Placement and Calibration of Sensors
Calibrating Toxic Gas Sensors
EVM Series User Manual
57
Caution
Due to the presence of toxic gas during the calibration process, appropriate safety
procedures should be followed.
Additionally, you will want to ensure that your calibration is performed in an area
known not to contain hazardous or interfering gases if ambient air will be used as the
zero gas for operation. If this is not possible, pure bottled air (Nitrogen is
recommended) should be substituted. Instructions for both procedures are provided
below. You only need to perform one or the other.
Toxic Gas Zero Calibration
When conducting a zero cal for toxic gas, you will want to use a cylinder of Nitrogen or pure air with the
cal cup placed over the air inlet cover. (See “Applying a gas sensor” for details).
NOTE:
If you are in clean air environment, you can use room air (for all toxics except for ozone).
Ozone Calibration for Zero and Span
For an Ozone calibration, a zero calibration is performed with Nitrogen and a span calibration is
performed using an ozone generator.
NOTE:
It is recommended to factory calibrate the ozone sensor on a yearly basis.
Performing
a
Zero cal for toxic gas
1.
While the instrument is powered off,
connect
the pure air cylinder, regulator, inert tubing, and cal
cup to the EVM.
2.
Power on the EVM by pressing the
On/Off/Esc
.
3.
In the start screen, press the
Down
▼
arrow to select
Calibration
and press the
Enter
.
4.
Press
▲
/
▼
Arrows
to select the toxic you want to calibrate.
5.
Press the
Cal
soft key and a specific toxic gas
(i.e., CO) Calibrate Set Point screen
will appear.
Selecting a sensor
Press Up or Down Arrow on
keypad
Cal soft key
Figure 4-18: Selecting sensor for calibration process
