The design of a good sensor is the result of experience plus technology. It is generally understood that a sensor converts a physical quantity through a circuit into a description that can be expressed in another intuitively expressible physical quantity. For example, it is converted into a signal such as a higher voltage and current that depends only on the measured physical quantity, and then displayed. So need to pay attention to a few points:
1. Generally, the measured physical quantity is very small, and usually has conversion noise inherent to the physical conversion element of the sensor. For example, the signal strength of the sensor at 1 magnification is 0.1~1uV, and the background noise signal at this time has such a large level, even annihilating it. How to take out the useful signal as much as possible and reduce the noise is the primary problem in sensor design.
2, the sensor circuit must be simple and refined. Imagine an amplifying loop with a 2-stage active filter with a 2-stage active filter that amplifies the signal and amplifies the noise. If the noise does not significantly deviate from the spectrum of the wanted signal, the filter is amplified at the same time. The signal to noise ratio has not improved. Therefore, the sensor circuit must be refined and simple. To save 1 resistor or capacitor, you must remove it. This is a problem that many engineers who design sensors are easy to ignore. It is known that the sensor circuit is troubled by the problem of noise, and the more complicated the circuit is modified, the more complicated it becomes.
3. Power consumption issues. The sensor is usually at the front end of the subsequent circuit and may require a long lead connection. When the sensor consumes a lot of power, the connection of the leads will introduce all the unnecessary noise and power supply noise, making subsequent circuits more difficult to design. In the case of sufficient use, how to reduce power consumption is also a small test.
4. Selection of components and power supply circuit. The selection of components must be sufficient, as long as the device specifications are within the required range, and the rest is the circuit design problem. The power supply is a difficult problem in the sensor circuit design process. Don't pursue the power supply index that cannot be achieved. Choose an op amp with a good common mode rejection ratio. Use a differential amplifier circuit to design the most common switching power supply. The device will meet your requirements. The retreat of the power supply must be designed reliably and follow the requirements of the device manual.
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