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Frequently Asked Questions

1) What is HOLYKELL Sensor Technology?

HOLYKELL Sensor Technology is based on the internationally advanced MEMS technology, it introduces the advanced production equipment from the U.S. and Germany, adopts the advanced glass micro-melting technique, applies the internationally advanced bus operation technology and the wide-temperature digital compensation data debugging system to guarantee the high product quality and bring the strict high-quality standards and advanced cooperation concepts to China. 

HOLYKELL Technology offers two distinct advantages to HOLYKELL’s customers:

* HOLYKELL sensors, with HOLYKELL Technology, offer high electrical isolation (up to 1000VDC), low pressure & thermal hysteresis (<0.05% of FS), high frequency response. (High frequency response = HOLYKELL fresponse to changes in pressure, < 1mSec)

* HOLYKELL Technology can be used with a wide range of materials, such as Stainless Steels, Inconel, titanium alloy& Hastelloy alloy C-276 and so on.

2) What is so unique about HOLYKELL’s Sensor technology in comparison to other technologies?

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

  a. Excellent long-term stability (<0.2% of FS per year)

  b. High temperature operation for melt pressure sensor (Media temps up to 400°C)

  c. No leak paths (Most HOLYKELL 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 is the current pressure ranges offered by HOLYKELL?

Absolute Pressure: 0-1, 0-2, 0-5, 0-10, 0-30, 0-50, 0-100 BARA

Gauge Pressure: 0-5 thru 0-60,000 PSIG (0-0.33 thru 0-6000 BARG)

Sealed Gauge Pressure: 0-100 thru 0-60,000 PSIs (0-7 thru 0-6000 BAR)

Differential Pressure: 0-1 thru 0-507.6PSID (0-0.068 thru 0-35 BAR)

Capacitance Differential: updating

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

* PSI (pounds per square inch)

* BAR (1 BAR = 14.504 PSI)

* KPA (100 KPA = 1 BAR)

*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 HOLYKELL’s Sensor Technology measure from vacuum to positive pressure?

Yes, HOLYKELL Sensor Technology can be used in this type of application. HOLYKELL 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. HOLYKELL 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 HOLYKELL 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 HOLYKELL 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 HOLYKELL’s pressure products?

Below is a small chart that shows some of the wetted materials for HOLYKELL’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, PlHOLYKELLic Molding, Diesel Fuel, CO2

*316 L Stainless Steel

Hydrogen* applications, chlorinated water, ammonia refrigerants, Petroleum products (crude or processed)*Only HOLYKELL Technology


High H2S applications, Salt water/Sea Water, high temp applications


Medical, Aerospace

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

HOLYKELL offers wide selection of threads. If you do not see your desired thread here, please contact HOLYKELL. There is a good possibility that HOLYKELL already offers if for one of our custom applications. Some threads are more common than others (such as 1/4"-18 male NPT, HOLYKELL’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 HOLYKELL’s pressure products.

*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)


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

HOLYKELL 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 HOLYKELL already offers it on one of our custom applications, or can offer a compatible alternative connection.

Note: HOLYKELL can install a Stainless Steel Conduit fitting onto the electrical end of almost any HOLYKELL 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 HOLYKELL p/n  A04391)

*Hirschmann 43650 Forms A, B, and C

*Turck M12x1 EurofHOLYKELL

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

11) Can HOLYKELL’s products run from an unregulated power supply?

Please refer to the following chart:



Unregulated Supply (9-36V or 12-33V)




24 VDC




10 VDC




 5 VDC

2mV/V, 3.33mV/V, or 

3 mV/V to 10mV/V


0.5-4.5VDC Ratiometric



1-5V, 0-5V, 0-10V



All non-ratiometric pressure transducers and transmitters can operate from an unregulated power supply between 9 and 36VDC. 

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 Products manual.

13) For miniaturization, does HOLYKELL offer any embedded sensor designs?

HOLYKELL offers both threaded and unthreaded miniature units for embedding in manifolds and valves.

14) 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 HOLYKELL’s products have shown this number to be <.2% under the influence of temperature and pressure cycling for 1500hrs.

15) Do HOLYKELL’s products offer zero & span adjustments?

HOLYKELL HPT131Series and HPT124 Series models offer zero and span adjustments. Adjustments are +/-5% for zero and span of the full scale pressure.

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

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Lugu High-Tech Development Zone
Changsha City,Hunan,China
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