Detcon DM-200 - Manual (Page 17)

Model DM-200
DM-200 Instruction Manual Rev. 2.0 Page 13 of 40
3.4 Calibration - Toxics
3.4.1 Calibration Procedure - Zero
NOTE: Before performing a zero calibration, be sure there is no background gas present or
apply a zero gas standard for 1-2 minutes prior to performing zero calibration.
a) Enter the calibration menu by holding the programming magnet stationary over “PGM 1” (see Figure
4) for 3 seconds until the display reads “1-Zero Cal 2-Span Cal”, and then withdraw the magnet.
b) Next, enter the Zero Cal menu by holding the magnet stationary over “PGM 1” for 3 seconds until the
display reads: “Auto Zero”, then withdraw the magnet. The sensor has now entered the Auto Zero
mode which lasts for 7 seconds. When it is complete the display will read “Zero Complete” for 2
seconds and then report the date of the last span as a reminder. Following that the display will read
“Return to Normal Operation” for 3 seconds and then Auto Zero is complete. If applicable, remove
gas.
NOTE: If the circuitry is unable to adjust the zero to the proper setting, the sensor will enter a
calibration fault mode which will cause the display to alternate between the sensor’s current
status reading and the calibration fault screen which appears as: “Zero Cal Fault”.
NOTE: Upon entering the calibration menu, the 4-20 mA signal drops to 3.5 mA until the unit
returns to normal operation.
NOTE: When a “Zero Cal Fault” occurs, the sensor microprocessor retains its previous zero
calibration reference.
3.4.2 Calibration Procedure - Span
NOTE: It is best practice to do a Zero Cal just prior to a Span Cal.
Material Requirements
• Detcon PN 327-000000-000 Programming Magnet
• Span gas containing the target gas in air or nitrogen. The target gas concentration is recommended at
50% of range (which is the factory default) at a controlled flow rate of 500 ml/min. Example: for a
Model DM-200-H2S sensor with a range of 0-100 ppm, a test gas of 50 ppm is recommended. For a
sensor with a range of 0-10ppm a test gas of 5 ppm is recommended, etc. Other concentrations can be
used as long as they fall within 10% to 90% of range. See below for details. See section 3.6.1 if you
do not know the sensor target gas or range of detection.
CAUTION: Verification of the correct calibration gas level setting and calibration span gas
concentration is required before “span” calibration. These two numbers must be equal before
proceeding.
Calibration consists of entering the calibration function and following the menu-displayed instructions. The
display will ask for the application of span gas in a specific concentration. This concentration is equal to the
span gas level setting. The factory setting for span gas concentration is typically 50% of range, but may be
different depending on gas availability. For normal calibration, a span gas containing a concentration equal to
50% of range is required. If a span gas containing 50% of range is not available, other concentrations may be
used as long as they fall within 10% to 90% of range. However, any alternate span gas concentration value
must be programmed via the calibration gas level menu before proceeding with span calibration. Follow the
instructions below for span calibration.