Manual
Version
Page
DB04A
EN A1-9
PKP Prozessmesstechnik
16
2.17. Operation with other gases
Each measuring device can store data for up to 3 types of gas or operational states that need to be
defined at the time of purchase.
CMOS gas flow sensors are not linear (The output is linearized) and respond different to each gas.
If the gas or gas composition is different than the gas that the unit was calibrated for, the unit will
not measure accurately. It is possible to program up to 3 different gases and gas mixtures, but this
needs to be done at the factory. Please contact PKP for additional information.
Note:
Please note that, among other effects, the zero-point error (offset display) will be higher if the
device is not operated with the type of gas, for which it had been calibrated. A difference in zero
indication is also possible if the used pressure is different than specified.
2.18. Pressure loss
Our thermal mass flow meters have a low pressure drop. The pressure drop depends mainly on
the medium, the pressure conditions and the flow rate. In chapter
6.11 Pressure Loss
you find the
pressure drop for the most common gases. PKP has a calculation program for the other gases.
Please note that the size of the pipes has a large effect on the pressure loss. For example from
around 60 ln/min, we recommend a pipe inside diameter of at least 10 mm.
Please also note that some fittings have a reduced diameter and can cause considerable pressure
drop in your system. Be especially careful with vacuum applications, please select a relative big
pipe diameter).
2.19. Temperature compensation
The
DB04A
thermal mass flow meters measure the mass flow of gases, the result being largely
independent of pressure and temperature. In addition to the fundamental principle an internal
sensor measures the gas temperature and, with the help of a 3-dimensional table of interpolation
values, a correction factor is calculated automatically. The flow indication is thus temperature-
compensated.
2.20. Pressure compensation
During calibration, the specified operating pressure is taken into account. Changes to the pressure
conditions may introduce an additional error. This is around ±0.2% per bar.
Please note that the control behavior is influenced by substantially different pressure conditions.
(relevant for units with an intergrated needle valve only)
2.21. Response time
The response time is time required to display 98% of its final value after a sudden change in flow.
This response time for the DB04A 2 is around 300 ms but is dependent on your filter settings.
2.22. Filter settings
The filter settings smoothens the reading of pulsating or noisy flows. It can be set through the set-
up menu.
