The industrial field has many sensor applications, temperature sensing, pressure sensing, humidity sensing and so on. And because of the more demanding environment in the industrial field of sensor performance also puts forward a lot of challenges, such as NTC sensors need to be in a high-temperature environment for temperature measurement, but also need to reliably complete the circuit protection function.
In industrial scenarios, these various sensors play out what effect, and what need to pay attention to it?
Industrial NTC applications
From the industrial application point of view NTC can be said to be very wide range of applications, such as some power conversion circuit, UPS, drives, control cabinets and fire detectors and so on. In the power conversion, the more common IGBT distributed temperature monitoring. Because of the use of IGBT, MOSFET these devices power conversion involves AC/DC, DC/DC, DC/AC these processes will heat, these heat needs to be monitored to avoid IGBT, MOSFET damage due to overheating.
In distributed IGBT temperature monitoring, the most common NTC application is mounted on the heat sink of the PCB board, which is very simple to install and can be fixed with screws. Generally, screw-in NTCs are used in this application, which makes deployment easy and allows for customized sensor designs based on wire lengths after the front end has been secured with a screw ring. In this application, the NTC needs to be sealed with a metal label housing to ensure good thermal coupling of the NTC. Generally speaking, the NTC's high temperature resistance of 125°C can be adapted to most applications, but if the industrial scenario has more stringent high temperature requirements, it is necessary to strengthen the sensor probe.
Combined with practical use cases, the scenario will have some different requirements for temperature monitoring. For example, in the UPS system, the NTC is required to monitor the temperature of at least three locations, one is in the heat sink out to monitor the temperature of the rectifier and inverter; the second is in the BMS to monitor the temperature of the BMS, especially to monitor the lithium-ion batteries, because lithium-ion batteries are not heat-resistant, and almost every battery temperature to monitor to ensure that the BMS will not overheat; the third is to monitor the temperature of the entire UPS system inside the cabinet, which requires the use of the NTC to monitor the temperature. Third, the temperature of the entire UPS system is monitored inside the cabinet, and the number of NTCs to be used depends on the size of the UPS.
In this power conversion applications, the modularization trend is very obvious, in order to comply with this trend NTC in the design and manufacture of a lot of attention needs to be paid to the place. First of all, the semiconductor process of sintering and bonding must be used to connect the chip NTCs to the board. In order to enhance the thermal performance of the NTC, some manufacturers will also use screen printing technology to carry out the coating to ensure that the reliability of the industrial high temperature period can be guaranteed. These bondable chip NTCs can be mounted directly to the IPM to measure the temperature near the IGBT, and because they are attached directly to the board, they have excellent thermal coupling properties.
Pressure Sensing in Industry
Another major category of sensing applications is pressure sensors. There are many industrial applications that utilize hydraulic or pneumatic equipment, which require pressure sensors to control the pressure of gases and fluids. Silicon piezoresistive pressure sensing element is often used in industrial scenarios pressure sensing, the principle of operation is actually a Wheatstone bridge, when the pressure of the gas or fluid acting on the diaphragm of the element so that the diaphragm deformation, several resistors produce deformation, resulting in the output of the different outputs, and then determine the size of the output to determine the size of the pressure.
Pressure measurement is divided into many kinds of pressure, some measure gauge pressure, some measure the back side of the absolute pressure, some measure the front side of the absolute pressure, each type of measurement has a different measuring range. It should be noted that some of the measured body is corrosive, it is necessary to choose the oil-filled core, that is, the chip is encapsulated in the oil-filled core, and then the entire core into a pressure sensor, in order to avoid direct contact with the component corrosion of the measured body resulting in damage. In fact, here is also related to the choice of the backing glass, gauge pressure, back absolute pressure, front absolute pressure need to choose the choice of backing glass are not the same.
Pressure sensor overpressure ability is very intuitive performance, in order to enhance the overpressure ability, can be realized by reducing the cavity volume or increase the bonding area of the silicon glass. This enhancement is significant and can sometimes double the overpressure capability of the device.
Aluminum Electrolytic Capacitors for Industrial Inverter Applications
The use of inverters can be found everywhere in the industrial field, both to achieve energy saving and to reduce the loss of the motor, thus improving the life of the motor. The inverter part of the frequency converter will generate large ripple during modulation, and the energy absorption and release during the modulation process need to be supported by sufficient DC-LINK capacitance.
Aluminum electrolytic capacitors are a common choice in industrial inverters, we know that there are a variety of capacitors in the capacitor family, and the biggest feature of aluminum electrolytic capacitors is the largest capacity per unit volume and the lowest cost per unit capacity, these two features make it the first choice for industrial inverters. Need to pay attention to the quad-core inverter capacitor rated voltage need to reserve a safety margin, usually reserved 5% to 10%, some in the peak of the basis plus 50V or even higher.
Servo inverters are similar to general-purpose inverters, but because servo inverters respond faster and more accurately, it requires greater overload capacity requirements. Therefore, the aluminum electrolytic capacitors used in servo inverters will have a higher voltage rating than the same type of general-purpose inverters, and this requirement is known in the industry as the fast charge/discharge requirement. The current industry does not have a common standard for fast charging and discharging, but basically will be required to meet the following conditions, for the bullhorn type capacitors, charging and discharging voltage differential voltage to 150V, frequency 6Hz, to be able to meet the 50 million cycles, for the bolt-type capacitor differential voltage is also to 150V, frequency 3Hz, to meet the 20 million cycles. Simply put, the general inverter 220V aluminum electrolytic capacitors used in 400V, while the same servo needs to be required in the case of 450V.
Summary
The process industry has a large cluster of machines or systems and interconnections that depend on sensors for proper functioning, and sensors in industrial applications play a vital role. These sensors need to be selected to take into account the harsh requirements of the industrial environment and be reliable enough to eliminate blind spots in the factory process, thus achieving high quality production.