Suppliers target broader application base
Makers cater to industrial automation and measurement requirements while boosting penetration in various sectors. Suppliers of transducers in China are stepping up R&D efforts to meet broadening applications, lining up miniaturization and integration on the agenda. In addition to strengthening expertise in industrial automation and measurements, they are eyeing sectors, particularly automotive, which is considered a future high-growth area. To achieve both objectives, manufacturers continue to explore technologies on design, materials, production, reliability and testing.
At present, most products from local makers are based on customized designs, which are largely determined by functions required by buyers. This in turn dictates the type of sensor, the complexity and size of the signal converting and amplifying circuit, and the additional components to be used. All have a bearing on the dimensions of the transducer. Nevertheless, companies continue to follow the miniaturization trend, looking to benefit further from the release of more compact sensors, SMD inputs and PCBs.
A growing number of manufacturers are also developing integrated models, which combine two or more sensors to provide measure and control functions for complex applications. Such variants can improve operation speed and efficiency in industrial automation and process management. An example is Tongdy Control Technology Co. Ltd’s CO2 duct probe model for office and residential use. The product has a built-in nondispersive infrared CO2, and combined temperature and humidity sensors. The first boasts self-calibration and up to 15-year life span. The unit comes with an optional LCD screen. To enhance response time, makers are using such sensor types, which can measure broad signal bandwidth and reduce delay. Conditions such as steady state, transient and random are considered in the selection of the added component to avoid distortion and error in testing.
Suppliers believe integration will boost the development of intelligent types. As such, some are incorporating MCUs in transducer circuits to enable more functions, which include automatic compensation, communication, self-diagnosis and logic processes. Henan Hanwei Electronics Co. Ltd’s digital intelligent pressure model adopts a 16-bit MCU and has 4 to 20mA output. Its RS-485 ports allow connection to various products. The unit supports field bus and other communication protocols. In addition, it has capacitive sensors for high accuracy and stability.
Multifunction and intelligent kinds are expected to dominate the market in coming years. This is because of the line’s expansion beyond traditional applications in the industrial sector. Demand from automotive control, medical equipment, security, and energy and environment control systems is in fact accelerating developments in the category.
For design and manufacturing, makers continue to adhere to existing standards, including ISO, ANSI, ASTM and JIS. They ensure compliance with CE, UL, RoHS and ATEX. China’s transducer and sensor industry remains on the growth path and is expected to keep the momentum in years to come as manufacturers sustain technological innovations. Total sales are projected to reach $9.3 billion by year-end, from $6.3 billion in 2009. These registered a 15 percent increase last year and exceeded 20 percent in 2008 despite the global financial crisis.
Most makers are raising capacity by 10 to 50 percent until 2011 because of a demand boost from the industrial control, instrument and automotive sectors. To achieve this target, they are improving automation, which remains a major challenge.
China’s transducer sector, which began in 1958, saw an influx of many key makers that established their own operations or entered into joint ventures in the country in the past 20 years. Among them are Fuji, Hitachi, Siemens, ABB, Endress+Hauser, Honeywell, Rosemount and Yokogawa. Although it intensified competition, the migration benefited the local segment, contributing to overall improvements in technology and production.
At present, there are more than 500 suppliers, according to the China Sensor Trade Association. Small operations with a low lot capacity account for over 95 percent of the pool. They are based in Beijing, Tianjin, Shanghai, and the provinces of Shanxi, Guangdong, Zhejiang, Jiangsu and Liaoning. 3,000-model transducer selection
The selection from China includes 3,000 transducer models, representing a tenth of the worldwide total. It spans various subcategories, with pressure, temperature, piezoelectric, gas, humidity, magnetic, liquid-level, capacitance, acoustic, current and optic variants on offer. By target application, these are further subdivided into industrial, automotive, telecom, consumer electronics and special instrument types.
Pressure units come in a number of varieties that match industrial control, traffic, military and aerospace requirements. One of the mostwidely available is the strain-gauge kind. It converts pressure into an electrical signal using the physical deformation of strain gauges. The last are bonded onto the diaphragm of the transducer and wired into a wheatstone bridge configuration. The response to a deflection of the diaphragm when pressure is applied produces an electrical resistance change proportional to it.
In terms of electrical output, three types of pressure transducers are available. These are millivolt, 0 to 5V voltage output and 4 to 20mA output. Products can reach an accuracy of ±0.075 percent based on analog output. Makers hope to achieve ±0.05 percent or even lower with the latest sensor releases. The latter includes capacitive vacuum, fiber-optic or silicon MEMS types.
The temperature segment includes models suitable for industrial control, household appliances, medical equipment, buildings and automotives. Often found in automatic control systems, the component transforms temperature into mechanica l movement, pressure, or electric voltage, which is processed in a controller and applied to an actuator controlling heat. Two-terminal integrated circuit variants are the most-popular. These convert -200 to 1,600 C temperature to 2-terminal 4 to 20A DC current signals, providing input for temperature display and adjuster or recording machines for precise measure and control. Available piezoelectric versions suit various requirements. Their diaphragms are utilized as pressure sensors in speakers, and fluid ejection and pumping, and printing applications. The ceramic type, meanwhile, is employed in adaptive structures for vibration control and acoustic noise suppression in space, civilian and military systems. The last covers launch vehicles, space platforms, aircraft, submarines and helicopters.
For the metallurgy, oil, chemical and watercraft industries, makers supply a selection of gas transducers in various response time, distance and flow rate specifications. All are key parameters in determining gas concentration and providing output to instruments. Units also measure operating temperature and humidity. The mainstream accuracy achieved is 2 percent, but companies are confident it can be brought down to 1 percent or below with the use of new sensors.
Humidity types come in a range of models for laboratories, heating, ventilation and air-conditioning systems, and equipment used in areas where humidity control is necessary. These allow the activation of alarms and auto-shutdown of ventilation systems at predefined minimum and maximum limits.
For point and level measurements, suppliers provide a range of magnetic, liquid-level, capacitance, acoustic and optic variants. The products target industrial control, oil, chemical and automotive applications.
The selection of current transducers is based on the Hall effect technology. The components are made using open- and close-loop methods. Models adopting the first adopt the simplest form of Hall effect and have the advantages of light weight, small construction and low power consumption, making them cost effective options. Close-loop versions boast a compensation circuit for improved performance in terms of accuracy, linearity, wide bandwidth, low gain drift and fast response time. Makers expect no price adjustments for the rest of the year, noting current quotes are at almost 2009 levels. The slight variance in certain models is due to labor costs and fluctuation in the currency exchange rates. Most companies anticipate expanded capacity will help off set an increase in production outlay.
Materials & components
Transducers consist of sensors, PCBs, resistors, capacitors, inductors, ICs, displays and connectors. The first is the key component.
Pressure versions include resistance and semiconductor strain gauge, inductive, capacitive and piezoresistive units. The last is the most- widely adopted because of its low cost, high precision and good linearity.
There are 3,000 types of locally made sensors, comprising entry-level and midrange models. Many makers, however, prefer to source upscale units mostly from Japan and the US. All import MCUs as well, but turn to the domestic supply for the rest of the components.
To reduce dependence on foreign providers, makers are planning to boost core competitiveness in R&D and manufacture. At present, only large enterprises have such capability. Henan Hanwei, which mass-produces gas transducers, is among them.