Additionally, clock inaccuracy can be corrected. This can be done using the setting
at “Cal.” in ppm (parts per million). The clock frequency can be increased with pos -
itive values and decreased with negative. The sign changes to minus at +254 ppm.
10.3. Shut-off Timer
The VM31 has a shut-off timer to help prolong the
battery operating life. To set the shut-off timer, open
the main menu by pressing F3, select “Device set-
tings” and “Shut-off timer”. Press keys ▼▲ to se-
lect the timer duration from the options 1, 5, 15 and
60 minutes. To deactivate the timer select ('none').
The switch off timer starts to run after the last press
of a button. If a button is pressed the timer will
restart the count down for the set duration.
10.4. Battery Type
While non-rechargeable batteries have a cell voltage
of approx. 1.5 V, NiMH rechargeable batteries de-
liver around 1.2 V per cell. The discharge curves
are also different. The VM31 battery indicator can
be adjusted to both types. To select the battery,
open the main menu by pressing F3, select “Device
settings” and “Battery type”.
Within the sub-menu select “Battery type” (Figure
40) pressing ▼ selects between “Alkaline” (non-
rechargeable, 1.5 V) or “NiMH” (rechargeable,
1.2 V).
If the battery power drops below 10 % the battery
indicator becomes red. Further measurements can
be taken until the power supply reaches 3 V in
keeping with the device specifications. At this point
the battery level indicator is completely empty and
the device switches itself off automatically.
10.5. Display Brightness
In the menu “Device settings”/ “Display brightness”,
press the keys ◄► to adjust the display settings ac-
cording to your working environment. The main
purpose of reducing display brightness is to save
battery power. Current consumption increases by
approximately 20 % between the minimum and
maximum setting. The difference can be even
higher, depending on the display content.
10.6. Menu Language
Open the menu “Device settings” / “Menu lan-
guage” to change the display language. The avail-
able languages depend on the firmware installed.
25
Figure 39: Shut-off timer
Figure 40: Battery type
Figure 41: Brightness
