KEM
Technical Support:
41
ANNEX I. FLOW CALCULATION
The KEM has four inputs for connecting Hall effect flow sensor. The operation of this
type of sensor is based on a flow of water that enters the sensor and rotates a turbine,
which is connected to a magnet that activates a Hall effect sensor that emits an electrical
pulse.
The KEM measures the number of pulses read over a period of time (frequency), so it is
necessary to apply the following formula to calculate the flow rate:
𝐹 =
𝐾 · 𝑄
60
− 𝑎 = 𝐾
′
· 𝑄 − 𝑎
Being:
𝐹
=
𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑖𝑛 𝐻𝑧 𝑜 𝑠
−1
𝐾
=
𝐾 𝐹𝑎𝑐𝑡𝑜𝑟 𝑖𝑛 𝑝𝑢𝑙𝑠𝑒𝑠/𝐿
𝐾′
=
𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝐾 𝑖𝑛 (𝑝𝑢𝑙𝑠𝑒𝑠 · 𝑚𝑖𝑛)/(𝐿 · 𝑠)
𝑄
=
𝐹𝑙𝑜𝑤 𝑖𝑛 𝐿/𝑚𝑖𝑛
𝑎
=
𝐸𝑟𝑟𝑜𝑟 𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛 𝑖𝑛 𝐻𝑧
Depending on the flow meter, the value of
𝐾
and
𝑎
may be different, so it is necessary
to include these constants in ETS
when selecting “Custom Flow Sensor” (see section
2.3.2). These values are given in the flow meter datasheet.
Important:
It is very important to know
how to correctly differentiate whether the constant
provided by the flow meter manufacturer is the K constant or the K Factor. The
K factor is usually indicated with units of pulses/L. If this information is not
included, the formula above is usually included with the constant K and the
error correction
.
If the manufacturer provides the K constant, it is necessary to multiply this
value by 60 to enter it in the K Factor parameter.