17
4.8 Using 00.16131.501040’s analogue 4 to 20 mA output
16131.5 gives users the option to use 4 to 20 mA output instead of its digital output. When using 4 to
20 mA output, please read this chapter first.
Using the 4 to 20 mA output provided by 00.16131.501040 is easy. The instrument can be connected
directly to commonly used data-logging systems.
The irradiance, E, in W/m2 is calculated by the formula:
E = 1600·(I - 4 x 10
-3
A)/(16 x 10
-3
A)
I: Current output in A
E: Solar irradiance in W/m2
By convention 0 W/m2 irradiance corresponds with 4 x 10
-3
A transmitter output current I. The
transmitted range, which is the irradiance at output current of 20 x 10
-3
A, and is typically 1600 W/m2.
It is important to realise that the signal wires not only act to transmit the signal but also act as
power supply for the 4-20 mA current loop circuit!
Figure 4.8.1
Electrical diagram of the connection of 00.16131.501040 to a typical ampere meter or
datalogger with capability to measure current signals.
Usually a 100 Ω shunt resistor (R) is used to convert the current to a voltage (this will then be in the
0.4 – to 2 VDC range). This resistor must be put in series with the blue wire of the sensor.
00.16131.501040
brown [+]
blue 4 to 20 mA output
A
ground
power supply 5 to 30 VDC
ampere meter
I = 4 to 20 mA
shield
