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1. What type of pressure is the transmitter intended to measure? First, determine the maximum pressure value that needs to be measured in the system; generally, it is necessary to choose a transmitter with a pressure range that is about 1.5 times greater than this maximum value. This is mainly because in many systems, especially those involved in water pressure measurement and processing, there are peak values as well as continuous irregular fluctuations; such sudden peaks can damage pressure sensors. Sustained high pressure levels or values slightly above the transmitter’s calibrated maximum can shorten the sensor’s lifespan, and it also leads to a decrease in accuracy. Therefore, a buffer can be used to reduce pressure spikes, but this will slow down the sensor’s response speed. Therefore, when selecting a transmitter, the pressure range, accuracy, and stability must be taken into full consideration. 2. What kind of pressure medium? Viscous liquids and mud can clog the pressure connections, while solvents or corrosive substances may damage the materials in the transmitter that come into direct contact with these media. The factors mentioned above will determine whether to choose a direct isolation film and materials in direct contact with the dielectric. 3. What level of precision is required for the transmitter? Factors that determine precision include non-linearity, hysteresis, non-repeatability, temperature, zero-point offset, and the influence of temperature. But due mainly to non-linearity, hysteresis, and non-repeatability, the higher the precision, the higher the price. 4. Temperature range of the transmitter Typically, a transmitter is calibrated for two temperature ranges: one is the normal operating temperature, and the other is the temperature compensation range. The normal operating temperature range refers to the temperature range within which the transmitter can function without being damaged; outside this temperature compensation range, it may fail to meet the required performance specifications. The temperature compensation range is a typical range that is smaller than the operating temperature range. Operating the transmitter within this range will definitely ensure that it meets its intended performance specifications. Temperature affects its output in two ways: one is zero drift, and the other is an impact on the full-scale output. For example: +/-X%/℃ of full scale, +/-X%/℃ of the reading, +/-X% of full scale when outside the temperature range, +/-X% of the reading within the temperature compensation range; the absence of such parameters leads to uncertainty in use. The change in the transmitter output is caused by pressure changes or by temperature changes. The effect of temperature is the most complex part when understanding how to use transmitters. 5. What kind of output signal is required? Outputs in mV, V, mA, and frequency as well as digital outputs – the choice of output depends on various factors, including the distance between the transmitter and the system controller or display, the presence of \"noise\" or other electronic interference signals, whether an amplifier is needed, and the location of the amplifier. For OEM devices where the distance between many transmitters and controllers is short, transmitters with mA output represent the most economical and effective solution. If it is necessary to amplify the output signal, it is best to use a transmitter with built-in amplification. For long-distance transmission or in the presence of strong electronic interference signals, it is best to use mA-level output or frequency output. In environments with high RFI or EMI levels, in addition to choosing mA or frequency output, special protection or filters also need to be considered. 6. What excitation voltage to choose? The type of output signal determines which excitation voltage should be selected. Many transmitters have built-in voltage regulation circuits, allowing for a wide range of supply voltages. Some transmitters are designed for fixed-volume measurement and require a stable operating voltage; therefore, the operating voltage determines whether a sensor with a regulator should be used. When selecting a transmitter, both the operating voltage and the system cost need to be taken into consideration. 7. Is a interchangeable transmitter required? Determine whether the transmitter needed can be used in multiple systems. Generally speaking, this is very important, especially for OEM products. Once the product reaches the customer, the cost incurred by the customer for calibration is quite high. If the products have good interchangeability, then even changing the transmitters used will not affect the performance of the entire system. 8. The transmitter needs to maintain stability after operating for an extended period. Most transmitters experience \"drift\" after being used beyond their intended limits; therefore, it is essential to understand the stability of a transmitter before purchasing it. This preliminary assessment can help avoid various problems that may arise during future use. 9. Transmitter Enclosure The enclosure of the transmitter is something that is often overlooked – specifically its frame – yet this aspect will gradually reveal its shortcomings over time as it is used. When selecting a transmitter, it is essential to take into account the future operating environment of the transmitter, such as the level of humidity, how it will be installed, and whether there will be severe impacts or vibrations.