Information

2 Fluke Calibration How to choose a pressure comparator
Features to look for in a gas pressure
comparator
• Test port connections. Using a pressure
comparator to calibrate a device requires
that both a reference gauge and a device
under test to be connected to the compara-
tor. If your normal workload includes gauges
with a wide variety of pressure ranges and
connection types, then choose a type of con-
nection that allows you to quickly switch out
the reference gauge, and one that can easily
handle the types of connections you nor-
mally see in your lab.
• Pressure pump. Pressure pumps are ideal
for pressures of 2 MPa (300 psi) and below. If
you are working with higher pressures, you
probably should consider another pressure
generation method.
• Fine adjustment. If your procedure requires
fine adjustment of the pressure at the test
point, then make sure the comparator has
the ability to provide fine adjustment and is
sufficient for your application.
• Pressure supply connection. For higher
pressure applications where a connection to
supply pressure is feasible, consider pressure
comparators that can make use of that supply
pressure versus manual pumps. Your techni-
cians will thank you for it.
Gas pressure comparators
A gas pressure comparator is normally used
for calibrating at relatively lower pressures. Its
main benefit is cleanliness. If the device being
tested is used in a process that doesn’t tolerate
liquid contaminants, then you’ll probably want
to use a gas pressure comparator. Most gas
pressure comparators allow you to adjust and
regulate the supply pressure, either through a
pump or a needle valve.
Pump-based gas pressure comparators like
the Fluke Calibration P5510 are best suited for
pressures below 2 MPa (300 psi). A pump has
the advantage of not requiring an external gas
supply, allowing you to use the comparator in
more applications. The drawback is that you
have to pump harder to get higher pressures,
and your hands and arms can get tired.
For pressures above 2 MPa (300 psi) that still
require gas media, many users find it easier
to use a pressure comparator that meters in
pressure from an external supply. To enable
the supplied gas to be metered precisely, fine
needle valves control both the gas supply into
the system and the gas exhaust out of the
system.
The pressure comparator may also use a
variable volume to allow for small changes in
pressure. This can be used to make fine adjust-
ments so that either the reference gauge or
device under test are reading on the cardinal
point. The Fluke Calibration P5513 is a good
example of this type of pressure comparator.
Whereas a pump based gas pressure com-
parator is limited by the force the operator can
apply, this type of comparator is limited only by
the maximum working pressure of the internal
components and the pressure of the supply gas.
Gas (pneumatic)
Manual pump
and less than
300 psi?
Yes
P5510
No
P5513
Test port
connections
Fine adjustment screw press
Features to look for in a gas pressure
comparator, as shown on a Fluke Calibration
P5513 Pneumatic Comparison Test Pump.