Use case B (Performance Ratio)

3 micro-inverter connected PV-modules measure DC

Use case

There are 3 different PV-modules that are grid connected using 3 micro-inverters. We are interested in the DC Performance Ratio of these modules. This means that we will measure the DC output of each module and compare this to factory specifications and the light received.

We will need to measure the irradiance and the electrical DC output power of each PV-Module before it is converted to AC by the micro-inverters.

Every PV-Blocks system uses the PV-Base pack. We will start the configuration by adding that.

PV-Base pack

The PV-Base pack is the heart of any PV-Blocks system. It is responsible for computing(PV-LINK), power(PV-PSU) and communications(PV-BASE). Without these 3 DIN-rail components a PV-Blocks system cannot be used.

PV-Blocks to use

The PV-PSU is a high quality 24VDC power-supply. It is used to power the PV-Link computer and all connected PVBlocks.

More info…

The PV-LINK is an industrial computer that runs a robust Linux distribution. All measurements are orchestrated by this component. It runs a local database to store up to 10 years of continuous data (depending on the system size), as well as a webserver that can be used to configure the system. The computer can be connected to the internet to access the pvblocks cloud, however it will run perfectly without an active internet connection as well.

More info…

The PV-Base is the communication gateway to all installed PVBlocks.

More info…


To measure the irradiance there are several possibilities. First we have to choose between a pyranometer, a Si-pyranometer and a silicon reference cell. There are several reasons why you would choose one over the other. For now the decision about the irradiance sensor type is left to the user, of course you can contact us directly to help you select the best irradiance sensor.

An irradiance sensor can have an analog or digital output. Both types are supported by PV-Blocks.

Analog Sensors:

An analog irradiance sensor is a device that outputs a voltage that represents the irradiance received by the detector. This voltage is measured and converted to irradiance by the PV-Blocks systems. The PV-Block to use for this is the PV-IRR.

Digital sensors:

Digital sensors have gained popularity over the last years as these are less sensitive for noisy environments. A digital sensor communicates over a digital bus to transfer the measured irradiance. Typically multiple digital irradiance sensors can be connected to one bus. The PV-Blocks system supports many digital irradiance sensors for example the MS80S of EKO Instruments. The PV-Block to use for digital irradiance from EKO Instruments is the PV-MOD-MSXXS.

Irradiance PV-Blocks

The PV Irradiance block is a DIN-rail module that has 4 analog inputs. Each input can measure a voltage between 0-100mV. You can connect any analog sensor directly to this PV-Block.

More info…

This PV-Block enables the measurement of digital irradiance sensors from EKO Instruments (MS40S, MS60S, MS80S). Up to 4 irradiance sensors can be connected to a single PV-MOD-MSXXS.

More info…


For this system we will use a high class digital pyranometer(MS80S) from EKO Instruments. As this is a digital sensor, we will have to add the PV-MOD-MSXXS PV-Block to the system. The PV-MOD-MSXXS PV-Block can measure up to 4 digital EKO pyranometers, but for this use case we will only connect one MS80S.

DC Output

The second parameter to measure is the DC output of each PV-Module. The DC output can only be measured ‘before’ the micro-inverter. To measure this DC output, we will use a PV-MON. The PV-MON is a high precision instrument that can be connected between a PV-Module and the rest of the PV-system. It will measure the current and voltage continuously. The PV-MON has a fixed temperature sensor that can be used to measure the PV-module temperature. This temperature can be used to eliminate temperature effects on the calculation of the PR, but is not strictly required for this use case.

The PV-MON is a high precision instrument that can be connected between a PV-Module and the rest of the PV-system. It will measure the current and voltage continuously. The PV-MON has a fixed temperature sensor that can be used to measure the PV-module temperature. There is the possibility to connect an analog irradiance sensor (0..100mV)

More info…

This PV-Block communicates directly to EKO pyranometers MS40S, MS60S and MS80S

More info…


We will add the PV-MOD-MSXXS and 3 PV-MON DC meters to the system

The resulting system to measure the Performance Ratio is now ready to install. It has a PV-BASE pack, a PV-MOD-MSXXS and 3 x PV-MON.

Web interface

The operator can setup the PV-Blocks system by means of an ethernet connection using any web browser. Setting up the system in completely handled by the internal webserver. The PV-Blocks system runs standalone and does not need any maintenance besides a regular backup. The measured values are stored locally on the internal computer. Depending on the amount of PV-Blocks connected, about 10 years of data can be stored locally. Measured data can be downloaded from the web-interface directly.

Application Programming Interface (API)

The PV-Blocks system is completely open to developers by means of an extensive API. Developer can create their own programs to retrieve the data and analyze it in any possible way. An example python script is included with the system that should help a developer to get started.

PV-Blocks Cloud

You can use the PV-Blocks cloud to off-load all data automatically online. Dashboards (Grafana) can be build directly and shown to any audience. Of course the cloud solution complies to the highest security standards.