Kipp&Zonen AMPBOX Amplifier - Manual (Page 13)

Before installing the AMPBOX you should be aware that we do not supply the cable between the AMPBOX and the data acquisition
system. In fact the AMPBOX is supplied without any cables. The cable from the radiometer to the AMPBOX can be ordered together
with the radiometer.
Note Install the AMPBOX as close as possible to the radiometer. The cable between the AMPBOX and data acquisition
system can be over 100 meters.
Example:
You would like to connect a CMP10 pyranometer to the 4 to 20 mA inputs of your data acquisition system. The distance
between the two components is 45 meters.
Solution:
Order a CMP10, including adjusted AMPBOX and 50 meters of cable. When receiving the instrument and the cable with plug
attached, cut off 45 meters of cable and use the plug with 5 meters of cable to connect the instrument to the AMPBOX. The other 45
meters can be used to connect the AMPBOX to the data acquisition system.
Another option would be to purchase a separate cable with the specific length.
3.1 Installing AMPBOX on 4 to 20 mA current loop input
The next illustration shows how to connect the AMPBOX to a data acquisition system that can be configured to provide the power
for the current loop.
Note Install the AMPBOX as close as possible to the radiometer. The cable between the AMPBOX and data acquisition
system can be over 100 meters.
E = irradiance level
I
out
= current recorded by the data acquisition (4 to 20 mA)
I
offset
= zero offset from AMPBOX (4 mA)
Gain setting = (see chapter 2.2)
E
offset
= zero offset from irradiance
Examples of irradiance calculations:
• Standard gain setting of 2 mV / 1 mA
E = (I
out
- I
offset
) * gain setting / S
instrument
• Adjusted gain for radiometers (except pyrgeometers)
E = (I
out
- I
offset
) * gain setting
• Adjusted gain for pyrgeometers
E = (I
out
- I
offset
) * gain setting - E
offset
13
3. Installing the AMPBOX
+
–
GND
Datalogger Radiometer Active Current Loop
+
+
–
–
Example when using standard gain setting of 2 mV / 1 mA and output is 12,04 mA and sensitivity is 13,15 µV
E = (I
out
- I
offset
) * gain setting / S
instrument
E = (12,04 mA - 4 mA) * 2 mV / 13,15 µV
E = 1222,81 W/m²
Example when using adjusted gain setting of 100 W/m² / 1 mA and output is 12,04 mA
E = (I
out
- I
offset
) * gain setting
E = (12,04 mA - 4mA) * 100 W/m²
E = 804 W/m²
Example when using adjusted gain setting of 25 W/m² / 1 mA for the pyrgeometer starting at -300 W/m² and output is 16 mA
E = (I
out
- I
offset
) * gain setting - E
offset
E = (16 mA - 4mA) * 25 W/m² - 300 W/m²
E = 0 W/m²
Note Gain setting can be calculated by dividing the entire span by 16.
Example: -600 to +200 W/m² span = 800/16 = 50 W/m² per 1 mA
3.2. Installing AMPBOX on 4 to 20 mA input that does not supply the 4 to 20 mA current loop
Some data acquisition systems cannot supply the power for the 4 to 20 mA current loop. In such situations an external power
supply unit is necessary. This power supply will then supply the active current loop required for the AMPBOX.
Note There is an internal diode that protects the AMPBOX from any damage when the power supply unit is connected
the wrong way around.
Note The power supply should be suitable to supply 7.2 VDC for the AMPBOX + the voltage drop over the cable loop at
20 mA. The practical minimum is 7.5 VDC and the maximum is 35 VDC. The voltage drop over the 4 to 20 mA current
loop cables can be calculated when the specifications of the cable are known.
Note Install the AMPBOX as close as possible to the radiometer. The cable between the AMPBOX and data acquisition system
can be over 100 meters. It’s therefore advised to install the PSU as close as possible to the data acquisition system.