PROM, PROM

PROM, PROM

In the early days of the development of the microcomputer, the BIOS was stored in a ROM (Read Only Memory). The internal data of the ROM is burned in a special way in the manufacturing process of the ROM. The contents of the ROM can only be read and cannot be changed. Once it is burned in, the user can only verify whether the written data is correct. No further modifications can be made. If you find any errors in the data, you can only make a copy if you don't use it. ROM is produced on the production line. Due to its high cost, it is generally only used in high-volume applications.

Fundamental:

Due to the inconvenience of ROM manufacturing and upgrading, a PROM (Programmable ROM) was later invented. Initially, there is no data inside the PROM made in the factory. The user can write his own data with a dedicated programmer, but this opportunity is only once. Once it is written, it cannot be modified. If an error occurs, it is written. The chip can only be scrapped. The characteristics of the PROM are the same as those of the ROM, but the cost is higher than that of the ROM, and the speed of writing data is slower than that of the ROM. Generally, it is only suitable for a small number of occasions or for pre-production verification of the ROM.

The EPROM (Erasable Programmable ROM) chip can be repeatedly erased and written, which solves the drawback that the PROM chip can only be written once. The EPROM chip has a very obvious feature. On the ceramic package on the front side, a glass window is opened through which the integrated circuit can be seen. The ultraviolet light can be erased through the hole to illuminate the internal chip. The internal data, the EPROM eraser is used to complete the chip erase operation. The writing of the data in the EPROM requires a dedicated programmer, and a certain programming voltage must be added when writing content to the chip (VPP=12-24V, depending on the chip model). The EPROM model starts with 27, such as 27C020 (8*256K) is a 2M Bits capacity EPROM chip. After writing the data, the EPROM chip also seals the window with an opaque sticker or tape to protect the data from the surrounding ultraviolet rays.

Explosion Proof Temperature Sensor

The model of explosion-proof temperature sensor is wzpk-22i-b, which is made of stainless steel and has explosion-proof performance. If you want to conduct reliable temperature measurement, you first need to select the correct temperature instrument, that is, the temperature sensor. Thermocouple, thermistor, platinum resistance (RTD) and temperature IC are the most commonly used temperature sensors in testing.

The changes of physical parameters with temperature include expansion, resistance, capacitance, electromotive force, magnetic properties, frequency, optical characteristics, thermal noise and so on. With the development of production, new temperature sensors will continue to emerge.

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