Eriez E-Z TEC IV, Installation, Operation And Maintenance Instructions

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Conversely, if you prefer to manually reset the reject
device after each rejection, you will set SW1-9 UP
for manual reset of a Direct Reject, and you can set
the Direct Reject Time to its minimum setting with
no need for fine adjustment.
In most cases, however, it will be desirable to set
the Direct Reject Time to a value less than the
maximum but greater than the minimum. Your
objective is to set the minimum Reject Time that
always results in rejection of detected metal. By
minimizing the Reject Time, the loss of
uncontaminated product will be minimized, and
the time available for resetting your reject device
will be maximized, thus making it more likely that
the device will be able to reject the next
contaminated item.
Follow this procedure:
1. Be sure your metal detector is properly ad-
justed for Sensitivity (in accordance with the
previous section), before attempting to adjust
the Direct Reject Time.
2. Connect your reject device to the Direct Relay
terminals in the E-Z Tec Power Supply Housing.
3. Prepare at least one product item with typical
contamination, and arrange to pass it through
the metal detector in a manner typical of pro-
duction conditions.
IMPORTANT WARNING!
If you are working with a reject system that
incorporates a fast acting valve or gate (these
are typical of vertical drop installations), DO
NOT ATTEMPT TO PASS THE PRODUCT
THROUGH THE REJECT AREA BY HAND.
Failure to heed this warning may result in se-
vere personal injury.
4. Adjust the Direct Reject Pot to its approximate
midpoint.
5. Activate the system and pass the contaminated
product through the metal detector. The reject
device should activate (if it does not, return to
the previous section and recheck the metal
detector sensitivity settings). If the contami-
nated product is rejected, repass the item(s),
repeating this step a number of times until (a)
you are convinced that contaminated product
will be rejected reliably at this Direct Reject time
setting, or (b) at least one contaminated item
has been missed because the Direct Reject
time setting was too short (ie. the reject de-
vice reset before the contaminated product
passed).
6. If (a) is true in step 5, then reduce the Direct
Reject Pot setting and repeat step 5. Continue
this process until (b) becomes true or until the
Direct Reject Pot reaches its minimum setting.
7. If (b) is true in step 5, increase the Direct Re-
ject Pot setting slightly (by approximately half
the amount that you last reduced it, or by an
amount corresponding to half of the initial set-
ting if you haven’t reduced the setting yet).
Repeat step 5 until you are convinced that the
contaminated product will be rejected reliably
at this Direct Reject Pot setting. This is the
minimum Direct Reject time setting for your
system for the particular product and contami-
nant that you have tested, and should be used
whenever this combination is being inspected
by the metal detector.
TIMED REJECT
The TIMED REJECT mode is used more often than
Direct Reject. This mode makes use of timers that
allow rejects to occur after a delay. For example,
suppose product is being conveyed on a conveyor
belt, and any metal detected in the product stream is
to be rejected with an air blast. The metal detector is
located close to the infeed end of the conveyor. The
air blast reject is positioned near the output end of the
conveyor. When metal is detected by the metal
detector, a timer is used to delay the reject command
until the metal reaches the reject device. This delay
time is called TRAVEL TIME. When the metal reaches
the reject device, a second timer is initiated to hold
the reject device on until the metal is rejected. This
time interval is called the TIMED REJECT TIME, and
it controls the duration of the output signal at the
TIMED RELAY terminals on the Power Supply Board.
Configuring Analog Metal Detector (cont.)