After a calibration, the instrument reported "ignition failure" - one of the most frustrating malfunctions in the use of the calorimeter. Fortunately, the HZ-384A manual provides a detailed list of six possible causes of ignition failure, and by troubleshooting in order, the problem can be identified.

Reason 1: The circuit is not connected or the ignition wire has poor contact

This is the most common reason. After tightening the oxygen bomb cover, the ignition cap (electrode connector on the cover) must be in reliable contact with the ignition socket of the instrument, and both ends of the ignition wire inside the oxygen bomb must be in good contact with the two electrodes respectively.

Inspection method: Click on "System Test" → "Ignition Test" on the interface, and observe whether the ignition indicator light is on. If the ignition circuit is normal, the indicator light will be on; If it doesn't light up, it means the circuit is broken. Check whether the connecting wire and oxygen bomb are placed in place, and whether the ignition cap and socket are in reliable contact.

Reason 2: The sample is damp (splashed with oxygen too quickly)

The oxygen filling speed is too fast, and the high-speed oxygen flow will splash the powder in the crucible or bring external moisture into the projectile, causing the sample around the ignition wire to be wetted and difficult to ignite.

Solution: Slowly open the valve during oxygenation to allow the pressure to rise slowly and avoid impacting the sample. If it has been splashed, dry the sample again and try again.

Reason 3: Poor contact between the ignition wire or cotton thread and the sample

The ignition wire needs to touch (not pierce) the surface of the sample, and one end of the cotton thread is pressed into the sample as the ignition wire. If both are suspended above the sample, only the filament burns off during ignition, and the heat is not enough to ignite the sample.

Solution: Reinstall the sample, confirm that one end of the cotton thread is pressed into the sample, and the ignition wire is located about 1mm above the sample.

Reason 4: Both electrodes are too dirty

After long-term use, the surface area of the electrode becomes carbonized and oxidized, leading to a decrease in conductivity and insufficient ignition current. Carefully sand the contact surfaces of the two electrodes with sandpaper, restore the metallic luster, and then try again.

Reason 5: Oxidation of ignition cap

The surface of the ignition cap (wiring terminal) on the oxygen bomb cover oxidizes and turns black, increasing the contact resistance. Polish the oxide layer with fine sandpaper to restore conductivity to the contact surface.

Reason 6: Short circuit between the two electrodes and the crucible

This is the most serious situation - the ignition wire or wire comes into contact with the crucible, and the ignition current directly goes through a short-circuit path without passing through the sample, which may also burn the crucible and electrodes. Replace the crucible with a new one, reinstall the sample, and confirm that the ignition wire does not touch the side wall and bottom of the crucible.