Dielectric Technologies MGD-2002 Manuel utilisateur
Service Information
Should a question, comment or problem arise, the information
below is provided as a guide. The number to call is (207) 647-9495
or toll free at (877) 247-3797 with the appropriate extension given
below.
When returning a unit for factory service or calibration, call the
customer service department at ext. 116 for a material return
authorization number (MRA). The device should be boxed securely
and contain information as to the person to contact, with telephone
number, billing information, and return shipping information. If
the device is being sent to the factory for service, a written statement
of the problem or symptoms should then be included. The MRA
number must be on the outside of the package or indicated on the
shipping label.
Dielectric Technologies
RR #2 Box 756
Bridgton Commerce Center
Bridgton, ME 04009
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Table of Contents
Preparation................................................................. Page 1
Specifications............................................................. Page 2
Warnings.................................................................... Page 3
Disclaimer.................................................................. Page 4
Operations
a) Overview.................................................... Page 5
b) Theory of Operation................................. Page 5
c) Key-by-key................................................ Page 10
d) Liquid Crystal Display (LCD)........................ Page 12
e) LCD Status Icons......................................... Page 13
Maintenance
a) Cleaning and Inspection............................ Page 14
b) Filter Replacement.................................... Page 14
c) Clearing the Silica Gel Filter....................... Page 15
d) Battery Replacement................................. Page 16
e) Battery Recharging.................................... Page 16
f) Calibration................................................. Page 17
Parts list
a) Standard Package....................................... Page 18
b) Replaceable Parts...................................... Page 18
c) Accessories................................................ Page 19
Warranty........................................................ Back Page
ii
PREPARATION
UPON DELIVERY
1) Immediately inspect the MGD-2002 for any physical damage that
may have been caused during shipping. NOTE: The Manufacturer’s
warranty does not cover damage caused in transit. You must notify your
carrier immediately for any damage claims.
2) Turn the device over and open the battery compartment door.
Remove the battery to expose the device information placard. Write
the unit serial number on the warranty information card.
3) Connect the battery plug to the main logic board. Close the
battery compartment door and secure with the quarter turn fastener.
4) Plug the Universal power supply into a convenient AC wall outlet
(First), then plug the other end into the device (Second).
NOTE:
Charge battery for 2 hours before operating the
Multi- gas detector for the first time!!
5) Complete the warranty information card supplied with the
instrument, and return it for your warranty registration.
6) Check the silica gel filter. Ensure the color is blue. Refer to page
#14 for filter changing instructions, or page #15 for filter clearing
instructions.
7) Before turning the device on, connect either the needle probe or
one of the extension rods to the probe assembly. Then connect the
probe assembly to the detector. The probe assembly has check valves
that keep the ambient air from deteriorating the effectivenesss of the
silica gel filter.
1
Specifications
Dimensions: (LxWxD) 33.7cm x 12.3cm x 8.3cm
(13.3in x 4.9in x 3.3in)
Weight: (MGD-2002 only) 1400 grams ( 3.1 lbs)
(Shipping) 6800 grams (15.0 lbs)
Temperature Range : -10c to +45c
(+14F to +113F)
Humidity Range : 20% RH to 50% RH
Sensitivity: (Min) 25 PPM
(Max) 1,000,000PPM (100%)
(Increment) 25 PPM
Selectivity : Hydrogen(H2) / Helium (He)
Resolution: (Low range) +/- 25 PPM
(High Range) +/- 0.2 %
Response Time: 2 Seconds (approx.)
Audio Out : Pulse Width Modulation
LCD: 128 Bit X 64 Bit Dot Matrix
With long life backlight
Processor: (Type) Infineon (16 Bit)
(Speed) 20 MHZ
(ROM) 512 KBytes
Battery: (Voltage) 7.2 VDC
(Type) Nickel Metal Hydride
(Weight) 383.0 grams
(Run Time) 6-8 Hours Continuous
(Charging Cycles) 300 - 500
(Charging Volts) 9.5 - 14 VDC @ 2A
2
User Safety Warnings
IMPORTANT: It’s imperative that the user of this device observe all
safety guidelines listed below to prevent personal injury, property
damage or damage to this detector.
• Do not operate the device if it has been damaged. Refer to qualified
factory service personnel referenced in the front of the manual.
• Do not disassemble the device as it will void your warranty. Only
qualified factory service personnel should perform repairs.
• Do not draw water into the helium detector. Water vapor in the air
is normal, and the silica filter is designed to eliminate this amount
of moisture. However, water will not only adversely affect this
unit’s operation, but may cause severe damage. Water found
inside the unit will also void your warranty.
• Use precautions when operating the detector in rain, snow or
adverse conditions. Although the detector is water resistant, it is
not waterproof. Do not allow water to accumulate on the faceplate,
as it could migrate into the electronics.
•Do not use the probe tip to dig in the soil, or in any manner other
than directed in this manual.
• Although this device has been designed to operate with a battery
voltage as low as 6V, do not operate the detector when the battery
indicator displays 1/4 battery or less. False readings will occur
when operated under this condition. Refer to page #16 for
replacing the battery or recharging the battery.
3
Disclaimer
The Occupational Safety and Health Administration
(OSHA) states that the lower explosive limit for hydrogen
(H2) gas is under 5%. Any concentration above this
level, whether intentionally mixed or accidentally trapped
in a confined space is highly explosive and unstable.
Since the MGD-2002 is capable of detecting both
Hydrogen (H2) and Helium (He) gas without any operator
intervention, we recommend that if you do use Hydrogen
(H2) gas, mix the remaining 96% with Helium (He) gas
for 100% usability and added safety.
4
MODEL MGD-2002 MULTI-GAS DETECTOR
OPERATIONS
OVERVIEW
The MGD-2002 Detector is a portable leak locating and pinpointing
device that detects both Hydrogen (H2) and Helium (He) when used as
a tracer gas in a multitude of pressurized systems. The characteristic of
being lighter than air allows both Hydrogen (H2) and Helium (He) to
penetrate small leaks rapidly and permeate through the densest soils
and pavements quickly. The leak can therefore be pinpointed easily
with this detector.
Our helium detector products are used today in many industries and
applications including: Military RF systems, High Voltage AC power
systems, High definition television, Chemical manufacturing, Cellular
and Analog telecommunication, and industries utilizing above and below
ground storage tanks.
THEORY OF OPERATION
The MGD-2002 Multi-Gas Detector is a 16 Bit microprocessor
controlled precision instrument that operates on the principle of
changing thermal conductivity to locate a specific tracer gas as well as
quantify its local concentration. Air, or what we term as “Air”, is actually
made up of a wide range of gasses. Some of those gasses are pure
elements, some are naturally occuring simple compounds, while others
are complex man-made compounds. Table #1 on the next page shows
a list of the twelve most abundant gasses that comprise what we term as
“AIR” . The table has been arranged in decreasing concentration order,
yet also provides other useful information such as chemical name,
chemical symbol, percent in normal air, concentration in parts per million,
parts per billion, and atomic weights.
The naturally occuring elemental gasses are Nitrogen (N2), Oxygen
(O2), Argon (Ar), Neon (Ne), Helium (He), Krypton (Kr), Hydrogen
(H2), and Xenon (Xe). Note that the subscript of 2 in the atomic symbol
shows that the gaseous form of the element normally occurs when it is
5
Table #1
bonded with another of it’s own kind. If the elemental gas does not
have a subscript, that gas has a full outer electron shell and will not
react or bond with any other element. These few elements are known as
“Nobel” gasses.
All the gasses listed in Table #1, as well as those that are not, all
possess an intrinsic property called “Thermal Conductivity”. For brevity
we will refer to thermal conductivity as TC, and it has a unit of measure
of W/ m*k. One way to explain TC is it’s ability to absorb heat or wisk
away heat from a heat source. An easy way to think about this is to
remember how hot you feel when you sweat. Air helps to cool your
body temperature. Table #2 on page 7 shows the TC for clean dry air
(CDA) as well as it’s nine most abundant components. For example, CDA
has a TC constant of 0.026 since it’s mostly comprised of nitrogen
(78.1%) that has a TC of 0.026. The next most abundant gas is oxygen
(20.9%) with a TC of 0.027 , which is remarkably close to nitrogen, and
thus stays very close to 0.026. The third highest concentration in CDA
is Argon (0.9%) with a TC of 0.018, but since it’s relative abundance in
6
Table #2
the atmosphere is so small, it has a very small impact on the overall TC
of air.
Note that as the numbers increase, the TC of the gasses increase,
with Hydrogen (H2) and Helium (He) being the most thermally
conductive. It’s this distinction between the TC of CDA as compared to
the TC of hydrogen or helium that we are interested in.
Our MGD-2002 is designed with two ranges. The low range detects
gas between 25 and 20,000 parts per milion (PPM) in increments of 25
ppm. Mathematically, 20,000 ppm is a concentration of 2%.
The high range is between 2% and 100%. Calibration of the MGD is
accomplished via the microprocessor. Initially when the sample air
contains no (zero) tracer gas, it will draw in 100% CDA. The micro-
processor is then told that the reading it’s getting is to be refered to as
“Zero”. Using a known controlled volume of CDA, 2% tracer gas (Scientific
grade) is injected into a closed loop. The accuracy of the gas is 2.00%,
and the detector should read 2.00%. This setting is then stored in
memory. The last calibration
point is to draw in 100%
scientific grade tracer gas,
and the reading stored in
memory. Since the TC of the
tracer gas is constant, the
readings observed are
directly proportional to the
concentration received.
Another way to state this is
that two points make a
straight line, and the more
points given, the more
accurate the straight line will
be. After the calibration
process, any concentration
sampled will fall on the line.
TESTING THE THEORY:
We at the manfacturing
facility have the capacity to
mix any concentration of gas
7
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