Thermo Scientific APEX 100, User Manual

Page: 49 / 442

Thermo Scientific APEX User’s Guide
Page 49
6) Press the Go button. The detector immediately starts measuring (calibrating) the
background X and R noise thresholds, and the monitor screen (below) presents a bar
graph of the progress of the calibration process. The calibration takes roughly
20 seconds to complete.
Calibrate Noise Thresholds
When finished, the monitor screen disappears and the “Calibrate Noise Threshold” menu
(shown in step 5) reappears. The screen now displays the calibrated (measured) values
for the X and R noise thresholds and, because these are background values, the
numbers should be low. If the numbers are high (that is, larger than 1,000 for X and
larger than 200 for R), it may be difficult to detect small metal contaminants over the
background noise.
•
Reducing High X Noise Thresholds
An X-threshold in excess of 1,000 usually indicates there is a problem with
excessive vibration in your conveyor application. As a general rule, as the
severity of the vibration increases, the X-threshold also increases. Thus, if higher
conveyor speeds cause the X-threshold to increase, vibration is the likely cause.
Possible remedies include making sure the detector is completely isolated
mechanically from your conveyor, and/or installing shock mounts for the
detector.
• Reducing High R Noise Thresholds
An R-threshold in excess of 200 usually indicates that one (or more) of the
following conditions is present.
o
Excessive noise from electro-magnetic currents (EMCs) and variable
frequency drives (VFDs). Rectify by installing an isolation transformer
and/or line reactors.
o
Metal in the detector’s metal-free zone. Rectify by removing the metal.
o
A ground loop is present in the conveyor. Rectify by installing plastic
rollers in the conveyor.
7)
If you want to manually key in a different value for either the X or R noise threshold,
make sure the “Calibrate Noise Thresholds” menu (shown in step 5) is displayed.
Navigate to the appropriate menu (X or R) and press the Go button. An input screen
appears, allowing you to manually enter a value.