The heartbeat detector pcb board
Since the negative temperature coefficient resistor (NTC) itself has a very large change in the resistance value in a temperature range of 100 degrees or more. The resistance value from room temperature 25 ° C to 150 ° C is more than 32 times. Taking NCP18XH103F0SRB as an example, the resistance at 25 ° C is 10 kΩ, and the resistance at 150 ° C is 0.3085 kΩ. Depending on the characteristics of the PCB design circuit, if a single NTC is used to measure a wide range of temperatures, such as -40 ° C to +125 ° C, the temperature measurement system will have a low resolution over a certain temperature range.
NTC is a type of thermistor. A thermistor is a type of sensor resistor whose resistance changes with temperature. The English "thermistor" of the thermistor is a combination of the words Thermal and resistor. Thermistors are a class of variable resistors that are widely used in various electronic components, such as inrush current limiters, temperature sensors, duplex fuses, and self-regulating heaters. The thermistors are divided into positive temperature coefficient and negative. There are two types of temperature coefficients. The NTC mentioned in this paper is a thermistor whose resistance value decreases with increasing temperature. NTC is also commonly used in low-precision temperature measurement systems as one of the components for temperature monitoring and over-temperature protection of products.
It can be used as a position reference for SMT parts. SMT personnel or QC usually check whether the parts on the board are consistent with the BOM. It is convenient to check whether the parts are correct by CRD. The maintenance department of the maintenance department needs to check whether the specific parts are damaged when checking the bad lines and parts according to the schematic. The CRD allows the repair personnel to quickly find the electronic parts that may be problematic on the circuit board.
It would be better if each installer had a computer that could open Gerber so that the repairer could use Gerber to search for parts and know where each part is.
Print alignment between layers: 0.05mm (minimum)
▪ Precision of the positioning hole: 0.02mm (minimum)
▪ Offset precision for profile cutting: 0.05mm (minimum)
The minimum printed offset of the overall conductive trace and trim is 0.12mm = 0.05+0.02+0.05 (applicable to products with two layers above the conductive layer, if it is a single layer, the minimum offset is 0.07mm) This will be related to the fact that some lines should not be too close to the design of the trim, because the line is too close to the edge and it will be easier to absorb moisture, which will increase the chance of electron migration.