Photovoltaic Instrumentation

Photovoltaic instrumentation consist of different measurement instruments used in photovoltaic systems. Most common are different panel meters, such as V-meters, A-meters, Ah- or kWh-meters. They could be produced as part of other devices like inverters or charge regulators or as standalone meters for wall mounting or with mounting clips for 35 mm DIN rail mounting. Ah-counters can be used for battery monitoring. Such instruments helps us to estimate how much battery capacity was used and how much could still be employed. Application of kWh-counters in grid connected systems calculate how much electricity was produced by the photovoltaic system and transferred to the public grid, and how much electricity was transferred from the public grid to households. More sophisticated measurement instruments used by professionals include PV array analysers, thermal cameras, solar radiation measurement instruments and solar simulators.

Field application of Solmetric instruments
(courtesy: Solmetric)

PANEL METERS

A general recommendation for PV instrumentation design and application include: A careful A-meter design is required for use in PV systems. In PV systems large currents can occur, therefore, only suitable shunts should be used. Even if a proper shunt is applied, you should consider a cooling necessity. Always apply a suitable circuit breaker. Always apply a proper cable. Thin cable can cause unexpected loss or fire in case of large currents. Never use cheap panel meters or other equipment, which is not intended for application in DC/photovoltaic systems. How to build digital A-meter – some instructions A simple digital A-meter can be build by an advanced hobbyist. I have provided some general information and design rules. Most of DVA meters are based on ICL7106 or its low power derivates or successors. This is most commonly applied cirquit for DVM applications. However, there are some disadvantages to this circuit for application in PV systems. Separate GND and IN-LO signals are required. In most cases you cannot simply connect IN-LO and GND pin. Some precautions should be taken and some special design techniques should be applied. For details please see the links below. You can use any other similar ADC, but MAX131/MAX138 are preferred due to some advantages, such as low power consumption and included internal band-gap reference. The advantages of the circuit are: Wide supply voltage range from 3V to 30V; for low voltage power supply low voltage OpAmps should be used, very low power supply current < 1mA, wide current sense range depending on a current shunt used, with ICL7660 as voltage converter, single supply is adequate. Similarly a digital V-meter can be constructed.

Panel meters producers - web sites

Murata Power Solutions - Murata Power Solutions - C&D Technologies has over 25 years of experiences in designing and manufacturing digital panel meters. Today company is focusing on specific applications of 2-wire meters, process monitors and AC or DC A-meters that are the easiest- to-use, most affordable meters available.

Xantrex - VA-meters and batery bank monitors. Detailed description available in accessories section.

Bogart Engineering - Bogart Engineering - TriMetric battery monitor.

Helios Technology - Helios Technology - modules, charge regulators and various accessories (displays) for use in low voltage DC systems (mobile and marine sollutions).

High current resistors

Riedon - Riedon is a resistor manufacturing company, specializing in Power Resistors, Precision Resistors, and High Temperature Resistors.

Caddock - high performance film resistors. Current sense film resistor also available.

Isabellenhütte - precision resistors and resistor networks. Current sense resistors also available.

PV ARRAY MEASUREMENT EQUIPMENT

Array I-V curve tracers

Solmetric - The Solmetric PV Analyzer is a complete electrical test solution for verifying photovoltaic array performance. For each string, the analyzer measures current and power as a function of voltage. Measured results are compared to the performance predicted by advanced built-in models.

Ingenieurbüro Mencke & Tegtmeyer - Ingenieurbüro Mencke & Tegtmeyer offer wide range of profesional measurement instruments like I-V curve analysers, dataloggers, sun simulators, sensors etc.
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PV Engineering - The cutting-edge photovoltaic measuring devices (field tester) series PVPM allow the measurement of the I-V-curve of the generator as well as the instant display of the peak power (extrapolated to STC) and the internal serial resistance.
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HT Italia - offers professional photovoltaic testers for power quality analysis and testing on photovoltaic installations.
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Stratasense - Wireless Current vs Voltage (IV) Curve Tracer, a unique solution for acquiring the current versus voltage curves of operating solar modules, enabling easy instrument deployment and no facility modifications.

Seaward - The Solar PV range of products from Seaward includes the PV100 Solar PV installation tester and a range of accessories and software required by IEC 62446 and most certification schemes.

EKO instruments - The I-V curve tracer enables quick measurement of the performance of photovoltaic device without any influence of solar irradiance behaviors.

Daystar - Daystar sells photovoltaic test equipment manufactured by Raydec, Inc.

Other measurement equipment

amprobe - clamp meters, solar analyzers and solar power meters

FLUKE - The clamp meters allow measurement of the electric current in the conductor without having to make physical contact with it, or to disconnect it for insertion through the probe. Fluke’s clamp meters offer flexibility and user friendliness with easy to use products and large display screens.

SOLAR SIMULATORS

Solar simulators producers

Spitzenberger - test and simulation systems for regenerative energy sources photovoltaics/wind energy.
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THERMAL CAMERAS & IMAGING

Originally developed in building construction and industrial thermal analysis thermal cameras are nowadays very useful tool for detailed thermal inspections of solar arrays. With periodical inspections array problems (module hot spots) can be detected in advance so that large mailfunctions and yield (money) loss can be prevented right on time.

Thermal camera producers

Fluke - Fluke thermal imagers (sometimes referred to as infrared cameras, thermal cameras, or infrared imagers) capture images of infrared energy or temperature. Using patent-pending IR-Fusion technology, Fluke thermal imagers combine the power of infrared images with visible light images on the same display.

PCE Group - different thermal camera models available. The use of these thermal imaging cameras is extensive. In addition to inspection and industrial maintenance, thermal imaging cameras are a tool of interest for builders and architects. They also help investigators to determine infrared characteristics of various components.
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Testo - Testo's product portfolio also includes different thermal camera models suitable for PV arrays inspection.
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InfraTec - our product range comprises entry level devices, professional and universal cameras, high-end solutions and industrial thermal cameras.
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SENSORS AND ACTUATORS

Sensors for use in PV tracking systems

ELGO Electronic - inclinometric measuring system, magnetic linear and angular measuring systems for use in solar tracking systems.
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ADDITIONAL INFORMATION

Books

	Badescu, V. editor: Modeling Solar Radiation at the Earth Surface; Springer, 2008, ISBN 978-3-540-77454-9.
	Sayigh, A.A.M., Editor: Solar Energy Engineering; Academic Press, 1977, ISBN 0-12-620850-6.
	Rösemann, R.: Solar Radiation Measurement, From Sensor to Application; Gengenbach Messtechnik, 2004, ISBN 3-936947-70-8.
	Hulstrom, R.L. editor: Solar Resources, Solar Heat Technologies: Fundamentals and Applications; MIT Press, Cambridge, MA, 1989, ISBN 0-262-08184-9.
	Kondratyev, K.YA.: Radiation in the Atmosphere; International Geophysics Series, Volume 12, Academic Press, 1969.

Reports

Guide to Meteorological Instruments and Methods of Observation; WMO-No. 8, Seventh edition, 2008, ISBN 978-92-63-10008-5.

Papers

Freire, R.C.S. et al.: Dynamic Response of a feedback Thermorestive Electrical Substitution Pyranometer; Journal of Solar Energy Engineering, Volume 120, May 1998, p.126-130.