Model 70 Smoke Meter.

This instrument has been designed to satisfy the requirements for a continuos smoke meter for testing oil fired appliances to DOBETA Standards.

The principal of operation is the deposition on a moving strip of filter paper of gas-borne carbon in a continuously aspirated sample of flue gas. The resultant stain is assessed by comparison with the standard Shell-Bacharach Smoke Scale on a time basis.

The flue gas sample passes from the rifled inlet on the front panel through a condensation trap and heater block to the sampling head, which is fitted with PTFE orifice plates above and below the filter paper. The heater block is heated electrically to a temperature adequate to prevent condensation of moisture; the temperature is controlled be a solid state proportional controller and can be set to any temperature between 120(C to 200(C.

The sample is aspirated by an oil-free vacuum pump, the vacuum being controlled by a valve on the front panel and indicated on an adjacent vacuum gauge. The filter paper is drawn through the sampling head by a high torque motor/gear unit with a capstan drive incorporating a time marker for correlation purposes.

Including full instruction manual.

Although the Model 70 was originally designed to test oil fired burners in 1968, over the years a large number of specials have been built with such applications as measuring exhaust fall out at the end of a main runway at Heathrow, diesel exhaust with British Rail and coal dust. In fact any application where carbon particles are to be measure under transient conditions.