DH Instruments E-DWT-H, Руководство по эксплуатации и обслуживанию

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3. OPERATION
Page 43 © 2009 DH Instruments, a Fluke Company
 PRINCIPLE
The RPM4-E-DWT measures gauge pressure at the height of the E-DWT’s top surface TEST
port. Frequently, when performing a calibration or test, the device or system under test is at
a different height than the E-DWT’s TEST port. This difference in height, frequently called
head , can cause a significant difference between the pressure measured by the E-DWT-H at
its TEST port height and the pressure actually applied to the device under test at a different
height. When that is the case, it is useful to make a head correction to the pressure
measured by the RPM4-E-DWT in order to predict the pressure actually applied at a different
height.
RPM4-E-DWT can accurately determine “head” pressures for liquids (oil, water) as the
pressurized medium. In calculating the head value, standard gravity (9.80665 m/s
2
) is used.
A custom liquid density may also be specified.
The [HEAD] function key is used to specify the height difference between the E-DWT-H
TEST port and another height. Entering a height of zero turns the function off. The height
units and the test medium can be changed using [SPECIAL] , <3Head> (see Section 3.9.3).
Note
An oil head has a pressure value of about 0.04 psi/inch (0.1 kPa/cm).
 OPERATION
Note
For the head function to be used as described here, the RPM4-E-DWT
must be AutoZeroed to the TEST port reference level following the
AutoZeroing instructions in Section 3.7.10.
To access the HEAD function, press [HEAD] . The display is:
1. Test fluid currently specified for the head correction.
2. Edit field for head height.
Edit head height:
+ 14 in oil
Edit the head height to the desired value. Press [ENT] to return to the MAIN RUN screen
with the new head correction active. Press [ESC] to return with no changes.
Note
For the head function to be used as described
here, the RPM4-E-DWT must be AutoZeroed to
the TEST port reference level following the
AutoZeroing instructions in Section 3.7.10.
The reference height of the RPM4-E-DWT
pressure measurement is the E-DWT-H TEST
port weep hole. The head height should be
entered as a positive value if the device or
system under test is higher than the reference
level and negative if it is lower.