S0 is a mechanical flow indicator. It is identical with our S2/S25, but this model does not have any micro swithes. It will be used as a direct reading flow monitor within the chosen measuring range. As option you can have the scale direct reading in ie; m3/h, GPM aso.
The price is a little bit lower than for the S2/S25 and you will have a very robust flow indicator for harsh environments.