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Pressure Sensors Special Feature

Pressure Sensors Special Feature

  • Chapter 1
  • What is a pressure sensor? 
 

 

 
 

1. Outline

 

 

 
 
Pressure sensors
A pressure sensor is a device that converts the pressure of a fluid such as a gas or liquid into an electrical signal. Broadly speaking, the pressure sensor references are divided into the following three types.
a. Gauge [based on “atmospheric pressure”]
b. Absolute [based on “absolute vacuum”]
c. Differential [Measures the difference between two pressures.]

 

 

2. Operating principles

 

 

 
 

Pressure sensors generally use a diaphragm that formed strain gauges on, and measure its strain (or deflection) due to applied force over the diaphragm area.

Our company, Nidec Copal Electronics offer two types of pressure sensors as sensing methods: a method using a diffusion type semiconductor (Silicone MEMS) and a method using a thin film gauge with SUS diaphragm. Each type has its own characteristics, and we have a wide variety of pressure sensor products by properly using these two type methods according to the application and market requirements.

Let's take a closer look at the operating principle for each type.

 
Ⅰ. Silicone MEMS (Si-MEMS)
Sensor chip_Si-MEMS
 
Cross-section of Sensor chip_Si-MEMS
 
Cross-section of diaphragm_Si-MEMS
Si-MEMS diaphragm
cross-section drawing
The Si-MEMS utilizes the piezoresistive effect in which the electric resistivity varies depending on the stress applied to the resistors. A sensor chip is made of single-crystal silicon. The chip structure allows the diaphragm to deform once the chip receives pressure.

The four strain resistors, connected as shown in the schematic below, constitute a Wheatstone bridge circuit. This bridge circuit is driven by constant current (nominal 1.5 mA DC). When pressure is applied, the resistance values of R2/R3 increase while those of R1/R4 decrease, bringing about inequality in the bridge circuit and causing a voltage difference at the output end. This voltage difference turns into an output voltage proportional to the pressure. Even when negative pressure is applied, the polarities are also inverted to the same orientation as when a positive pressure is applied.

To explain the pressure and output characteristic, the deformation of the diaphragm is illustrated in a magnified manner in the diaphragm cross-section drawing on aboveright, but the degree of deformation is as so small as several micrometers. Therefore, the mechanical deformation of the diaphragm is hardly recognized in appearance.

  • strain gauge pattern_Si-MEMS
  • Wheatstone bridge circuit_Si-MEMS
 
Ⅱ. Thin film sensor (SUS diaphragm)
Cross-section of Sensor chip_SUS
Cross-section of thin film sensor
Thin film sensor
cross-section drawing
Ⅱ. Thin film sensor (with SUS diaphragm)
A thin film sensor is structured by forming a thin film gauge on a metal SUS diaphragm via an insulating film. When pressure is applied, the metal diaphragm deforms and the thin film gauge formed on the diaphragm distorts, which then detects changes in the resistance value of the gauge.

In a thin film sensor, as with Si-MEMS, four thin film resistors are connected as shown in the schematic below to constitute a Wheatstone bridge circuit. The thin film resistors are driven by constant voltage. The metal diaphragm deforms once it receives pressure, the thin film resistors formed on the diaphragm distort, which then detect any changes in the resistance value of the gauge. Thus, a voltage signal in proportion to the pressure can be obtained.

  • Wheatstone bridge circuit_Thin film gauge (on SUS diaphragm)
 
  • Chapter 2
  • Introduction of our pressure sensors
 

 

 
 

1. Milestones

 

 

 
 

We've been supplying pressure sensors for about 40 years, beginning with the manufacturing and sales of pressure sensors for electronic sphygmomanometers in 1980. Thanks to you, our pressure sensors are widely used in various industries such as semiconductor manufacturing equipment, industrial equipment, medical equipment, analysis equipment, measuring equipment, and hydraulic equipment such as machining centers.

  • Nidec Copal Electronics Pressure Sensor Business Milestone
  • Sano Plant satellite-photo
  • Sano R&D center

The business base will be the Sano Plant in Tochigi Prefecture, Japan. We handle everything from sensor chips to final pressure sensor products, and today it has grown into a leading business of our company.

 

2. Abundant standard product lineup

 

 

 
 
Pressure sensor products
We offer a variety of pressure sensor products with different product types, such as module types, built-in amplifier types, pressure switches that open and close the contacts of pressure-sensitive elements by applying a specific pressure value, and pressure gauges with a display function. We have a large selection.
The types of pressure sensor elements are the semiconductor Si-MEMS and the thin film sensor with SUS. Among them, there are two types of Si-MEMS methods; one is a silicon single crystal type dedicated to non-corrosive gas as a medium, and the other is a dual diaphragm structure type that is placed a SUS diaphragm in the wetted part, that can also apply for liquids as a medium. We use each of these sensor elements appropriately according to the application and environment, and develop them into various final products.
MethodSi-MEMS (Si single crystals)Si-MEMS (Dual diaphragm)Thin film sensor with SUS
Structure
Si single-crystal element is bonded to the glass base by means of anodic bonding via Na ions contained in the glass. The Si single-crystal element directly receives the medium. An SUS diaphragm is bonded to the housing by means of laser welding, and conveys pressure to the silicone sensor chip via the silicone oil. A thin film gauge is formed by means of vapor deposition on a SUS diaphragm via an insulating film.
Media Dedicated for noncorrosive gas Gas or liquid that does not corrode the SUS material in the wetted part Gas or liquid that does not corrode the SUS material in the wetted part
Features
  • • Although the characteristics change depending on the temperature,
    these models exhibit high reproductivity under certain temperatures.
  • • Capable of receiving high pressure and outputting high voltage at a high accuracy (approx. 100 mV at rated pressure of 100 kPa)
  • • Free from mechanical movable part, a long service life can be achieved
  • • With a high mass productivity, manufacturing at a lower cost is achieved.
  • • Suitable for vacuum, high and low temperature applications
  • • Exhibits less temperature-dependent characteristic change
  • • Single-model mass-production leads to manufacturing at a lower cost
  • • Compatible with electrolytic polishing

Our pressure sensor series lineup

Pressure
transducer
(Module)

P-2000, P-3000S P-8300, P-8305, P-8505

Pressure
transducer
with Amp.

PA-20, PA-100, PA-500 P-7100, PA-750/758, PA-800, PA-830/838, PA-838-D, PA-850/858, PA-860/868
High vacuum: PA-920S/928S
High temperature: PA-930/930-A
Pressure switch PS20, PS30, PS40, PS6, PS60 PS8, PS83, PS85, PS86 High vacuum: PS91, PAS91
  • Pressure gauge
  • Handheld digital manometer
PG-30, PG-200,PG-100N PG-35, PG-75, PG-208, PG-100B High vacuum: PG-20, PG-35L
High pressure: PG-35H
*In addition, we have a standard lineup of two series of pressure indicators, PZ-30 and PZ-200.

In recent years, we've been aggressively releasing new products such as types with a built-in small amplifier with ratiometric output and types for high vacuum and high temperature using the thin film sensor elements with SUS, and we are expanding our business domain.

 
  • Chapter 3
  • Strengths of our pressure sensors
 

 

 
 

1. In-house integrated production

 

 

 
 

We manufacture in-house from sensor elements by making full use of semiconductor technology, and further develop and manufacture pressure sensor final products through processes such as mounting, temperature compensation, electronic circuit addition and casing, etc.


  • Silicone wafer ⇒ Sensor chip

  • Pressure sensor module

  • Pressure sensor products
    with amp.

A major feature of our pressure sensor is that we handle everything from development design to sensor element manufacturing process and product assembly process / calibration under the integrated quality control of our pressure sensor business based on high-mix low-volume production. Our strength lies in this business structure, which is capable of responding to special specifications and various customer needs in detail.

 

2. Special products (Customizations)

 

 

 
 
― Policy for custom support ―
In our pressure sensor business, while enhancing the standard product lineup mentioned above, we've been actively responding to custom support and joint development according to individual requests from the market and customers, with the following customer-first policy.

Our policy for customizations is as follows:

  1. If we can apply our existing products / technologies and judge that they can be commercialized in consideration of business feasibility, we will actively accept custom support.
  2. Even if the technology we have is scarce at the time of your request, we will consider it positively if we judge that joint development is possible.
  3. We will proactively propose the products and services that our customers need by collecting information by industry unique to us.

Our pressure sensors have a total of 92 models, and the P/N of models is 1,992. Of these, Customizations, so-called Special products, accounts for nearly 80% of the total on a monetary basis, and as the results show, we have provided many custom products and services that meet the individual needs of the market and customers. Introduce some examples of the special products bellow.

 

Customization examples

Electrolytic polishing + Degreasing + Clean packaging
Electrolitic polishing / Degreasing / clean packaging are often required as essential for in-line piping applications in semiconductor manufacturing equipment. First, in "Electrolitic polishing", the flatness is improved by chemical polishing so that impurities do not remain in the pressure receiving part. In addition, "Degreasing" prevents contamination by cleaning the organic matter in the pressure receiving part. Similarly, "Clean packaging" prevents contamination from the outside and guarantees the clean condition of the pressure sensor product until it is used by the customer.
 
PA-750/758 series: Compatible with cable connectors and Direct cable from body
  • Standard model
  • (1) Cable with connectors
  • (2) Direct cable from body

The PA-750/758 standard series uses a connector cable that the body and cable can be attached and detached, and the cable tip has a lead wire. We have both achievements in supporting (1) the installation of designated tip connectors and (2) direct cable removal from the main unit.

 
PS20 series: Special fitting

  • Standard model
  • Special fitting

The PS20 standard series is M5 male screw or block M5 female screw, but we have made a proposal to meet the market needs to extend the tip of the block, make an hole for M5 female screw, and fix it with a mounting screw.

 
Other examples
Specification / Performance change
Pressure range / Pressure unit Pressure range: Provision of range other than that in standard products, change of standard pressure unit (e.g. PSI, etc.)
Performance Accuracy enhancement (e.g. output calibration error, improvement of temperature characteristic, improvement of pressure resistance, etc.)
Output Analog output value, support for I2C/SPI, and others
Power voltage Change to desired power voltage
Ambient temperature Change to specification suitable for desired ambient temperature
Switch setting Shipment with a desired pressure threshold setting
Zero adjustment Addition of zero adjustment setting
Appearance / shape change
Fitting Shape, size, material, etc.
Cable                         Length, lead wire diameter, connector processing, terminal processing, tag attachment, etc.      
OEM design Name plate, panel design, casing color, etc.
Others
Custom development   Manufacturing of circuit board, unit design, custom-made shape, etc.              
 

With our experience and expertise, we will propose the best products and services that meet your needs. Please feel free to contact us from the button below.

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