BRONKHORST®
Page 8
MASS-VIEW®
series
9.17.051
The pressure loss across the needle can be described by:
∆P =
k 𝜌
𝑛
T ∅
2
𝑣𝑛
P
𝑜𝑢𝑡
𝑖𝑛 𝑤ℎ𝑖𝑐ℎ 𝑃
𝑜𝑢𝑡
= 1𝑏𝑎𝑟𝑑 𝑎𝑡 20°𝐶 𝑎𝑛𝑑 1 𝑎𝑡𝑚
The spring force in the upstream membrane valve closes the valve in the “zero” flow situation. By
opening the needle valve the ΔP will increase, so far that the membrane lifts up and compensates the
spring force. In the equilibrium position the flow will be constant even when the upstream pressure (P
in
)
changes. However when the upstream pressure increases, it will cause a small effect on the spring force,
which means that the ΔP to open the membrane valve will be a little smaller. This results in a lower
flow.
In practise the deviation of the ideal straight line will be less than 0,5-1% per bar.
1.11 Electronics, display and 4-way button
The
MASS-VIEW
®
has a bright graphical OLED display,
clearly visible over any angle, which allows reading of
actual flow (value and bar graph), total flow and gas type.
The three display options can be changed using the 4-way
button This button is a navigation joystick which has
UP/DOWN/LEFT/RIGHT keys and a centre push (ENTER)
key.
4-way button
