Parr Instrument 1356 - Manual (Page 19)

19
Low Oxygen Charge
Low Oxygen Pressure - signifies low oxygen pressure in the line filling the bomb. The
pressure switch must reach 27 (400 psi) atmospheres in this line otherwise there is the
display of this error message. Our recommended oxygen line pressure to the calorimeter
is 440-450 psi to allow for some pressure drop in the line to the calorimeter’s oxygen
solenoid
The most common cause is low oxygen pressure in the oxygen cylinder. Another
common reason for this error message is partially plugged orifice at the input of the
oxygen solenoid block and generally occurs when replacing the oxygen tank. We
recommend wiping the threads on the oxygen cylinder before attaching the oxygen
Regulator to the replacement tank. Close the valve for the oxygen tank. The problem may
be resolved by reversing oxygen connections at the solenoid block assembly. .Move the
connection from the input connector of the block to the output connector of the block
assembly. Cycle the oxygen fill process with the tank valve open to flush any particles
which may be blocking the orifice. After the completion of the fill process, close the
oxygen tank valve to avoid emptying the tank. If the error 78 message occurs at the end
of this process, oxygen is not flowing to the solenoid block assembly or the pressure
switch is faulty. If oxygen is being supplied to the block, then failure of the pressure
switch to close may be confirmed with an ohm meter measurement of approximately zero
resistance across pins 10 and 11 of the 11 position Wago Connector during the fill
process with the oxygen connections still in the reversed position. If one does not have a
filter in the oxygen line to the calorimeter, we recommend that a 359VB filter be
installed.
5. Miscellaneous
Accuracy & Precision-1356 Calorimeter
There are several considerations on must review to obtain the utmost accuracy and
precision. The water should be measured as accurate as possible, if one measures the
water to .5 ml or grams, this should be sufficient for most work.
1. The water residue in the bucket and on the bomb should be removed after each test.
2. The sample should be weighed to a minimum of .1 mg, preferably to .01 mg for each
test.
3. The acid titer should be made after each calibration test.
The fuse wire should be measured after each test.
4. The calibration tests should be reviewed to ensure that good work is being done. The
range of the calibration tests should not be greater than 12 cal/C. to give a relative
standard deviation of .20% which all 1356 calorimeters are capable of obtaining.
5. The starting temperature of each test should be T temperature +/- 1 C. for the best
accuracy