FAQ - Frequently Asked Questions

WARNING: The filter is made of glass. Handle carefully to avoid breaking it. Broken glass may cause injuries.

 

When the graphite furnace is heated, the light radiated from the tube surface passes through the emission detection hole of the graphite cap and enters the temperature sensor. Then it passes through a filter to irradiate a photocell. A constant relation exists between the graphite tube temperature and the output signal from silicon photocell, and this relation has been stored in the instrument memory. The current that flows to the graphite tube is automatically controlled so that the output signal from the silicon photocell corresponds to the temperature setting.
Therefore, when the light path from the graphite tube to photocell is obstructed by soot, the signal from photocell will be smaller than that in normal case. As the result, even after the tube reaches the set temperature, the current flowing to the tube will be increased, and the graphite tube will be heated at a temperature which is extremely higher than that in normal case.

 

Argon gas flows to the light inlet at a rate of about 0.5 L/min to prevent intrusion of soot and smoke expelled from the tube. But when the graphite furnace is used every day, perform cleaning once a week. Or when it is used only every few days, perform cleaning before measurement using the following procedure.

 

1. Loosen the set screw on the upper side of sensor block, and pull the photocell unit backward to remove it from the sensor block.
2. Wipe the filter of the photocell unit with a clean paper cloth.
3. Wipe the inner surface of the sensor block hole in which the photocell unit was mounted.
4. Fit the photocell unit in the sensor block again as it was and fix it with the set screw.