Thermo Scientific APEX 100, Руководство пользователя

Страница: 71 / 442

Thermo Scientific APEX User’s Guide
Page 71
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, 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 application. As a general rule, as the severity of the
vibration increases, the X-threshold also increases. Possible remedies include
making sure the detector is completely isolated mechanically from the
surrounding duct, 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.
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.
X Threshold