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"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
First off as indicated more information is needed. Height of level being measured, Medium being measured ie water, oil, LNG etc... pressurized or unpressurized measurment... The most help might come in the form of a instrument engineer on the team to help in providing this selection and calabration of instrument....