Pressure Sensors Special Feature

Pressure Sensors Special Feature

1. Outline

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 COMPONENTS 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)

 

 

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.

Ⅱ. Thin film sensor (SUS diaphragm)

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.

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.

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

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.

Method	Si-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.

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 ―

Our policy for customizations is as follows:

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

Appearance / shape change

Others

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.

• 
  FAQ