Parr Instrument 1341 - Manual (Page 12)

1341 Plain Jacket Calorimeter
P a r r I n s t r u m e n t C o m p a n y 12
Magnitude of Errors
The following examples illustrate the magnitude
of errors which may result from faulty calorimeter
operations. They are based upon an assumed test
in which a 1.0000 gram sample produced a 2.800 ºC
temperature rise in a calorimeter having an energy
equivalent of 2400 calories per °C.
• An error of 1 milliliter in making the acid titration
will change the thermal value 1.0 cal.
• An error of 1 centimeter in measuring the
amount of fuse wire burned will change the
thermal value 2.3 cal.
• An error of 1 gram in measuring the 2 kilograms
of water will change the thermal value 2.8 cal.
• An error of 1 milligram in weighing the sample
will change the thermal value 6.7 cal.
• An error of 0.002 ºC in measuring the tempera-
ture rise will change the thermal value 4.8 cal.
If all of these errors were in the same direction, the
total error would be 17.6 cal.
Maintenance
Calorimeter Maintenance
The high polished chrome finish on the calorimeter
bucket is needed to minimize heat transfer. If this
finish becomes dull, the bucket should be replaced.
Also check the bucket stirrer frequently to be sure
that it turns freely. Any drag or friction in the stirrer
will cause slow and erratic temperature response
in the calorimeter. Add a few drops of machine oil
annually to the small hole in the top of the stirrer
assembly. Move the shaft of the assembly up and
down to distribute the oil thoroughly.
General Cleaning Instructions
Wipe exterior surfaces with lightly dampened cloth
containing mild soap solution.
Fuse Ratings
The replacement of protective fuses should be
performed by qualified personnel.
Part No. 139E21 used in Ignition Unit 2901EB:
Slow blow, 5.0 Amps, 250 VAC
Part No. 139E8 used in Ignition Unit 2901EE:
Slow blow, 2.5 Amps, 250 VAC
Electric Ignition Problems
If the indicator light does not come on when the
firing button is pressed on the ignition unit there is
either an open circuit in the system or a fault on the
A1580E circuit board. An open circuit can usually
be located with an ohmmeter. Flex the lead wires
during any continuity check as the wires may be
broken and making only intermittent contact. If the
red indicator light glows during ignition but the fuse
wire does not burn, check the system for a voltage
leak to ground, most likely in the insulated electrode
on the bomb head. Check the electrode using the
high impedance scale on an ohmmeter and replace
the electrode insulator and seal if leakage is indi-
cated.
If test methods for hazardous materials require the
operator to stand away from the calorimeter when
firing the bomb, move the ignition unit to a protect-
ed location and add longer wires to the calorimeter.
Although remote firing is not necessary for most
samples, the operator should always step back from
the calorimeter when firing the bomb.
Caution!
Do not have the head, hands or any parts of
the body over the calorimeter when firing
the bomb; and continue to stand clear for 30
seconds after firing.