What is the difference between selecting a negative pressure and a gauge pressure transducer?

It is proper to use an absolute pressure transmitter for negative pressure measurement. If negative pressure is to be used, a differential pressure transmitter can be employed with the positive and negative pressure sides connected in reverse.

There is no problem using an absolute pressure transmitter; however, if a negative pressure transmitter can be used, there is no need for an absolute pressure transmitter, as the price difference is quite significant...

One method involves applying pressure on the negative-pressure side to create negative pressure, while the other involves drawing air from the positive-pressure side. Which one do you use? They are quite different, right?

There have been several posts in the past discussing the selection of gauge pressure and absolute pressure transmitters; I will explain this from a process perspective (purchased in bulk, please don’t criticize if there are mistakes). 1. For a mixed gas phase, with three parameters: pressure/temperature/composition, once two of them are determined, the third is also \"determined\". The process generally involves using pressure/temperature to determine whether the components meet the design requirements. 2. Under the pressure mentioned above, what matters in the manufacturing process is the absolute pressure. Think about the saturated vapor pressures listed in the property tables – they are all given in absolute pressure units; that’s exactly why. 3. For positive pressure, since there is 1 atmosphere acting as a base for calculating the gauge pressure, the value is quite high; even if the atmospheric pressure changes by 5 KPA (from summer to winter), the impact is not significant. 4. In high-vacuum processes, if a gauge pressure transmitter is used, the local/seasonal atmospheric pressure must be added to convert it into \"absolute pressure\". If the atmospheric pressure changes by 5 KPA, the error in this conversion is significant (since the range of measurement is already small). 5. Although the process team specified that measurements should be taken in terms of gauge pressure (for example, –90 KPaG), they might actually be thinking of absolute pressure. Therefore, it is necessary to discuss this with the process team to determine whether gauge pressure is appropriate, considering the variations in atmospheric pressure. 6. Generally, a negative pressure below -80 KPaG requires the use of an absolute pressure transmitter. Anyway, the absolute pressure transmitter from the original poster can be used; it’s just a bit more expensive.