Measuring Principle; Zero Point Calibration - testo 400 Bedienungsanleitung

testo 454
Ein/On
Main menu
Special function
Pressure
Input
Air pressure
Reducing piece
White pipe
Black pipe
Absorber pipe
Pump ball
Green
connection
testo 400...
I/O
Main menu
Special
Parameter
Absolute pressure
Input
Air pressure
Silicone pipe
The probe is based on the (single beam) infrared absorption
principle.
Ambient air containing CO
consists of a small pipe metallized on the inside. An infrared
source is located at one end and a detector at the other end. An
optical filter is also integrated in front of the detector. This allows
only one wavelength through and that is the wavelength absorbed
in the CO . The more CO
2
less of this special wavelength passes through the optical filter to
trigger a signal in the detector. This means the smaller the
detector´s signal the more CO
chamber.
Connect the CO probe to channel 1 in the measuring instrument
2
and switch on the instrument. The black cap must be attached to
the top of the probe. The sample gas enters the absorption
chamber through the condensation trap
( diffusion mode).
The CO value measured is shown in the display as a ppm unit.
2
The maximum value measured is 10,000 ppm (corresponding to 1
vol%).
Note that the CO measured value depends on the absolute air
2
pressure and temperature. This effect is compensated in the
instrument. To do this, enter the current absolute air pressure in
the testo 454 or testo 400/650/900 via the height table (see left
for instructions on input). If this data deviates to a large extent
from the real air pressure the result measured will be invalidated.
The temperature is compensated automatically.
Approx. 1 minute is necessary in order to adapt the CO
concentration in the absorption chamber to the outside world.
Swing the probe gently back and forth in order to reduce the
adjustment time.
Hold the probe as far away as possible from your body in
order to avoid any influence which the CO 2 in your breath
may have on results.

Zero point calibration

The adjustment set consists of:
a small absorber pipe for CO
a pump ball with valves
a reducing adapter
and 3 small connection pipes (refer to connection
instructions on the diagram left).
Depending on the application, we recommend a new calibration
once or twice a year. The following are some of the reasons for a
new calibration: normal probe drift (referring to time and
application), major or rapid changes in temperature, impact,
service activities, dirt on the optical components.
The following tasks have to be carried out before calibration:
• Switch on measuring instrument with CO
• The probe must be switched on for at least 10 minutes before
the actual calibration.
• Remove the probe cap
• Check the CO absorber pipe for any discoloration which could
2
disrupt operation and replace if necessary.
2
CO

Measuring principle

enters the absorption chamber. This
2
found in the absorption chamber, the
2
is located in the absorption
2
Operating instructions
with adjustment set 0554.0020
2
probe connected.
2
PROBE
2
2