Q:
Should cost be the deciding factor in purchasing
a transducer?
A: Cost of components is always a driving consideration to any
system designer. Unfortunately, the cost of diagnosing and servicing
a control system because of a failed transducer is many times
the cost of the transducer. Make sure you deal with a company
you know that meets their claimed specifications. Complaints of
electronic failures, excessive thermal drift or leaking cables
abound in the industry. Sometimes the devices just don't meet
the claimed specification. Companies that manufacturer poor transducers
do thrive - they make money because they are always selling replacements
units.
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Q:
What is the operating pressure range or
required over pressure range for the application?
A: As well as taking into account the normal working pressure
of the sensor, you should review the maximum possible overrange
to which a sensor is likely to be subjected in your application.
In addition, the type of pressure measurement may affect the
sensor life. For instance, continual pressure pulsing of certain
sensor types will cause fatigue. Sensors cover pressure ranges
from 15 PSI to 10,000 PSI full range. High overload protection
has become a very important factor in sensor performance. HYDAC
strain gauge sensors, with a built in positive overload stop,
take 200% overload as standard. In high fatigue areas, special
units are offered to withstand hostile environments.
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Q:
What types of pressure reference are there?
A: Gauge Pressure - The measurement is referenced to the atmospheric
pressure. Zero is set at atmospheric pressure.
Sealed Gauge Pressure - The measurement is referenced to a sealed
internal reference pressure. Zero is set at atmospheric pressure.
Absolute Pressure (A) - Measurement is referenced to an internally
sealed vacuum. Zero is usually set at absolute zero.
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Q:
What is the excitation voltage and required
output?
A: HYDAC¹s basic sensor has a 4-20 mA or 0-10 VDC output from
a 10-30 VDC unregulated supply.
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Q:
What are pressure and electrical interface
requirements?
A: You may choose to make the electrical termination of your
pressure sensor either by connector or cable. HYDAC pressure
sensors are offered with 3 types of 4 pin electrical connectors
(mating part supplied in some cases) or a one meter (39 inches),
4-core cable (additional length by request).
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Q:
What is the required accuracy?
A: Accuracy is a measured term used to determine the nonlinearity,
hysteresis and non-repeatability of a pressure unit, together
with thermal characteristics. Another point to consider is long
term stability and repeatability if you require a sensor with
repeatable measurement over a long period of time.
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Q:
What is the pressure medium and operating
environment?
A: You must determine the suitability of a transducer for liquids
or gases and its ability to withstand corrosion. Also, consideration
must be given to areas like vibration, shock, etc. HYDAC standard
transducers are made using 316 stainless steel and can withstand
most dry gases and pressure medium such as lubrication oil,
hydraulic oil, harsh chemicals, etc.
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Q:
What is the operating temperature range?
A: There are two factors when determining operating temperature
range of the pressure sensor: what is the media temperature
and to what temperature is the complete sensor exposed? If the
media temperature is excessively high, fitting a standoff pipe
between the media and the sensor may reduce it. Temperature
compensation of HYDAC sensors is normally up to a maximum of
100 °C (212 °F) and operating temperature range from -25 °C
to 85 °C (-13 °F to 185 °F).
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Q:
Is HYDAC willing to manufacture a non-standard
type of pressure sensor?
A: Yes, HYDAC manufactures non-standard pressure sensors. A
large part of our business dealing in pressure sensors is generated
from non-standard type of applications. Some are very minor
changes such as non-standard pressure ranges, pressure ports
etc. Still others are full custom designs. As a guide line,
the type of questions which we will ask before we can accept
a non-standard project are: Annual quantity, minimum purchase
quantities, design time requirements etc.
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Q:
What type of technology does HYDAC use
for its pressure sensors?
A: Currently HYDAC uses thin-film and ceramic sensor technology
for its sensors. Your specifications talk about proof and burst
pressures.
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Q:
What do these specifications refer to?
A: The proof pressure is the maximum pressure, which can be
applied to a transducer, which does not cause irreversible damage.
The burst pressure is the applied pressure, which causes permanent
damage.
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