In general VEE is very good at converting data to the type needed and so you should find that asReal32() is not required if, for example, you are using something like
read the data from the anemometer using an instrument transaction object convert to windspeed in knots using a formula object
The problem I am guessing is that the instrument you are using for the conversion, which may be a multimeter or the like, is coming back with a response that you have not considered e.g. overrange, the meter has not responded within the timeout etc. What I would suggest you do is to log the responses from the instrument ( there are several tools in VEE and Agilent's IO libraries that can help there ) and see what it comes up with when the asReal32() call fails.
You could of course chop off the leading text using something like strFromThru but a simple way is to use a I/O -> From -> String object and set it up to READ TEXT x REAL32 which will extract the first number-like part of the string and convert it to a value for you.
read the data from the anemometer using an instrument transaction object
convert to windspeed in knots using a formula object
The problem I am guessing is that the instrument you are using for the conversion, which may be a multimeter or the like, is coming back with a response that you have not considered e.g. overrange, the meter has not responded within the timeout etc. What I would suggest you do is to log the responses from the instrument ( there are several tools in VEE and Agilent's IO libraries that can help there ) and see what it comes up with when the asReal32() call fails.