Thermo Scientific Sarasota FD900, User Manual

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4-2
User Guide for Sarasota ID900, FD900, & PD900 Gas Density Meters Thermo Fisher Scientific
Calibration
Liquid Checks
Liquid Checks
In a jar large enough to hold the sensor, take a sample of clean liquid with
density within the instrument’s calibrated range. Check the sample density
with a hydrometer and its temperature with a thermometer.
Connect the density meter to a Sarasota HME900 that is correctly
configured and programmed with the density meter coefficients. Immerse
the sensor body completely in the liquid, press the DENSITY key to read
the density calculated by the computer.
If the hydrometer and computer readings differ by more than ±2 kg/m
3
,
move the sensor head in the liquid to help move any bubbles attached to
the spool. Check that the temperature indicated by the computer is
consistent with the temperature of the liquid measured with a
thermometer. If the indication is unstable or still in error, clean the
instrument as detailed in “Cleaning” (Chapter 5).
Vacuum Point
Cleaning
Gas density meters should be checked using Tvac vacuum point check.
This is a check that the time period at vacuum is the same as when tested at
vacuum during factory calibration. Any buildup of dirt on the spool will
give a positive shift to the time period at vacuum, damage to the spool may
cause negative or positive shifts of timeperiod.
The best method of checking the time period at vacuum Tvac of the
transducer is to install it in an approved calibration test chamber. However,
if this impractical, the test can be performed using a seal housing/retractor.
In this scenario, fully withdraw the density meter into the seal housing and
close the isolation valve. If offline, use a blanking flange to seal the housing.
Connect to a vacuum pump and observe the time period as the vacuum is
pulled. Allow time for a good vacuum, which is indicated as a steady period
reading. Note the periodic time and the instrument temperature.
Correct for temperature of Tvac on the calibration sheet and compare the
temperature corrected period with the Tvac on the calibration sheet. The
measured value should be correct to within the accuracy stated for the
instrument on the calibration sheet.
If there is a large error, check the following:
●
Ensure a vacuum <5 mm of mercury has been obtained (<0.01 kg/m
3
).
●
Ensure no dirt or other contamination is affecting the chamber spool or
body.
●
Ensure there is no damage to the spool.