* Swiss PMI index rises to 52.5 points
* Back in expansion zone for first time in 17 months
* Swiss industry appears to have passed trough - PMI authors
ZURICH, Feb 1 (Reuters) - Swiss manufacturing grew for the first time in 17 months in January, suggesting companies were benefitting from a fall in the franc's value against the euro as hopes rise that the euro zone can ride out its debt crisis.
The Swiss purchasing managers' index rose to a seasonally adjusted 52.5 points in January from a revised 49.2 points in the previous month, data showed on Friday, beating the average analyst forecast for a reading of 50.5 points.
It was the first time the indicator had risen above the 50 mark, which separates growth from contraction, since August 2011.
"Since the start of 2013 the domestic currency has lost strength. Simultaneously with the depreciation, industry appears to have finally passed the trough," said Credit Suisse and the SVME purchasing managers' association.
Swiss exporters, hurt by the strength of the safe-haven franc since the start of the financial crisis, have welcomed the weakening of the currency to a 22-month low against the euro last week as confidence returns to the euro zone.
More than half of Swiss exports are sold in the euro zone, where the region's crisis had dampened demand and in turn dragged on growth in Switzerland.
Still, the data contrasts with a fall in the closely-watched KOF barometer of sentiment to its lowest in eight months in January, hit by worries that much of Europe will struggle to generate growth for the foreseeable future.
Analysts have suggested the KOF may have painted too rosy a picture in the past and is now playing catch-up with other leading indicators, like the PMI. (Reporting by Caroline Copley; editing by Patrick Graham)