SMA Sunny Boy Control - Manual (Page 104)

Sunny Boy Control
SMA Technologie AG
User Manual SUNBC-14:NE0206 100
Hardware-Based Configuration
The analog input channels are activated by selecting a measurement range in the
menu “Setup…Plus I/O…Analog In-1”. The name and the unit of the channel to
be displayed can be renamed according to the sensor. The value to be displayed is
calculated based on the measured signal according to gain and offset.
The gain factor is obtained by dividing the display range by the measuring range.
The offset is calculated by subtracting the product of the gain factor and lower end of
the display range from the lower end of the measuring range.
Expressed in formulas:
M is a value measured in a range between Ml and Mu in the unit V, mV or mA, ac-
cording to the selected function.
D is the value displayed in a range between Dl and Du.
Gain:
G = (Du - Dl) / (Mu - Ml)
Offset: O = Dl - (G * Ml)
Displayed value: D = (G * M) + O
A pyranometer has an output voltage of 0–10 V. This corresponds to
radiation of 0–1,350 W/m².
Ml = 0 V, Mu = 10 V, Dl = 0 W/m2, Du = 1,350 W/m²
G = (1,350 - 0) / (10 - 0) = 135
O = 0 - (135 * 0) = 0 W/m²
If M = 5 V: D = (M * G) + O = 5 * 135 + 0 = 675
A temperature sensor with a converter outputs 4–20 mA. This corre-
sponds to a temperature range of -30–+80 °C.
Ml = 4 mA, Mu = 20 mA, Dl = -30 °C, Du = +80 °C
G = (80- (-30)) / (20 - 4) = 110 / 16 = 6.875
O = -30 - (6.875 * 4) = -30 - 27.5 = -57.5 °C
If M = 4 mA: D = (M * G) + O = 4 * 6.875 - 57.5 = -30