Solar Instruments Accessories
Should I use a CVF 3 ventialtion unit in a warm environment and do I need a heater?
The CVF 3 increases the accuracy and maintenance interval by:
In the morning dew on the domes is prevented (ice in your region will be no problem)
Dirt (dust) deposit on the domes is less with ventilation
Zero offset is less because airflow keeps dome and body temperature closer together.
The use of the heater in the CVF 3 is not really necessary. (Although also dew is removed quicker)
Here the first item is really the most important one. If dew deposit is no problem the CVF 3 can be omitted.
How often should I clean the filters of the CVF 3 ventilation unit?
1) The filters are designed to use for a year in normal circumstances. Extreme circumstances like in factories with a lot of soot or chemical emission are a exception.
2) When they are dirty the filters can be washed out with water. After being dried a cleaned filter can last another year.
Can I order a new filter for my CVF 3 ventilation unit?
Filters can be ordered in sets of 5 (number 2682-916).
What is the accuracy calculation from a radiometer to the input of the AMPBOX? And the accuracy calculation out of the AMPBOX?
The AMPBOX can be delivered in two versions:
- standard, then the gain is 1 mV = 1 mA
- adjusted, then the gain is set to 0 – 1600 W/m2 = 4 – 20 mA
The AMPBOX has a 20 bits A/D on the input and a 16 bits A/D on the output.
The maximum error from the AMPBOX is ±0.05% of span or ±10 µV (over the full temp range)
This means in daily use that the additional error of the AMPBOX is far below 1 W/m2 for all radiometers.
What does “gain range” mean in the AMPBOX specification? And how is this value useful?
The gain range is the ability to adjust the amplification to the sensitivity of the radiometer:
- Gain adjust --> 0.1 to 4 mA/mV
- Input voltage range --> -12 to 50 mV
As mentioned above the amplification can be adjusted to 0- 1600 W/m2 = 4 – 20 mA.
In this case 100 W/m2 change on the input gives 1 mA change on the output.
The benefit is that two different sensors with different sensitivities have an identical output from the AMPBOX.
In the AMPBOX specification what does “Zero adjust” mean? And how is this value useful?
The zero adjust is used for the pyrgeometer to allow negative inputs.
The pyrgeometers are adjusted for -300 to +100 W/m2 = 4 to 20 mA.
So 100 W/m2 change on the input gives 4 mA change on the output. The zero point for the pyrgeometer is set to 16 mA. This is because a pyrgeometer can be more negative than positive.
What is the benefit of using a ventilation unit?
To keep the outer dome at the same temperature as the surrounding air temperature. This will keep the zero (a) offset as low as possible. But also to keep the dome as dry and clean as possible (from rain snow, ice and dirt).
The ventilation unit has a 5 W and 10 W heater. When do I need 5 W and when do I need 10 W?
Advised is to use the 5 Watt heater to keep the offset (a) as low as possible. This can be used during the whole day. If the surrounding temperature is above zero this could be sufficient. Below zero degree Celsius the extra 5 Watt (10 Watt total) can be used. We recommend to use the 10 Watt heater only during the morning (few hours around (preferable before) sunrise) to get the dome clean when measurement starts. After that the heater can be set back to 5 Watt.
How can I enable the 5 W or 10 W heater option of my CVF 3 ventilation unit?
By applying power to pin 6 or 7 for 5 W and both for 10 W.
Can I convert the current output (mA) of an AMPBOX to Volt?
Yes you can, by using a shunt resistor and a suitable power supply unit (PSU). You will need a shunt resistor of 500 Ω to convert the output current (4..20mA) to a voltage output of 2-10V. Or you will need a shunt resistor of 50 Ω to convert the current to a voltage output of 0.2-1V.
The AMPBOX has a range of range 0 - 1600 W/m2 for 4-20mA. The CMP 3 pyranometer has a sensitivity of 16,51 μV/W/m². And the PQS 1 PAR quantum sensor has a sensitivity of 5,59 μV/μmol/m²s. How can we calculate the output signal?
The AMPBOX is set for 0 - 1600 W/m2 for 4 – 20 mA
For CMP 3 with 16.51 μV sensitivity, this is 0 - 16.51 * 1600 μV =0 - 26.416 mV for 4 - 20mA (delta = 16 mA)
Sensitivity AMPBOX = 26.416 mV per 16 mA = 1.651 mV per 1 mA or 1651 μV per 1 mA
Now connected PAR with 5.59 μV/μmol. 1651 / 5.59 = 295.35 μmol per mA
Therefore:
0 μmol = 4 mA
295.35 μmol = 5 mA etc.
4725.6 μmol = 20mA as maximum input
Can we measure low level photosynthesis radiation (0,1 μmol/m²s) with the PQS 1 and the AMPBOX?
No, 0,1 μmol/m²s input will result in a very small change on the output of the AMPBOX (around 4,00033 mA). This is outside the accuracy of the AMPBOX and the accuracy of the PAR Lite.
Can I use a METEON data logger in combination with the AMPBOX?
No, the METEON will not work together with an AMPBOX.
With a 10 Ohm resistor the 20 mA output from the AMPBOX can be converted to 0.2 V max signal (max for the METEON). But the METEON cannot deal with the zero offset from the AMPBOX (4 mA).
Each AMPBOX corresponds to a specific pyranometer, could you please specify this?
If the AMPBOX is purchased together with a new pyranometer, or for use with an existing pyranometer, it has the sensitivity of that pyranometer programmed internally. In this case 0-1600 W/m2 of irradiance on the pyranometer produces 4-20mA from the AMPBOX. The serial number of the pyranometer matching the AMPBOX should be present on a label on the AMPBOX.