Questions regarding the selection of gauge ranges.

The ranges of instruments such as thermometers, pressure gauges, flow meters, and level gauges are determined based on process calculations. The instrument range is then determined based on the design data sheet.

Generally, the range is set at 10-20% above the maximum display value of the process medium being measured; the alarm signal can be adjusted according to the actual requirements of the process!

It is determined in conjunction with the process requirements, and the selection design specifications should also be taken into account.

What was said upstairs is correct, but it seems something is missing. My usual approach is as follows: (1) For on-site instruments such as pressure gauges and bimetallic devices, I determine the standard pressure measurement range by taking into account the conditions specified in the process requirements, as well as regulatory standards (such as pulse pressure). For example, if the normal pressure of the material is 0.5 MPa and the regulations require a range of 1/3 to 2/3 of this value (with different ranges for pulsating and high/medium pressures), I usually choose 1/2 of that value. If the options provided are 0–0.6, 0–1.0, or 0–1.6 MPa, I will definitely choose 0–1.0 MPa. (2) For flow rates, I first determine the appropriate type based on the regulations, and then consider the process conditions along with the information provided in the samples. For instance, if the maximum/normal flow rate of the material is 80 t/h and the measurement range indicated in the samples is 3–200 t/h (sometimes values are given in cubic units and need to be converted), then I usually specify a measurement range of 0–100 t/h or 0–120 t/h. (3) For magnetic flap switches, the length should be selected to match the distance between the instruments. (4) Differential pressure, radar, etc. are also a bit different. . . . . . . . .