Backlight; Low Battery Indicator; Auto Power Off; Ppm-Calibration - Wohler CM 220 Bedienungsanleitung

4. Operating instructions
Wöhler CM 220
4.4 Measurement
The meter measures the CO concentration at the sensor and displays the
reading in ppm. It also indicates the maximum value (at the lower side of the
display) of all readings since it is powered on. Users can reset the maximum
value by pressing the backlight-key for two seconds in the measuring mode.

4.5 Backlight

The meter features backlight function for using in dark areas. Press the back-
light to activate and switch off the backlight. (Figure 3.2, key 1).

4.6 Low battery indicator

The low battery indicator appears in the display when the battery voltage gets
low. The measured values may be more inexact now. In this case you have to
change the batteries.

4.7 Auto power off

The meter turns itself off automatically after 15 minutes non-operation. (It will
not auto power off during the calibration).

5. 0-ppm-Calibration

Calibrate the meter in an area free of CO. To enter the calibration mode, turn
off the meter and press the power-key and the backlight-key simultaneous-
ly for two seconds. „ppm" will blink in the upper display and the calibration
value „0" at the lower side. Now the meter is running the 0 ppm calibration as
a default.
Now the meter calibrates automatically. The LCD is displaying a blinking
ppm value and it stops blinking when the calibration is completed. This takes
about 10 minutes.
Note: Do not be alarmed if high ppm or minus value shows up when entering
the calibration mode. It will go down and approach to 0 in seconds.
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