{"id":1775,"date":"2024-10-11T10:06:32","date_gmt":"2024-10-11T09:06:32","guid":{"rendered":"http:\/\/guemisa.es\/?post_type=documentos-pdf&#038;p=1775"},"modified":"2026-11-03T13:42:35","modified_gmt":"2026-11-03T12:42:35","slug":"magnituds-radiacio-solar","status":"publish","type":"documentos-pdf","link":"https:\/\/guemisa.es\/ca\/documentos-pdf\/magnitudes-radiacion-solar\/","title":{"rendered":"Mesura de la radiaci\u00f3 solar: magnituds, piran\u00f2metres i pirheli\u00f2metres"},"content":{"rendered":"<div class=\"gm-doc gm-m-guemisa\">\n<p class=\"k\">Tutorial t\u00e8cnic \u00b7 GUEMISA<\/p>\n<div class=\"meta\"><span>Irradi\u00e0ncia W m-2<\/span><span>Piran\u00f2metre<\/span><span>Pirheli\u00f2metre<\/span><span>Radiaci\u00f3 directa, difusa i global<\/span><span>Heli\u00f2graf<\/span><\/div>\n<div class=\"resp\"><b class=\"t\">Resposta r\u00e0pida<\/b>La radiaci\u00f3 solar global \u00e9s la suma de la radiaci\u00f3 <b>directa, difusa i reflectida<\/b>. Es mesura amb piran\u00f2metres (global i difusa, interval espectral de 0,3 a 3,0 \u03bcm) i pirheli\u00f2metres (directa, sobre seguidor solar); la unitat recomanada d'irradi\u00e0ncia \u00e9s <b>W m<sup>-2<\/sup><\/b>.<\/div>\n<h2>Magnituds de la radiaci\u00f3 solar<\/h2>\n<div class=\"tw\"><table><thead><tr><th>Magnitud<\/th><th>Definici\u00f3<\/th><th>Com es mesura<\/th><\/tr><\/thead><tbody><tr><td>Radiaci\u00f3 directa<\/td><td>Prov\u00e9 directament del disc solar<\/td><td>Amb sistemes de seguiment del moviment del Sol<\/td><\/tr><tr><td>Radiaci\u00f3 difusa<\/td><td>Prov\u00e9 de les reflexions a l'atmosfera<\/td><td>Amb sistemes d'ombrejament del disc solar<\/td><\/tr><tr><td>Radiaci\u00f3 reflectida<\/td><td>Radiaci\u00f3 reflectida per lentorn de la superf\u00edcie receptora que incideix en una superf\u00edcie inclinada; el seu valor mitj\u00e0 \u00e9s el 20% de la radiaci\u00f3 global sobre superf\u00edcie horitzontal<\/td><td>No sol mesurar-se<\/td><\/tr><tr><td>Radiaci\u00f3 global<\/td><td>Suma de les radiacions directa, difusa i reflectida, rebuda per unitat de superf\u00edcie<\/td><td>Sol mesurar-se sobre superf\u00edcie horitzontal; de vegades a la disposici\u00f3 dels panells<\/td><\/tr><\/tbody><\/table><\/div>\n<p>El 95% de la radiaci\u00f3 solar extraterrestre es troba entre 0,2 i 3 \u03bcm. La radiaci\u00f3 terrestre \u00e9s d'ona llarga: a 300 K, el 99,99% de la seva energia t\u00e9 una longitud d'ona superior a 3 \u03bcm.<\/p>\n<h2>Unitats i espectre<\/h2>\n<div class=\"tw\"><table><thead><tr><th>Magnitud<\/th><th>Unitat recomanada<\/th><\/tr><\/thead><tbody><tr><td>Irradi\u00e0ncia (pot\u00e8ncia)<\/td><td>watts per metre quadrat (W m <sup>-2<\/sup> )<\/td><\/tr><tr><td>Exposici\u00f3 radiant (energia)<\/td><td>juliols per metre quadrat (J m <sup>-2<\/sup> )<\/td><\/tr><tr><td>Irradi\u00e0ncia espectral<\/td><td>W m <sup>-2<\/sup> nm <sup>-1<\/sup><\/td><\/tr><tr><td>Exposici\u00f3 radiant espectral<\/td><td>J m <sup>-2<\/sup> nm <sup>-1<\/sup><\/td><\/tr><\/tbody><\/table><\/div>\n<div class=\"tw\"><table><thead><tr><th>Banda<\/th><th>Interval<\/th><\/tr><\/thead><tbody><tr><td>Llum visible (99% de la radiaci\u00f3 visible)<\/td><td>400 nm a 730 nm<\/td><\/tr><tr><td>UV-A<\/td><td>315-400 nm<\/td><\/tr><tr><td>UV-B<\/td><td>280-315 nm<\/td><\/tr><tr><td>UV-C<\/td><td>100-280 nm<\/td><\/tr><tr><td>Radiaci\u00f3 solar extraterrestre d'ona curta (97%)<\/td><td>0,29 \u03bcm a 3,00 \u03bcm<\/td><\/tr><\/tbody><\/table><\/div>\n<h2>Exactitud, precisi\u00f3 i per\u00edode dintegraci\u00f3<\/h2>\n<p>L'exactitud expressa la incertesa en la concordan\u00e7a entre el valor mesurat i el veritable valor. La precisi\u00f3 de l'instrument est\u00e0 determinada per:<\/p>\n<ul><li>La resoluci\u00f3: la variaci\u00f3 m\u00e9s petita de radiaci\u00f3 que es pot detectar.<\/li><li>Les variacions de sensibilitat degudes a alteracions de les variables ambientals.<\/li><li>La no-linealitat de la resposta.<\/li><li>La desviaci\u00f3 de la resposta espectral respecte a la postulada.<\/li><li>La desviaci\u00f3 de la resposta direccional (coseno\u00efdal i azimutal).<\/li><\/ul>\n<p>Es recomana registrar amb una freq\u00fc\u00e8ncia un ordre de magnitud superior a la requerida: dades hor\u00e0ries si es requereixen diaris, i dades minutals si es requereixen horaris.<\/p>\n<h2>Pirheli\u00f2metres i radiaci\u00f3 directa<\/h2>\n<p>El pirheli\u00f2metre mesura la radiaci\u00f3 solar directa amb la superf\u00edcie receptora disposada normalment als raigs incidents. Inclou un obturador per mesurar nom\u00e9s la radiaci\u00f3 del Sol i una regi\u00f3 anular del cel molt propera. Als instruments moderns abasta un semiangle de 2,5\u00ba aproximadament; als antics era d'uns 8\u00e8.<\/p>\n<div class=\"tw\"><table><thead><tr><th>Tipus<\/th><th>Caracter\u00edstiques<\/th><\/tr><\/thead><tbody><tr><td>Patr\u00f3 primari (absolut)<\/td><td>Definiu l'escala d'irradi\u00e0ncia total sense rec\u00f3rrer a fonts de refer\u00e8ncia; receptors de cavitat i mesuradors diferencials de flux calor\u00edfic calibrats el\u00e8ctricament<\/td><\/tr><tr><td>Patr\u00f3 secundari<\/td><td>Compensaci\u00f3 \u00c5ngstr\u00f6m i disc de plata; es calibren per comparaci\u00f3 amb un patr\u00f3 primari<\/td><\/tr><tr><td>Primera i segona classe<\/td><td>Detectors de termopila; registre continu; precisi\u00f3 anual superior a l'u per cent (primera classe) i al dos per cent (segona); temps de resposta m\u00e0xim de deu segons (primera) i trenta segons (segona)<\/td><\/tr><\/tbody><\/table><\/div>\n<p>La mesura de la radiaci\u00f3 directa exigeix orientaci\u00f3 perpendicular als raigs solars que s'aconsegueix amb seguidors solars. Per triar un seguidor es considera la precisi\u00f3 del seguiment, la precisi\u00f3 del rellotge, el pes que pot suportar i els dispositius que es poden acoblar.<\/p>\n<h2>Piran\u00f2metres: radiaci\u00f3 global i difusa<\/h2>\n<p>El piran\u00f2metre mesura la radiaci\u00f3 solar procedent d'un angle de 2\u03c0 estereorradians sobre una superf\u00edcie plana, en un interval espectral de 0,3 a 3,0 \u03bcm. Es disposa en posici\u00f3 invertida per mesurar la radiaci\u00f3 global reflectida. Per a la radiaci\u00f3 difusa es cobreix el component directe amb un sistema de pantalla o banda d'ombra.<\/p>\n<div class=\"tw\"><table><thead><tr><th>Caracter\u00edstica<\/th><th>Patr\u00f3 secundari<\/th><th>Primera classe<\/th><th>Segona classe<\/th><\/tr><\/thead><tbody><tr><td>Resoluci\u00f3 (variaci\u00f3 m\u00ednima detectable a W m <sup>-2<\/sup> )<\/td><td>\u00b1 1<\/td><td>\u00b1 5<\/td><td>\u00b1 10<\/td><\/tr><tr><td>Estabilitat (% de l'escala completa, variaci\u00f3\/any)<\/td><td>\u00b1 1<\/td><td>\u00b1 2<\/td><td>\u00b1 5<\/td><\/tr><tr><td>Resposta coseno\u00efdal (% de desviaci\u00f3 per a altura solar de 10\u00ba)<\/td><td>&lt;\u00b1 3<\/td><td>&lt;\u00b1 7<\/td><td>&lt;\u00b1 15<\/td><\/tr><tr><td>Resposta azimutal (% de desviaci\u00f3 per a altura solar de 10\u00ba)<\/td><td>&lt;\u00b1 3<\/td><td>&lt;\u00b1 5<\/td><td>&lt;\u00b1 10<\/td><\/tr><tr><td>Resposta de temperatura (% d'error m\u00e0xim)<\/td><td>\u00b1 1<\/td><td>\u00b1 2<\/td><td>\u00b1 5<\/td><\/tr><tr><td>No linealitat (% de l'escala completa)<\/td><td>\u00b1 0,5<\/td><td>\u00b1 2<\/td><td>\u00b1 5<\/td><\/tr><tr><td>Sensibilitat espectral (% de desviaci\u00f3, 0,3-3 \u03bcm)<\/td><td>\u00b1 2<\/td><td>\u00b1 5<\/td><td>\u00b1 10<\/td><\/tr><tr><td>Temps de resposta (resposta del 99%)<\/td><td>&lt;25 s<\/td><td>&lt;1 min<\/td><td>&lt;4 min<\/td><\/tr><\/tbody><\/table><\/div>\n<div class=\"figs\"><figure><a href=\"https:\/\/guemisa.es\/wp-content\/uploads\/2026\/11\/magnitudes-radiacion-solar-figura-p10-2.png\" target=\"_blank\" rel=\"noopener\"><img decoding=\"async\" src=\"https:\/\/guemisa.es\/wp-content\/uploads\/2026\/11\/magnitudes-radiacion-solar-figura-p10-2.png\" alt=\"Piran\u00f2metre amb banda d&#039;ombra per a la mesura de la radiaci\u00f3 difusa\" loading=\"lazy\"><\/a><figcaption>Piran\u00f2metre amb banda d'ombra per a la mesura de la radiaci\u00f3 difusa<\/figcaption><\/figure><figure><a href=\"https:\/\/guemisa.es\/wp-content\/uploads\/2026\/11\/magnitudes-radiacion-solar-figura-p11-1.png\" target=\"_blank\" rel=\"noopener\"><img decoding=\"async\" src=\"https:\/\/guemisa.es\/wp-content\/uploads\/2026\/11\/magnitudes-radiacion-solar-figura-p11-1.png\" alt=\"Seguidor solar amb instruments per a radiaci\u00f3 directa, difusa i infraroja\" loading=\"lazy\"><\/a><figcaption>Seguidor solar amb instruments per a radiaci\u00f3 directa, difusa i infraroja<\/figcaption><\/figure><\/div>\n<h2>Hores de sol, espectre i adquisici\u00f3 de dades<\/h2>\n<p>Les hores de sol es registren amb l'heli\u00f2graf de Campbell Stokes: una bola massissa de vidre d'aproximadament 96 mm de di\u00e0metre i un casquet met\u00e0l\u00b7lic conc\u00e8ntric on s'introdueix cada dia una tira de cartolina amb divisi\u00f3 hor\u00e0ria; el Sol crema empremtes segons la intensitat dels raigs.<\/p>\n<figure><a href=\"https:\/\/guemisa.es\/wp-content\/uploads\/2026\/11\/magnitudes-radiacion-solar-figura-p12-1.png\" target=\"_blank\" rel=\"noopener\"><img decoding=\"async\" src=\"https:\/\/guemisa.es\/wp-content\/uploads\/2026\/11\/magnitudes-radiacion-solar-figura-p12-1.png\" alt=\"Heli\u00f2graf\" loading=\"lazy\"><\/a><figcaption>Heli\u00f2graf<\/figcaption><\/figure>\n<p>La distribuci\u00f3 espectral es mesura amb espectroradi\u00f2metres. Els senyals dels sensors s'emmagatzemen en un datalogger connectat a un PC, per cable s\u00e8rie, xarxa telef\u00f2nica (MODEM) o Internet si l'equip permet una adre\u00e7a IP.<\/p>\n<h2>Preguntes freq\u00fcents<\/h2><details class=\"faq\"><summary>Qu\u00e8 \u00e9s la radiaci\u00f3 solar global?<\/summary><p>La radiaci\u00f3 solar rebuda per unitat de superf\u00edcie: suma de les components directa, difusa i reflectida.<\/p><\/details><details class=\"faq\"><summary>Amb quin instrument es mesura la radiaci\u00f3 directa?<\/summary><p>Amb un pirheli\u00f2metre muntat sobre un seguidor solar.<\/p><\/details><details class=\"faq\"><summary>Qu\u00e8 mesura un piran\u00f2metre?<\/summary><p>La radiaci\u00f3 solar procedent d'un angle de 2\u03c0 estereorradians en una superf\u00edcie plana, a l'interval de 0,3 a 3,0 \u03bcm.<\/p><\/details><details class=\"faq\"><summary>Quina unitat es recomana per a la irradi\u00e0ncia?<\/summary><p>Vats per metre quadrat (W m-2); per a l'exposici\u00f3 radiant, juliols per metre quadrat (J m-2).<\/p><\/details><details class=\"faq\"><summary>Com es mesura la radiaci\u00f3 difusa?<\/summary><p>Amb dispositius d'ombreig: bandes d'ombra o seguidors solars amb ombrejament puntual del Sol.<\/p><\/details><details class=\"faq\"><summary>Quina freq\u00fc\u00e8ncia de registre es recomana?<\/summary><p>Un ordre de magnitud superior a la requerida: dades hor\u00e0ries per a requisits diaris i minutals per a requisits horaris.<\/p><\/details>\n<h2>Relacionat<\/h2><ul class=\"rel\"><li><a href=\"https:\/\/guemisa.es\/ca\/categoria\/sensors-meteorologics\/\">Sensors meteorol\u00f2gics<\/a><\/li><li><a href=\"https:\/\/guemisa.es\/ca\/categoria\/radiacio-solar-llum\/\">Radiaci\u00f3 solar \u2013 Llum<\/a><\/li><li><a href=\"https:\/\/guemisa.es\/ca\/documents-pdf\/escala-de-vent-beaufort\/\">Escala de vent Beaufort<\/a><\/li><li><a href=\"https:\/\/guemisa.es\/ca\/categoria\/data-logger\/\">Data Logger<\/a><\/li><li><a href=\"https:\/\/guemisa.es\/ca\/documents-pdf\/fulla-sensors-sector-solar-eolica\/\">Inclin\u00f2metres TST-1x i YCA360 per a solar i e\u00f2lica<\/a><\/li><li><a href=\"https:\/\/guemisa.es\/ca\/informacion-tecnica\/\">Tota la informaci\u00f3 t\u00e8cnica de GUEMISA<\/a><\/li><\/ul>\n<p class=\"pdf-fin\">A sota, el document original en PDF per consultar-lo o descarregar-lo.<\/p><\/div>","protected":false},"featured_media":14179,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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