DH Instruments E-DWT-10000-AF, Руководство по эксплуатации и обслуживанию

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E-DWT-10000-AF OPERATION AND MAINTENANCE MANUAL
© 2008 DH Instruments, a Fluke Company Page 40
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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 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 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).
An oil head has a pressure value of about 0.04 psi/inch (0.1 kPa/cm). As a general rule with
RPM4-E-DWT A70M/A7M-AF, use of the HEAD function to assure in tolerance measurements is
necessary only when the head exceeds 28 in. (70 cm) at 10 000 psi (70 MPa) or 0.28 in (0.7 cm)
at 100 psi, and proportional to these values in between.
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OPERATION
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.
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 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.