C-Tech H1820, Product Manual, Page: 8 / 10

- 6 -
switch the calibration mode. The upper row of digit shows 1 or 2 or 3 or 4, and short press the
“Units” to exit the calibration mode 1. Atmospheric correction: showing CAL-1 means snort
pressing the “HOLD”, and at this time the show of the lower row of Ni xie tube shifts from empty
to sequentially lit --, and returns to the normal mode. This calibration is just a translation curve
(exercised under atmospheric pressure ) (the air pressure needs, during calibration, greater than
85kap, otherwise a fault will appear).

Calibration mode 2, vacuum calibration: showing CAL- 2 , short press the “HOLD1”.At this time,
firstly judge whether the current air pressure is lower than15kpa. If it isn't, the lower row of Nixie
tube will exhibit Error, and press any key to return to the normal. If it is, the exhibition of the lower
row of Nixie tube will shift from empty to --, and return to the normal mode. This calibration will
change the slope of the curve (performed in the vacuum environment) (the air pressure needs
lower than 15kap, during calibration, otherwise a fault will appear).

Calibration mode 3, custom calibration: showing CAL- 3, short press the “HOLD” the lower row of
Nixie tube will show six “0” (000000), and the decimal point will be displayed at paralleled
position in light of the current unit. At this time, the rightmost number will flash. In this preference,
short press the “HOLD” to switch the cursor location, and “Max” is for digit minus, “
℃/℉
key” for
digit plus (settings range 0- 60kpa). After setting the value, short press the “HOLD”: for
calibration, and at this time, the exhibition of the lower row of Nixie tube shifts from empty to
sequentially lit -- and returns to the normal. This calibration will change the slope of the curve
(under specified negative pressure).

Calibration mode 4: resume the factory-set calibration value, showing CAL-4, short press the
“HOLD”, and the pressure curve will return to the factory settings.
Warranty
Thank you for choosing our products, we will provide you with the following services and promises.

The warranty period of this product is 1 year.

After the warranty period expires, repairs will be charged for replacement parts.

After the failure, please contact the manufacturer, we will give you the most complete service in
the shortest time.