Control And Altering Of Alarm Thresholds - Inficom MCT150 Manual De Instrucciones

INFICON
Monitoring units and detectors has built in "fail safe" circuit that enables un failure
indication in case of sensor error. The same alarm occurs in case of the sensor signal
reaches below 0,1 VDC due to an incorrect adjusted GV-offset e.g.

12. Control and altering of alarm thresholds

On the vertical PC-board of the i LDM150 / LDM150R units, there are three (3) potentiometers for
adjustment of alarm thresholds for C, B and A alarm
Altering alarm thresholds:
After connecting the instrument, the three actual thresholds of C, B & A alarms are visualized on the
bottom row of digits. Adjust at the corresponding potentiometer, to reach desired value.
In the datasheet of the actual sensor head, the desired alarm levels can be read as PPM / % values
and as a corresponding voltage value VDC. In order to check the corresponding PPM / % value for a
threshold value in VDC, one starts by finding the VDC value at the vertical axel. Then following an
imagined horizontal line until it reaches the graph, and thereafter following an imagined vertical line
until it reaches the horizontal axel of the diagram.
On the horizontal axis the corresponding PPM / % value can be read. If one likes to find the
corresponding VDC-value for a certain PPM / % value, the procedure is to be carried out in the
opposite order. (See the picture below)
Alarm thresholds should be chosen within the area of the solid line of the graph. If
values are chosen from the area of the dotted line, there are significant risks of
distortion with false alarms or total absence of alarm consequently.
743-600-G1 MCT150 Operating Manual 200304 8/64