology
• Inconel
  High H2S applications, Salt water/Sea Water, high temp applications
• Titanium
  Medical, Aerospace

9) What type of mechanical interfaces are offered by AST for the pressure/process port?

AST offers wide selection of threads. If you do not see your desired thread here, please contact AST. There is a good possibility that AST already offers if for one of our custom applications. Some threads are more common than others (such as 1/4"-18 male NPT, AST’s most common thread) and will have shorter lead times and wider availability.

NPT (National Pipe Thread)
This is the most common thread family for AST’s pressure products.

• 1/8-27" NPT, both Male and Female* (rated up to 10,000 psi)
  *AST’s 1/8"-27 Female NPT is only offered in a the Panel Mount style preferred by most of AST’s 1/8"-27 Female NPT users. Please click here for more info on AST’s innovative Panel Mount design.
• 1/4-18" NPT, both Male and Female (rated up to 10,000 psi)
• 1/2-14" NPT, both Male and Female (rated up to 5,000 psi)

SAE (Society of Automotive Engineers) and UNF (Unified Fine) Threads
Great choice for pressure ranges up to 25,000 psi

• 3/8"-24 UNF, a.k.a. SAE 3 (Limited availability)
• 7/16"-20 UNF, a.k.a. SAE 4 (Female available with flare seating and internal Schraeder Depressor Pin)
• 9/16"-18 UNF, a.k.a. SAE 6
• 9/16"-18 UNF with 37° Flare, a.k.a. AN6 (Most commonly available for pressure 10,000 PSI and above.)

Metric Threads

• M12*1.5 Male (Very limited availability)
• M14*1.5 Male
• M16*1.5 Female (To be used with a metal dual cone seal. For extremely high pressures only 40,000 and above)
• M18*1.0 (Very limited availability)
• M20*1.5

Other

• 1/8" BSPP (British Standard Pipe Parallel) Male (Up to 15,000 psi)
• 1/4" BSPP Male (Up to 15,000 psi)
• G 1/4 Male (DIN 3852, Part 2, Type E, to be used with DIN 3869 ring seal.)
• 1/4 VCR Male (Often electro polished for use with high purity applications.)
• F250C Female Autoclave (With seating for a metal cone seal. For pressures from 20,000 to 40,000 psi)

10) What type of electrical interfaces are offered by AST?

AST offers a wide variety of options for hooking up the electrical end of your pressure sensors. Below are some of the more common options. If you do not see the desired electrical connection in this list, there is a good possibility that AST already offers it on one of our custom applications, or can offer a compatible alternative connection.

Note: AST can install a Stainless Steel Conduit fitting onto the electrical end of almost any AST product with a cable selected as the electrical connection.

• Cable options for Non-submersible sensors:
  24 AWG cable in 2 ft, 4 ft, 6 ft, & 10 ft
• Cable options for Submersible sensors:
  22 AWG cable in 6 ft, 10 ft, 15 ft, 20 ft, 25 ft, 35 ft, 40 ft, 50 ft, 75 ft, 100 ft, 150 ft
• Various In-line Connectors (Molex, Deustch, Amp/Tyco, Packard/Delphi) attached to the end of the cable
• Packard/Delphi Metripack 150 series, 3-pin Connector (Common Automotive Connector, Mates with AST p/n A04391)
• Hirschmann 43650 Forms A, B, and C
• Turck M12x1 Eurofast

Please visit our Media / Technical Center for availability on each product and wiring: Media Center

11) Can AST's products run from an unregulated power supply?

Please refer to the following chart:

All non-ratiometric pressure transducers and transmitters can operate from an unregulated power supply between 10 and 32VDC. For 4-20mA, it is important to have sufficient supply to maintain the minimum compliance voltage of 9V while driving long cable lengths. Ratiometric units must be supplied with regulated power supply, usually 5V.

12) How do I wire my pressure sensor?

Please view our wiring diagrams for both wire and connector electrical connections in our Media/Technical Center. Back to top

13) What are the advantages/disadvantages of each electrical output type AST offers?

Please review the following pdf document for electrical output information:

• Output Signal

14) Are AST's products able to withstand electrical interferences, such as EMI/RFI, transient, and ESD?

Some of AST's pressure products are designed to stand high levels of electrical interference such as EMI/RFI, electrical transients and ESD. These products are called "stand-alone" products. Radiated susceptibility up to 100V/m, transients to +/- 2kV and ESD levels of 8kV are standard features of a stand-alone product and comply with EN50082-2. To see which sensors meet CE EN61326, view our Products Page.

15) What agency approvals do AST's products meet?

AST currently offers a variety of UL, cUL, CE, and CSA (ATEX and CRN pending) agency approvals.

Please view the following product page site for a complete listing of AST products with their agency approvals:

• Products Page

16) Are AST's products approved for Canadian markets?

AST's products have been tested by UL and conform to Canadian Standards (CSA 157 and 213). UL has authorized AST to print the cUL logo on our labels as part of this certification. This certifies that AST sensors tested through Underwriters Laboratories in accordance with CSA standards.

17) What is meant by "panel mount" pressure sensor?

A panel mount is a unique design that replaces the traditional sensors and bulk head fitting with a single design. This allow the media to be kept outside the panel box while maintaining maximum safety of the system. Some applications include gas cabinets, pump controls, natural gas flow control and refrigeration/HVAC. Please view our AST4200 as well as a detailed Application Note.

18) For miniaturization, does AST offer any embedded sensor designs?

AST offers both threaded and unthreaded miniature units for embedding in manifolds and valves. Please view our Application Note.

19) What does long-term stability mean? How does it affect the measurements?

Long-term stability is normally associated with the change in zero offset due to aging of component and relaxation of the metallic diaphragm over a period of time. It normally causes the zero reading to go high or low over time. Independent tests carried out on AST's products have shown this number to be <.25% under the influence of temperature and pressure cycling for 1500hrs.

20) Do AST's products offer zero & span adjustments?

AST4310 (Class 1, Div 2) and AST4410 (Class 1, Div 1) offer zero and span adjustments. Adjustments are +/-5% for zero and span of the full scale pressure.

21) Can AST supply front-end pressure sensor subassemblies for customers to value add in house?

Yes, AST can supply either compensated or uncompensated front-end subassemblies. Electrical interface is by means of the Molex connector, flex strip or hook-up wires.

22) What is the best way for me to contact AST with regards to my sensor needs?

The best method for prompt response is to visit the Contact Us web page. You may also call/fax our offices in NJ (Phone: 973-448-1901; Fax: 973-448-1905) or your local factory trained sales representative (please see Local Reps section).

23) What is AST's return policy?

Warranty Workmanship - AST, Inc. pressure sensors and transmitters have a limited one-year warranty to the original purchaser. AST will replace or repair, free of charge, any defective pressure transmitter. This warranty does not apply to any units that have been modified; misused, neglected or installed where the application exceeds published ratings. AST's pressure sensors are made with pride in New Jersey, USA. If in the area please feel free to stop by for a visit!

Installation/Applications - The purchaser is responsible for media compatibility, functional adequacy, and correct installation of the transmitter.

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