Product Speed And Filtering The Signal; Rejecting The Product; Reject Duration - Thermo Scientific Apex Service Manual

Product Speed
and Filtering the
Rejecting the

Reject Duration

Thermo Fisher Scientific
REC 4258 Rev C
The product may be fed on a conveyor belt at a particular speed. The
metal detector needs to know the speed so it can "recognize" signals
generated by metal. Metal signals can be very small and it is important
Signal
to have the metal detector set up to filter-out unwanted signals leaving
only the metal signal.
APEX uses a digital filter to help it detect metal signals. The filter is
linked to belt speed and is initially calibrated (or learnt) by passing a
metal test-stick through the aperture on the conveyor belt. Once
calibrated, the filter tracks any adjustments to the entered belt speed
automatically.
APEX works with variable speed machines. You fit a speed sensor
(delivering electrical pulses when rotated) to the conveyor. The pulses
connect to an input and when actual belt speed changes, APEX
maintains its filter at the optimum setting for detecting metal.
A metal detector must detect metal and reject the product containing
metal into a quarantine container further down the line. For conveyor
Product
applications, belt speed influences when the product is rejected and so
it is important that this is accurately entered on the main menu.
Various hand-held devices can be used to determine belt speed.
Assuming belt speed (and filter) is calibrated; enter the reject distance
(middle of reject arm to metal detector). Both belt speed and reject
distance determine when a contaminated product is ejected into the
reject bin.
Alternatively, you can enter the reject time and tweak this value until
it is correct. APEX allows you to do this and in some applications this
may be more appropriate then a distance measurement i.e. vertical
drop machines dealing with bulk flowing product.
APEX automatically adjusts reject time/distance values for conveyor
applications if a belt-speed sensor is applied.
The length of time that the reject operates for is application dependant.
Most conveyor applications should be set so that the reject effectively
extends and returns in the shortest possible time. Other applications
demand longer times to guarantee successful metal rejection because
of product flow variations.
Reference Material
Reference Material 6-5