**DP Transmitter Elevation and Suppression Corrections for Level Measurement**

When installing a DP transmitter to measure liquid level, configuration of the transmitter often must include an adjustment for one of two conditions introduced by the mounting arrangement.

**Elevated Span –**The Lower Range Value (LRV) of the transmitter needs to be configured above 0.**Suppressed Span –**The LRV of the transmitter needs to be configured below 0.

A brief discussion of how to make adjustments for elevation and suppression follows. Then two examples of the calculations needed to determine configuration parameters are given. Finally, a brief procedure that does not involve calculations is provided.

The range of the transmitter can be set anywhere, forward or reverse acting, as long as the following criteria are met:

LRL ≤ LRV ≤ URL

LRL ≤ URV ≤ URL

Span = [URV – LRV] ≥ Min Span

Note that the URL (Upper Range Limit), LRL (Lower Range Limit), and Min Span are transmitter dependent.

** ELEVATION CALCULATION EXAMPLE **

The below figure shows a sample transmitter installation.

**1. Calculate the differential pressure as follows. **

Pressure_{@DP} = (H × SpG)_{High Side} – (H × SpG)_{Low Side}

where H = Height

**2. Calculate the LRV when the tank is empty. **

LRV = (120 x 1.0)_{High Side} – (0 x 1.0)_{Low Side}

LRV = +120 inH2O

**3. Calculate the URV.**

URV = LRV + Span

URV = +120 + 100

URV = 220 inH2O

Therefore, transmitter range should be 120 to 220 inH2O

** SUPPRESSION CALCULATION EXAMPLE**

The below figure shows a sample transmitter installation.

**1. Calculate the differential pressure as follows. **

Pressure_{@DP} = (H × SpG)_{High Side} – (H × SpG)_{Low Side}

where H = Height

**2. Calculate the LRV when the tank is empty. **

LRV = (0 x 1.0)_{High Side} – (100 x 1.0)_{Low Side}

LRV = -100 inH2O

**3. Calculate the URV.**

URV = LRV + Span

URV = -100 + 100

URV = 0 inH2O

Therefore, transmitter range should be -100 to 0 inH2O

Source : Siemens Pressure Transmitter

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## 13 comments

Would like to ask how these articles can be downloaded. Many thanks to you Sir, this information is very helpful to aspiring young technical personal.

very good description

Thank you for those very important calculation for DP transmitters presented in a very simple and understandable way.

How to save or download those valuable techniques ?

thank you once again

Best regards.

Abdulkhaliq Albelushi

hii can you please tell what H2O SpG=1 means

Specific gravity of the liquid inside tank. Here it is assumed sg=1

thank you

dear, sir thank u very much for the calculation of level measurement

thank you very much

Merci beaucoup

Please how do you calebrate the level transimeter when it is showing default on URV and LRV and and it ends at 46% as the maximum.

check all the specification on HART and then adjust the SPAN at 0%..25%..50..75..100%

sir ,what is catch spot phenomenon in level transmitter?

Very good info