Expert’s Answer: Smar LD300

Hey there! First, before I get into the units for pressure, I would like to remind you of something. The Smar LD300 series differential pressure transmitter can be used not only for pressure measurement but also for a handful of other applications such as level and flow. If you would like to know a bit more about what you can do with differential pressure transmitters you can check our guide for differential pressure transmitters here.

Courtesy of SMAR

At this point, we can come back to your question on pressure measurement. The LD300 series has all of the most common units available. On whole, it is important to note that all the units are a conversion of the reference unit. In this case, the reference unit is inH²O at 20 ° Celsius. In practice, what the sensor does is take the reference unit and convert it to the desired unit. Another important point to consider is that the LD300 display uses a 4 1/2 digit display. As a result, the largest indicator possible will be 19999. At any rate, bear that in mind when you choose your unit to be displayed.

The Units

Ok, enough theory and let’s answer your question! Here is the list of units available on the LD300 series:

  • inH2O
  • inHg
  • ftH2O
  • mmH2O
  • mmHg
  • psi
  • bar
  • mbar
  • gf/cm2
  • kgf/cm2
  • Pascal
  • Torriceli
  • atm
  • Mpa
  • inH2O @ 4 oC
  • mmH2O @ 4 oC
  • mH2O
  • mH2O @ 4 oC
One more thing

There is one last important thing to remember before we close out this topic. If you are planning to use the LD300 series differential pressure transmitter to measure a variable other than pressure itself, the value of the variable is calculated by adopting the working range limits as a reference. Which means that you will have to set up a value for 0 and 100% manually in order to the transmitter calculate the new unit.

Courtesy of SMAR

For example, in a level measurement application, you should set the LRV (Lower range value) as the lower level of your tank and the URV (Upper range value) as the maximum volume of your tank. In conclusion, If you have any questions on how to do that we explain it in our articles about level measurement using differential pressure transmitters in open and closed tanks.

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