can anyone recommend a pH meter + acidifcation method

Hi my blueberry lvs have got very yellow, I've just noticed, despite them growing in pots.  Can anyone recommend a pH meter - digital or strips of paper ?- whats the best for long term monitoring ?

I was going to apply ferrous sulphate as a foliar feed as a quick fix before going on hoiiday.  I imagine in the long term I need better monitoring, and slower applictions of ferrous sulphate.

Amy advice appreciated.

Thx

Are you sure that this is the problem if they're in pots of ericaceous soil? The soil doesn't cease to be acidic - or are you watering with hard water rather than rainwater? Try watering with sequestrine of iron, ferrous sulphate as a foliar feed is unlikely to work. The bushes don't need acid, they need the normal nutrients from soil which they cannot absorb if the soil is alkaline.

There is a very simple stick in the ground meter to measure aidity - accurate enough for most general purposes.  I grow bluberries in the ground, but top dress with ericaceous compost and water with a good seaweed and iron mixture during the summer.  So far they have done very well and given lots of delicious fruit.