Calibration; Equipment; General Notes; Section 6: Calibration - Laversab 6600 User Manual

Rev. b4 high accuracy automated pressure controller

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6.1

This calibration procedure requires the following equipment:

1. Vacuum pump.

2. Pressure supply of clean, dry air ("Zero" Air preferred) at 35 psia

3. Pressure standard having accuracy of at least 0.002 inHg up to 38 inHg and an

accuracy of at least 0.003 inHg from 38 inHg to 60 inHg.

6.2

The transducers inside the 6600 are sensitive to the change in density of the medium being

used. The unit must be calibrated with Dry Air only. Calibrating with Nitrogen or any

medium other than Dry Air will give erroneous results.

Because the transducers are medium-sensitive, care must be taken to ensure that the hoses

used in the calibration system do not out-gas. Normally, PVC hoses, or refrigeration type

hoses have a tendency to out-gas. The ideal hoses to use are Teflon or Teflon-coated hoses

because they have a very low absorption and out-gas coefficient. Stainless steel hoses may

also be used.

If the wrong type of hoses are used, then the typical results obtained will show that the error

increases as the pressure increases. Also, it is very unlikely that the repeatability of the

indicated pressure will be less than 0.002 inHg at 60 inHg. If the system cannot achieve

repeatability of 0.002 inHg or less, then the most likely cause is the out-gassing of hoses.

In the following sections, the instructions call for generating a pressure of 1.000 inHg abs.

using the Pressure Standard. If your Standard cannot generate such a low pressure, then

please generate as low a pressure as possible provided it is less than 4.0 inHg abs.

The 6600 has a drift of typically 0.005 %FS per year. Therefore it needs to be calibrated once a

year to perform adequately as a calibration standard for air data equipment.

SECTION 6

CALIBRATION

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