T4-08 GLOW WIRE TEST APPARATUS – MOTOR DRIVEN – REMOTE CONTROLLED - AUTOMATIC is intended for testing the flammability and ignitability of components and materials. It includes electronic feed back heating current stabilizer ‑ regulator, A‑meter, thermometer, motor drive, timer and remote controller. This apparatus consists of control unit and mechanical unit.

CONTROL UNIT

Electric circuit is built in compact housing on which is located mechanism for performing the test. Measuring instruments and components for controlling the operation of apparatus are located on the front plate of apparatus. The source of heating current is toroidal transformer that is controlled (its primary side) through ERT-200. Electronic circuit ERT‑200 operates as regulator of heating current and from the selected moment on, as heating current stabilizer. The circuit includes microprocessor that continually monitors the amplitude of heating current. The current level information is obtained through the measuring current transformer. Potentiometer, that is located on the front plate, is intended for heating current regulation (adjustment).

To enable more precise current (temperature) regulation ten‑turn potentiometer with 1000 digital dial is built‑in. It is also divided in two ranges. When the requested temperature stabilizes, push‑button should be pressed. In this moment the microprocessor memorizes the current information that matches requested temperature. Processor monitors the changes in current amplitude that can be generated as a consequence of mains voltage variation (fluctuation) or the change of resistance in heating circuit. Processor corrects all changes in heating current (standard requests that the heating current should remain stable during the test). When current stabilization is turned on the lamp in the push‑button is lit. During this time it is not possible to adjust the heating current by potentiometer. Stabilization can be also turned off.

Electric circuit also contains control and switching elements for controlling the electric motor drive that slowly moves tested sample to the wire loop after its activation by remote controller. Just before the sample contacts the glow wire loop it slows down, and at the time of contact the timer is activated which, after 30 seconds (or other set time), returns the carriage with the sample to the start position. According to the latest standard the test shall be done in the test chamber (see. our T1-14). Test chamber is necessary to avoid contamination with toxic gasses that might be produced during the test and to minimize air movement during the test.

MECHANICAL UNIT

Mechanism with wire loop, thermocouple and motor drive is located on the cover of electric unit. Heating transformer and current transformer are mounted on the bottom side of the cover, so that complete cover is easy removable. Carriage with sample mounting support is so designed that it can be easily removed from the guiding tracks. All regulating elements of the mechanism are equipped with handle‑screws to enable easy operation. Wire loop and thermocouple are easily exchangeable. Apparatus also has scales for depth of penetration and flame height reading with zero point adjustments.

PROTECTION

The apparatus is protected against overheating, short circuit and break off in the circuit. In the thermometer are built in three limit comparators, of which the first is used as protection against too high temperature that could shorten the life time of the thermocouple. It switches off the heating of glow wire at a temperature 1000°C, which is 40°C over max. temperature that is requested by standard (960°C).

In case of short circuit between the loop carrying rods or between the heating current leads in manual or stabilization mode, processor detects irregular conditions and turns the heating off. This is indicated by blinking of signal push‑button. After the cause of interruption has been removed, heating can be turned on by pressing “STOP” and “START” push‑button. In case of break off in the circuit or bad connection in the heating current in manual or stabilization mode, processor detects irregular conditions and turns the heating off. This is indicated by blinking of signal push‑button. Heating can be turned on by pressing “STOP” and “START” push‑button.