4"12-Z 1 - part - usaid

.- The 1261
Calorimeter
Operates in a compact, self-contained
jacket with a built-in oxygen filling
system.
EFFECTIVE THERMAL JACKETING
Outstanding thermal Jacketing IS provided In the
1261 Calorimeter by a circulating water system which
maintainS a forced flow around the sides and bottom
of the bucket chamber and through the cover as well.
The water In this system IS recirculated continuously
by a bUilt-in, high capacity pump. Since all tests are
run by Isoperlbol methods, the Jacket temperature
remaIns constant dUring a run and no water
additions are needed. Also, no water additions or
waiting period are required at the end of a run since
the jacket does not have to be recycled back to a
fixed starting temperature. Jacket heating IS provided
by a sealed ImmerSion heater operated by the
calorimeter controller In conjunction with a bUilt-in
thermistor probe.
MOLDED FIBERGLASS AND
BRASS CONSTRUCTION
To ensure minimal heat leak and long service life,
both the outer case and the water jacket are made of
a high strength, compression molded, fiberglass
reinforced polyester resin. These parts are
assembled Into a sturdy, light weight structure which
can be used wIth aCidic water supplies or In a
corrosive laboratory atmosphere without damage to
the Instrument. The Inner bucket chamber IS made of
nickel brass for good corrosion resistance and
proven heat transfer characteristics.
A RELIABLE OXYGEN BOMB
Each 1261 Calorimeter IS equipped wIth a Parr
1108 Oxygen Bomb In which samples can be burned
completely and safely with full recovery of all
combustion products. The bomb IS held In an oval
bucket, covered with two liters of water. An Impeller
driven by a motor mounted Within the cover produces
excellent Circulation around the bomb.
A BUILT-IN OXYGEN FILLING SYSTEM
To Increase the speed, reliability and safety of the
bomb filling operation, the 1261 CalOrimeter has a
bUIlt-in automatic system for filling the bomb WIth
oxygen to the desired operating pressure ThiS IS
Installed Within the calOrimeter, leaving only a short
filling hose extending from the Jacket To fill the bomb
the operator SImply slips a connectIOn fitting onto the
bomb Inlet valve and pushes a button to start the
filling sequence Filling then proceeds automatIcally
at a controlled rate to a pre-set pressure. He then lifts
the connector from the bomb and proceeds WIth the
test. If. for any reason, the bomb pressure did not
reach the desired level, an error message Will
indicate a low charge The filling rate IS regulated so
that oxygen enters the bomb at a Uniform, controlled
rate, avOiding any sudden blast that might blow a
powdered sample out of the combustion cup. Safety
provisions are Included to prevent an aCCidental
overcharge to the full pressure of the oxygen supply
tank.
PREaSE ELECTRONIC THERMONIETRY
Temperatures are measured with a high preCISion
electrOniC thermometer bUilt Into the calOrimeter,
uSing a speCially deSigned thermistor network to
obtain excellent linearity and high resolution In
differential temperature measurements. ThiS custom
deSigned system WIth ItS associated software
provides a umform scale over a Wide range of
operating temperatures so that the energy eqUIvalent
(EE value) for the calOrimeter remains remarkably
constant as compared With less stable systems uSing
diodes or other temperature sensors ThiS stability IS
confmned by many users who report that they find It
necessary to recheck the energy eqUivalent only
once or twice monthly unless a major component of
the system has been changed.
The temperature sensor IS sealed In a 118" dla
stainless steel probe held In a fixed mounting on the
calOrimeter cover, where It IS raised and lowered With
the cover Measurements over the 20 0 to 40 0 C
workmg range can be obtained With 0.0001 0 C
resolution The absolute accuracy IS less precise
(+1-a 1 0 C) but thiS does not affect differential
measurements. Tailored software converts all
readings to CelSIUS values Instead of ambIguous
resistance umts No mercurial thermometers are
required.