Chapter 10. Sensors

The anemometer Thies First Class Advanced X is a cup anemometer that can be connected to an RS-485 client port and offers a list of aggregated information like vibration frequency, inclination, corrected an uncorrected wind speed. Thanks to the digital communication over an RS-485 bus, this supplementary information can synchronously be requested by Meteo-42.

The corrected wind speed (EC 61400-12-1 Edition 2.0 compliant) is the result of correcting the influence of the atmospheric pressure on the measured wind speed. Meteo-42 will acquire the measurement values of the lower table every second, including measured frequency, corrected and uncorrected wind speed and 3-axis vibration frequencies.

If a Modbus RTU implementation is used ('Thies FCA X - Modbus', 'Thies Anemometer FCA X vibration extended - Modbus' or 'Thies Anemometer FCA X inclination extended - Modbus') and the option RS-485 sensors check is active, the sensor will be uniquely identified during configuration by requesting its hardware ID, which will be written in the configuration file. The calibration table, which is applied to the measured frequency resulting from the uncorrected wind speed at the second position of the table, is also requested and saved in the configuration file. If any changes are detected in either the hardware ID or the calibration table, it is reflected in the logbook, including the time stamp when the calibration was performed and the number of the calibration certificate.

The propeller anemometer can measure horizontal or vertical wind speed. However, it is not classified according to MEASNET and IEC. The anemometer is widely used to measure vertical wind speed to analyse turbulences and the wind load of a turbine.

The anemometer uses a transducer which converts linearly the rotational speed into DC voltage levels. It must be connected to an analog voltage channel (Ax) of your Meteo-42 data logger. Signal polarity relative to the connection pins is shown in the wiring diagram of the sensor. In applications measuring vertical air flow, the sensor is usually connected so downdrafts produce a negative signal and updrafts a positive signal.

The sensor can easily be configured in the Meteo-42 web interface via the Sensor Helper (see Section 5.1.2, “Sensor Helper”). Different calibration offset and slope values can be introduced depending on the signal polarity. Negative Signal slope and offset will be applied to negative voltage measurements, resulting in a negative wind speed, whereas standard slope and offset will be applied to positive voltage measurements, resulting in a positive wind speed.

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Meteo-42 stores all electrically measured values to the source data (see Section 6.7, “Access to Source Data”). The calculated wind speed in m/s is saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	The CSV file contains for all active channels the electrical values according to the chosen statistical interval.

Ammonit recommends installing digital wind vanes TMR to determine the wind direction. Wind vanes TMR deliver higher precision and are less susceptible to mechanical wear because of their solid state design. Ammonit offers wind vane Thies First Class TMR 10-bit serial-synchron and wind vane Thies Compact TMR 10-bit serial-synchron.

Each wind vane TMR requires one digital channel, whereas potentiometer wind vanes require two analog voltage channels each. By installing wind vanes TMR instead of wind vanes POT, analog voltage channels are available for other analog sensors, e.g. barometric pressure sensor, temperature or humidity sensors.

	Tip
	Considering a measurement system with wind vanes TMR a smaller Meteo-42 model with less channels can be sufficient.

Wind vanes TMR are connected to digital channels (Dx). Refer to Figure 13.11, “Electrical Connection Plan: Digital Serial for Serial Wind Vane (Thies TMR)” for the connection diagram. Further details about digital channels can be found in Section 11.3, “Connecting Sensors to Digital Channels” and Section 12.2, “Electrical Characteristics”.

Wind vanes can easily be configured in the Meteo-42 web interface via the Sensor Helper (see Section 5.1.2, “Sensor Helper”). The offset and installation offset are entered in degrees. The slope is also shown, but changing it is strongly discouraged. The 10-bit gray code measured by the digital channel is multiplied by the slope to produce an angle. The 10-bit gray code is between 0 and 2¹⁰, so any slope besides 360 / 1024 = 0.3515625 will produce incorrect results. If the wind vane calibration indicates a slope close to 1, the product of the two slopes could be configured instead, but doing so is not recommended.

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

To determine the wind direction with a potentiometer wind vane, e.g. Thies First Class and Thies Compact, Ammonit recommends using a five wire connection between data logger and wind vane. This five wire connection eliminates voltage drops across the connection cables and also eliminates the negative impact of voltage drops in the sensor's supply. Select the Generic Analog Wind Vane sensor type to connect any wind vane using this equation with the voltage range -10 V–+10 V.

The five wire connection method makes use of two consecutive analog voltage channels of the Meteo-42 data logger: A_n, A_n+1. A_n records the total voltage of the potentiometer (voltage between vane supply and Ground), A_n+1 measures the voltage between wiper and Ground. The following equation shows the calculation of the wind direction (D).

Refer to Figure 13.7, “Electrical Connection Plan: Analog Voltage (Potentiometric Wind Vane)” for the connection diagram. Further details about analog voltage channels can be found in Section 11.1, “Connecting Sensors to Analog Voltage Channels” and Section 12.2, “Electrical Characteristics”

	Important
	If potentiometric wind vanes, e.g. Thies First Class, Thies Compact, Vector W200P, Vector W200P/L, NRG #200P additional resistors for current limitation have to be used in the wiring setup. Contact Ammonit regarding further details about the accessory module!

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Meteo-42 stores all electrically measured values to the source data (Section 6.7, “Access to Source Data”). The calculated wind direction in ° (degree) is saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	The CSV file contains the electrical values according to the chosen statistical interval for all active measurement channels.

Certain wind vanes have an RS-485 interface. Meteo-42 data loggers can address up to 24 smart sensors on the RS-485 buses.

	Important
	If you intend to connect more than one sensor to an RS-485 client port, all connected sensors must use the same protocol and serial settings. Additionally, each sensor needs a unique ID (RS-485 address), which has to be configured for the sensor. The transmission mode for all RS-485-connected sensors has to be configured as half duplex. See Section 11.6, “Connecting Sensors to RS-485 Client”.

Wind vanes can easily be configured in the Meteo-42 web interface via the Sensor Helper (see Section 5.1.2, “Sensor Helper”). See Table 10.11, “Configuration of RS-485 Wind Vanes” for the configuration of RS-485 wind vanes.

Meteo-42 stores all measured values to the source data (Section 6.7, “Access to Source Data”). The wind direction in ° (degree) is saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

The Kintech Geovane™ can be connected to Meteo-42 on two different ways: via RS-485 or three analog channels (two analog voltage channels A and one counter C).

It is possible to combine the True-North direction with a measured wind direction at one-second level by means of the Evaluation Helper formula Wind direction true-north. The results will be included in a new column of the CSV statistics files.

Supported NMEA telegram: $WIMWV,<dir>,<ref>,<spd>,<uni>,<sta>*<chk><CR> <LF>

Before connecting any Thies sensor to an RS-485 client port, it has to be configured. Three Thies ultrasonic types are available: 2D compact, 2D and 3D. You can use the Thies Device Utility software to configure your sensors (Thies Device Utility software).

Ammonit recommends configuring Thies ultrasonic sensors as follows:

Required settings

Further Thies-specific settings

	Tip
	For more information about Thies acoustic virtual temperature, see sensor's manual.

Before connecting any Lufft sensor to Meteo-42, it has to be configured. Download and install the software UMB-Config-Tool and follow the next steps:

Before connecting any Gill sensor to Meteo-42, it must be configured accordingly.

	Note
	Any wind magnitude lower than defined by sensor's parameter K (default 0.050 m/s) will omit the wind direction.

	Important
	Gill Wind Master sensors with firmware v7.01 can be networked with other Wind Master units on a 2-wire RS-485 bus. Units with older versions cannot be networked.

RTDs measure the temperature by correlating the resistance of the RTD element with temperature. Those sensors provide high accuracy and repeatability; the sensors are suitable for precision applications. RTDs use electrical resistance and require a power source to operate.

Platinum Resistance Thermometers (Pt100 / Pt1000) are classified according to DIN EN 60751 - see tolerance classes below.

Pt100 / Pt1000 sensors have to be connected to the analog voltage channel and the current source of Meteo-42 data loggers. The sensors can easily be configured via the Sensor Helper (see Section 5.1.2, “Sensor Helper”) in the Meteo-42 web interface.

Meteo-42 saves all electrically measured values in V to the source data (Section 6.7, “Access to Source Data”). The calculated value for temperature ( °C) is saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	The CSV file also contains for all active channels the electrical values according to the chosen statistical interval.

Some available temperature humidity sensors have to be connected to a Meteo-42 RS-485 client bus. The sensors can easily be configured in the Meteo-42 web interface via the Sensor Helper (see Section 5.1.2, “Sensor Helper”).

	Important
	If you intend to connect more than one sensor to an RS-485 client port, all connected sensors must use the same protocol and serial settings. Additionally, each sensor needs a unique ID (RS-485 address), which has to be configured for the sensor. The transmission mode for all RS-485-connected sensors has to be configured as half duplex. See Section 11.6, “Connecting Sensors to RS-485 Client”.

Meteo-42 saves all measured values to the source data (Section 6.7, “Access to Source Data”). The values for temperature (°C) and humidity (%) are saved to the CSV file ( see Section 6.6.1, “Ammonit Meteo-42 specific details”).

Certain barometric pressure sensors have to be connected to a Meteo-42 RS-485 client bus The sensors can easily be configured in the Meteo-42 web interface via the Sensor Helper (see Section 5.1.2, “Sensor Helper”).

	Important
	If you intend to connect more than one sensor to an RS-485 client port, all connected sensors must use the same protocol and serial settings. Additionally, each sensor needs a unique ID (RS-485 address), which has to be configured for the sensor. The transmission mode for all RS-485-connected sensors has to be configured as half duplex. See Section 11.6, “Connecting Sensors to RS-485 Client”.

Meteo-42 saves all measured values to the source data (Section 6.7, “Access to Source Data”). The air pressure value in hPa is saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

Pyranometers measure the global horizontal radiation. They are also used as reference instruments thanks to their measurement precision. The use of this sensor is crucial for measurements with solar-powered applications.

Meteo-42 indicates for pyranometers the global horizontal irradiation (GHI).

Pyranometers, e.g. MS series of EKO Instruments or CMP series of Kipp & Zonen, have to be connected to analog voltage channels (Ax). Refer to Figure 13.2, “Electrical Connection Plan: Analog Voltage (Pyranometer)” for the connection diagram.

The output signal (U) from the pyranometer is proportional to the solar irradiance (E) in W/m².

Sensitivity is an internal parameter of the sensor, which is important to calculate the radiation in W/m². The value is given in the calibration certificate of the sensor.

Meteo-42 saves all electrically measured values in V to the source data (Section 6.7, “Access to Source Data”). The calculated values for solar radiation are saved in W/m² to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	The CSV file also contains for all active channels the electrical values according to the chosen statistical interval.

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Some pyranometers can or must be connected to an RS-485 client port. For EKO pyranometers, it is also possible to use the M-Box RS-485 Modbus RTU adapter and connect analog pyranometers to an RS-485 client bus. If more than one sensor is connected to an RS-485 client bus, they must be configured with a unique Modbus ID and they must all share the same protocol and serial settings (see Section 11.6, “Connecting Sensors to RS-485 Client”).

	Important
	MS-90+ systems are preconfigured and must be handled as a unit. The sensitivity value of MS-90 and the RS-485 address of the MS-80S are already configured in the C-Box. It is very important to keep the system as a unit and don't exchange the sensors without adapting the C-Box configuration to prevent communication problems and data loss.

The pyranometer Delta-T Sunshine SPN 1 measures global horizontal and diffuse irradiation in W/m². It provides 2 analog voltage outputs (Ax) for global and diffuse irradiation, and 1 digital output (Dx) for sunshine duration.

Additionally, Meteo-42 estimates the direct normal irradiation based on the values of global horizontal and diffuse irradiation according to the general formula: Global Horizontal Irradiation = Diffuse Horizontal Irradiation + Direct Normal Irradiation * cos(θ), where θ is the solar zenith angle

The order number for Delta-T Sunshine SPN 1 is S65100.

Important

In order to estimate direct normal irradiation (DNI) and sun status, latitude and longitude of the measurement station have to be entered in the System → Administration menu (see also Section 4.2, “System Administration”). If any estimated values should be included in the CSV statistics file, the values have to be selected in the Data → Statistics menu under Select statistics (see also Section 6.3.1, “Configuring Statistics and CSV files”).

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Pyrheliometers are used to measure the direct irradiance emitted by the sun in a 5 degree angle. The sensors have to be connected to the analog voltage channels (Ax) of Meteo-42.

The output signal (U) from the pyrheliometer is proportional to the solar irradiance (E) in W/m².

Sensitivity is an internal parameter of the sensor, which is important to calculate the irradiation in W/m². The value is given in the calibration certificate of the sensor.

Meteo-42 indicates for pyrheliometers direct normal irradiation. Additionally, the data logger estimates DNI * cos(θ) and sun status based on the recorded values for direct normal irradiation. In order to estimate sun status and DNI * cos(θ), latitude and longitude of the measurement station have to be entered in the System → Administration menu (see also Section 4.2, “System Administration”)

The sensor often comes with built-in Pt100 sensor and thermistor. The Pt100 sensor can be connected to the current source (see Section 11.4, “Connecting Sensors to Current Source”) of Meteo-42.

If the built-in Pt100 sensor should be connected to Meteo-42, pyrheliometer and Pt100 sensor have to be configured separately in the Sensor Helper: Pyrheliometer via sensor type Solar Sensors and Pt100 via sensor type Hygro/Thermo.

	Important
	Do not connect the thermistor to Meteo-42!

Important

In order to estimate sun status and direct normal irradiation [DNI * cos(θ)], latitude and longitude of the measurement station have to be entered or acquired with a GPS device in the System → Administration menu (see also Section 4.2, “System Administration”). If any estimated values should be included in the CSV statistics file, the values have to be selected in the Data → Statistics menu under Select statistics (see also Section 6.3.1, “Configuring Statistics and CSV files”).

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Sunshine duration sensors indicate the sunshine status as defined by the WMO (sunshine = irradiation exceeds the level of 120 W/m²). The sensor measures the irradiation and switches the output voltage high or low to indicate sunny or not sunny conditions.

Sunshine duration sensors, e.g. Kipp & Zonen CSD 3, have to be connected to analog voltage channels (Ax). If direct irradiation should be measured, connect this output also to another analog voltage channel (Ax). Refer to Figure 13.2, “Electrical Connection Plan: Analog Voltage (Pyranometer)” for the connection diagram.

The output signal (V) indicates sunshine or no sunshine. Additionally, the calculated direct irradiation can be measured. The output signal (mV) for direct irradiation is proportional to the direct irradiation (W/m²).

Sensitivity is an internal parameter of the sensor, which is important to calculate the radiation in W/m². The value is given in the calibration certificate of the sensor.

Meteo-42 saves all electrically measured values in V to the source data (Section 6.7, “Access to Source Data”). The calculated values for direct irradiation are saved in W/m² to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Meteo-42 saves all electrically measured values to the source data (Section 6.7, “Access to Source Data”). The calculated direct irradiation in W/m² and the current sun status are saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	The CSV file contains for all active channels the electrical values according to the chosen statistical interval.

EKO Instruments high precision STR Sun Tracker provide high tracking reliability, enhanced functionality with fully automated set up procedure through a built in GPS receiver. The compact sun trackers are suited to support all kinds of measurement sensors to measure Global, Diffuse and Direct Radiation.

EKO Sun Trackers must be connected to an RS-485 client port by means of an RS232 to RS-485 adapter.

Date, time and location are acquired from the sensor by means of commands TM and LO. If the data logger values are significantly different, Meteo-42 will get automatically synchronized and the changes will be logged in the logbook. This synchronization happens in two cases: when configuring the sensor and, if RS-485 sensors check is active, on every CECS reboot. If you want to trigger the synchronisation routine, you can access the configured EKO Sun Tracker for editing and save it again without changing the configuration.

According to the configured polling rate, which is 1 s per default, the calculated angle according to the GPS information and the current angle are requested and recorded.

	Important
	Make sure that no other method to synchronize date and time is active (Section 4.2, “System Administration”).

Measure Global, Diffuse and Direct Radiation from two LiCor sensors as well as the temperature. The average values from both sensors are also calculated.

Sensors for measuring photovoltaic module temperature.

Precipitation sensors are designed to measure the quantity and intensity of precipitation striking the earth’s surface. Precipitation is best measured with a tipping bucket device. Precipitation, collected over a surface of 200 cm², is moved through an inflow sieve into a tipping bucket. When the bucket has collected 2 cm³ = 0.1 mm of precipitation, it tips over. This measurement principle is based on the “Guide to Meteorological Instruments No 8, WMO”. Precipitation sensors are typically applied for meteorological assessments.

Precipitation sensors, e.g. Young precipitation sensor, have to connected to counter channels (Cx). Refer to Figure 13.10, “Electrical Connection Plan: Pulse Counter with Pull-up Module for Precipitation Measurement” for the connection diagram.

The output signal (I) from the sensor is proportional to the precipitation quantity (N).

Slope is an internal parameter of the sensor, which is important to calculate the precipitation quantity according to the measurement rate set in the sensor configuration. The value is pre-configured in the Sensor Helper (see Section 5.1.2, “Sensor Helper”).

	Important
	If you install calibrated sensors, enter the values given in the calibration protocol.

Meteo-42 saves all electrically measured values in Pulse [I] to the source data (Section 6.7, “Access to Source Data”). The calculated values are saved to the CSV file (see Section 6.6.1, “Ammonit Meteo-42 specific details”).

	Note
	The CSV file also contains for all active channels the electrical values according to the chosen statistical interval.

	Important
	If you plan to install precipitation sensor Thies or Young, you have to implement an accessory module! Refer to the data sheet and contact Ammonit for further details.

	Note
	For technical details and electrical characteristics of sensors, refer to the data sheets, which can be downloaded from the Ammonit website.

Laser precipitation monitors measure various precipitation details, i.e. intensity of total, liquid and solid precipitation as well as the precipitation amount and the SYNOP parameter.

Thies Laser Precipitation Monitor (LPM) sensor performs a new calculation every minute, after the first 5 minutes of operation. Meteo-42 requests data with a 1 s rate in order to guarantee a valid measurement per minute with a working sensor.

Thies LPM has to be connected to RS-485 client port.

	Note
	SYNOP (surface synoptic observations) is a numerical code used for reporting weather observations, also called FM-12 by the World Meteorological Organization. Refer to Thies LPM sensor's manual for more information.

The Sineax DM5 and CAM are universal measurement devices for heavy-current systems.

For more information refer to Gossen Metrawatt Sineax documentation.

SYCBA Monitor can monitor the consumption and power system of equipment powered by direct current through autonomous power systems. Typical applications are to monitor the load and consumption operation of systems with photovoltaic (or mini-wind) power and with batteries to power devices in 12 or 24 VDC or monitor night beacons, heating systems, timed operation systems, etc.

	Important
	For the operation Meteo-42 the internal biasing of the device must be disabled. This is done by setting S1 (SW1-SW4) switches to OFF.

Meteo-42 can acquire LiDAR ZX 300 live and averaged wind data measurements and include them in the measurement CSV files or share them over SCADA. At the the sensors list under Other Sensor, you can select LiDAR ZX 300 for averaged data or LiDAR ZX 300 Live for live data.

The LiDAR ZX 300 must be powered and connected to an RS-485 client port of the Meteo-42 before configuring it, otherwise an error will appear and the sensor will not be saved. The heights will be automatically requested from the sensor. For each height, an RS-485 channel (RxCy) will be configured. If both live and averaged data are requested, a maximum of 4 heights can be set at the LiDAR ZX 300.

	Note
	For more information about how to electrically connect LiDAR ZX 300 and Meteo-42 please contact us.

	Important
	Measurement polling interval for averaged data is 1 minute per default. To ensure a valid measurement per interval it must always be lower than the statistics time interval (see Section 6.3, “Statistics Data Files”).

It is possible to connect the Wildlife Acoustics Song Meter SM3BAT or SM4BAT FS to an RS-485 client interface. This allows a real time monitoring of bat passes and pulses, as well as of the status of the SM3BAT/SM4BAT flash memory card and power supply.

	Note
	An external RS232 to RS-485 adapter is required.

Scheduling: The SM3BAT can be programmed to monitor during specific periods of the day, and “sleep” during other parts of the day to conserve power. When the SM3BAT is sleeping, it will not respond to Meteo-42 messages. Thus, the SM3BAT needs to be programmed when to be monitoring for bats e.g. 24 hours or just at night, etc..

Recording: The SM3BAT normally records the ultrasonic echolocation audio data on up to 4 SDHC or SDXC flash cards. Full spectrum recordings can typically consume 1-2GB of card space per night depending on bat activity. The flash cards will eventually fill up. Normally, the SM3BAT would shut down if it is no longer able to make recordings. However, for this application, it is desirable to continue monitoring, updating bat counters, and responding to requests. If the interface to Meteo-42 is detected, then the SM3BAT will continue monitoring for bats even if the flash cards are full, but no new bat activity data will be recorded. This condition is indicated by the flash card 100% full indication in the response messages.

Bat Activity: Echolocating bats typically produce individual ultrasonic “pulses” continuously while they fly for navigation, avoiding obstacles, and hunting for food. The frequencies, bandwidth and duration of pulses vary from species to species and with the functional needs of the bat at the time (e.g. many bats will increase bandwidth and decrease duration as they close in on prey). The SM3BAT can be configured to recognize pulses that may be tuned to specific bats in a given area. This includes specifying the minimum and maximum frequencies and minimum and maximum durations of a pulse. These parameters can be tuned to recognize echolocating bats while avoiding false positives from other ultrasonic noise sources such as wind, rain, and insects. The optimum parameters will depend on the specific bats and insects likely occurring in a given area. A “bat pass” refers to a series of pulses recorded as a bat flies by the microphone. Additional parameters in SM3BAT help define what a bat pass is including the maximum trigger duration and the maximum time between pulses (the trigger window). A bat pass begins with the first detected pulse, and ends when either no pulses have been detected after the maximum time between pulses has occurred, or when the maximum trigger duration has been reached. SM3BAT will not count a bat pass unless it contains at least two pulses. In this way, the SM3BAT can count passes and pulses detected on an ongoing basis and report these counts to the customer equipment.

The SkyScan SG1000 lightning detector can detect the presence of lightning or thunderstorm activity occurring within 64 km of your location. It detects the characteristic electromagnetic emissions from individual lightning strokes and uses patented technology to determine the distance to the detected stroke. The distances are indicated in four ranges: 0-5 km; 5-13 km; 13-32 km; and 32-64 km. This allows you to track the approach of dangerous storm activity.

	Note
	More than one range can be detected simultaneously.

SG1000 may also identify certain types of especially strong storms. These storms can produce dangerous winds, heavy rains or tornadoes. When SG1000 detects lightning patterns indicating the presence of these storms, it activates the Severe thunderstorm alarm.

Four digital signals with complementary information are supplied by this lightning detector: Alarm, Error, Battery power and Baseline (see Table 10.30, “SG1000 status signals”).

Important

If the period of the digital output signal of the sensor is changed, it is necessary to configure the measurement rate at Meteo-42 accordingly. The period of the digital output signal can be set to a value between 2.0 and 4.8 seconds, being the default value 2.0. The measurement rate configured at the data logger for this sensor must be at least twice as long as the period duration of the digital output, in order to guarantee that a complete period is caught. The default measurement rate is 5 seconds.

Soiling and Irradiance Measurement Systems with the Atonometrics RDE300 Series measurement and control unit collect critical data for evaluating PV array performance. The systems can be used at operating PV power plants and pre-construction site survey locations.

Ammonit Soiling Measurement Kit uses the measurement method short-circuit current reduction due to soiling as specified in IEC 61724-1.

The temperature-corrected short-circuit current of a clean PV module is proportional to the irradiance. The measurement station determines the short-circuit current output as well as the module surface temperature from the backside of both soiled and clean PV modules. Based on these measurements, the effective solar irradiance (E_eff) can be determined by Equation 5.10, “Calculation of effective irradiance”. The soiling ratio (SR _ISC) is then obtained by dividing the measured soiled device short-circuit current by its expected short-circuit current, calculated using the normalization values previously determined (Equation 5.11, “Calculation of SR I_SC normalized according to IEC 61724-1”).

Figure 10.1. Ammonit Soiling Measurement Kit

	Important
	Ammonit Soiling Measurement Kit does not need to be calibrated on site to a specific soiling type. When the soiling composition changes throughout the year, the sensor will still accurately measure soiling without the need for re-calibration.

The Ammonit soiling measurement kit includes the following components: two Ammonit I-U Conversion Boxes, two Surface Temperature Sensors and two 30 W Photovoltaic (PV) Modules. PV modules must not be identical, the reference constants of each PV-module must be introduced for the effective irradiance calculation.

Figure 10.2. Ammonit Soiling Measurement Kit Effective Irradiance Soiled PV

An Ampere meter is used for each of the I-U Conversion Boxes. In order to achieve best match to the output voltage, the appropriate voltage range must be selected. If you are using CM8281, with a shunt resistor of 50 mΩ, you must select the ±1.0 V voltage range.

For each surface temperature measurement, a PT100 is used.

Figure 10.3. Ammonit Soiling Measurement Kit configuration

Figure 10.4. Ammonit Soiling Measurement Kit Normalization

	Important
	Both clean and soiled device must be cleaned before the normalization process!

The normalization of the system is performed according to the technical standard IEC 61724-1:2021. This process shall be repeated at least annually. Immediately following the normalization or following any significant rainfall, the measured soiling ratio I_SC should be close to unity. If the soiling ratio I_SC deviates more than 0.01 from the unity, the normalization must be repeated. Significant deviation from unity indicates a problem with the setup.

To start the normalization process you must press the Change button for the configured sensor at the sensors list. While in the sensor editing menu, you will find the option Normalize SD2100 at the bottom. For the normalization, a measurement rate of 1 second is required. Afterwards it is recommended to lower the measurement rate to 1 minute. Normalization is only possible after the effective irradiance evaluations of the clean and soiled devices have been configured. During the normalization process, the short circuit current and effective irradiance of both PV modules are measured and a corrected reference short-circuit current (I_SC0^Corrected) for the soiled device is calculated and saved in the configuration. This value is also reflected in the logbook. The corrected reference short-circuit current will be later applied for the soiling ratio calculation (see Soiling Ratio I_SC index). The soiling ratio evaluation can only be configured after the normalization process succeeded. After renormalization, the soiling ratio evaluation will be automatically removed and must be added again.

Figure 10.5. Ammonit Soiling Measurement Kit Soiling Ratio I_SC

Other standard metrics for the effects of soiling on energy production are available at the Evaluation Helper.

The Kipp & Zonen DustIQ is an instrument meant to measure and report the transmission loss (TL) and soiling ratio (SR) caused by light being blocked and reflected and subsequently not getting through the glass of the panel due to soiling of the panel.

	Important
	A local dust calibration of the device is required. The DustIQ leaves the factory calibrated for Arizona Test Dust (ATD) but it is very unlikely that the local dust composition matches this ATD and it is therefore advised to train each DustIQ for the local dust composition (see https://www.kippzonen.com/ for more information).

Before and after the calibration process, Ammonit recommends to read some relevant Modbus registers to record this values in the data logger logbook. The RS-485 Serial Interface must be used: register 2 (software version), register 34 (device status flags), register 35 (calibration flags), register 36 (current sensitivity value).

It is possible to connect up to 8 Modbus RTU sensors to RS-485 client port (see Section 11.6, “Connecting Sensors to RS-485 Client”). They can be combined with other Modbus RTU sensors implemented in Meteo-42 like Lufft sensors, but not with other protocols like Thies or Gill.

Figure 10.6. Generic Modbus RTU sensor configuration

The maximum quantity of consecutive registers that can be read from each sensor is 20. It is necessary to specify the first register (PDU addressing, first reference is 0) and the amount of registers. The function code is selectable between '03' (read holding registers) and '04' (read input registers).

Read registers will be evaluated according to the selected data type (see Table 10.36, “Data types available”). If a 32-bit data type is selected, each pair of registers will be merged. For each register pair (if 32-bit data type selected) or each individual register (if 16-bit data type selected), an evaluation is generated. E.g. reading 10 registers on RS-485 channel R1C1 will generate 10 evaluations if a 16-bit data type is selected (R1C1_1 to R1C1_10) and 5 evaluations if a 32-bit data type is selected (R1C1_1 to R1C1_5).

The resulting evaluations have no unit or evaluation type. You can create a new evaluation on top of each original evaluation by means of the linear equation from the Evaluation Helper (see Section 5.3.1, “Evaluation Helper”). Finally, it is necessary to properly select the evaluations to be included in the CSV statistics files in the Data → Statistics(see Figure 6.3, “Statistics Selection Page”).